Information Notice No. 80-34: Boron Dilution of Reactor Coolant During Steam Generator Decontamination
SSINS No.: 6835
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
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.
Page Last Reviewed/Updated Friday, May 22, 2015