Experimental Evaluation of the Fast-Neutron Passive Collar (FNPC) Performance and Comparison with Scintillation Based Collars
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
This report describes a new method for the verification of fresh low enrichment uranium (LEU) fuel assemblies that can reduce International Atomic Energy Agency (IAEA) inspection time in the field and be completely independent of operator declared burnable poison content. The passive measurement makes unattended mode operation practical, and thus provides the potential for reducing inspector time in the field for future applications. The new simplified passive neutron measurement uses the 238U spontaneous fission in LEU fresh fuel rods to self-interrogate the 235U mass in the neighboring rods. The measured response increases linearly with the increase in the linear density (LD) of 235U. The relatively high efficiency of the passive neutron detector (24%) provides good statistical precision (~ 2%) for the singles, doubles, and triples counting rates in the thermal-neutron mode. The three observables makes possible multiplicity analysis so that both the 235U LD and the effective burnable poison content can be determined independent of the operator declarations. This closes the potential diversion path of miss-declaration the burnable poison content. This report presents the detector design, the as-built system, the detector parameter measurements, the calibration, and the assay uncertainty estimates. The calibration measurements were performed using the Los Alamos Laboratory mockup PWR fuel assembly. The measurements were made in both the fastneutron mode (with Cd/Gd metal liners) and the thermal-neutron mode (no Cd/Gd liners).
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA). Office of International Nuclear Safeguards (NA-241)
- DOE Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1578024
- Report Number(s):
- LA-UR--19-32310
- Country of Publication:
- United States
- Language:
- English
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