ML20086S574

USRE-S1-74-01:discovered Two Singular Pipe Runs Passing Through Respective Containment Boundary W/Check Valves on Either Side of Containment.Caused by Oversight in Design. Four Check Valves Will Be Installed

ML20086S574
Person / Time
Site:	Surry
Issue date:	09/19/1974
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
USRE-S1-74-01, USRE-S1-74-1, NUDOCS 8403020439
Download: ML20086S574 (5)

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- Mr. ' orman C. Moseley, Director Serial No. 275 Directorate of Regulatory Operations P0&M/JTB:clu United States Ato.mic Energy Coamiccion Region 11 - Suite 818 Docket Hos. 50-280 230 Peachtree Strect, h'orthwest 281 Atlanta, Georgia 30303 License Nos. DPR-32

DPR-37

Dear Mr. Moseley:

Pursuant to Surry Power Station Technical Specification 6.6.B.2, the Virginia Electric and Power Company hereby submits forty (40) copics of Unusual Safety Related Lvent Report No. USRE-S1-74-01.

The substance e' this report has been reviewed by the Station Nuc.lccr Safety and Operating Committee and vill be placed on the agenda for the next meeting of the System Nuclear Safety and Operating Cornittee.

Very truly yours, MO.hb jd/

C. M. Stallings Vice President-Power Supply and Production Operations Encloseren 40 copies of USRE-S1-74-01 cc: Mr. K. R. Coller, Assistant Director for Operating Reactors 4 q) 10543

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. O V UNUSUAL SAFETY RELATED EVENT REPORT NO. USRE-SI-74-01 POTENTIAL DEGRADATION OF AUXILIARY FEEDWATER SYSTEM INSIDE CONTAINMENT AUGUST 30, 1974 DOCKET NOS. 50-280 50-281 LICENSE NOS. DPR-32.

DPR-37 SURRY POWER STATION VIRGINIA ELECTRIC AND POWER COMPANYJ i

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1. INTRODUCTION In accordance with Technical Specification 6.6.B.2 for Surry Power Station, Operating License Nos. DPR-32 and DPR-37, this report describes an unusual safety related event which was detected in connection with the "High Energy Line Modifications" presently being made at the station.

An unusual safety related event is defined by Technical Specification 1.0.J.3 as: "Any condition involving a possible single. failure which, for a system designed against assumed single failures, could result in a loss of the capability of the system to perform its safety function."

II.

SUMMARY

OF OCCURRENCE In December 1972, the AEC issued a letter concerning postulated pipe failures. As a result of the analysis of various postulated pipe failures, several modifications, which have been designated as "High Energy Line Modifications," were developed for the Surry Power Station.

One of these modifications is the cross connection of the auxiliary feedwater system of Unit Nos. 1 and 2. This modification consists of a pipe-run connecting the discharge side of Unit No. I auxiliary feedwater pumps to the auxiliary feedwater manifolds inside Unit No. 2 containment.

A second pipe run connects Unit No. 2 pumps to the manifold in Unit No. I containment. The installation of this modification was accomplished during the period January-July 1974.

A review of the installed system, pri-r to placing it in operation, revealed the following deficiency. The two singular pipe runs pass through their respective containment boundary with check valves on either side of the containment. Downstream of the inside check valve, a tee connection with short pipe runs is utilized to connect the croas-connect pipe to 1: - .m

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. O the two auxiliary feedwater manifolds. Thus, in effect, the redundant auxiliary feedwater piping inside of the containment is tied together without isolation valves and the redundancy of the auxiliary feedwater system would be lost in each containment. A single pipe rupture of the

-cross-connect piping, inside of the containment and downstream of the penetration check valves would negate the utilization of the auxiliary feedwater system for that unit.

e III. ANALYSIS OF OCCURRENCE -

The deficiency _noted was discovered during a preoperational checkout before the system was placed in service. The original design did not specify the installation of check _ valves to perform isolation in the event of a pipe rupture.

Established design review procedures had 'been followed; however, the oversight occurred. Personnel reviewing the system, prior to placing it into operation, discovered the deficiency.

IV. CORRECTIVE ACTION TO PREVENT RECURRENCE The corrective action planned is to install four check valves in each of the two cross-connect branch lines inside of each containment. This will effec * 'v isolate each of the auxiliary.feedwater headers in the event of a pit rupture inside of the containment and restore. the redundancy of the system. Two of the check valves 'have been installed on lone unit !and blind flanges have been installed on the other lines until the remaining two check valves are received and installed.

Based on our review the failure.to incorporate these-check valves in i

the original design'was an isolated occurrence; therefore, no changesLtoi the review procedures are warranted or necessary.

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, , V U V. ANALYSIS AND EVALUATION OF SAFETY IMPLICATIONS The auxiliary feedwater system is utilized during periods on loss of station power or other events which cause a loss of normal feedwater supply to the steam generators. Auxiliary feedwater is discharged to the steam generators through connections in each main feedwater line inside the containment. Check valves in both the main and auxiliary feedwater lines prevent a loss of feedwater, should a feedwater line rupture.

The possibility of losing all feedwater to a steam generator is remote and would require a multiple failure, i.e. , the failure of an auxiliary feedwater line inside the containment coupled with a loss of main feeduater.

A failure of either auxiliary feedwater line or the cross-connect line outside the containment would not significantly endanger the system as the failed section of piping would be isolated by check valves from the intact portion.

VI. CONCLUSIONS The licensee concludes that:

1. The event described herein was a design error.

2. The event described herein did not affect the .

safe operation of the station.

3. The event described herein did not affect the health or safety of the general public.

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