ML20209E021

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Forwards Evaluations of Listed Allegations.Allegation Classification,Per G Knighton 841130 Memo,Encl
ML20209E021
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 03/05/1985
From: Bosnak R
Office of Nuclear Reactor Regulation
To: Novak T
Office of Nuclear Reactor Regulation
Shared Package
ML17083B484 List:
References
FOIA-86-197 NUDOCS 8503110593
Download: ML20209E021 (13)
v • d • e


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UNITED STATES

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I MAR 5 1965 DOCKET No.:

50-323 MEMORANDUM FOR: Thomas M. Novak, Assistant Director for Licensing Division of Licensing FROM:

Robert J. Bosnak, Acting Assistant Director Components and Structures Engineering Division of Engineering

SUBJECT:

EVALUATION OF ALLEGATIONS ON DIABLO CANYON UNITS 1 AND 2 The Mechanical Engineering Branch has evaluated the following assigned allegations, shown in the enclosure:

368 890 1039 1423 1424 1425 1430 1432 1547 1548 1549 898 891 1431 1428 1433 1328 1429 1372 1434 1466 1469 1550 The classification of these allegations per Knighton's November 30,. 1984, memorandum is also included.

l l

Rob J. Bosnak, Acting Assistant Director Components and Structures Engineering Division of Engineering

Enclosures:

As stated cc:

F Cherny, DE

. Schierling, DL M. Ley, DL T. Sullivan, DE K. Manoly, RI f7 g

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7 CONTACT:

M. Hartzman, MEB:DE, x28445 j]

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s Task:

Allegation or Concern No.

368 898 1328 1372 1434 1466 1469 1550 ATS No.:

BN No:

RV 84A071 RV 84A073 RV 84A88 t

RV 84A91 Characteristics Deficiencies in the Diablo Canyon Project " Quick Fix" program.

Implied Significance to Plant Design, Construction, or Operation Piping supports: modified under the DCP " Quick Fix" program may contain deficiencies which could lead to pipe overloading.

Assessment df Safety Significance The staff's review of the " Quick Fix" program is fully (described in Section 6 l

of SSER 25, " Quick Fix Program, License Condition 2.C. ll)

Item 6."

Staff Position The staff has found the PG&E and IDVP responses to its review acceptable.

The findings are described in SSER 25, Section 6.

These allegations are th,erefore considered resolved.

Action Required

None, i

Task: Allegations or Concerns Nos: 890 891 ATS No:

BN No:

Characterization Same person who originally performed a calculation (designer) was also the person who checked the calculation (checker).

Design did not leave controlled documents that they needed to reduce the possibility of calculation errors.

PG8E stated otherwise.

Implied Significance to Plant Design, Construction, or Operation Possible design errors not discovered thru independent checking or thru lack of controlled design documents may lead to overestimation of piping support load carrying capacities.

Assessment of Safety Significance The concerds expressed in these allegations were previously addressed under Allegations 79, 82 and 97, SSER 22, which resulted in license conditions 2.C(11), Items 1 and 7.

These license conditions required PG&E to requalify independently in San Francisco all small bore piping computer analyzed supports which were dvaluted at the site.

Staff Position.

An NRC task group reviewed and audited the resolution of the license condition and found tham acceptable. These findings are fully described in SSER 25, Section 1.

These allegations are therefore considered resolved.

I Action Required i

None.

l

. Task: Allegation of Concern No. 1039 ATS No:

BN No:

Characterization Engineering group did not receive any technical guidance in perfonsing stress calculations. Consequently items were omitted in their calculations; also no training program documented.

Implied Significance to Plant Design, Construction, or Operation Small bore piping supports may have been designed incorrectly leading to overestimation of support load capacities.

Assessment of Safety Significance See Allegation of Concerns No. 890, 891.

Staff Position The audit which the NRC task group performed during the resolution of License Condition 2lC(11), Item 1 included interviewing, on a sample basis, personnel who were directly involved in the requalification of the pipe supports; and the review of various design criteria documents which provide guidance and instructions to designers. The technical training of the interviewed personnel was determined to be acceptable, and the design documents were also found to be acceptable in providing the required design guidance. This allegation is therefore resolved.

Action Required No'ne.

I i

i l

l I

. Task:

Allegation or Concern No.

1423 ATS No:

BN No:

Characterization PG&E made an incorrect statement when they stated that " warping normal and shear stresses were present in only a few cases due to the preponderatice of angle and tube steel shapes."

Implied Significance to Plant Design, Construction, or Operation The exclusion of. warping normal and shear stresses for beam shapes where these stresses may be'significant could lead to underestimation of the peak stresses in pipit:g supports.

Assessment of Safety Significance PG&E has sutisfactorily addressed this concern in response to License Condition 2.C.(II), Items 1 and 7, as described in SSER 25 Sections 1 and 7.

Staff Position The statement by PG&E is basically correct. Stresses due to warping effects are generally small for beam shapes such as angles and tubes, as stated in the engineering literature, and are therefore considered as secondary and negligible in the structural analysis of such members. The concern therefore has no basis and this allegation is considered resolved.

I Action Required None.

t

Task:

Allegation or Concern No.

1424 1431 ATS No:

BN No:

RV 84A88 Characterization PG&E should not have excluded certain snubbers on pipe qualified by the span rules from their review as discussed in the July 2, 1984 transcript.

The pipe stress group considered a pair of pipe supports in isolation when they must be considered in combination.

Implied Significance to Plant Design, Construction, or Operation Exclusion of snubbers from being reviewed may not ensure that these snubbers will operate properly under seismic conditions, thus inducing higher piping stresses than designed for.

Closely spaced supports designed without consideration of interaction effects may overstress the supported piping.

Assessment of Safety Significance

~

The concerns expressed in these allegations were addressed by PG&E in its response to License Condition 2.C.(ll), Items 2 and 3 regarding the general issue of proximity of rigid supports and snubbers to other rigid supports, snubbers aHd anchors for small bore piping.

(See SSER 25, Sections 2 and 3).

Staff Position i

An NRC task ~ group reviewed the PG&E response and found it acceptable.

These findings are fully described in SSER 25, Sections 2 and 3.

These allegations are considered resolved.

Action Required None.

i l

Task:

Allegation or Concern No.

1425 Allegation or Concern No.

1428 Allegation or Concern No.

1429 ATS No:

BN No:

RV 84A088 Characterization The alleger questions whether or not serious errors were found in light of the fact the NRC has only audited 21 of the 357 supports, of which only 191 were completed at the time of the audit.

Examination of the audit performed by the i

NRC into the 21 of 191 supports casts serious doubt as to what PG&E has not done, as well as the NRC staff's standards.

The modifications since 1981 are not enough to counteract the effects of a.75G earthquake.

Implied Significance to Plant Design, Construction, or Operation

~

There is a possibility that serious errors exist in the designs of the 357 small bore computer analyzed supports which could lead to underestimation of the loads acting on these supports and overstressing of the pipes, when subjected to-the Hosgri earthquake.

Assessment of Safety Significance i

An NRC task group audited the PG&E review of the designs of the 21 supports in depth to check compliance with License Condition 2.C.( 11), Items 1 and 7, including interviewing some of the analysts.

In addition, the review of the 357 supports constituted a second level review by the Bechtel San Francisec Office. No significant errors were found in the review.

Staff Position.

The results of the audit and the findings are described in detail in SSER 25, Sections 1 and 7.

The likelihood of finding serious errors in the supports which were not reviewed is considered to be very small. The audited supports were found to satisfy the appropriate design allowable under the Hosgri seismic loading, and, on a sample basis, all supports are considered as capable of sustaining the seismic loading due to the Hosgri earthquake. These allegations are therefore considered resolved.

Action Reouired None.

Task:

Allegation or Concern No.

1430 ATS No:

BN No:

RV 84A088 Characterization Concerns about (1) a branch line being subjected to axial buckling or tensile stress and (2) whether this was considered in the qualification of 15000 ft.

of small bore piping qualified by span rule.

Implied Signficance to Plant Design, Construction, or Operation Restrained lines subjected to large axial loads due to anchor movements may fail due to tensile tearing as compressive buckling or collaspe, if these failure modes were not considered in the design of 15000 ft. of small bore piping qualified by span rule.

Assessment of Safety Signficance The staff has evaluated the qualification of the 15000 ft. of small bore piping, based on a sample of 5000 ft. which were computer analyzed by PG&E. This evaluation'is described in SSER 25, Section 8.

In addition, the licensee has also addressed this allegation specifically.

Staff Position The staff has reviewed the licensees response to this allegation. He has stated that the computer analysis of the 5000 ft sample considered all problems that included prescribed seismic and thermal anchor motion. Supports were placed such that piping bending allowables were met.

This precludes the type of failure modes expressed in the concern. The staff finds the response acceptable and considers these concerns resolved.

Action Required No,ne.

. Task:-

Allegation or Concern No.

1432 Allegation or Concern No.

1433 ATS No:

BN No:

RV 84A088 Characterization Many of the lines subjected to high pressure and temperature will grow more than anticipated resulting in failure of the support or of the pipe.

The walkdown program,at Diablo Canyon did not include checking the seismic clearances on pipe and supports to ensure adequate clearance.

Implied Significance to Plant Design, Construction, or Operation Unaccounted for or unchecked radial growth of large bore pipes due to high temperature and:large internal pressure may cause binding within rigid supports, leading to support and pipe overloading and possible failure.

Insufficient seismic clearance may lead to impacting and damage to adjacent pipes or structures.

Assessment of Safety Significance PG&E has performed walkdowns of piping systems at elevated temperatures to verify that piping systems are restrained only as designed.

An NRC task group has Feviewed the PG8E procedures for walkdowns during initial plant heat up and during power assension, and participated in such walkdowns as required by License Condition 2.C,(13), Item 5 and described in SSER 25.

Staff Position l

The NRC task group determined that PG&E had conducted an acceptable visual verification that piping systems and supports were properly restrained to preclude damage during.heatup, power assension and seismic motion. This included verification that free movements of pipes within rigid restraints were not impeded due to binding, particularly for large bore hot piping.

Since such binding is precluded, the procedures automatically account for pipe radial growth. This allegation is therefore considered resolved.

Action Reauired None.

9-Task: Allegation or Concern No. 1547 ATS No:

BN No:

Characterization:

Change of seismic design reviews criteria for pipe supports which permitted supports which would have failed to pass in calculations.

Implied Significance to Plant Design, Construction, or Operation Piping support load capacity may be smaller than required, leading to possible overstress.

Assessment of Safety Significance The staff reviewed the technical instructions issued by PG&E for designers in San Francisco office re License Condition 2.C.(11) qualifying the piping supports as required by

, Item 1.

These instructions included the verification that the 16 ads from the latest pipe stress analysis were used.

Staff Position The NRC task group confirmed as part of the audit performed on the PG&E license condition effort, that the designers had verified that the latest loads had been used in the qualification of the piping supports. The allegation is therefore considered resolved.

Action Required None.

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Task: Allegation or Concern No. 1548 ATS NO:

BN No:

Characterization Failure to provide justification for use 5 X less pipe supports than AISC requirements.

Implied Significance to Plant Design, Construction, or Operation This allegation: pertains to the calculation of safe unbraced lengths for angle members. Exceeding these unbraced lengths can lead to lateral /tosional buckling of such. members.

Assessment of Safety Significance The staff has performed additional review of document's related to this issue and has also communicated with the AISC regarding the applicability of the l

Manual of Steel: Construction rules to the design of angle members in bending.

The AISC has stated that the unbraced length requirement in the manual is not applicable to angle members.

Staff Position The staff has accepted the technical basis used by the licensee for specifying the unbraced lengths of angle members used in piping supports, and has -

determined that there is no basis for the concern.

The allegation is therefore considered resolved.

Action Required None.

. Task: Allegation or Concern No. 1549 ATS No:

BN No:

Characterization Continued design errors due to inaccurate assumptions used in design calculations.

Implied Significance to Plant Design, Construction, or Operation Design errors may lead to underestimation of piping support load carrying capacities and piping overstress.

Assessment of Safety Significance

~

The concerns raised in this allegation have been addressed in the assessments of Allegations Nos. 1642-1648.

l Staff Position The resolution of this allegation conforms to those of Allegations Nos. 1642-1648.

l l

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' Classification of Allegation within MEB scope of Review (per memo of November 30, 1984 from George Knighton.)

368 D

890 D

891 D

1039 D

1328 D

1372 D

1423 R

1424 D

1425 D

1428 D

1429 D

1430 D

1431 D

1432 D

1433 D

1434 D

1466 D

1469 D

1547 0

1548 R

1549 D

1550 D

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