ATLAS Facility Description Report

Transcription

1 KAERI/TR-3754/2009 기술보고서 ATLAS Facility Description Report ATLAS 실험장치기술보고서 한국원자력연구원

2 제출문 한국원자력연구원장귀하 본보고서를 2009 연도 APR1400/OPR1000 핵심사고열수력종합 효과실험 과제의기술보고서로제출합니다 주저자 : 강경호공저자 : 문상기박현식조석최기용

3 ATLAS Facility Description Report April 2009 T Thermal Hydraulics Safety Research Division Korea Atomic Energy Research Institute

4 SUMMARY I. TITLE ATLAS Facility Description Report II. CONTENTS A thermal-hydraulic integral effect test facility, ATLAS (Advanced Thermalhydraulic Test Loop for Accident Simulation), has been constructed at KAERI (Korea Atomic Energy Research Institute). The ATLAS has the same two-loop features as the APR1400 and is designed according to the well-known scaling method suggested by Ishii and Kataoka to simulate the various test scenarios as realistically as possible. It is a half-height and 1/288-volume scaled test facility with respect to the APR1400. The fluid system of the ATLAS consists of a primary system, a secondary system, a safety injection system, a break simulating system, a containment simulating system, and auxiliary systems. The primary system includes a reactor vessel, two hot legs, four cold legs, a pressurizer, four reactor coolant pumps, and two steam generators. The secondary system of the ATLAS is simplified to be of a circulating loop-type. Most of the safety injection features of the APR1400 and the OPR1000 are incorporated into the safety injection system of the ATLAS. In the ATLAS test facility, about 1300 instrumentations are installed to precisely investigate the thermal-hydraulic behavior in simulation of the various test scenarios. This report describes the scaling methodology, the geometric data of the individual component, and the specification and the location of the instrumentations in detail. i

5 요약문 I. 제목 ATLAS 실험장치기술보고서 II. 내용 ATLAS(Advanced Thermal-hydraulic Test Loop for Accident Simulation) 는한국형신형원자로인 APR1400을높이비 1/2, 면적비 1/144로축소설계한열수력종합효과실험장치이다. ATLAS 실험장치는기본적으로대형냉각재상실사고, 소형냉각재상실사고, 주증기관파단사고, 증기발생기세관파단사고등원자로의안전관련된설계기준사고를대상으로열수력종합효과실험을수행할수있으며, 또한필요시에안전현안과관련된개별효과실험그리고사고관리전략의도출을위한실험의수행이가능하게다목적으로설계되었다. ATLAS 유체계통은원자로용기및모의노심, 일차계통배관, 가압기, 원자로냉각재펌프, 증기발생기, 이차계통, 안전계통, 보조계통을포함한다. ATLAS실험장치에서는다양한사고의모의에서요구되는물리적변수의측정을위해총 1300여개의측정기기가설치되었다. 본보고서에서는 ATLAS 실험장치설계에고려하였던축소모형방법론과각단위기기의규격및계측기기의사양과설치위치에대한상세정보를기술하였다. ii

6 Table of Contents SUMMARY (in English) i SUMMARY (in Korean) ii Table of Contents iii List of Tables v List of Figures vi 1. INTRODUCTION 1 2. SCALING General Scaling Principle Scaling of Major Components Reactor pressure vessel and core Pressurizer Safety injection tank Steam generator Reactor coolant piping Reactor coolant pump 8 3. ATLAS FACILITY AND EXPERIMENTAL CONFIGURATION General Presentation of the ATLAS Facility ATLAS DVI Experimental Configuration Geometrical data Reactor pressure vessel Core simulator 41 iii

7 Pressurizer Safety injection tank Steam generator Reactor coolant system piping Break simulation system Containment simulation system Reactor coolant pump Material properties Insulation Heat Loss INSTRUMENTATION Location and Specification of Instrumentation Temperature Pressure Flow rate Level Mass Power Instrumentations in the safety injection tank Instrumentations in the break simulation system Instrumentation Calibration Data Reduction and Conversion to Engineering Units Uncertainty Analysis REFERENCES 118 APPENDIX: List of Instrumentation 120 iv

8 List of Tables Table Major scaling parameters of the ATLAS 11 Table Global scaling results for single phase natural circulation of the reactor core 12 Table Global scaling results for two-phase natural circulation of the reactor core 12 Table Summary of the levels in the ATLAS SITs 13 Table Summary of the scaling parameters of the RCP 13 Table Inventory distribution in the ATLAS RCS 17 Table Elevation versus volume tabulation for core region in RPV 18 Table Elevation versus volume tabulation for downcomer region in RPV 19 Table Material volume of a SG 57 Table Inventory distribution in a SG 57 Table Dimensions of the primary piping 71 Table Thermal properties of 316 SS 82 Table Insulation thickness of the major vessels of the ATLAS 84 Table Insulation thickness of pipe lines of the ATLAS 84 Table Number and dimension of thermocouple sensors 88 Table Number of pressure sensors 90 Table Number of flow rate sensors 90 Table Number of level sensors 91 Table Tag names and specification of load cells 92 Table Uncertainty level of instruments 117 v

9 List of Figures Figure Schematic diagram of the SITs for APR1400 and ATLAS 14 Figure Flow diagram of ATLAS 20 Figure Bird s eye view of ATLAS 21 Figure Plan view of ATLAS 22 Figure Arrangement and labeling of primary legs 23 Figure Schematic diagram of loop connection 24 Figure Photograph of ATLAS 25 Figure Overview of ATLAS reactor pressure vessel 27 Figure Configuration of reactor pressure vessel 28 Figure Coolant flow in reactor pressure vessel 29 Figure Sectional regions for cross-sectional view 30 Figure Cross section A of reactor pressure vessel: UGSSP 31 Figure Cross section B of reactor pressure vessel: Loop connection 32 Figure Cross section C of reactor pressure vessel: FAP 33 Figure Cross section D of reactor pressure vessel: Core center 34 Figure Cross section E of reactor pressure vessel: Lower spacer 35 Figure Cross section F of reactor pressure vessel: Lower plenum 36 Figure Detailed geometry of upper plenum 37 Figure Detailed geometry of outlet plenum 38 Figure Detailed geometry of lower plenum including flow baffle 39 Figure Configuration of expansion joint 40 Figure Configuration of heater rod and unheated rod 42 Figure Configuration of core heater bundle 43 Figure Arrangement of core rods 44 Figure Axial power profile 45 Figure Pressurizer of ATLAS 46 Figure Configuration of surge line 47 Figure Detail of pressurizer nozzle and heater 48 Figure Relief valve line of pressurizer 49 Figure Safety injection tank of ATLAS 52 Figure Injection line from SIT-1 to RPV 53 Figure Injection line from SIT-2 to RPV 54 Figure Injection line from SIT-3 to RPV 55 vi

10 Figure Injection line from SIT-4 to RPV 56 Figure Steam generator of ATLAS 58 Figure Configuration of steam generator 59 Figure Coolant flow in SG secondary side 60 Figure Lower plenum of SG 61 Figure Configuration of U-tube assembly 62 Figure Economizer divider plate 63 Figure Configuration of middle SG vessel 64 Figure Configuration of upper SG vessel 65 Figure Configuration of separator and internal cylinder 66 Figure Details of separator 67 Figure Configuration of SG dryer 68 Figure Configuration of loop connection (plan view) 72 Figure Configuration of loop connection (side view) 73 Figure Position of surge line 74 Figure Dimension of hot leg 75 Figure Dimension of cold leg 76 Figure Dimension of intermediate Leg 77 Figure Configuration of DVI line break 78 Figure Break simulator for DVI line break (flow nozzle) 79 Figure Containment simulator of ATLAS 80 Figure RCP of ATLAS 81 Figure Specific heat and thermal conductivity of 316SS 83 Figure Estimated primary heat loss of the ATLAS 85 Figure Estimated secondary heat loss of the ATLAS 87 Figure Temperature sensors in core - Axial configuration 93 Figure Temperature sensors in core - Radial configuration (a) 94 Figure Temperature sensors in core - Radial configuration (b) 95 Figure Temperature sensors in RPV 96 Figure Temperature sensors in hot leg 97 Figure Temperature sensors in cold leg 98 Figure Temperature sensors in intermediate leg 99 Figure Temperature sensors in pressurizer 100 Figure Temperature sensors in SG 101 Figure Pressure transmitters in RPV 102 Figure Pressure transmitters in RCS loop (plan view, cross view) 103 vii

11 Figure Pressure transmitters in pressurizer 104 Figure Pressure transmitters in SG 105 Figure Flowmeters in RCS loop 106 Figure Flowmeters in SG 107 Figure Level transmitters in RPV (axial) 108 Figure Level transmitters in RCS Loop 109 Figure Level transmitters in PZR (axial) 110 Figure Level transmitters in SG (axial) 111 Figure Instruments in SIT 112 Figure Instruments in break simulation system 113 Figure Schematic diagram of signal processing scheme 116 viii

12 1. INTRODUCTION An integral effect test for about 50% DVI (Direct Vessel Injection) line break of the APR1400 (Advanced Power Reactor 1,400 MWe) using the ATLAS (Advanced Thermal-Hydraulic Test Loop for Accident Simulation) was endorsed and designated as ISP-50 by OECD/CSNI on December in Several evolutionary PWRs such as AP1000, APWR, and VVER-1000 adopt a DVI method for an emergency core cooling system instead of a conventional CLI (Cold Leg Injection) method because the DVI method is believed to have a better core cooling performance than the CLI method. However, the DVI nozzle which is directly attached to a reactor vessel is vulnerable to a postulated break and its break should be taken into account as one of the small break LOCA (Loss of Coolant Accident) categories from a safety viewpoint. In the event of a DVI line break, the vapor generated in the core is introduced to the RPV (Reactor Pressure Vessel) downcomer through the hot legs, the steam generators and the cold legs. Then the vapor should pass through the upper part of the RPV downcomer to be discharged through the broken DVI nozzle. Therefore, the behavior of the two-phase flow in the upper annulus downcomer is expected to be complicated and relevant models need to be implemented into safety analysis codes in order to predict these thermal hydraulic phenomena correctly. So far there is not enough integral effect test data for the DVI line breaks which can demonstrate the progression of the DVI line break accident realistically and can be used for an assessment and improvement of the existing safety analysis codes. The ATLAS will be used to provide the unique test data for the 2(hot legs) x 4(cold legs) reactor coolant system with a DVI of emergency coolant; this will significantly expand the currently available data bases for code validation. ISP (International Standard Problem) exercise using the ATLAS would contribute significantly to enhancement of understanding on the behavior of nuclear reactor systems with the DVI and to the assessment of existing and new thermal-hydraulic analysis codes such as TRACE, CATHARE, RELAP, TRAC, ATHELET, CATHENA, MARS and etc. The ISP exercise is also expected to help the ATLAS facility to be effectively verified by the international community. The ATLAS has been operated in order to investigate major design basis accidents and operational transients for a 1400 MWe-class evolutionary pressurized water reactor, APR1400, which was developed by the Korean industry [1, 2]. The ATLAS also incorporates several specific design characteristics of a 1,000 MWe-class Korean - 1 -

13 standard nuclear power plant, OPR1000 (Optimized Power Reactor 1,000 MWe) [3, 4]. The following section of this report gives general information about the ATLAS facility with emphasis on the facility configuration used for 50% DVI line break simulation. Detailed information about instrumentations will be introduced in the last section

14 2. SCALING 2.1 General Scaling Principle The ATLAS was designed to model a reduced-height primary system of a typical 3983 MWt PWR (Pressurized Water Reactor), APR1400. The ATLAS has the 1/2-height, 1/144-area and 1/288-volume scales for the APR1400. The ATLAS is scaled for fullpressure and full-temperature conditions of the APR1400, and uses water as the working fluid. The scaling of the ATLAS had been performed according to the three-level scaling methodology of Ishii et al. [5], which consists of the integral system scaling (global scaling or top down approach), the control volume and boundary flow scaling, and local phenomena scaling. The integral system scaling ensures the transient response for major variables in single-phase and two-phase flows to be preserved in the ATLAS facility according to the required scaling values. This scaling ensures that both the steady-state and dynamic conditions are simulated within each component. The integral system scaling results in the simulation of all the major thermal-hydraulic parameters in the ATLAS. The control volume and boundary flow scaling is based on the mass and energy balance between the various components. The scaling preserves the inter-component mass and energy flows as well as the mass and energy inventories in each component, thus they play a major role in the overall system scaling. Finally, once the integral system scaling, and the control volume and boundary layer flow scaling has been finished, then the third level of scaling for the important local phenomena should be carried out in order to preserve the important local phenomena and to reduce a possible scaling distortions. The important local phenomena can be identified from the PIRT (Phenomena Identification and Ranking Table). For the ATLAS facility, the PIRT was developed for large break loss-of-coolant accident, DVI line break, and MSLB (main steam line break) accident of APR1400. The main motive for adopting the reduced-height design is to allow the use of an integrated annular downcomer where the multidimensional phenomena can be important in some accident conditions with a DVI operation. According to the scaling law, the reduced height scaling results in time-reducing results in the model. For the one-half-height facility, the time for the scaled model is a square root 2 times faster than the prototypical time. The friction factors in the scaled model are maintained at - 3 -

15 the same values as those of the prototype. The hydraulic diameter of the scaled model is maintained the same as that of the prototype to preserve the prototypical conditions for the heat transfer coefficient. Major scaling parameters of the ATLAS are summarized in Table According to the scale ratio and scaling parameters, the ATLAS was designed as follows: Volumes: scaled by 1/288 to the reference plant, APR1400 Lengths (heights and elevations): scaled by 1/2 reduced-height. The break flow through various nozzles such as cold leg, hot leg and DVI nozzles are dependent on the bottom elevation of the nozzles, the scaled bottom elevations are preserved to that of the reference plant. Core power: The maximum core power of the ATLAS is 1.96 MW, which is equal to 10% of the scaled power. Fuel assembly: The diameter and pitch of the fuel rod and guide tube were designed to be the same as the reference plant. The length of the fuel rod and guide tube was scaled by the 1/2 reduced height scale. The total number of fuel rods was scaled by the area ratio of 1/144. This design preserves the heat transfer characteristics of the core. Flow rate: The flow rate of the reactor coolant pump was designed to have a maximum 25% of the scaled flow rate. The flow rate can be adjusted in proportion to the scaled core power in order to preserve the fluid temperature distributions with the reference plant. Pressure and temperature distributions: The distributions of pressure and temperature were preserved to be the same as the reference plant. Pressure loss: The pressure loss was designed to be the 1/2 of the reference plant. As far as possible, the effective pressure loss coefficients were designed to be the same as the reference plant. 2.2 Scaling of Major Components Reactor pressure vessel and core Ishii and Kataoka [6] derived global similarity parameters for single phase and two-phase natural circulation from the fluid continuity, integral momentum, and - 4 -

16 energy equations in one-dimensional, area-averaged forms along with the appropriate boundary conditions and the solid structure energy equation. The important dimensionless parameters characterizing geometric, kinematic, dynamic and energetic similarity are as follows: For single phase flow: Richardson number, friction number, modified Stanton number, time ratio number, heat source number, Biot number, pump characteristic number, axial length scale, flow area scale. For two-phase flow: Phase change number (or Zuber number), subcooling number, Froude number, drift-flux number, time ratio number thermal inertia ratio, friction number, orifice number. Table and show the scaling results for the global similarity parameters for reactor pressure vessel and core of the ATLAS. The scaling analyses for the following phenomena were performed for the reactor pressure vessel and core and the scaling distortions were estimated: Void fraction and mixture level in the core: They are relatively well preserved. Two-phase flow pattern in the core: The bubbly-to-slug flow transition becomes distorted at low pressure and low vapor velocity. Slug-to-churn flow transition is well preserved while the churn-to-annular and annular-to-annular mist flow transitions are delayed and occur at a higher velocity in the ATLAS (velocity scaling distortion factor 1.414). Flow reversal in the core: It is delayed and occur at a higher velocity in the ATLAS (velocity scaling distortion factor: 1.414). Onset of entrainment for film flow in the core: The entrainment begins at a higher velocity. Flooding in the core: It occurs at higher velocity as the liquid velocity increases. Thermal behavior of the heater rods: The surface temperature of the heater rod shows a little higher value than the prototype, but the distortion can be neglected. Stored energy of reactor vessel (especially for downcomer boiling): It is higher in the ATLAS (scaling distortion factor: about 2.6). Heat transfer enhancement by spacer grids: The prototype spacer grids are used in the ATLAS. The axial span of the spacer grids was adjusted to minimize the scaling distortion of the heat transfer and critical heat flux enhancements in the ATLAS. Coolant level and volume distribution: The coolant volume in the downcomer was increased due to the increased gap size of the downcomer. Thus, the coolant - 5 -

17 level in the downcomer will be smaller than the scaled level while the coolant level in the other part including the core will be larger than the scaled level. However, the whole coolant volume and level are similar to the scaled values of the reference plant. The local phenomena scaling results for the downcomer of the pressure vessel are as follows: Effect of surface tension and existence of the cap bubble: The surface tension effect can be occurred at pressures below 8.0 MPa in the ATLAS while there is no effect of the surface tension in the reference plant. The slug flow can occur in the ATLAS downcomer while the slug flow does not occur in the reference plant at pressures below 8.0 MPa due to the existence of cap bubble. Multi-dimensional phenomena: ATLAS downcomer has an aspect ratio of 5.94 which is more appropriate than a full height scale facility with the same volume scale as the ATLAS. However, the multi-dimensional phenomena such as ECC bypass, coolant mixing, and asymmetric thermal-hydraulic phenomena will be distorted in the ATLAS because the aspect ratio is greater than 1. Flooding: It is delayed up to higher velocity. Void fraction: It is relatively well preserved except for very low liquid superficial velocity less than about 0.1 m/s. Two-phase flow pattern: The slug-to-churn flow transition is well preserved. The distortions of the bubbly-to-slug and churn-to-annular flow transitions are significant at low pressure and low velocity conditions. ECC bypass phenomena: The onset of entrainment occurs at higher velocity than the scaled velocity in the ATLAS and the entrainment rate will be very low compared with the reference plant. Nevertheless, the ECCS bypass phenomena will be close to the reference plant because the scaling distortion of the Wallis number is not so large. Steam condensation: The quantity of the condensed steam will be large in the ATLAS due to a large surface area in the downcomer. ECC jet breakup and impingement phenomena: The SIT flow jet phenomena will be similar to the reference plant while SI flow can show a larger bypass than the reference plant. Stored heat of downcomer structure: The downcomer boiling will be suppressed compared with the reference plant because the stored heat of downcomer will be released quickly at the early stage of the accident

18 2.2.2 Pressurizer The pressurizer was designed in order that its volume, flow area and height ratios should be preserved according to the geometrical scale ratios. In order to preserve them, the following local phenomena were considered to be preserved in the pressurizer: Critical flow at surge line: The diameter of the surge line at the connection location to the hot leg was designed to preserve the critical flow at surge line. Froude number at the horizontal part of surge line: It is preserved in the ATLAS. Critical flow at safety valve: The diameter of the safety valve where the critical flow will occur was adjusted to preserve the critical flow at the scaled value. Off-take at surge-to-hot leg connection location: It is preserved Safety injection tank One of new design features of APR1400 [7] is the SIS (Safety Injection System), which has four mechanically independent trains and a DVI mode. Each train of safety injection system consists of a safety injection pump (SIP) and a passively operating SIT (safety injection tank). KAERI had performed various thermal hydraulic tests to evaluate and verify the performance of these new APR1400 design features. [8] Each of the four SITs of APR1400 has a fluidic device which passively controls the discharge flow rate into the reactor coolant system. In the APR1400 a high flow condition is changed to a low flow condition due to a fluidic device during an operation of the SIT. As the self-controlled fluidic device was not installed in the ATLAS [1], a set of characterization tests was performed to simulate its injection capability from the SIT for the APR1400 simulation. [9] In the ATLAS the required SIT flow rate in the high flow condition was acquired by installing orifices with an optimized flow area to throttle the SIT discharge line and the low flow condition was achieved by changing the opening of the flow control valve in the SIT injection line. The test results showed that the safety injection systems of the ATLAS could simulate the required high and low flow rates of the SIT for the APR1400 simulation efficiently. Figure shows the schematic diagram of the SITs for APR1400 and ATLAS. The Levels 1, 2, and 3 is the levels at the initial nominal level, the stand pipe top, and the fluid device bottom, respectively, for the APR1400, and the ATLAS levels are set to match the scaled volumes. The nominal volume of nitrogen gas - 7 -

19 above Level 1 is m 3 in the APR1400 and the scaled volume is m 3 in the ATLAS. The inner diameter and total volume of the ATLAS SIT are m and 0.4 m 3, respectively. Three SITs are used during the DVI line break simulation. Table shows the summary of the levels in the ATLAS SITs Steam generator The primary thermal-hydraulic phenomena in the primary side of the steam generator were identified as the natural circulation and the heat transfer. In order to preserve those phenomena, the overall pressure drop, overall heat transfer coefficient, and average temperature difference between primary and secondary sides should have proper scaled values. In overall, considering those phenomena and parameters, the U- tube diameter and pitch were reduced to keep hydraulic diameter and also heat transfer area of U tube was changed according to scale raw. The height and volume ratios of each compartment were conformed to the geometrical scale ratios. The downcomer of the secondary side of the steam generator was modeled using pipes rather than annulus in order to preserve the pressure drop and the thermalhydraulic phenomena while preserving the coolant volume Reactor coolant piping The horizontal sections of the hot leg and cold leg were designed to preserve the Froude number in order to have a similarity of the two-phase flow patterns. In the intermediate leg, the Froude number and area ratio were preserved in the horizontal part and in the vertical part, respectively, to preserve the loop seal clearing at SBLOCA Reactor coolant pump As the primary piping has a superior priority to the reactor coolant pump itself from the viewpoint of scaling, the suction and discharge nozzle sizes of the reactor coolant pump are determined beforehand. In general, a dimensional analysis is applied to the problems of hydraulics similitude. When the procedure proposed by Buckingham is applied to a centrifugal pump, three independent dimensionless criteria can be obtained such as specific speed (N s ), specific capacity (Q s ) and specific head (H s ) [10]. The subscript s indicates a specific quantity. For the flow to be dynamically similar, these three dimensionless parameters - 8 -

20 remain constant. However, in a practical sense, it is impossible to comply with all the requirements. According to the global scaling criteria, the flow rate and the head of the RCP are reduced by 1/203.6 and 1/2, respectively. The diameter of the impeller also has a constraint because the suction and discharge nozzle diameters are determined from the local phenomena scaling. The rotational speed of the impeller is also limited due to its size and manufacturing cost. The ratios of the dimensionless parameters of the RCP of the ATLAS to those of the APR1400 can be defined as follows: - Specific speed ratio (N sr ), (1) - Specific capacity ratio (Q sr ), (2) - Specific head ratio (H sr ), (3) where the subscripts m and p indicate a model pump of the ATLAS and a prototype pump of the APR1400, respectively. The subscript R indicates a ratio of model to prototype pump. Ideally, three ratios should be a unit to have a perfect similarity. However, the specific speed of the model pump has a much smaller value by one order of magnitude. Whereas, the specific capacity and the specific head of the model pump have larger values in the probable range of the impeller ratio. In order to improve the similarity between the model and the prototype pumps, the rotational speed of the model pump (N) should be increased whereas the flow capacity Q and the head H of the model pump should be decreased. It is noteworthy that the maximum core power of the ATLAS is 10% of the scaled value due to a limitation of the electrical power supply. It implies that the primary coolant flow rate is also reduced to 10% of the scaled value to maintain the same temperature difference across the core. Therefore, there is room for reducing the flow capacity Q and the head H of the model pump. On the other hand, it is necessary for the model pump to have a sufficient head to supply a coolant to the core from the - 9 -

21 viewpoint of an operation and maintenance. Considering all the above notions, the flow capacity Q and the head H of the model pump was determined to be 25% and 50% of the scaled values, respectively. The rotational speed N was also determined to be 3600 rpm from the same engineering judgment. A summary of the scaling parameters of the model pump is given in Table The present model pump installed at the ATLAS still has such distortion that the homologous curves of the prototype pump cannot be used without a verification. Therefore, a separate characteristic test program was performed to identify the characteristics of the model pump and to verify the similarity between the reactor coolant pumps of the ATLAS and the APR1400. The detailed information on the scaling of the RCP of the ATLAS can be found in the literature [11]

22 Table Major scaling parameters of the ATLAS Parameters Scaling ratio ATLAS design Length (height) l or 1/2 Diameter d or 1/12 Area d 2 or 1/144 Volume l or d 2 or 1/288 Core temperature rise T or 1 Velocity l 1/2 or 1/1.414 Time l 1/2 or 1/1.414 Power/volume l -1/2 or Heat flux l -1/2 or Core power l 1/2 or d 2 or 1/203.6 Rod diameter (core) 1 1 Rod diameter (steam generator) Number of rods (core) d 2 or 1/144 Number of rods (steam generator) 1/72 Flow rate l 1/2 or d 2 or 1/203.6 Pressure drop l or 1/2-11 -

23 Table Global scaling results for single phase natural circulation of the reactor core Design parameter ATLAS scaling ratio Richardson number 1.00 Friction number 1.00 Axial length scale 1.00 Flow area scale 1.00 Heat transfer coefficient (laminar) 1.00 Heat transfer coefficient (turbulent) 0.76 Modified Stanton number (laminar) 0.71 Modified Stanton number (turbulent) 0.54 Time ratio number 0.94 Biot number (laminar) 0.90 Biot number (turbulent) 0.68 Heat source number 0.78 Table Global scaling results for two-phase natural circulation of the reactor core Design parameter ATLAS scaling ratio Phase change number 1.00 Subcooling number 1.00 Froude number 1.00 Time ratio number 0.94 Thermal inertia number 1.28 Inlet subcooling 1.00 Exit quality 1.00 Friction number 0.71 Orifice number 1.00 Superficial velocity 0.71 Drift flux number (Bubbly-slug) 1.40 ~ 1.05 Drift flux number (Turbulent slug) 1.40 ~ 1.05 Heat transfer coefficient ~1 Modified Stanton number 0.71 Biot number

24 Table Summary of the levels in the ATLAS SITs Levels SIT-1 SIT-2 SIT-3 SIT-4 Level % 94.9% 94.2% 95.1% Level % 72.6% 72.0% 72.8% Level % 47.2% 46.6% 47.4% Table Summary of the scaling parameters of the RCP Parameters APR1400 (P) ATLAS (Ideal) ATLAS (M) Ratio (M/P) Remarks N (rpm) poles (ATLAS) Q (m 3 /hr) % of scaled value H (m) % of scaled value d (mm) Specific speed (rpm gpm 0.5 /ft 3/4 ) Approximate impeller diameter

25 Figure Schematic diagram of the SITs for APR1400 and ATLAS

26 3. ATLAS FACILITY AND EXPERIMENTAL CONFIGURATION 3.1 General Presentation of the ATLAS Facility The ATLAS facility [1, 2] has the following characteristics: (a) 1/2-height, 1/288- volume, full-pressure simulation of the APR1400; (b) geometrical similarity with the APR1400, including 2 (hot legs) x 4 (cold legs) reactor coolant loops, DVI of emergency core cooling water, integrated annular downcomer, etc.; (c) incorporation of specific design characteristics of the 1000-MW (electric) class OPR1000 such as a cold-leg injection and the low-pressure injection pumps, (d) a maximum 10% of the scaled nominal core power, and (e) simulation capability of broad scenarios, including the reflood phase of the large-break LOCA, small-break LOCA scenarios including the DVI line breaks, steam generator tube rupture, MSLB, midloop operation, etc. Scientific design of the ATLAS was accomplished from the viewpoints of both a global and local scaling based on Ishii et al.[5] s three-level scaling methodology. Key scientific design parameters of the ATLAS are summarized in Table The fluid system of the ATLAS consists of a primary system, a secondary system, a safety injection system, a break simulating system, a containment simulating system, and auxiliary systems. The primary system includes a reactor vessel, two hot legs, four cold legs, a pressurizer, four reactor coolant pumps, and two steam generators. Most of the safety injection features of the APR1400 and the OPR1000 are incorporated into the safety injection system of the ATLAS. It consists of four safety injection tanks (SITs), a high pressure safety injection pump which can simulate safety injection and long-term cooling, a charging pump for charging auxiliary spray, and a shut down cooling pump and a shutdown heat exchanger for low pressure safety injection, shutdown cooling operation and recirculation operation. The break simulation system consists of several break simulating lines such as LBLOCA, DVI line break LOCA, SBLOCA, SGTR, MSLB and FLB (Feedwater Line Break), etc. Each break simulating line consists of a quick opening valve, a break nozzle and instruments. It is precisely manufactured to have a scaled break flow through it in the case of LOCA tests. The containment simulating system of the ATLAS has a function of collecting the break flow rate and maintaining a specified back-pressure in order to simulate a containment

27 The secondary system of the ATLAS is simplified to be of a circulating loop-type. The steam generated at two steam generators is condensed in a direct condenser tank and the condensed feedwater is again injected to the steam generators. Besides, the ATLAS has some auxiliary systems such as a makeup system, a component cooling system, a nitrogen/air/steam supply system, a vacuum system, and a heat tracing system. Secondary and auxiliary systems are designed as simply as possible since the main focus of the IET (Integral Effect Test) using the ATLAS will be on the simulation of primary-system transients and accidents, except for a MSLB and a FLB. Figure shows a flow diagram of the ATLAS facility including an APR1400 DVI line break simulation. More realistic 3-dimensional view of the ATLAS is shown in Figure 3.1.2, including a reactor pressure vessel, two steam generators, four reactor coolant pumps, a pressurizer, and four safety injection tanks. Figure shows the plan view of ATLAS. Arrangement and labeling of the primary legs is also shown in Figure When a trip signal is generated to simulate a DVI line break of the ATLAS, a quick-opening valve of OV-BS-03 is fully opened to discharge the RCS inventories from the RPV into the containment simulator through a broken DVI nozzle. The ATLAS uses water as the working fluid and is scaled for prototypic pressure and temperature conditions. This selection achieves a fluid property similarity between the APR1400 and the ATLAS in a very simple manner. To allow for the simulation of high-pressure scenarios, the loop is designed to operate up to 20 MPa. Stainless steel is selected as the major construction material for most of the components to minimize corrosion problems. Figure shows the schematic diagram of loop connection, which shows the elevations of the ATLAS major components. The elevations are based on the reference point of RPV bottom. Table shows the inventory distribution in the ATLAS RCS and the total inventory was m 3, which was validated by the actual inventory measurement. Tables and show the elevation versus volume tabulation for core and downcomer regions in RPV, respectively. Their elevations are measured by level transmitters of LT-RPV-03 and LT-RPV-04A/B, respectively. The total height of the facility is about 30 m, i.e. 10 m under ground and 20 m above ground. All the major components, e.g. reactor vessel (RV), SGs, pressurizer, SITs, are located above ground. The ATLAS facility adopts a jet condenser for a heat removal from the secondary system to the component cooling water system and containment simulators to simulate the containment back pressure and measure the break flow rate. Figure shows a photograph of the front view of the ATLAS facility. Detailed ATLAS design and description of the ATLAS development program can be found in the literature [12]

28 Table Inventory distribution in the ATLAS RCS Region Volume (m 3 ) Remarks RPV-Core Core region RPV-Downcomer Downcomer region Hot Leg of 2 hot legs Cold Leg of 4 cold legs Reactor Coolant Pump of 4 RCPs Intermediate Leg of 4 intermediate legs Pressurizer Pressurizer Surge Line Steam Generator of 2 SG Total Total RCS inventory

29 Table Elevation versus volume tabulation for core region in RPV Elevation (m) Volume (m 3 )

30 Table Elevation versus volume tabulation for downcomer region in RPV Elevation (m) Volume (m 3 )

31 Figure Flow diagram of ATLAS

32 Figure Bird s eye view of ATLAS

33 Figure Plan view of ATLAS

34 Figure Arrangement and labeling of primary legs

35 Figure Schematic diagram of loop connection

36 Figure Photograph of ATLAS

37 3.2 ATLAS DVI Experimental Configuration Geometrical data Reactor pressure vessel The reactor pressure vessel and the core simulator are designed to preserve the distributions of the temperature, pressure, coolant volume, flow rate, and flow area. They are also designed to preserve the hydraulic diameter and important local phenomena. In designing the reactor vessel downcomer, the main focus was on the reproduction of the multidimensional phenomena related to a DVI as well as the preservation of the surface tension effect and the flow regime (especially for cap bubbles). During the local phenomena scaling analysis, several parameters are considered, including the void fraction, the mixture level, the transition criteria of a two-phase flow regime, flow reversal, ECC bypass, steam condensation, stored energy, pressure drop, etc. Most of the design parameters are based on the integral scaling parameters. However, the gap size of the downcomer annulus is intentionally increased to simulate the multidimensional behavior more realistically. The increased downcomer volume is compensated for by reducing the lower-plenum volume to maintain the total coolant volume ratio in the reactor vessel. It could affect the local phenomena such as the void fraction, hydraulic resistance, flow distribution, etc. The energy release from the reactor vessel wall in the downcomer region is highly distorted because of the increased surface area of the downcomer annulus in the ATLAS, and its effect on the void fraction will be more significant than that due to the increase of the downcomer gap. The skin frictional pressure drop also increases compared with an ideal one because of the increased length-to-diameter ratio in the ATLAS. However, an overall pressure drop along the downcomer is preserved by adjusting the form loss factor at the flow skirt. The preservation of the pressure drop might minimize the distortion of the flow distribution. Figures through shows the geometric details of ATLAS reactor pressure vessel. Figure shows the overview of ATLAS reactor pressure vessel. Figure shows the configuration of reactor pressure vessel and Figure shows the coolant flow in reactor pressure vessel. Figure shows the sectional regions for crosssectional view. Cross sections A through F, as shown in Figures through , are for the UGSSP (upper guide structure support plate), loop connection region, FAP (fuel alignment plate), core center, lower spacer grid, and lower plenum, respectively

38 Figures through show the detailed geometry in the upper plenum, outlet plenum and lower plenum including flow baffle, and Figure shows the configuration of expansion joint. Figure Overview of ATLAS reactor pressure vessel

39 Figure Configuration of reactor pressure vessel

40 Figure Coolant flow in reactor pressure vessel

41 Figure Sectional regions for cross sectional view

42 Figure Cross section A of reactor pressure vessel: UGSSP

43 Figure Cross section B of reactor pressure vessel: Loop connection

44 Figure Cross section C of reactor pressure vessel: FAP

45 Figure Cross section D of reactor pressure vessel: Core center

46 Figure Cross section E of reactor pressure vessel: Lower spacer

47 Figure Cross section F of reactor pressure vessel: Lower plenum

48 Figure Detailed geometry of upper plenum

49 Figure Detailed geometry of outlet plenum

50 Figure Detailed geometry of lower plenum including flow baffle

51 Figure Configuration of expansion joint

52 Core simulator A total of 396 electrical heaters and unheated rods are used to simulate the fuel rods. Since the diameter is maintained to be identical to that of the APR1400, the temperature of the fuel rods will reasonably represent the reference reactor during most accident conditions if the initial stored energy can be reasonably treated. The maximum core power will be limited to 10% of the scaled nominal power by considering the power limitation. A bundle of electric heaters is installed to simulate the reactor core, which is located in the lower part of a reactor pressure vessel. There are 390 electric heaters which are divided concentrically into 3 groups (Group-1, Group-2 and Group-3). Group-1, -2, and -3 heaters are located in inner, middle, and outer regions of the heater bundle, respectively, and they have 102, 138 and 150 heaters, respectively. The core heater bundle has 6 unheated rods additionally. The axial power profile of each heater rod is the chopped cosine power shape. The simulated fuel assembly type is 16 16, and the prototypical spacer grid is used. The outer diameter of heater rod is 9.7 mm, which is the same as the prototypical rod diameter of APR1400. Figures through shows the geometric details of ATLAS core simulator. Figure shows the overall configuration of heater rod and unheated rod and Figure shows the configuration of core heater bundle. Figure shows the arrangement of core rods and Figure shows the axial power profile Pressurizer The pressurizer is designed to closely follow the geometrical scaling laws and to allow for the required control functions. Particular attention is given to a proper simulation of the critical flow conditions in the surge line and safety valves. Figures through shows the geometric details of ATLAS pressurizer. Figure shows the schematic overview of the ATLAS pressurizer and Figure shows the configuration of surge line. Figure shows the detail of pressurizer nozzles and heater and Figure shows the relief valve line of pressurizer

53 Figure Configuration of heater rod and unheated rod

54 Figure Configuration of core heater bundle

55 Figure Arrangement of core rods

56 Figure Axial power profile

57 Figure Pressurizer of ATLAS

58 Figure Configuration of surge line

59 Figure Detail of pressurizer nozzle and heater

60 Figure Relief valve line of pressurizer

61 Safety injection tank The safety system of the ATLAS consists of the SIS and the SDS (safety depressurization system). The SIS consists of four SITs, two SIPs, two shutdown cooling system pumps, a charging pump, and a refueling water tank. Injection lines are provided to the reactor vessel downcomer (i.e., DVI) and cold legs to maximize the utilization of the ATLAS. The SDS is simulated by a depressurization valve in the single train instead of four depressurization valves in two trains for the APR1400. Figures through shows the geometric details of ATLAS SIT. Figure shows the overview of the ATLAS safety injection tank. Figures through show the injection lines from SIT-1, 2, 3, and 4, respectively, to the safety injection nozzle into the reactor pressure vessel Steam generator The ATLAS has two steam generators, which have the same designed specifications except for a break unit to simulate U-tube rupture. The break unit is installed in SG-1. Each consists of a lower plenum, a U-tube assembly, middle and upper SG vessels, two downcomer pipes, and other internals as shown in Figures and , which show the relative elevation of the feed water and the downcomer nozzles. The coolant flow in the secondary-side of SG is shown in Figure The whole of the SGs are made of stainless steel (STS 316) except for the U-tube made of Inconel 690. The U-tube rupture break units are not presented in this report. Table and show a material volume and an inventory volume of each section, respectively. (a) Lower plenum Figure shows a lower plenum, which consists of cylindrical body with hemispherical head, 1 hot-leg and 2 cold-leg nozzles, divider plate to prevent a leakage between the inlet and outlet sections, and a connecting flange. (b) U-tube assembly The U-tube assembly consists of a tube sheet, an economizer divider plate, 8 tube support plates, and 176 U-tubes. The tube sheet is installed between the lower plenum and the middle SG vessel, as shown in Figure , and it serves as a physical boundary between the primary and the secondary system. The 176 U-tubes and an

62 economizer divider plate and 12 guide plates to support the 8 tube support plates were welded upside of the tube sheet. The outer diameter, thickness and averaged length of U-tube are 14.2 mm, 1.1 mm and m, respectively. The U-tube assembly and the economizer divider plate can be seen in Figures and (c) SG vessel and downcomer piping The SG vessel can be divided into two parts, namely middle SG vessel and upper SG vessel as shown in Figures and , respectively. The middle and the upper SG vessel form a riser and steam dome section, respectively. The middle SG vessel has four nozzles for the connection of the two downcomer pipes and it also has two economizer nozzles. In the lower part of the middle SG vessel, a cylindrical flow skirt was installed to maintain the original flow path. The upper SG vessel has a main steam line nozzle and a downcomer feedwater nozzle located at the top of the upper SG vessel with a 60 o inclination angle from the vertical axis and lower-part as can be observed in Figure , respectively. Detailed configurations of the downcomer piping can be observed in Figure (d) Other internals Other internals are a steam separator, a dryer, and a downcomer internal cylinder. The downcomer internal cylinder is to simulate the annular downcomer geometry at the upper part of SG and it not only supports the steam separator but also serves as a conduit of steam generated from the riser section as can be seen in Figure Downcomer consists of an upper annular region and lower region comprising of the two piping with 87.3 mm (4 inch, Schedule 160, ANSI standard) located outside the SG vessel as shown in Figure Details of the separator and the dryer are presented in Figures and , respectively

63 Figure Safety injection tank of ATLAS

64 Figure Injection line from SIT-1 to RPV

65 Figure Injection line from SIT-2 to RPV

66 Figure Injection line from SIT-3 to RPV

67 Figure Injection line from SIT-4 to RPV

68 Table Material volume of a SG Items Volume (m 3 ) Material U-tube Inconel-690 Tube sheet SUS-316 Inlet plenum " Outlet plenum " Inlet-outlet divider plate " Downcomer section " Riser section " Steamdome section " Table Inventory distribution in a SG Items Volume (m 3 ) U-Tube (include tube sheet section) Inlet plenum Outlet plenum Downcomer region Riser section Separator region Steam Dome region

69 Figure Steam generator of ATLAS

70 Figure Configuration of steam generator

71 Figure Coolant flow in SG secondary side

72 Figure Lower plenum of SG

73 Figure Configuration of U-tube assembly

74 Figure Economizer divider plate

75 Figure Configuration of middle SG vessel

76 Figure Configuration of upper SG vessel

77 Figure Configuration of separator and internal cylinder

78 Figure Details of separator

79 Figure Configuration of SG dryer

80 Reactor coolant system piping The primary coolant piping of the ATLAS consists of two hot legs, four cold legs, and four intermediate legs. The general configuration of primary piping can be seen in Figures and , which show plan-view and side-view, respectively, with the relative locations of RPV, SGs, and RCPs. Major characteristics of the primary loop are summarized in Table The primary coolant piping is made of stainless steel (STS 316). The pressurizer surge line is connected to hot leg 2 (HL-2) as shown in Figure The configuration of hot leg, cold leg, and intermediate leg are shown in Figures , and , respectively Break simulation system A DVI line break is simulated by installing a break spool piece at one of the DVI nozzles. The configuration of break simulation system for the DVI line break is shown in Figure It consists of a quick opening valve, a break nozzle, a case holding the break nozzle, and a few instruments. A pressure transducer and two thermocouples were installed both upstream and downstream of the break nozzle. Detailed geometry of the break nozzle for the present DVI line break tests is shown in Figure The break nozzle is installed vertically downward at the discharge line of the DVI nozzle. The quick opening valve is opened within 0.5 seconds by operators when the test is initiated. The break flow is discharged to the containment simulating system. As an alternative measure to the break flow rate measurement in the containment simulation system, a direct break flow measuring method is being developed to complement the break flow measurement. A venturi will be installed at the discharge line of the break flow along with a capacitance sensor to measure the two-phase break flow rate Containment simulation system The containment simulation system is used to measure the break flow from the system and to provide an adequate backpressure to the system. The break flow is discharged to a containment simulation system, which consists of separating vessels and measuring vessels. Overall configuration of the containment simulation system is shown in Figure A separator is designed to be used for separating a two-phase break flow into water and steam flow. It will be used for most test cases except for the

81 LBLOCA which needs an additional separator to simulate both RPV and RCP sides. In the DVI line break test, only the one separating vessel SV-01 was used. The break nozzle was installed vertically downward at the exit of the DVI-4 nozzle. The break flow from the broken DVI nozzle was collected into the separating vessel, SV-01. The steam, which is separated in the separating vessel, was discharged through a silencer to the atmosphere. The steam flow rate is measured by a vortex-type flow meter at the discharge line. The separated water is drained to one of two measuring vessels, which are interconnected in the bottom. A load cell is installed on the bottom of each measuring vessel to weigh the accumulated water mass in the measuring vessel. Recently, the break flow measuring system has been improved reflecting the test data for LBLOCAs and DVI line breaks. Several design modifications have been made to the separating vessel to drain the separated water efficiently to the measuring vessel. The hemispheric bottom part of the separating vessel was reconstructed to be a coneshape with an enlarged diameter and several rib-like plates were vertically installed inside the vessel to prevent the water swirling effect. It was found from several characteristic tests that this modification considerably reduced the water accumulation inside the separating vessel, leading to a much improved break flow measuring performance Reactor coolant pump The reactor coolant pump of the ATLAS has the same loop configuration as the prototype reactor, APR1400. It has a vertically upward suction nozzle and a horizontally discharge nozzle. The suction and discharge nozzles of the reactor coolant pump are connected to a vertical intermediate leg and a cold leg, respectively. The detailed geometrical information can be seen in Figure

82 Table Dimensions of the primary piping Name Items Unit Value Remarks Hot leg Cold leg Intermediate leg Inner diameter m Area m length m Inner diameter m Area m length m Inner diameter m Area m length m Inner diameter m Area m length m Inner diameter m Area m length m ANSI 6in Sch.160 ANSI 4in Sch.160 ANSI 3in Sch.160 ANSI 4in Sch.160 ANSI 3in Sch

83 Figure Configuration of loop connection (plan view)

84 Figure Configuration of loop connection (side view)

85 Figure Position of surge line

86 Figure Dimension of hot leg

87 Figure Dimension of cold leg

88 Figure Dimension of intermediate leg

89 Figure Configuration of DVI line break

90 Figure Break simulator for DVI line break (flow nozzle)

91 Figure Containment simulator of ATLAS

92 Figure RCP of ATLAS

93 3.2.2 Material Properties All components of the ATLAS have been fabricated by austenitic stainless steel, including vessels, pipes, valves, and flanges in accordance with the ASTM standards, and those not covered in ASTM have been conformed to other nationally accepted codes and standards, such as JIS, BS or DIN. The physical properties of stainless steel 316SS are given below: Table Thermal properties of 316 SS T (K) Density Specific heat Thermal conductivity (kg/ m 3 ) (J/kg K) (W/m K) Polynomial correlations of the specific heat and the thermal conductivity of 316SS as functions of temperature using the data of Table are as follows: C p 4 2 = T T [J/kg-K] (3.2-1) 2 k = T [W/m-K] (3.2-2) where T is in Kelvin. Figures shows the variation of the specific heat and the thermal conductivity of 316SS with temperature

94 : C p table : C p correlation : k table : k correlation C p (J/kg-K) Cp k 20 k (W/m-K) Temperature (K) Figure Specific heat and thermal conductivity of 316SS Insulation All the major vessels of the ATLAS facility have been carefully insulated using perlite in accordance with the JIS A9512 standards. Insulation thickness of the major vessels is summarized in Table Valves have been insulated using 4-R cover in accordance with the JIS A9510 standards. The insulating materials have been wrapped with an aluminum corrugated plate with thickness of 0.4 or 0.6 mm in accordance with JIS H4010 standards. The thermal conductivities of insulating materials used are given below: 4-R cover : W/m K Perlite : W/m K Pipe lines have also been insulated using perlite material in accordance with JIS A9512 standards. The thickness of the insulation material depends on the pipe class

95 and the detailed specifications are shown in Table Final surface temperature is restricted below 40 o C to prevent a skin burn of operators. Table Insulation thickness of the major vessels of the ATLAS Vessels Insulation thickness (mm) Reactor pressure vessel 125 Pressurizer 125 Steam generator 125 Direct condenser in 2 nd system 100 Safety injection tank 40 Steam supply tank 75 Table Insulation thickness of pipe lines of the ATLAS Pipe lines Insulation thickness (mm) Hot leg (6 ) 100 Cold leg (4 ) 100 Intermediate leg (3 ) 75 Pressurizer surge line (2 ) 75 Main steam line (3 ) 75 External downcomer of SG (4 ) Heat Losses Separate heat loss tests have been performed to estimate the heat losses of the ATLAS as a function of fluid temperature. The heat losses of the primary and the secondary system have been evaluated by separate test procedures

96 (a) Heat loss estimation of the primary system As an integral approach, the primary system was heated up to a predetermined temperature and it was maintained at a constant temperature by controlling the core power. When the whole system reached a steady state condition, the core power supplied at that time was regarded as a heat loss of the primary system. During the test, four reactor coolant pumps were fully operated to ensure uniform temperature distribution along the reactor coolant system. The secondary side of steam generators was filled with air at atmospheric condition and the pressurizer was isolated from the primary system. This procedure was repeated at different fluid temperatures of 100 o C, 200 o C or 250 o C to obtain an empirical correlation for the heat loss of the primary system. Figure shows the estimated heat loss of the ATLAS primary system. Heat Loss - Primary Loop (kw) Heat Loss Measured Data Q loss = 0.091*(T-T atm ) 5/ Temperature ( o C) Figure Estimated primary heat loss of the ATLAS

97 Physically, a heat loss rate is determined by a free convection for a given temperature difference between an outer surface temperature and a surrounding temperature. It is known by Lienhard [13] that the heat loss rate due to a free convection for an arbitrary immersed geometry is proportional to a temperature difference with a power of 5/4. Based on separate effect test results for various specified temperatures, the following empirical heat loss correlation was developed for the primary system. Q 5/ 4 loss, p ( Tw Tatm ) = (3.2-3) where Tw and Tatm are a representative wall temperature and an atmospheric temperature ( o C), respectively. During the transient, Tw and Tatm were obtained by averaging the measured outer surface temperatures of the downcomer wall of the reactor pressure vessel at three different locations and the atmospheric temperatures surrounding the ATLAS at four distributed locations, respectively. The empirical correlation of Eq.(3.2-3) implies the total primary heat loss transferred to an environment, including the heat losses through flanges, valves, instrument lines, metallic structures, and insulation because an integral approach is adapted. (b) Heat loss estimation of the secondary system The secondary system of the ATLAS has no heat source. Therefore, the powercontrolled constant temperature method could not be applied to evaluate the heat losses of the secondary side. The heat losses of the secondary side of the SG have been experimentally determined by measuring the cool-down of the SG, which lasted about 15 hours. From measured time dependant temperature variations along with the geometric volume data and the related physical properties such as density (ρ) and specific heat capacity (Cp) of the steel structure and the fluid in the SG, a total heat capacity can be calculated. The heat loss rate is equal to the time variation of the total heat capacity as follows: Q ( svsc ps ( Ts Tatm ) + ρlvlc pl ( Tl T ) d = ρ ) (3.2-4) dt loss, s atm where V is the geometric volume (m 3 ) and the subscript s and l indicate steel structure

98 and liquid inventory, respectively. Figure shows the estimated heat loss of one steam generator based on Eq.(3.2-4). An empirical correlation for the secondary heat loss was also developed with a power relation and it was also plotted in Figure Heat Loss per 1 SG (kw) Heat Loss (kw) Experiment Eq. (1) Eq.1 Q loss = a*(t w -T atm ) b a = b = Temperature Difference (T w -T atm, o C) Figure Estimated secondary heat loss of the ATLAS

99 4. INSTRUMENTATION This chapter provides a description of the ATLAS instrumentation including sensor locations and specification, instrument calibration, data reduction and conversion to engineering units, and uncertainty analysis. 4.1 Location and Specification of Instrumentation Instrumentation signal of the ATLAS consists of measurement-based analog input signals and control-based in-out signals such as AI (Analog Input), AO (Analog Output), TC (Thermocouple), DI (Digital Input), DO (Digital Output), and SR (Serial communication). Instrument signals can also be categorized according to the instrument type such as the temperature, static pressure, differential pressure, water level, flow rate, mass, and power. In the ATLAS test facility, a total of 1,236 instrumentations are installed for the measurement of thermal-hydraulic phenomena in the components Temperature This section provides the exact location for each fluid and wall temperature measurement sensor implemented in the ATLAS major components. All the temperature sensors discussed hereafter are un-grounded K-type thermocouples. Table summarizes the number and the dimension of thermocouple sensors installed in each component of the ATLAS facility. Table Number and dimension of thermocouple sensors RPV SG PZR Loop SIS CS ETC Outer Diameter (mm) TH (Heater) TF (Fluid) / 1.0* TW (Wall) TI (Insulation) TA (Atmosphere)

100 *: Outer diameter of the thermocouples installed in the RPV is 1.0 mm. RPV: Reactor Pressure Vessel SG: Steam Generator PZR: Pressurizer Loop: Hot Leg, Cold Leg, Intermediate Leg, Reactor Coolant Pump SIS: Safety Injection System, HPSI, RWT (Refueling Water Tank), Safety Injection Tank CS: Containment Simulator ETC: Break Spool, Steam Supply System, Secondary System There are 390 electric heaters which are divided concentrically into 3 groups (Group-1, Group-2 and Group-3). Group-1, -2, and -3 heaters are located in inner, middle, and outer regions of the heater bundle, respectively, and they have 102, 138 and 150 heaters, respectively. Appendix a-1 summarizes the tag number and the location of the thermocouples installed in the core heater bundles. The axial location of the thermocouples and the spacer grids are shown in Figure and the crosssectional location of the thermocouples installed in the core heater bundles are shown in Figure The locations and the tag names of the thermocouples for measuring the wall and the water temperature of the reactor pressure vessel, the steam generator, and the pressurizer are shown in Figures through 4.1.8, respectively. The locations and the tag names of the thermocouples for measuring the wall and the water temperature in the reactor pressure vessel are shown in Figure The locations and the tag names of the thermocouples for measuring the wall and the water temperature of the each loop, i.e. hot leg, cold leg, and the intermediate loop are shown in Figures through 4.1.6, respectively. Figures and show the locations of the thermocouples installed in the pressurizer and the steam generator, respectively Pressure Absolute pressure and differential pressure are measured to obtain information on the pressure distribution and the system pressure in the ATLAS major components. Table summarizes the number of pressure sensors installed in each component of the ATLAS facility. All the pressure sensors are SMART type and the specification and the tag names of the pressure sensors are summarized in Appendix a

101 Table Number of pressure sensors RPV SG PZR Loop SIS CS ETC PT (Absolute pressure) DP (Differential pressure) The locations and the tag names of the pressure sensors for measuring the absolute pressure and the differential pressure in the ATLAS major components of reactor pressure vessel, reactor coolant system piping, pressurizer, and steam generator are shown in Figures through , respectively Flow rate Volumetric and mass flow rate are measured to obtain information on the flow rate in the ATLAS major components. Table summarizes the number of flow rate sensors installed in each component of the ATLAS facility. Vortex meter, turbine meter, Coriollis meter, and an average bi-directional flow tube (BDFT or BiFlow) are installed for measuring the flow rates in the ATLAS facility. The specification and the tag names of the flow rate sensors are summarized in Appendix a-3. Table Number of flow rate sensors RPV SG PZR Loop SIS CS ETC QV (Volumetric flow rate) QM (Mass flow rate) The locations and the tag names of the flow rate sensors for measuring the volumetric and the mass flow rate in the reactor coolant system piping and the steam generator are shown in Figures and , respectively Level Collapsed water levels are measured to obtain information on the level variations during the test in the ATLAS major components. The instruments for measuring the

102 collapsed water level are SMART type differential pressure transducers. Table summarizes the number of level sensors installed in each component of the ATLAS facility. The specification and the tag names of the level sensors are summarized in Appendix a-4. Table Number of level sensors RPV SG PZR Loop SIS CS ETC LT (Level transducers) The locations and the tag names of the level sensors for measuring the collapsed water level in the ATLAS major components of reactor pressure vessel, reactor coolant system piping, pressurizer, and steam generator are shown in Figures through , respectively Mass In the ATLAS test, the break flow is discharged to a containment simulation system, which consists of separating vessel and measuring vessels. The steam, which is separated in a separating vessel, is discharged through a silencer to the atmosphere. The steam flow rate is measured by a vortex-type flow meter at the discharge line. The water, which is separated in a separating vessel, is drained to one of two measuring vessels. A load cell is installed on the bottom of each measuring vessel to weigh the water mass. In the DVI line break test, only the one separating vessel SV-01 was used. The break nozzle was installed vertically downward at the exit of the DVI-4 nozzle. The break flow from the broken DVI nozzle was collected into the separating vessel, SV-01. The steam, which is separated in the separating vessel, was discharged through a silencer to the atmosphere. The steam flow rate is measured by a vortex-type flow meter at the discharge line. The separated water is drained to one of two measuring vessels, which are interconnected in the bottom. A load cell is installed on the bottom of each measuring vessel to weigh the accumulated water mass in the measuring vessel. The separating vessel is also designed to simulate a containment back-pressure by controlling its pressure by using a pressure control valve. Table summarizes the tag name and the specification of the load cells which are installed beneath the measuring vessels

103 Table Tag names and specification of load cells Tag Name Location Measuring Range Uncertainty LC-CS-01 MV-01 0 ~ 1500 kg % of Full Scale LC-CS-02 MV-02 0 ~ 1500 kg % of Full Scale Power Powers are measured in the core heater bundle and the reactor coolant pump in the ATLAS test. An alternating current (AC) is measured by current transformer (CT) and the electric power is measured and processed by power meter (Yokogawa WT 230). Maximum measuring error for electric power is 0.35% of full scale in the ATLAS test Instrumentations in the safety injection tank During the safety injection using the safety injection tank, important parameters such as temperature, pressure, level, and flow rate are measured as shown in Figure Instrumentations in the break simulation system In the break simulation system, important parameters such as temperature and pressure are measured as shown in Figure

104 Figure Temperature sensors in core - Axial configuration

105 Figure Temperature sensors in core - Radial configuration (a)

106 Figure Temperature sensors in core - Radial configuration (b)

107 Figure Temperature sensors in RPV

108 Figure Temperature sensors in hot leg

109 Figure Temperature sensors in cold leg

110 Figure Temperature sensors in intermediate leg

111 Figure Temperature sensors in pressurizer

112 Figure Temperature sensors in SG

113 Figure Pressure transmitters in RPV

114 Figure Pressure transmitters in RCS loop (plan view, cross view)

115 Figure Pressure transmitters in pressurizer

116 Figure Pressure transmitters in SG

117 Figure Flowmeters in RCS loop

118 Figure Flowmeters in SG

119 Figure Level transmitters in RPV (axial)