United States Nuclear Regulatory Commission - Protecting People and the Environment

Environmental Qualification of Safety-Related Electrical Equipment (Generic Letter No. 82-09)

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                               April 20, 1982 



Subject:  Environmental Qualification of Safety-Related Electrical 
          Equipment (Generic Letter No. 82-09) 

On January 20, 1982 the NRC published a proposed rule on the subject in the 
Federal Register. This proposed rule codifies the current NRC requirements 
on this issue. In addition, Regulatory Guide 1.89, which relates to the 
proposed rule, was issued for public comment on February 18, 1982. Comment 
period on the rule expired in March 22, 1982. Comments on the regulatory 
guide are due by April 23, 1982. 

Over the past six months, the NRC staff has worked with a number of 
licensees, at their requests, to respond to their technical questions and 
clarify certain aspects of the qualification requirements. These discussions
involved nine topics which are addressed in a question/answer form in the 
Enclosure. The answers in the Enclosure represent the NRC staff position 
concerning these topics. These positions will be used in the review of 
licensee submittals and will be incorporated into the proposed regulatory 


                                   Darrell G. Eisenhut, Director 
                                   Division of Licensing 

Question/Answer Form 


                    Clarification Questions and Answers 
                 on Environmental Qualification Requirements


     Q.   Given the interrelated activities associated with display instru-
          mentation (e.g., NUREG-0700, NUREG-0799, proposed Regulatory Guide
          1.97 and Equipment Qualification efforts), what display 
          instrumentation referenced in emergency operating procedures must 
          be identified in licensee submittal to the NRC? 

     A.   All display instrumentation referenced in the emergency procedures
          need not be identified. The NRC requires that licensees need only 
          identify and have available qualification documentation on those 
          operator display instruments which are safety-related (see 
          Question 2). If licensees have previously supplied a listing of 
          all display instrumentation referenced in emergency procedures, 
          licensees may identify (such as by the use of an *) which of those 
          instruments are safety-related. The staff will defer review of the 
          basis for this safety-related classification until other NRC 
          activities (1) have been implemented. When these other activities 
          are implemented, additional instruments presently not requiring 
          qualification may require upgrading to a safety-related status 
          and/or may require qualification. Licensees will be required at 
          that time to qualify this instrumentation in accordance with the 
          following criteria: 
          o    For new or upgraded instrumentation with a required operation
               date prior to the equipment qualification deadline, qualifi-
               cation must be accomplished by the equipment qualification 

          o    For new or upgraded instrumentation with a required operation
               date after the equipment qualification deadline, 
               qualification must be accomplished prior to equipment 
               operation and plant acceptance. 


     Q.   For Equipment Qualification purposes, what constitutes all safety-
          related electrical equipment? 

     A.   The Commission, in CLI-80-21, required the environmental 
          qualification of only safety-related electrical equipment. 
          Identification of the safety-related equipment installed at 
          specific plants can be obtained from FSARs, Technical 
          Specifications and other docketed correspondence 

(1)  Such activities include preparation of new emergency procedures 
     (NUREG-0799), control room design reviews (NUREG-0700), and upgrading 
     of accident monitoring instrumentation (Reg. Guide 1.97 and NUREG-0737). 

                                    - 2 -

setting forth NRC requirements or licensee commitments. Identification of 
safety-related equipment installed in harsh environments at specific plants 
must be supplied by the licensee. The necessity for upgrading 
nonsafety-related system to safety-related status will be the subject of 
other NRC reviews. 


     Q.   Please clarify the NRC requirements on replacement parts. 

     A.   In CLI-80-21, the Commission stated that unless there were sound 
          reasons to the contrary, replacement equipment should be qualified
          to the standards set forth in Category I of NUREG-0588. The 
          Commission's position was designed to promote the policy of 
          upgrading the environmental qualification and reliability of 
          installed safety-related electrical equipment. To meet this 
          overall goal, licensees must institute internal policy practices 
          consistent with the Commission's statement. 

          Situations may arise in which upgrading to NUREG-0588, Category I 
          of replacement equipment qualified to NUREG-0588, Category II or 
          the DOR Guidelines will not be compatible with overall station 
          safety and performance goals. Licensees must review such 
          situations on a case-by-case basis and determine that "sound 
          reasons to the contrary" do, in fact, exist which warrant the use 
          of replacement equipment (not necessarily in-kind) qualified to 
          the DOR Guidelines or NUREG-0588, Category II. For equipment 
          located in a harsh environment, licensees' procedures must provide 
          for documentation and substantiation of such determinations. 

          Conditions which reflect sound reasons why qualification standards
          for replacement of equipment in a harsh environment need not be 
          upgraded to NUREG-0588, Category I include the following: 

          1.   The licensee has replacement equipment in stock that meets 
               the DOR Guidelines or NUREG-0588, Category II, and 
               procurement actions regarding such replacement equipment had 
               commenced prior to May 23, 1980. 

          2.   Replacement equipment qualified to the NUREG-0588, Category 
               I standards does not exist. 

          3.   Replacement equipment qualified to the NUREG-0588, Category 
               I standards is not available to meet installation and 
               operation schedules. Equipment qualified to the DOR 
               Guidelines or NUREG-0588, Category II may be used for an 
               interim period until Category I equipment is obtained and an 
               outage of sufficient duration is available for replacement. 
               Justification for use of the non-Category I qualified 
               replacement equipment beyond this interim period must be 
               submitted to the NRC for approval prior to the end of the 
               interim period and in sufficient time for reasonable NRC 

                                    - 3 -

          4.   Replacement equipment qualified to NUREG-0588, Category I 
               standards would require significant plant modifications to 
               accommodate its use. 

          5.   Operating performance and reliability data for the Category 
               I equipment indicates poor overall equipment performance. For
               example, mean time to failure is significantly shorter for 
               the Category I replacement equipment. 

          6.   The use of replacement equipment qualified to NUREG-0588, 
               Category I standards has a significant probability of 
               creating human factor problems that will negatively affect 
               plant safety and performance, e.g., (1) knowledge, skills and 
               ability of existing plant staff require significant upgrading 
               to operate or maintain the specific Category I replacement 
               equipment; (2) the use of equipment qualified to Category I 
               standards creates a one-of-a-kind application; or (3) 
               maintenance, surveillance or calibration activities are 
               unnecessarily complex. 


     Q.   Can periodic surveillance, testing and maintenance programs 
          adequately demonstrate qualification of electrical equipment in 
          mild environments? 

     A.   For existing equipment located in mild environments, equipment 
          environmental qualification can be adequately demonstrated and 
          maintained by the use of the following three programs: 

          1.   A periodic maintenance, inspection, and/or replacement 
               program based on sound engineering practice and 
               recommendations of the equipment manufacturer which is 
               updated as required by the results of an equipment 
               surveillance program; 

          2.   A periodic testing program to verify operability of safety-
               related equipment within its performance specification 
               requirements (system level testing of the type typically 
               required by the plant technical specifications may be used); 

          3.   An equipment surveillance program which includes periodic 
               inspections, analysis of equipment and component failures, 
               and a review of the results of preventive maintenance and 
               periodic testing programs. 

          For replacement and new equipment, the licensee must also 
          establish and document the environmental design basis for the 
          equipment locations. The purchase specifications must reflect 
          those design basis environmental conditions that are bounding for 
          all applicable equipment locations. 

                                    - 4 - 


     Q.   For equipment qualifications purposes, what are the staff re- 
          quirements concerning submergence of equipment outside 
     A.   The Staff requires that the licensee submit documentation on the 
          qualification of safety-related equipment that could be submerged 
          due to a high energy line break outside containment. 


     Q.   Is the staff screening value of 4 x 107 rads applicable to all 
          operating reactors? 

     A.   No. This screening value is applicable only to PWRs with dry type 
          containments. However, for PWRs with dry type containments, the 
          licensee may choose to use plant specific analysis instead of the 
          screening value. For plants with other containment types, the 
          licensee must use plant specific analysis. 

          Acceptable to the Staff for equipment qualification purposes are 
          radiation values developed as part of the plant licensing process 
          provided that they are based on the TID14844 source terms and are 
          conservatively performed. In order to assure that the 
          methodologies are appropriate, the Staff requests two component 
          specific sample calculations (one for inside and one for outside 
          containment), and a brief written description of each of the 
          methodologies used, their application and associated 
          conservatisms. Such sample calculations and a statement by the 
          licensee that the values of radiation exposure of components so 
          derived are appropriate for environmental qualification of 
          equipment will satisfy the Staff's concern on the "Radiation 
          Specification Value" used during the qualification reviews. 


     Q.   Must the Staff value (identified in the SERs) of TSAT for PWRs and
          TSAT + 20F for BWRs be used as the maximum in-containment 
          temperature for the purpose of equipment qualification? 

     A.   No The Staff will accept the use of these values. However, an 
          acceptable alternative to the NRC staff's temperature criterion 
          used for the service conditions must base that service condition 
          on the FSAR analysis or other NRC approved analysis, provided that
          the specific analysis, or a summary of that analysis, together 
          with reference to the previous NRC acceptance of that analysis is 
          submitted by the licensee. In addition, some of the information in 
          the associated safety evaluation may require clarification. 

                                    - 5 - 


     Q.   The Staff has previously indicated that certain exceptions to the 
          one hour minimum operating time rule are permitted. Can further 
          clarification be provided? 

     A.   With regard to plants subject to the qualification requirements of
          the DOR Guidelines or Category II of NUREG-0588, for those pieces 
          of equipment tested prior to May 23, 1980, the test data and 
          analysis may be used to qualify the equipment to the required 
          operating time plus an appropriate margin. The one hour margin 
          requirement need not be applied. However, subsequent failures 
          should be shown not to be detrimental to plant safety. 

          The one hour time margin rule is not applicable to equipment whose
          safety function is performed prior to significant changes in the 
          environment at the equipment location. 

9.   AGING 

     Q.   Must a qualified life be developed for all safety-related 
          electrical equipment located in harsh environments? 

     A.   Section 7 of the DOR Guidelines and Section 4.2, Category II of 
          NUREG-0588, do not require a qualified life to be established for 
          all safety-related electrical equipment located in harsh 
          environments. A qualified life, in accordance with the provisions 
          in IEEE 323-1974, is required for equipment, including replacement
          parts, qualified to Category I of NUREG-0588 that is located in a 
          harsh environment. 

          An acceptable method for addressing in-service degradation is 
          through a preventive maintenance/surveillance program with 
          equipment and component refurbishment and/or replacement based on 
          known susceptibility to aging degradation, the results of 
          inspections, or manufacturers recommendations. These elements of 
          the program lead to an understanding on a device specific basis of
          the nature and extent of the increased stress levels encountered 
          during Design Basis Accidents and resultant degradation (if any) 
          which may occur. Arrhenius or other appropriate accelerated aging 
          methodologies may be used to establish replacement and 
          refurbishment schedules if the component's design and materials 
          application are sufficiently simple and the necessary data are 
          available to allow a meaningful application. 

          In plants subject to the qualification requirements of either the 
          DOR Guidelines or NUREG-0588 Category II, for equipment that has 
          been identified as being susceptible to significant degradation 
          due to thermal and radiation aging, the schedule for inspection of 
          and/or replacement of the susceptible components in that equipment 
          must be incorporated into the preventive maintenance and 
          surveillance programs, and that information should be incorporated 
          into the system component evaluation worksheets (SCEWS). For other 
          equipment, the aging column in the SCEWS should be marked "No 
          Known Susceptibility." 
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