ML20236A574
| ML20236A574 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/13/1987 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20236A560 | List: |
| References | |
| GL-87-11, NUDOCS 8710220374 | |
| Download: ML20236A574 (4) | |
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i' ENCLOSURE
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SAFETY EVALUATION COMANCHE PEAK STEAM ELECTRIC STATION, UNIIS 1 AND 2
.J ELIMINATION OF ARBITRARY INTERMEDIATE PIPE BREAKS
Background
In a letter dated May 2,1985," Texas Utilities Electric Company, applicant for the Comanche Peak Steam Electric Station (CPSES), Units 1 and 2, requested staff l
approval to eliminate from design consideration those pipe breaks generally re-ferred to as " arbitrary intermediate breaks." Arbitrary intermediate breaks-(AIBs) are defined as those break locations which, based on pipe stress analysis-results, are below the stress and fatigue-limits specified in Branch Technical I
l Position (BTP) MEB 3-1, but are selected to provide a minimum of two postulated breaks between the terminal ends of a piping system. The applicant specifically J
requested NRC approval of the application of alternative pipe break criteria to high energy piping systems, excluding the reactor coolant system primary loop, t
of CPSES Units 1 and 2 as follows:
1.
Arbitrary intermediate pipe breaks in all high energy piping systems identified in the May 2, 1985 letter, Attachment B-2, Table 1, will be eliminated from the structural' design basis.. Breaks will continue to be postulated at intermediate locations'where the stress criteria 'or fatigue criteria (applicable to Class l' piping only) of BTP MEB 3-1 1
are exceeded, hk PD A
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2.
The dynamic effects (pipe whip. jet impingement, andfcompartmenti l
pressurization loads)-associated with arbitrary intermediate pipe:
~ breaks will be excluded from the-CPSES design. basis'.
. 3.
~ The requirement for pipe whip restraints' and jet shields associated -
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with:previously. posttilated arbitrary intermediate pipe breaks will-
.be eliminated.
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The applicant responded to staff requests for additional information on;elim -
ination of arbitrary intermediate pipe' breaks on July-29,1986 :and October 21,:
1986. The latter response indicated that add t onallinformation on welded.
9 ii piping attachments and analyses on potential fatigue affects at welded: attach-ments within five nominal pipe diameters of the AIB to be eliminated would be-i provided for staff review.
1 Generic Letter 87-11, " Relaxation in Arbitrary Intermediate Pipe Rupture Requirements," was issued on June 19,.1987.. Generic Letter 87-11; revises BTP MEB 3-1 eliminating requirements to consider all dynamic effects and all environmental effects resulting from arbitrary intermediate pipe ruptures'.
However, a new and related provision-(Section~B.1.c.(5)) in revised BTP'MEB-3-1 specifies that-safety-related equipmen.-be environmentally' qualified in-t
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accordance with Standard Review Plan 3.11.
BTPMEB3-1nowspecifie's;thati required pipe ruptures and leakage cracks (whichever. control) must-be-included in-the' design. bases for environmental qualification of electrical-and mechan.ical' equipment both inside and.outside containment. AJuly/15,1987L l
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.3-letter from the applicant advised the staff that after considering the staff
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position in Generic Letter 87-11, they anticipated that the generic letter eliminated the'need to respond.to :taff request for additional information dated September 11, 1986 regarding welded piping attachments.
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Evaluation
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In.the request.for staff approval of its application of the alternative pipe l
break. criteria.to high energy piping systems described above, the applicant
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provided assurance that' elimination of arbitrary intermediate-pipe breaks, J
would not affect the environmental a'nalysis for equipment qualification. ~ 1n'
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addition, the applicant's July 29, 1986 response.(R210.8) 'to the staff's.
request for information (Q210.8) assures.that elimination of A1Bs will not.
reduce the environmental qualification of safety-related equipment.
Based on i
i its evaluation and when viewed in conjunc' tion with the staff positions of.
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Generic Letter 87-11, the ' staff finds that the applicant's alternative pipe i
break criteria for high energy piping is acceptable..However, the staff j
1 requires that the applicant not' allow any relaxation in the environmental l
qualification of safety-related mechanical and electrical 1 equipment as spe-L cified in Generic Letter 87-11 unless specific approval-from the' deviation is granted.
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Conclusion Based on its evaluation of the applicant's submittals and the staff positions contained in Generic Letter 87-11, the staff has determined that the applicant's request to eliminate arbitrary intermediate pipe ruptures from design consid-erations of CPSES Units 1 and 2, is acceptable and can be implemented without undue risk to public health and safety,.provided that, unless otherwise per-I mitted by the staff, the applicant maintains the environmental qualification of safety-related mechanical and electrical equipment.
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