Technical basis for inner container leak detection sensitivity goals in 3013 DE surveillance

Technical Report · Fri Aug 11 04:00:00 EDT 2017

DOI:https://doi.org/10.2172/1375143· OSTI ID:1375143

Berg, John M. ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

Helium leak checking of 3013 inner container lids is under consideration for addition to DE Surveillance tasks as an improved means to detect any through-wall flaws that may have formed during storage. This white paper evaluates whether leak checking at DE could replace and improve upon the current method of comparing gas compositions and pressures within the inner and outer containers. We have used viscous and molecular flow equations in ANSI N14.5 to calculate what the measured standard helium leak rate would be for hypothetical leaks of three different sizes. For comparison, we have also calculated the effects on gas composition and pressure differences as a function of pre-DE storage time for the same three leak sizes, using molecular and viscous flow equations as well as diffusion equations to predict the relevant gas transport. For a hypothetical leak that would be measured at 1x10^-7 std cc/sec, likely an achievable sensitivity using helium leak checking at DE, the calculations predict no measurable effect on pressure difference or gas composition as measured by DE gas analysis. We also calculate that it would take over 200 years for water vapor to diffuse through a 10^-7 std cc/sec leak enough to raise the RH outer container to half the RH value in the inner container. A leak 100 times larger, which would be measured at 1x10^-5 std cc/sec, the same water vapor diffusion would take at least 14 years. Our conclusion is that helium leak checking will be useful even at a sensitivity of 1x10^-5 std cc/sec, and a significant improvement over current DE methods at a sensitivity of 1x10^-7 std cc/sec.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Environmental Management (EM)
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1375143
• Report Number(s): LA--UR-17-25093
• Country of Publication: United States
• Language: English

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