Near Real Time Accountancy at JNC-1. Tokai Japan

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1 Tokai Japan Sébastien Richet, SGIM-IFC International Atomic Energy Agency

2 Foreword This work would not have been possible without the long lasting cooperation between the Facility operators, the expertise from NMCC, the support of the State representatives and the Operation Inspectors.

3 The Objective of Safeguards under a Comprehensive Safeguards Agreement is the timely detection of diversion of significant quantities of nuclear material from peaceful nuclear activities to the manufacture of nuclear weapons or of other nuclear explosive devices or for purposes unknown, and deterrence of such diversion by the risk of early detection.

4 For large plutonium bulk handling facilities, an annual material balance evaluation would not meet the timeliness goal, therefore the Department of Safeguards has introduced verification method M, which includes methods such as solution monitoring and Near Real Time Accountancy (NRTA). NRTA allows for early detection of diversion into MUF (based on operator data) and D (based on operator and inspector data)

5 The JNC-1 site in Japan includes four large Pu/MOX bulk handling facilities: - The Tokai Reprocessing Plant, TRP, - The Plutonium Conversion and Development Facility, PCDF, - The Plutonium Fuel Production Facility, PFPF (MOX), and - The Plutonium fuel fabrication facility, Plutonium Fuel Development Facility, PPFF (MOX)

6 NRTA has been introduced sequentially at PFPF (1999), TRP (2000), PPFF (2007) and is now implemented in PCDF, hence covering the entire process of the large plutonium bulk handling facilities at the JNC-1 Site The NRTA concept for MOX plants is different from the Reprocessing plant, and both concepts are combined for the Conversion plant.

7 In the case of JNC-1, D is evaluated based on the solution monitoring or measurements performed on site while NRTA concentrates on the MUF evaluation. All NRTA evaluations rely on the same logic with a limited complexity (setup, computation) for solid bulk and an extensive one for liquids (solutions in vessels). Experience shows that the system is very reliable and adaptable.

8 NRTA is an expert system based upon setup rules which are interpreted and combined with the declared data. JNC-1 NRTAs work on Oracle. Each NRTA s kernel, based on SQL Plus statements, provides the required outputs (MUF, CUMUF, Statistical analysis raw data). Each NRTA package then performs the required statistical analysis and generates the reports.

9 For vessels, NRTA sequentially calculates the height, the volume and the element weight to allow for comparisons with Solution monitoring results as well as with the declared values (consistency check). For powder and pellets, simpler functions based on the weights and concentration allow determination of the element weight.

10 NRTA relies on the propagation of systematic and random errors in multiplicative or additive models. For each vessel, the calibration curve is fitted by interdependent polynomials for which an error propagation matrix is defined. Each matrix together with all related functions (up to thousands of functions for complex cases like TRP) is utilized by the NRTA system.

11 NRTA propagates uncertainties for each of the individual measurements that are required to obtain the Element Weight such as concentration, gross weight, tare weight, pressures, calibration curves, etc. It generates partial derivatives which are then combined into variance components (systematic and random) for each measurement type.

12 NRTA Kernel links and processes TANK CALIBRATION TABLE HEIGHT TABLE FACILITY FUNCTIONS TABLE MEASUREMENT TABLE (DATA) PARTIAL DERIVATIVES PARAMETERS FOR VOLUME PARTIAL DERIVATIVES CALCULATION FOR VOLUME GENERIC DATA (i.e. Physical Constants) VOLUME TABLE MEASUREMENT STRUCTURE TABLE PARTIAL DERIVATIVES CALCULATION FOR ELEMENT WEIGHT

13 The statistical analysis mainly comprises: - MUF and CuMUF sequential evaluation - These are compared to two sigma error bars - GeMUF which estimates the expected value and compares it with the declared one. Unexpected changes result in jumps of the curve which are triggers for action or signatures of known processes (e.g. holdup-rinse sequence)

14 MUF Evaluation

15 CuMUF Evaluation

16 GeMUF test for the campaign based TRP Sequential GEMUF-Test 8.00E+01 Rinse 6.00E+01 Statistics Holdup 4.00E+01 Threshold 2.00E E Balance Period 10 12

17 Conclusion: The implementation of NRTA for the four facilities at the JNC-1 Site is currently under completion. The result is advantageous for the (enhanced understanding of the accountancy and ability for early detection of diversion into MUF) as well as for the operator (better control of the process).

18 Many thanks for your attention! For questions, please contact me: