ML20069G793

Corrected Version of Final Deficiency Rept Re Robertshaw Controls Thermostatic Valves.Initially Reported on 820820. Corrective Actions Described by Vendor Will Preclude Potential Problems

ML20069G793
Person / Time
Site:	Seabrook
Issue date:	09/20/1982
From:	Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE, YANKEE ATOMIC ELECTRIC CO.
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, SBN-327, NUDOCS 8210190136
Download: ML20069G793 (3)

Text

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I $)ESIGNATED ORIGINAL M commmm

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l September 20, 1982 SBN-327 T.F. Q 2.2.2 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 Attention: Mr. Richard W. Starostecki, Director Division of Resident and Project Inspection Re ferences: (a) Construction Permit CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) Telecon of August 20, 1982, J. DeVincentis (YAEC) to Walter Baunack (NRC Region I)

Subject:

Final 10CFR50.55(e) Report; Robertshaw Controls Thermostatic Valves

Dear Sir:

On August 20, 1982, a reportable 10CFR50.55(e) item was reported

[ Reference (b)) regarding a potential failure mode for certain Robertshaw Controls thermostatic valves which could result in overcooling of the diesel generator engine jacket cooling water system and subsequent engine damage.

This item was reported to the NRC by Colt Industries on May 25, 1982, and June 28, 1982, pursuant to 10CFR21.

The following information is provided per 10CFR50.55(e)(3) and is considered to be the final report on this item.

DESCRIPTION OF DEFICIENCY l

Diesel generator sets manufactured by Colt utilize a Robertshaw Controls (

thermostatic valve in the Jacket Water Cooling System. These valves incorporate an overrun assembly which absorbs excessive movement of the thermal assembly. The overrun length is set by an axial bolt and nut. If the not is not secured in place, and is able to backoff the bolt, the overrun assembly allows an increase in valve stroke. Tais additional valve stroke makes the thermal assembly control at a lower temperature.

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United Statoo Nucloce Reguistory Commission

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~ ~ Saptschar 20, 1982 Attentiont Mr. Richard W. Staroatecki Page 2 ANALYSIS OF SAFETY IMPLICATIONS Colt engineers have determined that for this valve failure mode, extreme overcooling with attendant risk of engine damage could occur with low raw water supply temperatures. The Seabrook D-G sets will utilize the Service Water System for removing heat from the Engine Jacket Cooling Water System.

The jacket water heat exchangers are designed to provide jacket cooling water 4

' a t 1100 with 900 service water, based os rated load operation. At reduced load, and with colder service water, a control valve malfunction could indeed cause overcooling in the engine, and a possible engine failure could constitute a substantial safety hazard. However, it is expected that this type of valve malfunction would be detected and corrected during periodic testing and maintenance operations.

CORRECTIVE ACTIONS When this problem was first reported, the overrun assembly design called for the nut to be staked in place. The design was revised by Robertshaw Controls to require soldering the out to the bolt. This design change was not backfitted to previously manufactured overrun assemblies, so that some assemblies with the staked constructiou were supplied for nuclear plant D-G sets af ter the design change was cade.

Colt has advised Robertshaw that the solder used to secure the nuts may be affected by certain corrosion inhibitors used in Jacket Cooling Water Systems. Ro bert shaw, therefore, has determined that overrun assemblies utilizing swagged locking should be installed as replacements in all suspect D-G sets.

Procedures for the replacement of the overrun assemblies and documentation sign-of f sheets are being prepared. Information relative to availability of replacement assemblies is also being developed. The replacement parts will be supplied by Robertshaw on a no-charge basis. The parts shipments wiJ 1 be accompanied by instructions, and sign off sheets.

Af ter replacement work is done, the completed sign off sheets will be returned to Robertshaw and Colt, so that close-out actions can be recorded and reported to NRC.

ANALYSIS AND EVALUATION i

If the control valve malfunction described above was undetected and/or uncorrected, overcooling of the diesel engine could occur, with attendant risk ,

l of engine damage. However, this type of valve malfunction would be evident ,

during periodic testing of the D-G sets, and appropriate corrective action 1

would be taken.

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U'nited Staden Nuclear Regulatory Commiccion Saptscher 20, 1982 Attention: Mr. Richard W. Starostecki Page 3 i t

f The corrective actions described by Colt and Robertshsw will preclude i

potential problems resulting from malfunction of the overrun assembly in the thermostatic valves. Installation of the replacement assemblies provided by i

Robertshaw will eliminate this potential problem. l Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY J. DeVincentis Project Manager ALL/dd e

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