Development test 105-623A: Relation between hand and flow seating of slug charges as they affect slug rupture rates

摘要

A large portion of the slug failures which occurred during 1955 were of the ''hot-spot'' type. Observation of these failures has shown them to be the result of intergranular corrosion attack of the aluminum jacket. Intergranular corrosion is presently considered to occur in water temperature above 150 C; a flow disturbance which causes non-uniform coolant temperatures is suspected as the cause of failure.The present of a cocked slug, or a bowed slug column, might provide this flow disturbance. 189-D laboratory tests have shown that flow seating the slug charge allows slugs to cock in the tube. It has also been found that these cocked slugs may be lifted to close proximity of the tube wall by the axial load on the slug column due to process water flow. It is believed that in cases such as this, slug and coolant temperatures may become critical. Present charging procedures allow for flow seating of the slug column. The distance the column is flow seated varied from very little to 3 or 4 inches depending on the particular charge. It is believed that this practice can lead to the situation observed in the laboratory tests. During the past two months, there has been an increase of failures of the ''hot-spot'' type at the DR pile. Therefore, this test proposes to evaluate the effectiveness of hand seating slug columns at the DR pile as outlined in this paper.