ML20155D596

Discusses Status of Util Efforts & Provides Schedule for Final Resolution of High Energy Line Break Issue.Corrective Actions Will Include Increased Component Thermal Protection, Addl Testing & Component Replacement

ML20155D596
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	04/08/1986
From:	Leblond P COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
1505K, GL-85-15, NUDOCS 8604170372
Download: ML20155D596 (2)

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N Commonwealth Edison

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) One First Nr,tional Plaza. Chictgo. Illinois i ^J Addrus R ply to: Post Office Box 767 s - Chicago, Illinois 60690 April 8, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Conunission Washington, DC 20555

Subject:

Zion Nuclear Power Station Units 1 and 2 High Energy Line Break (HELB)

NRC Docket Nos. 50-295 and 50-304 References (a): December 7, 1984 letter from E. L. Jordan to PWR OLs and cps transmitting Information Notice No. 84-90.

(b): February 25, 1985 letter from J. O. Cermak (WOG) to D. L. Wigginton (NRC).

(c): October 28, 1985 letter from J. O. Cermak (WOG) to D. L. Wigginton (NRC).

(d): Generic Letter 85-15 dated August 6, 1985.

Dear Mr. Denton:

Reference (a) provided the industry with notification of a potential problem concerning the effect of postulated releases of superheated steam on equipment qualification. References (b) and (c) outlined the Westinghouse Owners Group's approach to this issue and proposed schedules. This letter contains the status of Zion Station's efforts'and provides a schedule for final resolution of this issue.

The WOG mass-energy release calculations have been utilized to develop steam tunnel temperature profiles for the various break sizes.

Postulated breaks w' thin Zion's auxiliary building have been determined to be unaffected by this issue.

Further analysis is being conducted to determine if steamline isolation will occur prior to the release of superheated steam to the steam tunnel for each of the break sizes considered. This work will determine which of the temperature profiles / break sizes discussed above need to be considered for their effect on equipment operability.

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H. R. Denton April 8, 1986 Next, the specific components required to operate for the break sizes determined above will be identified. Then, a thermal las component heat-up study will be performed to determine equipment temperatures following the postulated spectrum of breaks discussed above. If the calculated compo-nent temperatures exceed the qualified temperature prior to the performance of the component's safety function, then corrective action will be taken.

These corrective actions will take the form of increased component thermal protection, additional testing, component replacement, or other similar actions. It is expected that the analyses and corrective actions

, described above will be completed by July 1, 1986, unless a specific corrective action will require a reactor shutdown. In that case, the work will be completed during the first unit shutdown of sufficient duration following July 1.

Reference (d) provided guidance on the treatment of noncompliances with 10 CFR 50.49 that are discovered after November 30, 1985. 10 CPR 50.49.e.1 states that the temperature profile to be utilized for equipment qualification conducted under 10 CFR 50.49 is to be obtained from "the most severe design basis accident". The design basis steamline breaks contained in Zion Station's FSAR consist solely of complete pipe severances. Thus, the spectrum of break sizes being considered for the HELB issue exceeds Zion's current design basis.

The data supplied by Westinghouse in WCAP 10961 indicates that for the 4.6 ft2 steamline break, steamline isolation occurs prior to the release of superheated steam to the steam tunnel. Thus, Commonwealth Edison anticipates that none of the component deficiencies that may be discovered will require immediate shutdowns under the provisions of reference (d) and 10 CFR 50.49.

Commonwealth Edison Company will notify you upon completion of all corrective actions. If any questions arise regarding this matter, please contact this office.

Very truly tours, hP. C. LeBlond Nuclear Licensing Administrator im cc: NRC Resident Inspector - Zion J. A. Norris - NRR 1505K