Patent Number: 
Section: claims

1. A method of storing a chimney assembly of a reactor pressure vessel during a nuclear reactor outage, comprising:detaching a chimney barrel with upper chimney partitions therein from a top guide assembly of the reactor pressure vessel, a height of the upper chimney partitions being less than a height of the chimney barrel so as to leave a plenum region in a top section of the chimney barrel, the top guide assembly including lower chimney partitions therein;removing the lower chimney partitions from the top guide assembly; andinserting the lower chimney partitions into the plenum region of the chimney barrel so as to be on the upper chimney partitions, the chimney assembly being a combination of at least the chimney barrel, the upper chimney partitions, and the lower chimney partitions. 2. The method of claim 1, wherein the upper chimney partitions are affixed to an interior of the chimney barrel. 3. The method of claim 1, wherein the lower chimney partitions are not affixed to the top guide assembly, the lower chimney partitions being removable from the top guide assembly via lifting. 4. The method of claim 1, wherein the plenum region has a size and shape that corresponds to a size and shape of the lower chimney partitions. 5. The method of claim 1, wherein the detaching includes placing the chimney barrel with the upper chimney partitions in a radiation-shielding storage location during the nuclear reactor outage. 6. The method of claim 1, wherein the detaching includes submerging the chimney barrel with the upper chimney partitions therein in a storage pool. 7. The method of claim 6, wherein the inserting includes the lower chimney partitions being submerged in the storage pool. 8. The method of claim 1, wherein the detaching includes maintaining an orientation of the chimney barrel. 9. The method of claim 1, wherein the removing the lower chimney partitions includes exposing a top guide grid thereunder, the top guide grid being fixed to a top end of a core shroud of the reactor pressure vessel. 10. The method of claim 1, wherein the nuclear reactor outage is at least one of a refueling outage and a maintenance outage.