United States Nuclear Regulatory Commission - Protecting People and the Environment

Safety Concerns Associated with Pipe Breaks in the BWR Scram System (Generic Letter No. 81-20)



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

                                 APR 10 1981

TO ALL BWR LICENSEES 

SUBJECT:  SAFETY CONCERNS ASSOCIATED WITH PIPE BREAKS IN THE BWR SCRAM 
          SYSTEM (81-20) 

Yesterday, we discussed With Your representatives the NRC's Office of 
Analysis and Evaluation of Operational Data report entitled, "Safety 
Concerns Associated with Pipe Break in the BWR Scram System." The Report 
describes a potential sequence of events which could result from a break in 
the BWR scram discharge piping during a scram condition concurrent with an 
inability to reclose the scram outlet valves. Concerns identified include 
the quality of the scram discharge volume piping, the ability to detect and 
isolate such a break, and potential water and steam degradation of available 
ECCS equipment as a result of the break. A number of recommendations were 
made in the report to remedy the potential concerns. 

We are presently studying these issues and recommendations to determine 
whether BWR design basis accidents should be modified and as a consequence 
whether appropriate actions should be taken for operating BWR plants.  The 
purpose of this letter is to provide to you the AEOD report so that you can 
evaluate its applicability to your plant and determine appropriate remedial 
measures, and to request information from you concerning your evaluation in 
order to assist in determining an appropriate course of action for the NRC. 

Therefore, pursuant to 10 CFR 50.54(f) please provide us in writing, under 
oath or affirmation, within 45 days of your receipt of this letter, the 
following information: 

     1.   A generic evaluation of the applicability of the indicated 
          sequences of events in the report to the BWR plant design, your 
          estimate of the probability of occurrence of such sequences, and 
          the bases for these conclusions, 

     2.   A generic evaluation of the applicability of the indicated safety 
          concerns and findings in the report relative to BWR plant 
          construction, design, and operation and the bases for these 
          conclusions, and 

.

BWR Licensees                       - 2 -

     3.   A generic evaluation of the recommendations listed in the report 
          discussing the degree to which the recommendations are being or 
          have been implemented with bases why the recommendations should or
          should not be completely implemented on BWRs. 

In addition, pursuant to 50.54(f) provide the following information in 
writing within 120 days of your receipt of this letter: 

     1.   Provide an evaluation of the applicability of the 45 day generic 
          evaluation to your plant. This evaluation should contain plant 
          specific considerations related to system design, instru-
          mentation, construction, operation, operator training, and 
          emergency procedures for your plant. 

     2.   In light of the AEOD report and the 45 day generic evaluation, 
          provide a plant specific evaluation of your facility's Scram 
          Discharge Volume System conformance to GDC 14, GDC 35 GDC 55, 
          SS50.2(v), 50.55a (including footnote 2): and SS50.46 of the 
          Commission's regulations. This evaluation should address which 
          portions of the Scram Discharge Volume System are considered to be
          part of the reactor coolant pressure boundary, the quality group 
          and safety class of the Scram Discharge Volume System, the codes 
          and standards used for the design, fabrication ,and inservice 
          inspection of this system and your bases for the above 
          classifications or groupings. 

     3.   Provide by analysis or reference a demonstration that a break 
          located anywhere in the Scram Discharge Volume System could meet 
          the requirements of 650.46 of the Commission's regulations, taking
          into account the environmental and flooding aspects of such a 
          break. 
.

BWR Licensees                        -3- 

This request for information was approved by GAO under a blanket clearance 
number R0072 which expires November 30, 1983. comments on burden and 
duplication may be directed to the U.S. General Accounting Office, 
Regulatory Reports Review, Room 5106, 441 G Street, N.W., Washington, D.C. 
20548. 

                              Sincerely, 


                              Darrell G. Eisenhut, Director 
                              Division of Licensing 
                              Office of Nuclear Reactor Regulation 

Enclosure: 
As stated 
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