Some Results in studying NPP accidents using PCTRAN-2 LOOP and WWER-1000 simulators

Transcription

1 Technical Meeting on Effective Utilization of Nuclear Power Plant Simulators as Introductory Educational Tools Some Results in studying NPP accidents using PCTRAN-2 LOOP and WWER-1 simulators Vo Hong Hai, PhD Department of Nuclear Physics, University of Science Vietnam National University - Ho Chi Minh City, Vietnam VIC, VIENNE, Austria May, 214

2 BRIEF INTRODUCTION 1. Full name: VO HONG HAI 2. Birthday : Working place: Present institution : University of Science, Vietnam National University Hochiminh city Department: Position: 4. Education: :Department of Nuclear Physics : Lecturer, : Head of Nuclear Energy Power Group, in the educational program of Nuclear Engineering Level Period of Time Name and Place Major fields of study Under-graduation University of Science, VNU-HCM Applied Physics Master University of Science, VNU-HCM Applied Physics PhD Osaka University, Japan Nuclear Physics 5. Current research 1. Advanced technique for Readout electronic in radiation system, Radiation measurements, Environmental radiation study, 2. GEANT4 simulations for radiation detector, 3. NPP PC-based simulations (PCTRAN, WWER-1).

3 PART I. PC-TRAN PWR 2 LOOP LOCA BREAK Accident AT COLD LEG PART II. WWER-1 1. Hot shutdown (EP) 1% power (fuel for load 1) 2. Xe oscillation study (fuel for load 1 and load 5 at BOC and EOC)

4 PART I. PC-TRAN PWR 2 LOOP LOCA BREAK Accident AT COLD LEG DEVELOPED By Dr. Li-Chi Cliff Po Micro-Simulation Technology

5 Category of PWR-type LOCA accidents Hot leg cold leg Broken completely Very small break Small break Large break Steam generator Pressurizer Reactor Cooling Pump Cold leg Reactor Hot leg E.g. LOCA break at Cold leg Ref. Nuclear safety, Nuclear Fuel Behaviour in Loss of coolant Accident (LOCA) Conditions, NEA, 29 5

6 PC-TRAN 2 LOOP (PWR-type 18 MWt) By Dr. Li-Chi Cliff Po Micro-Simulation Technology

7 LOCA large break at cold leg in PWR-2 LOOP using PC-TRAN-2-LOOP PCTRAN PWR 2 LOOP PWR-2 LOOP 18 MWt (6 MWe) - Westinghouse Large break LOCA at cold leg (57% break in area) Investigations of physical parameters in NPP 7

8 Group1: Reactivity, neutron power and thernal power Thong Newtron luong neutron power (%) Do phan Reactivity ung (%dk/k) (dk/k) LOCA accident (2 sec) Power (%) Cong suat (MW) Do Reactivity phan ung (dk/k) (%dk/k) 5 Reactivity = fuel + rod + Boron + H2O Boron HChat lam cham 2 O Nhien Fuel lieu Thanh Rod dieu khien Tong Total hop Time Thoi gian (sec) (s) Thoi Time gian (sec) (s) Thermal cong suat power nhiet Steam cong suat power hoi Electric cong suat power dien Time Thoi (sec) gian (s) Time Thoi (sec) gian (s) 8

9 Group 2: Pressure and temperature parameters in primary circuit Nhet Temperature do phan dinh ( ( C) C) Pressure Ap suat in chat reactor lam mat (kg/cm (kg/cm 3 ) 2 ) Temperature Nhiet do ( C) ( C) Chat Average lam mat Chan Hot leg nong Chan Cold leg lanh Time Thoi (sec) gian (s) Time Thoi (sec) gian (s) 8 7 Fuel Nhien lieu Clad Vo boc nhien lieu Thoi Time gian (sec) (s) 9

10 Group 3: steam generator and pressurizer Pressure Ap suat in trong steam binh generator sinh hoi (kg/cm 3 ) 2 ) Cong Heater suat power may at suoi Pressurizer cua Prz (kw) (KW) Water Muc level nuoc in trong steam binh generator sinh hoi (m) (m) Nhiet Average do trung temperature binh ( ( C) C) Thoi Time gian (sec) (s) Thoi gian (s) Average of hot Chat led and lam cold mat led Binh At pressurizer dieu ap Time Thoi gian (sec) (s) Thoi gian (s) 1

11 Group 4: In containment building Temperature at containment building ( C) Nhiet do nha lo ( C) Pressure Ap suat containment nha lo (kg/cm building 2 ) ( C) Thoi Time gian (sec) (s) Thoi Time gian (sec) (s) 11

12 Do phong Dose xa rate (msv/h) (CPM) Whole Body Dose Rate (msv/h) Group 5: radioactive-dose release Do phong xa (msv/h) Thyroid Dose Rate (msv/h) Containment khong khi nha Air Radiation lo Monitor Steam ong dan Line hoi Radiation Rad Monitor Condenser binh ngung Off-gas Rad Monitor Aux khong Building khi nha Air Rad phumonitor 2 khong khi nha lo ong dan hoi binh ngung khong khi nha phu At EAB Time Thoi gian (sec)(s) Thoi Time gian (sec) (s) 12

13 Thoi gian dap lo (s) Time reactor shutdown (sec) Thoi gian dap lo (s) Time reactor shutdown (sec) Reactor shutdown response versus reactor power with LOCA large break Reactor shutdown response versus LOCA break with reactor power 1% Ti LOCA le lo thung break (%) cm cm cm cm 2 49 cm Công Reactor suat power lo (%) Dien tich lo thung In area (cm 2 ) 13

14 PART II. WWER-1 (Russian type PWR 4 LOOP 3MWt) Reactor Operations: 1. Hot shutdown (EP) 1% power (fuel for load 1) 2. Xe oscillation study (fuel for load 1 and load 5 at BOC and EOC) WWER-1

15 1. Hot shutdown (EP) 1% power (Exe.F: in manual) - Fuel (load 1) - Hot shutdown (EP) - Power restore of reactor (using group 1 and Boron) Looking for stability of reactor response in long time running. Operating parameters are monitoring: 1/ Pressure in MSH and reactor core, 2/ Reactivity and boron, 3/ Control Rod position, 4/ Water level in pressurizer, 5/ N_POWER, 6/ OFFSET.

16 Power restore for reactor: Using Control Rod and Boron For shutdown reactor: Add boron to primary circuit: Boron concentration in the primary circuit is in the range g/kg, 16

17 Neutron power (%) 45 days Neutron power (%) 45 days Neutron power (%) shutdown Neutron power (%) 45 days 1 day 11 days Neutron POWER Boron 12g/kg (at shutdown) 6 g/kg (at power restored) Boron 14.5g/kg 6.9 g/kg Boron 14.62g/kg 7.1 g/kg Boron g/kg 7.1 g/kg 17

18 Pressure (kg/cm 2.) 45 days Pressure (kg/cm 2.) 45 days Pressure (kg/cm 2.) Pressure (kg/cm 2.) 45 days 11 days Pressure in MSH and reactor core. reactor core reactor core Main Steam Collector Main Steam Collector Boron 12g/kg (at shutdown) 6 g/kg (at power restored) Boron 14.5g/kg 6.9 g/kg reactor core reactor core Main Steam Collector Main Steam Collector Boron 14.62g/kg 7.1 g/kg Boron g/kg 7.1 g/kg 18

19 Water level (mm ) Water level (mm ) Water level in pressurizer 11 days 45 days Water level (mm ) Water level (mm ) 45 days 45 days EP: Lower limit=5 Boron 12g/kg (at shutdown) 6 g/kg (at power restored) Boron 14.5g/kg 6.9 g/kg Boron 14.62g/kg 7.1 g/kg Boron g/kg 7.1 g/kg 19

20 45 days 45 days shutdown 11 days 1 day 45 days Reactivity and boron. Boron 12g/kg (at shutdown) 6 g/kg (at power restored) Boron 14.5g/kg 6.9 g/kg Boron 14.62g/kg 7.1 g/kg Boron g/kg 7.1 g/kg 2

21 CR position CR position Control Rod position. Group 1 Group 1 Boron 12 g/kg (shut down) 6 g/kg (restore) Boron 14.5 g/kg 6.9 g/kg Group 1 Group 1 Boron g/kg 7.1 g/kg Boron g/kg 7.1 g/kg 21

22 OFFSET (%) OFFSET (%) OFFSET (%) OFFSET (%) AXIAL OFFSET AO=(w T w B ) / =(w T w B ) AO is defined as the percentage ratio of the difference of the power at the top of the core W T and in the bottom half of the core W B. Boron 12 g/kg (shut down) 6 g/kg (restore) Boron 14.5 g/kg 6.9 g/kg Boron g/kg 7.1 g/kg Boron g/kg 7.1 g/kg 22

23 AXIAL OFFSET (AO) OSCILLATION

24 INTRODUTION Power spatial oscillations due to the transient xenon spatial distribution are well known as xenon oscillations. The appearance of xenon oscillations due to periodic deviation from an equilibrium distribution of iodine, xenon and neutron flux density is characteristic for WWER-1 reactors. Xenon oscillations can be conventionally divided into axial, radial, diametral and azimuthal oscillation. [1]. Paul L.Roggenkamp (2), The influence of Xenon-135 on Reactor Operation, WSRC-MS [2]. P.E.Filimonov and S.P.Aver yanova (21), Maitaining an equilibrium offset as an effective method, [3]. V.A.Tereshonok, V.S.Stepanov, A.P.Povaro, O.V.Lebedev, and V.V.Makeev (22), Xenon oscillations in a VV É R-1 core, Atomic Enerdy, Vol.93, No. 4, (UDC ).

25 1. Axial xenon oscillations arise with the change of the following: - Position of the regulating group of control rods in the control and safety system (CSS) of the reactor at constant power. - Reactor power with a constant position of the control rods. - Position of the regulating group of control rods and reactor power, simultaneously. 2. Radial xenon oscillation can arise, for example, after the following rods, which are lowered into the core are extracted: - The central control rod. - The group of control rods located tin the central in the central or peripheral part of the core.

26 3. Diametral xenon oscillations arises when an individual rod, located at the core periphery, has fallen (or been lowered) and is extracted from the core. 4. Azimuthal xenon oscillations are initiated by successive (in a clockwise or counterwise): - Lowering followed by extraction of control rods positioned symmetrically with respect to the core center. - Extraction, one by one, of control rods, symmetrically arranged relative to the core center, from the CSS group lowered into the core with a time delay before the next control rod is extracted.

27 THEORETICAL APPROACH Characteristics of xenon: - Xenon absorption micro-cross section is very large σ a Xe = 2,5 1 6 b (the maximum absorption cross section of all). - To reach equilibrium concentration very fast, after 3h 4h for Xe-135 (loss of reactivity). - Increase of xenon poisoning after reactor stopped. - Increase or decrease transient reactivity because the changing of the Xe-135 concentration, after the power had changed.

28 Iodine and xenon concentrations can be expressed: di dt = Y IΣ f φ λ I I t dxe dt = Y IΣ f φ + λ I I σ a,xe Xφ λ Xe Xe Y I, Y Xe : Iodine and xenon yields. λ i, λ x 1/h : Iodine and xenon decay constants. Σ f 1/cm : Macroscopic fission cross section. σ a (cm 2 ): Microscopic absorption cross section of xenon. φ 1/(s. cm 2 ) : Effective neutron flux at full power.

29 Xe t = p I + p Xe Σ f φ 1 e λ Xe p IΣ f φ e λit e λ t λ I λ Xe With, e λ = λ Xe + σ Xe φ λ Xe When t, xenon concentration reach equilibrium: Xe = p I + p Xe Σ f φ = p I + p Xe Σ f φ λ Xe λ Xe + σ Xe φ + If the neutron flux is in the low range (σ Xe φ λ Xe ), the concentration of xenon-135 is proportion to φ and enrichment. + If the neutron flux is in the high range (σ Xe φ λ Xe ), the concentration of xenon-135 is only proportion to enrichment: Xe = p I + p Xe Σ f φ λ Xe + σ Xe φ p I + p Xe Σ f σ Xe

30 Xenon poisoning index: q Xe = Xeσ Xe Σ a = p I + p Xe Σ f Σ a Loss of reactivity due to xenon poisoning: ρ Xe = q Xe θ = Σ f Σ a θ p I + p Xe θ: probability of the thermal neutron is absorbed.

31 Axial offset of power distribution are define: AOp = Q t Q b Q t + Q b Q t, Q b : Powers in upper and lower half reactor cores, respectively.

32 Xe (power and offset) oscillations at BOC and EOC for load 1 and load 5 RESULTS - Run the simulator with tasks A5_Xe (power and offset) oscills for BOC of 1 load A6_Xe (power and offset) oscills for EOC of 1 load A5_Xe (power and offset) oscills for BOC of 5 load A5_Xe (power and offset) oscills for EOC of 5 load LOAD 1 LOAD 5

33 Offset (%) Reactivity ($) Position (%) N-Power (%) YS5S36-BOC N_POWER-BOC Time (hours) Time (hours) OFFSET-BOC Time (hours) REACTIVITY-BOC Time (hours)

34 Offset (%) Reactivity ($) Position (%) N-Power (%) YS5S36-EOC Time (hours) N_POWER-EOC Time (hours) OFFSET-EOC1 REACTIVITY-EOC Time (hours) -1.2 Time (hours)

35 Offset (%) Reactivity ($) Position (%) N-Power (%) YS5S36-BOC Time (hours) N_POWER-BOC Time (hours) OFFSET-BOC Time (hours) REACTIVITY-BOC Time (hours)

36 Offset (%) Reactivity ($) Position (%) N-Power (%) YS5S36-EOC N_POWER-EOC Time (hours) Time (hours) OFFSET-EOC Time (hours) REACTIVITY-EOC Time (hours)

37 Several subjects we have been working using IAEA PC-SIMULATORS PC-TRAN 2-LOOP LOCA accidents (small break, large break) RCP trip (graduation thesis - 214) FWP trip PC-TRAN/SFP AC loss power (graduation thesis - 214) WWER-1 RCP trip, FWP trip restore power (graduation thesis - 214) start up and shutdown (graduation thesis - 214) Xe oscillation (graduation thesis - 214) reactivity effects CONVENTIONAL PWR FWP TRIP

38 - University of Science-HCMC has three nuclear educational programs in Nuclear Physics and Nuclear engineering; - We have a long history in Nuclear Physics, established in However, we are far from the nuclear engineering and nuclear technology. - We are now at the beginning step for the mission of training in nuclear engineering to satisfy the government s demand of nuclear human resources for nuclear power plant in the future. - IAEA objectives: Learn how these tools using for educations and training, assist in education engineering researchers, engineering. Allows students explore for various plant response. - NPP PC-based simulators are very tools for education about NPP operation, safety, etc. We need some supports from experts for NPP PC-based simulators.

39 Student Seminar on NPP simulator, May, 214 Thank you!