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Information Notice No. 80-34: Boron Dilution of Reactor Coolant During Steam Generator Decontamination
SSINS No.: 6835 Accession No.: 8008220239 IEIN 80-34 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C. 20555 September 26, 1980 Information Notice No. 80-34: BORON DILUTION OF REACTOR COOLANT DURING STEAM GENERATOR DECONTAMINATION Description of Circumstances: Recently two instances of boron dilution of the reactor coolant system have occurred. Both cases were a result of high pressure washing of the steam generator tube sheets for decontamination to reduce the radiation levels during eddy current testing and related steam generator work. On May 29, 1980, Trojan Nuclear Plant miscalculated the excess boric acid required to offset the demineralized water used in washing the tube sheets. This resulted in the boron concentration of the primary coolant being reduced to less than the minimum required by the Technical Specifications. The dilution was, however, expected since the wash water was allowed to enter the reactor vessel through the nozzles. On July 5, 1980, San Onofre Unit 1 inadvertently diluted the reactor coolant boron concentration when the high pressure demineralized flushing water leaked by a dislodged nozzle seal. The inflatable seals had been installed to prevent the non-borated water from entering the reactor. The resulting boron concentration was greater than required for shutdown margin, but the positive reactivity added was in excess of that allowed by the Technical Specifications. This Information Notice is provided to identify potential problem areas involved with decontaminating specific areas of steam generators. It is expected that recipients will review the potential hazards involved and consider increased monitoring of 1) inflatable seal performance, 2) vessel level, and 3) boron concentration. Increasing the boron concentration of the primary system prior to performing any decontamination activities or using borated water for washing should also be considered. It is expected that recipients will review this information for possible applicability to their facilities. No specific action or response is requested at this time. If you have any questions regarding this matter, please contact the Director of the appropriate Regional Office.
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