United States Nuclear Regulatory Commission - Protecting People and the Environment

Actions Required from OL Applicants of NSSS Designed By W and CE Resulting from NRC B&O Task Force Review of TMI2 Accident (Generic Letter 80-20)



GL80020                                                  
                                                      
                                  UNITED STATES 
                         NUCLEAR REGULATORY COMMISSION 
                            WASHINGTON, D.C.  20555 

                                March 10, 1980 
                                          

TO ALL PENDING OPERATING LICENSE APPLICANTS OF NUCLEAR STEAM SUPPLY 
  SYSTEMS DESIGNED BY WESTINGHOUSE AND COMBUSTION ENGINEERING 

SUBJECT:  ACTION REQUIRED FROM OPERATING LICENSE APPLICANTS OF NUCLEAR 
          STEAM SUPPLY SYSTEMS DESIGNED BY WESTINGHOUSE AND COMBUSTION 
          ENGINEERING RESULTING FROM THE NRC BULLETINS AND ORDERS TASK 
          FORCE REVIEW REGARDING THE THREE MILE ISLAND UNIT 2 ACCIDENT 

In our letter of September 27, 1979 to all pending operating license 
applicants concerning followup actions resulting from our reviews regarding 
the Three Mile Island Unit 2 accident, we indicated that each applicant 
would receive additional guidance from the NRR Bulletins and Orders Task 
Force. This guidance would be related to (1) Auxiliary Feedwater (AFW) 
systems, and (2) analyses for small break loss-of-coolant accidents and 
inadequate core cooling, including guidelines for emergency operating 
procedures. 

The purpose of this letter is to advise you of the information we require 
related to Auxiliary Feedwater systems.  The requirements were identified 
during the course of the NRR Bulletins and Orders Task Force review of 
nuclear steam supply systems designed by Westinghouse and Combustion 
Engineering in light of the Three Mile Island Unit 2 accident. 

Auxiliary Feedwater (AFW) Systems 

The Three Mile Island Unit 2 accident and subsequent investigations and 
studies highlighted the importance of the AFW system in the mitigation of 
transients and accidents.  As part of its assessment of the Three Mile 
Island Unit 2 accident and related implications for operating plants, the 
staff evaluated the AFW systems for all operating plants having nuclear 
steam supply systems designed by Westinghouse and Combustion Engineering. 

The objectives of the staff's study, related to operation of nuclear steam 
supply systems designed by Westinghouse, were (a) to identify necessary 
changes in AFW system design or related operating procedures at operating 
plants in order to assure continued safe operation of these plants, and (b) 
to identify other system characteristics in the AFW system design of these 
plants which on a long-term basis may require system modifications. 

To accommodate these objectives the staff reviewed plant-specific AFW system
designs in light of current requirements, and assessed the relative 
reliability of the various AFW systems under various loss-of-feedwater 
transients, one of which was the initiating event at Three Mile Island Unit 
2, and other postulated potential failure conditions by determining the 
potential failure conditions by determining the potential for AFW system 
failure due to common causes, single point vulnerabilities and human error. 
.

It should be noted that, because of time and personnel limitations, our 
evaluation of AFW systems was limited to operating reactors at the time 
these studies were initiated.  Our review of these systems resulted in the 
identification of changes required for current AFW systems.  Some of these 
changes were generic and others were plant specific.  A summary of the 
techniques used in our evaluation is provided in Enclosure 1.* 

With respect to operating license applications such as yours, we will 
require that you (a) provide an evaluation which shows how your AFW system 
meets each requirement in Standard Review Plan 10.4.9 and Branch Technical 
Position ASB-10-1, (b) perform a reliability evaluation similar in method to 
that described in Enclosed 1 that was performed for operating plants and 
submit it for staff review, and (d) respond to Enclosure 2, which requests 
the information necessary to determine the design basis for your AFW system 
flow requirements and to verify that your AFW system will meet these 
requirements. 

We recognize that operating license applicants for certain facilities, e.d.,
Salem Unit 2, and North Anna Unit 2, may be essentially identical to plants 
for which we have identified AFW system modifications.  In such instances, 
information already provided for the operating plants may be directly 
applicable to plants under review for an operating license.  It is 
acceptable to the staff if you reference such information in your response.  
However, you must also include a description of any differences between the 
operating plant and the plant under review for an operating license and 
provide justification in order for us to determine if the resolution for the 
operating plant is applicable to your facility. 

Provide the information discussed above as an amendment to your application. 
Your schedule for submittal should take into consideration that the current 
version of the Task Action Plan requires staff review and approval of this 
information prior to issuance of a full power license. 

                                      D. F. Ross, Jr., Acting Director 
                                      Division of Project Management 
                                      Office of Nuclear Reactor Regulation 

Enclosures:
As Stated 

cc:  Service Lists 

* Enclosure 1 is Appendix 3 to the staff generic evaluation of Westinghouse 
  designed plants.  The techniques described and recommendations are 
  applicable to Combustion Engineering designed plants. 

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