Optimization of combined delayed neutron and differential die-away prompt neutron signal detection for characterization of spent nuclear fuel assemblies
- Los Alamos National Laboratory
- NON LANL
The Next Generation Safeguards Initiative (NGSI) of the U.S. Department of Energy (DOE) has funded multiple laboratories and universities to develop a means to accurately quantify the Plutonium (Pu) mass in spent nuclear fuel assemblies and ways to also detect potential diversion of fuel pins. Delayed Neutron (DN) counting provides a signature somewhat more sensitive to {sup 235}U than Pu while Differential Die-Away (DDA) is complementary in that it has greater sensitivity to Pu. The two methods can, with care, be combined into a single instrument which also provides passive neutron information. Individually the techniques cannot robustly quantify the Pu content but coupled together the information content in the signatures enables Pu quantification separate to the total fissile content. The challenge of merging DN and DDA, prompt neutron (PN) signal, capabilities in the same design is the focus of this paper. Other possibilities also suggest themselves, such as a direct measurement of the reactivity (multiplication) by either the boost in signal obtained during the active interrogation itself or by the extension of the die-away profile. In an early study, conceptual designs have been modeled using a neutron detector comprising fission chambers or 3He proportional counters and a {approx}14 MeV neutron Deuterium-Tritium (DT) generator as the interrogation source. Modeling was performed using the radiation transport code Monte Carlo N-Particles eXtended (MCNPX). Building on this foundation, the present paper quantifies the capability of a new design using an array of {sup 3}He detectors together with fission chambers to optimize both DN and PN detections and active characterization, respectively. This new design was created in order to minimize fission in {sup 238}U (a nuisance DN emitter), to use a realistic neutron generator, to reduce the cost and to achieve near spatial interrogation and detection of the DN and PN, important for detection of diversion, all within the constraints of a single practical instrument. Both DN and PN detections are active techniques using the signal from the most prominent fissile isotopes of spent nuclear fuel that respond the best to a slow neutron interrogation, {sup 235}U, {sup 239}U and {sup 241}PU. The performance is characterized against a library of 64 assemblies and 40 diversion scenarios at different burnup (BU), cooling-time (CT) and initial enrichment (IE) in fresh water.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 1043535
- Report Number(s):
- LA-UR-10-08013; LA-UR-10-8013; TRN: US1203258
- Resource Relation:
- Conference: Waste Management 2011 ; March 3, 2011 ; Phoenix, AZ
- 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
COOLING TIME
DELAYED NEUTRONS
DESIGN
DETECTION
EDUCATIONAL FACILITIES
FISSION
FISSION CHAMBERS
FRESH WATER
FUEL PINS
NEUTRON DETECTORS
NEUTRON GENERATORS
NEUTRONS
NUCLEAR FUELS
OPTIMIZATION
PROMPT NEUTRONS
PROPORTIONAL COUNTERS
RADIATION TRANSPORT
SIGNALS
SLOW NEUTRONS
WASTE MANAGEMENT