United States Nuclear Regulatory Commission - Protecting People and the Environment

High Boron Concentrations (Generic Letter No. 85-16)



                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                           WASHINGTON, D. C. 20555

                               August 23, 1985

TO ALL LICENSEES OF OPERATING REACTORS AND APPLICANTS FOR AN OPERATING 
LICENSE (Generic Letter 85-16) 

Gentlemen: 

SUBJECT: HIGH BORON CONCENTRATIONS 

Boron Injection Tanks were originally incorporated into Westinghouse plant 
designs as a means of mitigating steam line break events. To overcome the 
reactivity addition resulting from a rapid cooldown, a high concentration of
boron in the form of boric acid was used in the injection tanks. High 
concentrations of boron result in maintenance and operational burdens to 
licensees because of the need to prevent boron precipitation. 

In the recent past, there have been incidents at operating reactor plants in
which boric acid has crystallized in the internals of vital safety related 
pumps and piping, thereby rendering those systems inoperable. One example is
an incident at Indian Point 2 on December 28, 1984 in which the safety 
injection system was inoperable because all three pumps in the system were 
frozen with crystallized boric acid. 

Over the past several years, the analysis methods for calculating the 
consequences of a steam line break have improved. These revised calculations
demonstrate that the negative reactivity that needs to be added is lower 
than originally thought and consequently the need for highly concentrated 
'boron injection is reduced or eliminated. Many licensees with Westinghouse 
plants (e.g. Surry 1&2), have requested that they be allowed to either 
physically remove the boron injection tank from the safety injection piping, 
or at least reduce boron concentrations in the tank to the leVels safely 
used in other sections of the safety injection piping and refueling water 
storage tank (e.g., to 2000 ppm). To support their requests, licensees have 
submitted new analyses of the steam line break event that demonstrated the 
regulatory criteria (i.e., 10 CFR 100 guidelines dose values) were met. The 
staff has reviewed these analyses and granted these requests. 

In light of the safety risks inherent in the present system and these new 
calculations which show a reduced need for boron injection, the staff 
encourages you to reevaluate the need for maintaining high concentrations of
boron in your boron injection tanks. In the event you perform a reanalysis 
of the steam line break event or any other event which requires or assumes 
credit for boron injection, the staff is willing to consider a relaxation of
excess conservatism in your analyses, provided the relaxation can be 
justified. As a result, it may be possible to remove the boron injection 
tanks or reduce the boron concentration. 


8508210258 

                                    - 2 -

If you require any further information regarding this subject, please 
contact your project manager. 


                                   Hugh L. Thompson, Director 
                                   Division of Licensing 
                                   Office of Nuclear Reactor Regulation 

cc:  List of Generic Letters 
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