MCO combustible gas management leak test acceptance criteria

Spent Nuclear Fuel (SNF) Project Product Specification

“…The maximum backfill gas temperature impacts the minimum molar quantity of helium added to an MCO. The MCO gas temperature of 50°C at the minimum backfill pressure specified in Section 4.4.2.4 results in a minimum helium inventory consistent with that used to evaluate leak rate criteria in Sherrell(1999b).…”

“…The MCO void gas backfill pressure after drying is based on establishing a positive internal gas pressure within the MCO with respect to atmospheric conditions to preclude air in leakage during transport and storage. A minimum backfill pressure of 9.5 psig supports maintaining a positive internal gauge gas pressure at MCO temperatures as low as -31 "C (Sherrell 1999b). The HNF-SD-SNF-OCD-001, Rev.…”

“…Since tcmpcratarc affccts the mass of backfill helium addcd to an MCO, the backfill gas pressure must be measured after the cask/MCO assembly tempeiature has been adjusted to the backfill gas temperature criterion. Sherrell (1999b) detemiined that the MCO backfill gas temperature is within the required temperature range of 0°C to 5OoC after drylng if the MCO is cooled for at least 5 hrs with tempered water flowrate ofat least 15 gpm and inaxinnun tempered water chiller discharge temperature of 15°C * 0.5"C.…”

“…This gaseous leakage rate is based on a clean seal and a clean sealing surface at the final mechanical closure boundary. The mechanical seal leakage rate is evaluated in Sherrell (1999b) based on a total reference air integrated leak rate of lxlO-'std cin'/sec air as measured per ANSI N14.5-1987. The leak rate criterion is defined as IxlO-' cm'iscc of dry air, corrected to an absolute pressure of 1 atin and 2 5 T , that will flow through a leak path rroni an upstreani cavity with absolute pressure of 1 atin into a downstream cavity that has been evacuated lo less than or equal to 0.01 atm.…”

Design verification and validation plan for the cold vacuum drying facility

“…The CVD Facility will leak test the MCO's top closure seals prior to releasing it for shipment to the CSB. The leak test must demonstrate that the total integrated leak rate past the MCO's top closure seals does not exceed 1 x l o 5 std cc/s (Sherrell, 1999).…”