Nondestructive measurements of residual ²³⁵U mass of Israeli Research Reactor-1 fuel using the Advanced Experimental Fuel Counter

Journal Article · Sat Mar 14 00:00:00 EDT 2020 · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

DOI:https://doi.org/10.1016/j.nima.2020.163797· OSTI ID:1821369

Levi, Itamar ^[1]; Trahan, Alexis Chanel  ^[2]; Ben-Meir, Kobi ^[3]; Ozeri, Offir ^[3]; Krakovich, Alexander ^[3]; Pesach, Asaf ^[1]; Rivin, Oleg ^[1]; Rael, Carlos D.  ^[2]; Swinhoe, Martyn T.  ^[2]; Menlove, Howard Olsen ^[2]; Hazenshprung, Nir ^[3]; Marlow, Johnna B.  ^[2]; Neder, Izhar ^[3]

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1. Nuclear Research Centre-Negev, Beer Sheva (Israel)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Soreq Nuclear Research Center, Yavne (Israel)

In 2018, a measurement campaign took place with participants from Los Alamos National Laboratory (LANL), the Nuclear Research Centre-Negev (NRCN) and Soreq Nuclear Research Center (SNRC) at the Israeli Research Reactor-1 (IRR-1) in which 14 of the reactor’s used fuel assemblies (FAs) with varied amount of depletion were measured with the nondestructive assay instrument Advanced Experimental Fuel Counter (AEFC). Designed for safeguards purposes, the AEFC measures both neutrons emitted from the FA (passive neutrons) and fission neutrons induced by an external neutron source (in this experiment, ²⁵²Cf). Signals recorded with the AEFC include total neutron count rates (Singles), time-correlated neutron count rates (Doubles), and total gamma-ray count rates. The ²³⁵U content of the FAs was previously assessed by two independent methods: (1) measurement of the transparency of the FA to low-energy gamma rays from an activated rhenium source (rhenium gamma transmission, or the RGT method) and (2) calculation of the 30-year burnup history of the core using detailed three-dimensional Monte-Carlo core depletion calculations. The results from the FAs that had been measured via the RGT method were used to construct the calibration curves, which translate the AEFC count rates to ²³⁵U mass. Then, the calibration was evaluated using AEFC measurements of six additional FAs that were not measured via the RGT method. From the results, it was determined the Doubles calibration curve was more reliable than that of the Singles and follows a simple second-order polynomial fit for the whole range of residual ²³⁵U mass content, albeit with larger statistical uncertainty. Detailed uncertainties quantification was conducted for both the AEFC Singles and Doubles. This includes the analysis of statistical uncertainties, calibration uncertainty, and random uncertainties due to the sensitivity of the AEFC to several sources of uncertainty, namely the FA position, FA orientation, interrogation source position, and ambient pool temperature. Finally, an overall total uncertainty of 6 g of ²³⁵U is estimated for the Singles and Doubles, which is mainly due to calibration uncertainty (for the Singles) and statistical uncertainty (for the Doubles), and which constitutes 3%–6% of the ²³⁵U total mass in the FAs, depending on their level of depletion.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1821369
• Alternate ID(s): OSTI ID: 1605606
• Report Number(s): LA-UR-20-22493; TRN: US2214337
• Journal Information: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 964; ISSN 0168-9002
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

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