Method and apparatus for preparing spent nuclear fuel for dry storage
View Patent ↗A system and method for drying cavities containing spent nuclear fuel is devised. The invention utilizes a non-intrusive procedure that is based on monitoring the dew point temperature of a non-reactive gas that is circulated through the cavity. In one aspect, the invention is a system for drying a cavity loaded with spent nuclear fuel comprising: a canister forming the cavity, the cavity having an inlet and an outlet; a source of non-reactive gas; means for flowing the non-reactive gas from the source of non-reactive gas through the cavity; and means for repetitively measuring the dew point temperature of the non-reactive gas exiting the cavity.
1. A method of preparing spent nuclear fuel for dry storage drying comprising:
a) flowing a non-reactive gas through a cavity containing spent nuclear fuel;
b) repetitively measuring dew point temperature of the non-reactive gas exiting the cavity;
(c) drying the non-reactive gas that exits the cavity after the dew point temperature is measured;
(d) subsequent to step (c), re-circulating the dried non-reactive gas through the cavity in a closed flow loop; and
(e) subsequent to step (d), upon the dew point temperature of the nonreactive gas exiting the cavity being measured to be at or below a predetermined dew point temperature for a predetermined period of time, discontinuing the flow of the non-reactive gas and sealing the cavity.
2. The method of claim 1 wherein step (a) comprises flowing the non-reactive gas through the cavity containing the spent nuclear fuel at a predetermined flow rate.
3. The method of claim 2 wherein the cavity has a volume and the predetermined flow rate is chosen so that the volume of the cavity is turned over 25 to 50 times per hour.
4. The method of claim 1 wherein the predetermined dew point temperature is selected to correspond to a desired vapor pressure within the cavity.
5. The method of claim 1 wherein the predetermined dew point temperature is in a range of approximately 20 to 26° F., and the predetermined time is in a range of approximately 25 to 35 minutes.
6. The method of claim 5 wherein the predetermined dew point temperature is approximately 22.9° F. and the predetermined time is approximately 30 minutes.
7. The method of claim 1 wherein step d) comprises drying the non-reactive gas with a desiccant.
8. The method of claim 1 wherein step d) comprises drying the non-reactive gas by chilling the non-reactive gas.
9. The method of claim 1 wherein the non-reactive gas is nitrogen, carbon dioxide, light hydrocarbon gases, or a noble gas selected from the group consisting of helium, argon, neon, radon, krypton, and xenon.
10. The method of claim 1 wherein the predetermined dew-point temperature is selected to correspond to a vapor pressure of 3 Torr or less in the cavity.
11. The method of claim 1
wherein the predetermined dew-point temperature is selected to correspond to a vapor pressure of 3 Torr or less in the cavity;
wherein step (a) comprises flowing the non-reactive gas through the cavity at a predetermined flow rate that results in a volume of the cavity being turned over 25 to 50 times per hour;
wherein the non-reactive gas is helium;
wherein the cavity is formed by a canister, and the canister is positioned in a cask.