ML20080T005

Summary & Evaluation Rept of Rl Cloud & Assoc Rept, Diablo Canyon Unit 1 Idvp - Small Bore Piping Rept

ML20080T005
Person / Time
Site:	Diablo Canyon
Issue date:	09/01/1983
From:	BROOKHAVEN NATIONAL LABORATORY
To:
Shared Package
ML20080S984	List: ML20080S989 ML20080S991 ML20080S994 ML20080S998 ML20080T003 ML20080T005 ML20080T009 ML20080T013 ML20080T016
References
FOIA-83-483 NUDOCS 8310180623
Download: ML20080T005 (6)

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SUMMARY

AND EVALUATION REPORT

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Independent Design Verification Program:

Small Bore Piping Report

, Report No. ITR '30, Revision 0 f

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h Autho r Robert L. Cloud and Associates, Inc.

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-INTRODUCTION

-The Interim Technical Report 30 (ITR 30) was prepared by Robert L. Cloud and associates '(RLCA) for the Diablo Canyon Nuclear Power Plant Independent Design Verification Programl(DCNPP-IDVP). The report summarizes the IDVP review of the methods used to qualify small bore piping which is not computer analyzed (span rules) and the field verification of the implementation of these span rules for a sample of small bore systems. The span rules were found to generally satisfy the licensing criteria and to be correctly impl emented.

SUMMARY

OF REPORT A large number of Design Class 1 piping systems in the DCNPP were '

qualified using_ span rules. These rules specify the maximum allowed distance between supports, the span, and provide guidelines for support placement. Two groups of piping _were qualifed by this method. The first group consisted of

• field routed piping 2 inches in diameter or smaller, and the second group consisted of office designed piping with diameters between 2-1/2 and 6 inches.

, Pacific Gas and Electric (PG&E) Drawing No. 049243 " Pipe Supports for Field Run,' Design Class 1 Piping Diablo Canyon" established the span rules for the first group, while PG&E Drawing No. 049239 " Pipe Support Spans for Non-Analyzed Class I Piping Diablo Canyon" established the span rules for the second group.

The methodology implicited in both sets of span rules involves limiting the seismic response of piping systems by controlling the length of spans between, and the placement of, seismic ivpports. The methodclogy is based on enveloped Hosgri floor response spectra with 2% damping and maximum floor eccentricities. Implementation requires the use of enginac.'ing judgment as the rules do not address all possible piping configurations. If properly applied the method yields a fundaaental natural frequency in excess of 15 Hz for the piping system under consideration.

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'The verification included a review of the span rules to establish that

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piping designed to comply with the rules satisfied licensing criteria and c field verification of compliance with the rules. In the review, the para-neters to be'used for the ' sample selection were first established. This included a consideration of pipe size, material properties, design tempera-tures, pressures and natural frequencies. Next, analyses were performed fo^

four small~ bore piping configurations described in the rules (single span, multiple spans, multiple spans with 2 changes in ' direction and an offset case) considering pressure, gravity and seismic loadings and the effects of welded attachments (i.e. , lugs installed to provide axial . constraint). Stresses were then calculated based on equation 12 of ANSI B31.lb 1973, combined and com-pared to the allowables of ANSI B31.1,1973 for both normal conditions and faulted conditions. All analyses for all configurations were not made.

Instead, a representative sample was used. .

The paraneters used in the sample analyzed were chosen to minimize the degree of conservatism in the stress results and or to correspond to prevalence in the field. Summarizing the parameters chosen and the selection criteria:

Sample sizes 2", 3" and 4" because they are widely used.

Schedule 10S and 40 as they gave the lowest natural frequencies.

Allowable stress of 12000' psi and Young's Modulus of 27.7 x 106 psi ,

corresponding to lower strength bound for materials.

- Temperatures of 165*F for S.S. and 200 F for steel corresponding to maximum temperatures.

Pressures of 50 psig and 255 psig for 2", 3", and 4" SCH10S pipe respectively and 700 psig and 1085 psig for 2", 3" and 4" SCH 4G

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pipe respectively corresponding to maximum pressures.

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Uninsulated pipe weight corresponding to span rule limitation.

In addition, for the seismic loading, horizontal and vertical envelope spectra were developed considering Hosgri spectra for elevations at or below 140 feet, in the containment and auxiliary buildings, using maxinum building eccentri-cites.

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The report provides tabulated listings of the results of this review.

Pipe stresses -for small bore piping met the licensing criteria for normal and Hosgri condi t. ions. Some comparisons to results presented in the PG&E Hosgri reevaluation report showe[f that the PGSE stress estimates were higher than those calculated in this review. Lastly, frequency estimates below 15 Hz were noted for several span rule configurations.

Field verification for a sample of three runs of small bore piping, each including more .than twenty supports, was performed. The verification address-ed conformance of as-built conditions to the span rules, documentation of support types, locations ano dimensions, and the reasonableness of the IDVP analysis assumptions. The selected piping was found to be installed in accordance with the span rules. However, pipe routing and suport configura-tions were observed on other pipe runs which were not spccifically addressed ,

by the span rules and were presumable designed by PGSE using engineering judgment. The use of engineering judgment by PG&E in applying the span rules will- be the subject of further IDVP serification following the Diablo Canyon Project corrective action program.

Nine error and open item reports were issued as a result of the span rule review and field inspection, E01's 1024,1043-1048,1058 and 1059. Except for E01's 1058 and 1059 all E0I's were issued to note differences between the field condition and design isometrics. All these were closed as deviations when further review indicated the correct quantities or dimensions were used in the design analyses. E01 1058 was classed a A/B error and was issued to note the possibic exceedance of allowable stresses for certain one or two lug configurations, assuming a ' maximum pipe span. Further analyses showed the stresses to de below allowables. E0I 1059 was classed an error A/B and noted disciepancies in the PGSE repor't, Preliminary Blume Report, and the fact that the span rules did not address insulation weight or 6 inch piping.

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Although the span rules generally satisfied the licensing criteria the following generic concerns were noted: .

The span rules do noi. address insulated' pipe.

The span rules do not limit the areas were small bore piping is installed and may not satisfy _ licensing criteria for high seismic response areas.

The Hosgri report allows the design of 6 inch pipe by the span rules, but these rules do not _ address 6 inch pipe.

The fundamental frequency for _ some span rule configurations are less than 15 Hz.

For 3 and 4 inch pipe, the span rules do-not limit the unsupported distance from a change of direction containing a axially re-strained run of pipe.- ,

A demonstration of'the conservatism of the span rule approach was not presented in the Blume Report, as implied in the Hosgri Repo rt.

In addition, the use of engineering judgement, the verification of maximum vertical and horizontal spans and the field marking of hangers were items noted. All these items and concerns will be addressed by the DCP corrective action program and verifled by the IDVP.

EVALUATION RLCA has made.a reasonable ef fort to assess the adequacy of span rule' criteria. Conservative assumptions, coupled with acceptable analysis techniques were usea to investigate the rules and establish the level of compliance with the licensing criteria. Although every variant allowed by the span rules'was not individually evaluated the bounding cases developed and analyzed seemed appropriate. The RLCA review did reveal and note various deficiencies and omissions in the criteria. The IDVP has committed to the persuance of these until final resolution. Accepting that a comprehensive description of the span rules was provided in the report and assuming that the

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RLCA calculations were correct, the review of these criteria is acceptable and demonstrates their general adequacy.

As may be inferred from the above, two weaknesses in the report are the failure to present the span rules in total and the lack of any real descrip-tion of the models used in their verification. Without this information neither the comprehensiveners or correctness of the verification effort can be assessed. However, past detailed reviews of the RLCA verification ef forts

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have indicated they are both complete and correct.

The field verification performed was limited in scope and designed to verify the implementation of the span rules for pipe runs which matched span rule configurations. However, as stated in the report, numerous examples of pipe routing and support configurations not specifically addressed in the span ,

rules were noted and were presumably designed by the use of engineering j udg aer.t. This observation casts some doubt on the value of this verification e f fo rt. If the exception was the rule, then the fact that the rules are adequate is superfluous. A thorough. evaluation of these exceptions to establish their degree of compliance with licensing criteria must be under-taken to verify the PG&E design of small bore piping. The IDVP has committed to verify this use of engineering judgment by PG&E in applying the span rules following the DCP corrective action program.

One area neglected in this verification was the qualification of the supports used for small bore piping. Obviously these supports must be designed to carry generic, bounding loads, corresponding to the bounding conditions of the span criteria. Since RLCA has developed and analyzed bounding cases the inforration required for the support review should be

. ava il able. It is- anticipated that the IDVP will address this issue in a forthccming ITR en pipe supports (ITR 138). In any case, the verification of the PG&E design of small bore piping by span rules will not be complete mtil a corresponding review of small bore pipe supports is made.

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