United States Nuclear Regulatory Commission - Protecting People and the Environment

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. 

Page Last Reviewed/Updated Tuesday, November 12, 2013