05000369/LER-1982-039, Forwards LER 82-039/01T-0.Detailed Event Analysis Encl

Forwards LER 82-039/01T-0.Detailed Event Analysis Encl

ML20054M120
Person / Time
Site:	McGuire
Issue date:	06/30/1982
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20054M121	List: 05000369/LER-1982-039, Forwards LER 82-039/01T-0.Detailed Event Analysis Encl 05000369/LER-1982-039-01, /01T-0:on 820609,bolts Connecting RHR Heat Exchangers to Seismic Support Steel Found Missing.Caused by Misalignment Due to Design Error.Mod Designed to Negate Bolt Need & Tech Spec 3.5.2(c) Temporarily Waived
References
NUDOCS 8207090275
Download: ML20054M120 (4)

LER-1982-039, Forwards LER 82-039/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
3691982039R00 - NRC Website

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s e r.- power,0 June 30, 1982 u3. ce3 Mr. J. P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Re: McGuire Nuclear Station Unit 1 Docket No. 50-369

Dear Mr. O'Reilly:

Please find attached Reportable Occur'!ence Report R0-369/82-39. This report concerns T.S. 3.5.2, "two independent.'ECCS subsystems shall be operable with each subsystem comprised of:...c. one operable residual heat removal pump,...".

This incident was considered to be of no significance with respect to the health and safety of the public.

This event was the subject of a technical specification change submitted by Mr. A. C. Thies' (DPC) letter of June 9, 1982.

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PBN.ls Attachment cc: Director Records Center Office of Management and Program Institute of Nuclear Power Operations Analysis 1820 Water Place U. S. Nuclear Regulatory Commission Atlanta, Georgia 30339 Washington, D. C.

20555 Mr. P. R. Bemis Senior Resident inspector - NRC McGuire Nuclear Station OW1W.1. CVh 8207090275 820630 7[

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DUKE POWER COMPANY MCGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NO. 82-39 Report Date: June 30, 1982 Facility: McGuire Unit 1, Cornelius, NC Identification:

Bolts which connect the top of the residual heat removal (ND) heat exchangers to seismic support steel were found to be missing.

Description

On June 7, 1982, while Construction personnel were trying to fasten the Unit 2 ND heat exchcngers to the overhead structural steel they found that the holes in the steel w'ere out of alignment with the holes in the heat exchanger lugs.

Since the common structural steel drawings that were used to install steel on both units showed no changes for Unit 1, the personnel checked the Unit 1 ND heat exchangers and found that the bolts were not installed. Construction QA contacted station licensing personnel and informed them of the problem. Construction QA also contacted Design Engineering (D.E.) and asked them to determine the impact of the missing bolts on the safety of the ND heat exchangers. On June 9, 1982 Mechanical D.E. responded that the east-west movement of the top of the ND heat exchanger during a seismic event with the bolts missing could place stresses on the heat exchanger that exceeded the design basis. Meanwhile, both NRC resident inspectors were notified as well as a regional inspector who was visiting in the company offices at the time.

Design Engineering decided that the problem could be corrected within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and the NRC agreed to give an exemption from Technical Specifications to cover that period.

Shims were installed to lessen the clearance between heat exchanger lugs and the supporting steel. The structural steel was then strengthened to compensate for the modified loading method.

Unit I was operating at 75% power during the incident. Both ND heat exchangers were declared inoperable under Technical Specification 3.5.2(c) on June 9, 1982 as soon as the problem was identified. A temporary exemption from T.S. 3.5.2(c) was granted to last for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> while repairs were made.

Repairs were completed on both heat exchanger supports on June 10, 1982. The design reviews were completed and the two heat exchangers were declared operable on June 11, 1982.

Evaluation: The ND heat exchangers are vertically oriented cylinders approximately 25 feet long.

Structural support was provided by a steel frame connected to the bottom of the heat exchangers.

In addition, an overhead seismic support was also built.

Due to an error in design, holes in the plates welded to the bottom of the overhead seismic support were misaligned with the holes in the seismic lugs on the heat exchanger by approximately 3/16 inch so that the bolts could not be installed without some modification. The same crew that erected the seismic support and anchored it to the walls was responsible for bolting it to the heat exchanger.

It has not been possible to determine why the crew failed to get the misalignment problem resolved and complete the connection.

O Report No. 82-39 Page 2 Two of the inspection programs that are used to control work in this area are the M-10 program, which covers bolting of equipment to structural steel and the bolting of structural steel to walls, and the M-18 program, which covers bolting structural steel members together.

Some construction personnel feel that the missing bolts would clearly fall under the M-10 program, but others feel that the M-18 program could be construed to apply as well. The significance of which inspection program would apply involves document reviews conducted after the inspections were complete.

The reviewer would examine the document package to verify that inspection forms to cover all of the work were present. ND documents were reviewed prior to the provi-sional turnover to steam production in 1977, but the structural steel was not included in the turnover and may not have been complete at that time.

Another document review and reinspection program occurred from November, 1980 through January, 1981.

Reviewers checked to see that the documentation contained in each package covered all of the work done on the structures. The ND heat exchanger packages contained two M-10 and one M-18 forms that related to the overhead structural steel.

The M-10 forms documented inspections of wall anchor bolts as indicated by the bolt sizes specified, the anchors to be used, and the general locations of the fasteners. The M-18 form, however, could be construed to include all of the wall anchor, structural steel internal, and structural steel to ND heat exchanger bolts involved with the upper ND structural support. This form specified the bolts and steel to be inspected by the civil design drawing number on which the structures were shown and the general physical location of the structures in the plant. A comment under the RESULTS OF INSPECTION section of the form states " Anchor Bolts & A325 Bolts checked and found to be acceptable".

("A325" is an American Society of Testing Futerials Specification which identifies the strength characteristics, but not the size, of the bolts.)

Inspection documents were initiated by one of two methods when this work was being done.

Construction technical support personnel could generate the forms before they were needed or upon request of the craf t personnel doing the work.

It is not possible to determine which method was used in generating the ND heat exchanger structural steel forms; but, however it was done, the M-18 form was certainly broad enough to include the missing bolts.

The effect of the misaing bolts on the safety of the ND system was that the top of the heat exchangers could move further in the east-west direction during a seismic event.

The design limited movement to about 1/16 inch, however, movement of the heat exchanger without the bolts could have been as much as one inch before contact was made with the support. Once contact was made, the angle iron would have deformed, allowing some additional movement.

Piping attached to the heat exchanger would plastica 11y deform when subjected to loading of this magnitude, possibly resulting in a failure of the system. The foregoing scenario assumes the worst possible alignment of all the components. A realistic case would be less severe.

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Safety Analysis

llad a seismic event occurred with the defective ND supports un-corrected, some damage to the ND piping or heat exchangers could have resulted.

Both heat exchangers could have been affected by east-west accelerations.

No seismic events occurred before the discrepancy was corrected so the health and safety of the public were unaffected.

Report No. 82-39 Page 3

Corrective Action

A modification was designed to eliminate the need for the bolts by closing the gap between the lugs and the angle iron, and strengthening the support.

Shims were installed between the seismic lugs and the angle iron. Plates were then welded to the two existing plates adjacent to the shims. To compensate for the new stresses, additional stiffener plates were welded on each side of the existing stiffener plates with a 1/2" gap between the old and new plates.

Document packages for the other four heat exchangers with top mounted seismic supports were examined to insure that the mounting bolts had been installed and inspected.

M-10 inspection forms that identified the mounting bolts were especially looked for, and were found for the Moderating Heat Exchangers, Letdown Reheat Heat Exchanger, and Letdown Chiller Heat Exchanger, but not for the Letdown Heat Exchanger.

The Letdown Heat Exchanger was inspected and the mounting bolts were verified to be in place. The ND heat exchangers are unique in that the seismic support steel is free standing and does not depend on the heat exchanger for vertical support.

Structural steel on the other heat exchangers depends on the attachment bolts at the vessel for vertical support so the erection of the support requires installation of the bolts.

The inspection programs have been changed, since the ND heat exchangers were completed, to require the inspector to mark the construction drawings indicating which bolts and steel sections have been inspected. To prevent confusion on which inspection should cover bolting of structural steel to mechanical equipment the following statement has been added to the M-18 procedure:

"The M-18 inspector will j

be responsible for restraints and lateral supports attaching to mechanical equipment l

including bolting to the equipment." The policy on inspection document preparation has been modified to require preparation of the documents before a job begins.

In this way uncompleted documents would identify outstanding inspection requirements.

The modifications on the ND seismic supports were reviewed and the work inspected.

Q.A. document reviews will insure that inspection documents are complete.