Environmental Qualification of Safety-Related Electrical Equipment (Generic Letter No. 82-09)
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
April 20, 1982
TO ALL POWER REACTOR LICENSEES, APPLICANTS FOR AN OPERATING LICENSE, NSSS
VENDORS AND REACTOR VENDORS
Gentlemen:
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
guide.
Sincerely,
Darrell G. Eisenhut, Director
Division of Licensing
Enclosure:
Question/Answer Form
8204210295
.
Clarification Questions and Answers
on Environmental Qualification Requirements
1. OPERATOR DISPLAY INSTRUMENTATION
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
deadline.
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.
2. SAFETY-RELATED EQUIPMENT
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).
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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.
3. REPLACEMENT PARTS
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
review.
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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.
4. MILD ENVIRONMENT
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);
and
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.
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5. SUBMERGENCE OUTSIDE CONTAINMENT
Q. For equipment qualifications purposes, what are the staff re-
quirements concerning submergence of equipment outside
containment?
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.
6. RADIATION
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.
7. CONTAINMENT SERVICE CONDITIONS
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.
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8. ONE HOUR MINIMUM OPERATING TIME
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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