ML20236A574

Safety Evaluation Re Util 850502 Request to Eliminate Arbitrary Intermediate Pipe Breaks.Request Acceptable Provided Applicant Maintains Environ Qualification of safety-related Mechanical & Electrical Equipment

ML20236A574
Person / Time
Site:	Comanche Peak
Issue date:	10/13/1987
From:	NRC
To:
Shared Package
ML20236A560	List: ML20236A558 ML20236A574
References
GL-87-11, NUDOCS 8710220374
Download: ML20236A574 (4)

Text

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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 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 - ]

with:previously. posttilated arbitrary intermediate pipe breaks will-

.be eliminated.  ;

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4 'j, 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 ii t onallinformation on welded. 9 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 t environmentally' qualified in-

! 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 d l break. criteria.to high energy piping systems described above, the applicant .1 L'

l provided assurance that' elimination of arbitrary intermediate-pipe breaks, J would not affect the environmental a'nalysis for equipment qualification. ~ 1n' ]

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. i

.1 l 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-mitted by the staff, the applicant maintains the environmental qualification I of safety-related mechanical and electrical equipment.

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