ML20070M645

Part 21 Rept Re anti-rotation Keys for 6-inch MOVs Mfg by Velan.New Keys Machined on-site to Dimensional Requirements of New Drawings Supplied by Vendor Installed & Performed Satisfactorily

ML20070M645
Person / Time
Site:	Calvert Cliffs
Issue date:	04/26/1994
From:	Denton R BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-94 NUDOCS 9405020318
Download: ML20070M645 (4)

Text

,

<1 I< $

l l

Itontur E. Ihxs on llaltimore Gas and Electric Compmy Vice (* resident Calmt Cigs Nucle ar I'mru l'lant

~

Nuclear Energy 'I'3" C'A*' EI'b Y"'N"?

, i.ustry, Alaryland 2o(>$7 4to 5%2200 Ett 4455 li> cal 1Io 2(>o-4455 Baltimore j April 26,1994 l

l 4 I

l U. S. Nuclear Regulatory Commission i Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit No.1; Docket Nos. 50-317 10 CFR Part 21 Report Concerning Anti-Rotation Keys for 6-inch Motor-Operated Valves Manufactured by VrIan Baltimore Gas and Electric Company has recently discovered a problem with new vendor supplied anti rotational keys for 6-inch Velan motor-operated globe valves at our Calvert Cliffs Nuclear Power Plant Unit 1. This problem is considered to have presented a deviation in a basic component that could have created a substantial safety hazard at our facility and is reportable in accordance with 10 CFR Part 21 requirements.

This letter provides the information required to be reported to the Nuclear Regulatory Commission pursuant to 10 CFR Part 21. A verbal notification and written facsimile summary were submitted to the Nuclear Regulatory Commission Operations Center on April 1,1994.

I l Should you have any further questions regarding this matter, we will be pleased to discuss them with ,

you. l l

Very truly yours, l

n RED /CDS/bjd )

Attachment cc: D. A. Brune, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr., NRC r r, n 7 T. T. Martin, NRC P. R. Wilson, NRC R.1. McLean, DNR ,F

[g/f J. H. Walter, PSC 9405020318 940426

'fi PDR ADDCK 05000317 m _ _ _ _ _ - - - - -__ _ _ _ _ . -

U ____ ____PDR _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____ -

d NITACIIMENT (1) 10 CFR PART 21 REPORT CONCERNING ANTI ROTATION KEYS FOR 6-INCil MOTOR-OPERATED VAINES MANUFACTURED BY vel AN Calvert Cliffs Nuclear Power Plant, Unit 1 Docket No: 50-317 (i) Name and address of Individual making notification:

R. E. Den.,n, Vice-President, Nuclear Energy Baltinare i as and Electric Company Calvert Ciafs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, MD 20657 (ii) Ilusic Component Affected:

6-inch Motor-Operated Forged Bolted Bennet Globe Valve (iii) Firm Supplying Component:

Supplier / Fabricator:

Velan Valve Corporation 550 McArthur Montreal, Quebec I!4T 1X8 (iv) Nature of the Defect:

Calvert Cliffs Unit 1 is currently in a refueling outage. One of the actions performed during the outage was to replace the anti totation keys on all four 6-inch and one of eight 2-inch Velan Motor-Operated Globe Wives. Replacernent of the keys is recommended in Nuclear Regulatory Commission (NRC) Information Notice 93-42," Failure of Anti-Rotation Keys in Motor-Operated Valves Manufactured by Velan," and Velan Service Bulletin SB-106, " Globe Valve Stem Anti-rotation Key" The replacement keys are made of a tougher steel alloy that will not fail in a manner similar to that noted at other nuclear power plants. Key replacements at Calvert Cliffs are being done on these type of valves as they are overhauled during the refueling outages.

After replacement of a key in one of the 6-inch valves, the valve was stroked to verify proper operation. During this stroke test the key was observed to slip through its yoke (valve bushing) so that it was no longer performing its anti-rotation function. The valve stem then rotated freely inside the yoke, preventing the valve from moving. The key was examined and found to be undersized for its keyway. The same problem was noted for all four 'U_ nit 16-inch valves (1 MOV-615,625,635, and 645). The 6-inch valves are safety-related Low Pressure Safety Injection (LPSI) loop isolation valves. The problem did not exist for the 2-inch IIi,h 3 Pressure Safety Injection (IIPSI) loop isolation valve that had it's key replaced.

Investigation of the problem concluded that the keyway depth in all of the 6-inch valve stems is deeper than shown_in the vendor's drawings. The vendor has discovered that a design change to the 6-inch valves in the early 197ts increased the depth of the key slot in the valve 1of3

t NITACllMENT (1) 10 CFR PART 21 REPORT CONCERNING ANTI ROTATION KEYS FOH 6-INCII MOTOR OPERATED VALVES MANUFATURED BY VELAN stems. The vendor postulates that the deeper key slot was then compensated for by fabricating keys of proper dimensions to fit into the resulting keyways. This has been verified by measurement of one of the old keys that was removed from a 6-inch valve at Calvert Cliffs.

However, the ven6r now recognizes that the corresponding dimensional corrections to the key were not formally incorporated by revising the drawing of the key. Thus, when new keys were fabricated to the drawing dimensions,20 years later, they were too small for our valves.

The LPSI loop isolation valves isolate the LPSI supply. headers from the HPSI supply headers. Both the high pressure and low pressure safety injection systems utilize the same injection now path down stream of their isolation valves. The LPSI and HPSI loop isolation valves are normally shut. Each valve has a hand switch in the Control Room and 0-100 percent open valve position indication. The valves can be throttled to supply flow at a desired rate during an accident scenario. The valves automatically open upon receipt of a Safety Injection Actuation Signal to inject coolant into the Reactor Coolant System after a loss-of-coolant accident. Failure of the valves to operate properly could adversely affect the ability of the plant to adequately respond to a loss-of-coolant accident event. This problem with the anti-rotational keys would also prevent local manual operation of the valves.

(v) Date on Which Defect was Identified:

We determined on April 1,1994, that this defect could have created a Substantial Safety Hazard a_t Calvert Cliffs had the undersized keys gone unnoticed after installation and the valves placed back in service.

(vi) Number and location of Comp <ments:

There are four 6-inch valves on each unit resulting in a total of eight. These valves are located in the Auxiliary Building Penetration Room for each Unit.

(vil) Corrective Actions Taken:

We have communicated this problem to the vendor. Utilizing data supplied by us, the vendor has supplied a design drawing to us which has the correct key dimensions. We have machined new keys on-site to the dimensional requirements of these new drawings for the four affected valves on Unit 1. The new keys were installed and performed satisfactorily. The valves were tested both statically and dynamically using VOTES equipment and found satisfactory.

We have been in contact with the vendor to attempt to determine the extent of this problem and whether it applies to other valves that may have been supplied by Velan to Calvert Cliffs or other Nuclear Power Plants. Velan has stated that they are reviewing other globe stem and key drawings to ensure that this error does not apply to other valve sizes as well. They plan to issue a formal notification of their findings in approximately 30 days.

A NETWORK message has been issued to make other industry personnel aware of this potential prob em.

When we replace these keys on the Unit 2 valves we plan to take measures to ensure that proper size and material keys are used.

2 of 3

~.

A'ITACllMENT (1),

10 CFR l' ART 21 REl' ORT CONCERNihG ANTI ROTATION KEYS FOR 6-INCII MOTOR-OPERATED VALVES MANUFACTURED IlY VEIAN 'l I

(vill) Other Advice Related to Purchasers or Licensecs: )

Other licensees replacing these keys should ensure that the dimensions of the new keys are appropriate for the dimensions of the keyways in their valves.

1 l

l 3 of 3