ML19323G519

Submits Supplemental Reply to IE Bulletin 79-14, Seismic Analysis for As-Built Safety-Related Piping Sys. to Date, 352 of 589 Seismic Class I Isometric Packages Have Been Audited & 479 Field Audit Craft Actions Completed

ML19323G519
Person / Time
Site:	Fort Saint Vrain
Issue date:	04/23/1980
From:	Swart F PUBLIC SERVICE CO. OF COLORADO
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
IEB-79-14, NUDOCS 8006040040
Download: ML19323G519 (4)

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April 23,1980 .___ .-

Fort St. Vrain Unit No. 1 P-80091 ' '

Mr. Karl V. Seyfrit, Director -

Nuclear Regulatory Commission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive .

Suite 1000 Arlington, Texas 76012

Subject:

Safety Related Piping System Audit

References:

PSC. Letter P-79161 dtd 8/1/79 PSC Letter p-79198 dtd '9/4/79 PSC Letter P-79238 dtd 10/15/79 PSC Letter p-79292 dtd 12/4/79 PSC Letter P-80029 dtd 2/15/80

Dear Mr. Seyfrit:

This supplemental reply to I&E Bulletin 79-14 is to continue PSC's October 15, 1979 commitment to report in summary fann discrepancies and corrective ections associated with the Fort St. Vrain seismic review program and to report the status of program progress.

To date, 352 seismic Class I isometric packages out of a total Class I population of 589 have been audited. Included therein are 313 out of 348 sensitive system isometric packages. Sensitive systems,

! f.e., systems which must remain operable in order to protect the health l

and safety of the public in the event of an accident as defined in the FSAR, Design Basis Accident Number One, continue to have high audit priority. The piping system isometrics which will be audited are divided into two segments, 21/2 to 8 inch and 10 inch and above for analysis purposes. Auditing of the 21/2 to 8 inch sensitive system isometrics, and hangers has been completed. The remaining 2 1/2 to 8 inch non-sensitive systems should be complete relative to audit within 60 days. By December 1980, all seismic Class I and Class II 21/2 and larger plant piping systems attached to Class I piping and Class I piping supports will have been audited and the craft actions which were issued in the audit phase of the program will have been completed.

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Mr. Karl V. Seyfrit April 23,1980 Page 2 i i

To date, 701 field audit craft actions have been initiated of which 479 have been completed by construction. The numerical difference-between " initiated craft actions" and " craft actions completed by construction" reflects the review, approval and construction process required by the seismic program procedures. Because one of the craft actions may resolve more than one discrepancy, the discrepancies are being reported as percentages of the total discrepancies identified rather than by the number of craft actions as was reported in our letter of February 15, 1980. (PSCLetterP-80029, attached.) l The most common types of corrective actions are as follows:

1. Remove undocumented attachments from the hanger structure.

2. Modification of "U"-bolts.  !

3. Restoration of hanger structures to intended configuration. l NOTE: Table 1 contains a more detailed tabulation of audit discrepancies.

The types of corrective actions listed in Table 1 are the same as were reported in our February 15, 1980 program status report. The majority of these corrective actions continue to be within the AISC portion of the hanger structure and occur on nearly every pipe hanger.

From the PSC sample audit conducted in August 1979, it was concluded that hanger discrepancies do not normallv result in hanger stress criteria violation and those instances in the sample audit when hangers were over stressed, the associated piping systems remained within FSAR allowable stress limitations. Since the intent of the field audit craft action program is to identify and resolve the major hanger discrepancies, PSC will have effectively eliminated all of the major discrepancies which may have resulted in hanger impairment upon completion of the craft action program. It is PSC's conclusion that upon completion of the field audit craft action program for sensitive systems, the health and safety of the public will be ensured.

As discussed in our letter of February 15, 1980, we have modified our seismic review program to utilize analytical methods to document the seismic adequacy of all the 21/2 to 8 inch piping systems which are consistent with the analytical methods by which the 10 inch and larger systems were seismically qualified. I&E Bulletin 79-14 requires the licensee to reanalyze only the specific portion of a system which is affected by an as-built vs as-analyzed nonconformance. The additional effort to omputer analyze the 21/2 to 8 inch piping systems will provide PSC with upgraded and consistent seismic documentation which will verify the conservative nature of both the original design and the current field audit craft action program.

Mr. Karl V. Seyfrit April 23,1980 Page 3 The audit and field audit craft actions will be complete by December 1980, which will bring Fort St. Vrain into basic compliance with the intent of I&E Bulletin 79-14. However, the expanded analytical seismic program which includes the AISC hanger structure, computer analysis and complete seismic redocumentation will require a completion date between June and September,1981. This extension is due to the quantity of computer analysis necessary to redocument all Class I 21/2 to 8 inch piping systems, availability of pipe stress and structural stress analysis and computer processing limitations relative to the number of analyses that can be processed at one time. If, during the document review and computer analysis process utilizing expanded criteria, a system impairment is identified, PSC will follow the necessary Technical Specification action statements. If there are any questions, please contact this office.

Very truly yours,

[

b , M /A M Frederic E. Swart Nuclear Project Manager FES/Lf1M/pa j Attachment 1

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a TABLE I CORRECTIVE ACTION

SUMMARY

Discrepancy Type Percent *

> 1. Repair structural welds 8%

2. Remove undocumented attachment from hanger structures 16%

3. Shim plates - minor item incorporated into item 5

4. Modify U-bolts 17%

5. U-bolt adjustment 8%

6. Restore hanger structures to intended configuration 17%

7. Install lugs and clips 6%

8. Add nuts and washers and tighten loose hardware 9%

9. Install new hanger 10%

10. Install clamps 4%

11. Change anchor bolts 5%

• Frequency of occurrence of a discrepancy type as a percentage of total discrepancies identified.

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O i jazd puhuc service company *e conende 16805 Rd.191/2, Plattevil' e, Colorado 80651 February 15, 1980 Fort St. Vrain Unit No. 1 P-80029 Mr. Karl V. Seyfrit, Director Nuclear Regulatory Comission Region IV Office of Inspection and Enforcement 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012

Subject:

Safety Related Piping System Audit

Reference:

PSC Letter P-79161 dated Aug. 1, 1979 PSC Letter P-79198 dated Sept.4,1979 PSC Letter P-79238 dated Oct. 5, 1979 NC t.etter P-79292 dated Dec. 4,1979 NRC Letter G-79210 dated Dec.14, 1979

Dear Mr. Seyfrit:

This supplemental reply o I&E Bulletin 79-14 is to satisfy PSC's commitment in the October 15, 1979 letter (P-79238, attached) to report in suninary form all discrepancies and corrective actions associated with our seismic review program. In addition, this letter is intended to supply additional information necessary to facilitate the NRC evaluation for further exten:fon of PSC's ,

completion date for this bulletin. The following paragraphs present the program status and the justification for PSC's request for an extension.

To date, 221 Class I isometric ' .kages out of a total population of 589 have been audited of which 200 are s.nsitive system isometric packages. Sensitive systems are defined as those systems which must remain operable in order to protect the health and safety of the public in the event of a accident as defined in the FSAR, Design Basis Accident Number One. We anticipate completing the sensitive system audit in May,1980 and completing the audit of the remaining seismic Class I systems in September, 1980. These estimated completion dates are based upon inclusion of the American Institute of Steel Construction l (AISC) portion of the hanger structure as part of our field audit program as l l

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rww m y c er J l O D defined in SDCC Procedure number 005. Experience has indicated that approximately 75 to 80% of the required audit time is associated with the AISC portion of the hanger support steel. This results from the need to confinn all physical measurements and configuration details pertinent to a given support. These details include verification of weld sizes and types, element lengths and material size and shape, orientation and nature of the attachment between the piping and the support, proper location and identification, plus any other details needed to properly represent the structure for analysis. Discrepancies found during the audit are being resolved, as outlined in SDCC Procedure #012, by returning the discrepant item to it's originally intended configuration via a field audit craft action. The process of correcting any discrepancy is started as soon as it is identified by an auditor. Currently we have identified 437 discrepancies and have issued 270 craft actions to construction of which 155 are complete.

The numerical difference between " identified discrepancies" and " issued craft actions" reflects the review and approval process required by the seismic program procedures. To date, the majority of craft actions resolve discrepancies in the AISC portion of the hanger structure.

The most common types of discrepancies are as follows:

1. Repair of undersized welds.

2. Removal of non-documented attachments to the hanger structure.

3. Replacement of missing nuts, washers and shim plates.

4. Restoration of hanger structure to intended configuration.

NOTE: Table 1 contains a more detailed tabulation of audit discrepancies.

These types of discrepancies are similar to those found in PSC's sample audit completed in the latter part of 1979. The details of the sample audit have been presented in previous correspondence concerning this bulletin and discussed in several meetings with NRC I&E personnel. PSC has concluded from the sample audit that discreoancies between the as-built configuratica and hanger documentation would cccur on nearly every hanger, but as was demonstrated by the analysis performed on the sample audit discrepancies, the seismic design at Fort St. Vrain is so conservative that hanger discrepancies do not normally result in hanger stress criteria violation. In those instances in the sample audit when hangers were over stressed, the associated piping systems remain within FSAR allcwable stress limitations with the over stressed hanger excluded from the piping analysis. As a result, it is PSC's conclusion that even though discrepancies exist, system operability is not in jeopardy.

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Following the field audit and associated post audit drafting a 100%

QA field verification of the as-built drawings is being performed to snsure that quality documents are being utilized for seismic evaluation. The QA verification of the audit results has progressed to the point where evaluation of the as-built drawings has just begun. This evaluation consists of 1) an analytical engineering evaluation of the piping so as to confinn the piping reactionary loads which are used in the hanger analysis and 2) an analytical engineering evaluation of the hanger when there is a change in the input loads or if a discrepancy exists between the pre-audit and post-audit documentation. This process is required to completely document the seismic acceptability of the Class I piping systems. Computerized analytical methods, which are consistant with the methods used in 10 inch and above piping at Fort St. Vrain, will be used to perform all analytical engineering piping evaluations. Although this represents a change from our previous position, it is necessary because the statements in our October 15, 1979 letter implied use of simplified methods for evaluating 10" and above piping when in fact it was intended to use the original computerized methods. Also minor variations from the simplified analysis technique can not be quantitatively evaluated for the assessment of seismic acceptability. To date the piping evaluation program has not identified any reportable occurrences, however, should any be identified pSC will follow the necessaryTechnical Specification action statements.

In sunnary, PSC's audit results to date indicate that Fort St. Vrain does not have a seismic Class I piping configuration problem. Our discrepancies are almost entirely concentrated in the AISC pipe supports. The majority of these discrepancies are minor in nature but will result in craft actions on approximately 90% of the Class I pipe supports. The inclusion of AISC pipe supports details has resulted in a pmgram that is extensive but meets our interpretation of the intent of I&E Bulletin 79-14. PSC has chosen to proceed with our program as originally intended in that we continue to believe that the finished product is in the best interests of both the Commission and the Licensee. Our current project schedule has not changed in that we are projecting a project completion date of December,1980 with a pessimistic completion date of March, 1981.

. Very truly yours,,

[. A Frederic E. Swart Nuclear Project Manager LM1/RLC/scp Attachment I

Attachment

( ]) ,) P-80029 l

TABLE 1 Craft Action Sumary I t Discrepancy Type Quantity

1. Repair structural welds 117

2. Remove non-documented attachments 93 from Class I structures.

3. Add shim plates

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4. Modify U-bolt 29

5. U-bolt adjustment 55 i

6. Restoration of hanger structure to intended configuration 76

7. Install lugs / clips 23

8. Addition of nuts and washers 14

9. Install new hanger g

10. Install clamps 13

11. Change anchor bolts 1

437 Total k

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