Non-destructive assay of spent nuclear fuel using passive neutron Albedo reactivity
- Los Alamos National Laboratory
Passive Neutron Albedo Reactivity (PNAR) is one of fourteen techniques that has been researched and evaluated to form part of a comprehensive and integrated detection system for the non-destructive assay (NDA) of spent nuclear fuel. PNAR implemented with {sup 3}He tubes for neutron detection (PNAR-{sup 3}He) is the measurement of time correlated neutrons from a spent fuel assembly with and without a Cadmium (Cd) layer surrounding the assembly. PNAR utilizes the self-interrogation of the fuel via reflection of neutrons born in the fuel assembly back in to the fuel assembly. The neutrons originate primarily from spontaneous fission events within the fuel itself (Curium-244) but are amplified by multiplication. The presence and removal of the Cd provides two measurement conditions with different neutron energy spectra and therefore different interrogating neutron characteristics. Cd has a high cross-section of absorption for slow neutrons and therefore greatly reduces the low energy (thermal) neutron fluence rate returning. The ratios of the Singles, Doubles and Triples count rates obtained in each case are known as the Cd ratios, which are related to fissile content. A potential safeguards application for which PNAR-{sup 3}He is particularly suited is 'fingerprinting'. Fingerprinting could function as an alternative to plutonium (Pu) mass determination; providing confidence that material was not diverted during transport between sites. PNAR-{sup 3}He has six primary NDA signatures: Singles, Doubles and Triples count rates measured with two energy spectra at both shipping and receiving sites. This is to uniquely identify the fuel assembly, and confirm no changes have taken place during transport. Changes may indicate all attempt to divert material for example. Here, the physics of the PNAR-{sup 3}He concept will be explained, alongside a discussion on the development of a prototypical PNAR-{sup 3}He instrument using simulation. The capabilities and performance of the conceptual instrument will be summarized, in the context of (a) quantifying Pu mass in spent fuel assemblies and (b) detecting pin diversion (through a discrepancy between declared and measured properties of the fuel assembly) when the instrument is deployed. These quantitative capabilities are complementary to the 'fingerprinting' capability which is part of ensuring continuity of knowledge and custody of spent nuclear fuel.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1023436
- Report Number(s):
- LA-UR-10-04689; LA-UR-10-4689; TRN: US1104541
- Resource Relation:
- Conference: INMM51 ; July 12, 2010 ; Baltimore, MD
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ABSORPTION
ALBEDO
CADMIUM
CURIUM 244
DETECTION
ENERGY SPECTRA
NEUTRON DETECTION
NEUTRON FLUENCE
NEUTRONS
NUCLEAR FUELS
PHYSICS
PLUTONIUM
REFLECTION
REMOVAL
SAFEGUARDS
SLOW NEUTRONS
SPENT FUELS
SPONTANEOUS FISSION
TRANSPORT