Presentation to JAEA Visitors, July 24, 2012

Gavron, Victor¹ 

[1] Los Alamos National Laboratory

关键词: ACTINIDES;    BURNUP;    DETECTION;    DIGITAL FILTERS;    ENRICHED URANIUM;    FAST REACTORS;    FISSION;    ISOTOPES;    NEUTRONS;    OSCILLATIONS;    OXIDES;    PLUTONIUM;    RESEARCH REACTORS;    RESONANCE;    SLOW NEUTRONS;    SLOWING-DOWN;    SPENT FUEL STORAGE;    SPENT FUELS;    STORAGE;    THRESHOLD DETECTORS;   

DOI  :  10.2172/1047082
RP-ID  :  LA-UR-12-23178
PID  :  OSTI ID: 1047082
Others  :  TRN: US1203966

美国|英语

来源: SciTech Connect

【 摘 要 】

There are 7 Reasons for characterizing spent fuel nuclide concentrations: (1) Provide IAEA with the capability to independently verify the mass of plutonium at any site that has spent fuel; (2) Shipper/receiver difference; (3) Determination of the input accountability mass of an electrochemical (pyro-chemical) processing facility; (4) Continuity of knowledge at spent fuel storage site; (5) Optimal reloads through knowledge of true actinide content; (6) Burnup credit for fuel transport and storage; and (7) Provide confidence to the public that the shipment of spent fuel around the world is being undertaken in a rigorous manner, assuring that material is not diverted during shipment. Types of fuel of interest are: Fast Reactor Fuel, Normal burnup low enriched uranium (LEU), Mixed oxide (MOX), Low burnup LEU, and Research reactor. MCNPX calculates the slowing down and the energy spread for a given time. The principles are: (1) Neutrons slow down in LSDS; (2) Slow neutrons capture preferentially on a fission resonance; (3) Fission emits high-energy neutrons; (4) High-energy neutrons detected in threshold detector (that is not sensitive to slow neutrons) (e.g., {sup 238}U, {sup 232}Th); and (5) The detection time is characteristic of the slow neutron energy. Following each PSR pulse, the entire signal is digitized in 2 nanosecond intervals, and subsequently analyzed Analysis involves applying a digital filter to extract fission pulses in a background of initial oscillations and noise throughout. Some of the noise is not random. Depending on the threshold setting and filter parameters, both the normalization and the trend change. Original PNNL LSDS design required a 1-meter radius cylindrical LSDS. Much higher efficiency would allow us to use a (1.2m) LSDS (this is the LANL LSDS size), or a less intense source, or a combination of both. We still estimate 10{sup 16} total neutrons from the source to obtain 2-3% precision in {sup 239}Pu and {sup 235}U assay.