Problems in the Evaluation of Reactor Vessel Surveillance Capsules

Commercial PWR and BWR power reactors in the United States each contain a series of pressure vessel steel surveillance capsules. These capsules typically contain neutron dosimeters, thermal monitors, Charpy V-notch impact specimens, and tension specimens. These capsules are periodically removed during the life of a reactor and evaluated to determine the effect of radiation on the pressure vessel steel. The pressure-temperature operating curves for the plant are adjusted as necessary by using the surveillance capsule results.

Much valuable information has been obtained from pressure vessel surveillance capsules. There are, however, numerous problems which have been encountered during the examination of these capsules. These problems could lead to a decrease in the amount of useful information obtained from a capsule. Areas in which problems have been observed include the overall surveillance program, capsule design and construction, specimen preparation and documentation, specimen testing and evaluation, and reporting.

Problems typical of those which have been observed are presented. In addition, recommendations for prevention of these problems are made.