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Fast Neutron Collar Tests at Nuclear Fuel Fabrication Plant in Brazil

This study evaluates the performance of a fast neutron collar for measuring the 235U content in different fuel assemblies. The results show accurate measurements with shorter measurement times and low dependence on Gd content.

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Fast Neutron Collar Tests at Nuclear Fuel Fabrication Plant in Brazil

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  1. FAST NEUTRON COLLAR TESTS AT NUCLEAR FUEL FABRICATION PLANT IN BRAZIL • Marcos Grund; Geraldo Renha- CNEN • Anibal Bonino; Luis Machado – ABACC • Jonathan Beaumont; Jeon Jong; Mikhail Mayorov; Tae H. Lee -IAEA

  2. FNCL CHARACTERISTICS • Coincidence neutrons measurement; • Low dependence on Gd content (operator´s declaration are not required); • Can operate in “fast” or “thermal modes”; • Liquid cintilators (12); • Better accuracy; • Shorter measurement time. TESTING PLAN • Activity proposed under BRZ SP to IAEA Safeguards; • First commercial facility testing; • Two Am-Li neutron sources (one from IAEA and another from state); • One 137Cs calibration source from state; • FNCL cavity enlarging was required from state. PURPOSE • Evaluate performance in terms of measurement time, precision and systematic biases FACILITY CHARACTERISTICS • High background, temperature and humidity; • Two different Gd loading assemblies and one non Gd assembly type.

  3. Results

  4. RESULTS • Three kinds of fuel assemblies was measured: 2% Gd; 7% Gd and non Gd content; • An average bias of 0.96% was found (not significant); • All the results were less than 3 s (ITV-2010 for UNCL); • UNCL measurements shows a bias around 27% for BP for the same FA; • The results are displayed as g 235U /cm. • CONCLUSIONS • For the non-Gd assemblies, the bias was 8.3%. These assemblies, however has lower 235U linear mass loading (45% less). This should be further investigated; • The FNCL results showed that it can be used for 235U content in FA measurements, not depending on BP information from the operators. The BP influence on results was lower than the expected values and can be neglected.

  5. REQUIREMENTS • Structural reinforcement prior to be approved for safeguards use at the facility; • The FNCL should fit at a lift device available at the facility for xyz adjustment; • The source slab panel should be mounted as a pivoted door in order to improve safely handling. • RECOMMENDATIONS • Since the 137Cs calibration source was weak for energy calibration in the facility, due to background, for next measurements, a stronger source should be used; • At the acquisition and analysis software, inputting the acquisition time, operator´s declaration values on total 235U mass as well as activity length would be helpful; • Total 235U mass measured and OID could be displayed at the results; • Longer cabling are necessary (FNCL should be rised up to 5 meters, FA can not be rised); • FNCL should be left mounted at the facility (seals may be applied).

  6. ACKNOWLEDGEMENTS • INB Fuel Fabrication Plant. • THANK YOU!

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