Nondestructive determination of plutonium mass in spent fuel: prelliminary modeling results using the passive neutron Albedo reactivity technique
- Los Alamos National Laboratory
There are a variety of motivations for quantifying plutonium (Pu) in spent fuel assemblies by means of nondestructive assay (NDA) including the following: strengthening the capability of the International Atomic Energy Agency (LAEA) to safeguard nuclear facilities, quantifying shipper/receiver difference, determining the input accountability value at pyrochemical processing facilities, providing quantitative input to burnup credit and final safeguards measurements at a long-term repository. In order to determine Pu mass in spent fuel assemblies, thirteen NDA techniques were identified that provide information about the composition of an assembly. A key motivation of the present research is the realization that none of these techniques, in isolation, is capable of both (1) quantifying the Pu mass of an assembly and (2) detecting the diversion of a significant number of rods. It is therefore anticipated that a combination of techniques will be required. A 5 year effort funded by the Next Generation Safeguards Initiative (NGSI) of the U.S. DOE was recently started in pursuit of these goals. The first two years involves researching all thirteen techniques using Monte Carlo modeling while the final three years involves fabricating hardware and measuring spent fuel. Here, we present the work in two main parts: (1) an overview of this NGSI effort describing the motivations and approach being taken; (2) The preliminary results for one of the NDA techniques - Passive Neutron Albedo Reactivity (PNAR). The PNAR technique functions by using the intrinsic neutron emission of the fuel (primarily from the spontaneous fission of curium) to self-interrogate any fissile material present. Two separate measurements of the spent fuel are made, both with and without cadmium (Cd) present. The ratios of the Singles, Doubles and Triples count rates obtained in each case are analyzed; known as the Cd ratio. The primary differences between the two measurements are the neutron energy spectrum and fluence in the spent fuel. By varying the thickness of the cadmium layer surrounding the spent fuel, a high and a low neutron-energy-measurement condition can be produced. The neutron detectors can be used to detect total neutrons (Singles) and/or Doubles and/or Triples. If the geometry of the measurement situation is unchanged between the two measurements, the change in the Cd ratio between these two measurements can be attributed to a change in the fissile content of the sample.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 979682
- Report Number(s):
- LA-UR-09-07934; LA-UR-09-7934; TRN: US1003373
- Resource Relation:
- Conference: Waste Management 2010 ; March 7, 2010 ; Phoenix, AZ
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
ALBEDO
BURNUP
CADMIUM
CURIUM
FISSILE MATERIALS
GEOMETRY
IAEA
NEUTRON DETECTORS
NEUTRON EMISSION
NEUTRONS
NUCLEAR FACILITIES
PLUTONIUM
PROCESSING
SAFEGUARDS
SPENT FUELS
SPONTANEOUS FISSION
THICKNESS
WASTE MANAGEMENT