Validation of Gamma Dose Rate Calculation Methodology using the Morris and Turkey Point Measurements

Technical Report · Thu Jan 24 04:00:00 EST 2019

DOI:https://doi.org/10.2172/1493292· OSTI ID:1493292

Cao, Yan ^[1]; Feng, Bo ^[1]

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1. Argonne National Lab. (ANL), Argonne, IL (United States)

The ability to accurately predict the dose rates from the spent nuclear fuel assembly is very important for determining whether the used nuclear fuel is self-guarded and self-protected. Studies have shown that the direct numerical calculations of the dose rates gave a much lower value than a typical reference. This report summarizes the benchmark studies performed to evaluate the numerical methodologies used in calculating the gamma dose rates of the spent nuclear fuel assemblies. The Morris and Turkey Point experimental data for dose rates measured through air were used in the analyses. Numerical simulations of the gamma dose rate measurements included the fuel depletion analysis of the fuel assembly as well as its structural materials irradiated inside the reactor core, the radioisotopes decay, and photon transport simulations to calculate the gamma dose rates. The different factors which affect the calculated gamma dose rates were addressed. The calculated results were compared with the measured gamma dose rates. Good agreement was obtained when the detectors were placed at the middle of the fuel assembly region. The deviations of the calculated dose rates became larger when the measurements were performed at the top or bottom fuel assemblies. In these benchmark studies, the spent nuclear fuel assemblies were all PWR assemblies and had fuel burnup around 25 MWd/kg to 40 MWd/kg. Its cooling time before the measurements was around 1.8 years to 7 years. The used nuclear fuel assembly is usually self-protected while discharged from the core. Its radioactivity decreases and after a few tens of years it may fall down below the current threshold of 100 r/h. Future validation work is necessary in order to better evaluate the numerically calculated gamma dose rates with experiments performed for other types of fuel assemblies and for fuel assemblies with higher burnup and/or longer cooling times.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1493292
• Report Number(s): ANL--19/06; 150322
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS