10 CFR 50.71(e) - Maritime Administration - U.S. Department of ...

5.3.3 Local ShieldingUpdated Final Safety Analysis Report - (STS-004-002)Local shielding was provided on the demineralizers and filters of the primary loop purificationsystem. The design of these shields was based on an assumed fuel pin failure which exposes 5%(363 kg) of the fuel inventory to the primary coolant.The demineralizers were shielded with 4½ inches of lead. They were removed in March 1976. Thefilters are shielded with 2 inches of lead. They remain in place.5.4 Radiation Sources[Deleted]5.5 Shield Surveys[Deleted]5.6 Calculated Doses from Failed Fuel RodsAs of Revision III to the FSAR, past radiochemical data indicated that there had been no significant failedfuel in the reactor for approximately 15,000 effective full power hours (EFPH) of operation. From earlypower operation at Yorktown until August 1968, a period of approximately 6 years, the samples takenduring medium-and high-power operation had yielded essentially constant results. Representative valueswere 5.0E-2 µCi/ml and 3.0E-4 µCi/ml for the gross 15-minute degassed sample and the gross 1-houriodine activity, respectively, from samples taken upstream of the purification ion exchangers and filters.Approximately 90% of the measured primary water activity at medium- and high-power had been due toactivation of corrosion products and other impurities in the primary water.During the last voyage before the Shuffle Outage, evidence of a minor fuel failure was detected. Itappeared that small amounts of fission products were released to the primary coolant whenever there wasa significant change in reactor power level. Post shuffle operation indicated that the situation still existed;however, it did not limit operation or access anywhere on the ship.The primary and secondary shielding was designed to allow operation with failed fuel elements andfission products in the primary system. Continuous purification of the primary coolant restricted thefission product radioactivity levels in the primary coolant during operation and after shutdown. Theprimary loop purification system (PP) system is described in 9.2.1. During operation with Core Ia, thefission product activity was not significant compared to primary and secondary gamma radiation from thecore.During the entire lifetime of Core I, there was no other evidence of fuel failure based on the analysis ofprimary water samples.Rev. VI 55