ML20207H823

Responds to 860625 Request for Addl Info Re Util 851118 Request to Delete 800229 Confirmatory Order.Strengths in Response of Plant Sys to Transients & small-break LOCA & Ability to Contain Most Core Melts Indicated

ML20207H823
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	07/21/1986
From:	Farrar D COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
1843K, NUDOCS 8607250108
Download: ML20207H823 (9)

Text

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. - Commonwealth Edison 21 - 72 West Adams Street. Chicrgo, Illinois N# / Address Reply to: Post Office Box 767

%g Chicago, litinois 60690 -0767 July 21, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Zion Nuclear Power Station Units 1 and 2 Confirmatory order dated 2/29/80 Request for Additional Information NRC Docket Nos. 50-295 and 50-304 References (a): November 18, 1985 letter from Cordell Reed to H. R. Denton.

(b): February 29, 1980 letter from H. R. Denton to D. L. Peoples.

(c): June 25, 1986 letter from S. A. Varga to D. L. Farrar.

(d): August 26, 1985 letter from S. A. Varga to D. L. Farrar.

(e): December 20, 1982 letter from D. L. Wigginton to L. O. DelGeorge.

(f): July 2, 1984 letter from b. G. Eisenhut, Generic Letter 84-15.

(g): June 3, 1986 letter from P. C. LeBlond to H. R. Denton.

(h): August 29, 1980 letter from W. F. Naughton to H. R. Denton.

(1): September 8, 1981 letter from L. O. DelGeorge to H. R. Denton.

'l (j): December 28, 1984 letter from R. N. Cascarano to H. R. Denton.

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Dear Mr. Denton:

Reference (a) transmitted Commonwealth Edison Company's request to delete the February 29, 1980 Confirmatory order that was transmitted by reference (b). Reference (c) transmitted a request for additional information regarding six specific Order items. This letter provides the requested information.

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Mr. H. R. Denton July 21, 1986 Reference (c) specifically asks for additional information on each of the six identified Order items to indicate reasons that the removal of the requirement would not result in a significant reduction of plant safety. The additional information requested is provided in the attachment to this letter.

However, it is Commonwealth Edison's position that sufficient information and documentation already exists to justify removal of the Confirmatory order.

The reasoning provided in reference (a) clearly delineates Commonwealth Edison's position on this issue. The Zion Confirmatory Order was issued because the Zion site was believed to be a risk outlier.

Specifically, the NRC stated in reference (b);

Due to the relatively high population density surrounding the Zion site as compared to other nuclear power plant sites, the Zion site is believed to present a disproportionately high contribution to the total societal risk from reactor accidents. ...the Staff has identified a number of extraordinary interim measures that should be accomplished by the licensees and the Staff. These measures will significantly increase the level of safety at the Zion Station and thereby further reduce the

, probability of a severe reactor accident.

However, both the belief that the Zion site may be responsible for the higher societial risks and that the Order significantly reduces those risks have been dispelled. Specifically, the NRC Staff has concluded in section 1.3 of reference (d);

The staff concludes that Zion poses no undue risk to public health and safety. This conclusion does not depend upon the continued enforcement of the Directors Order of February 1980. Those few clauses of the Directors Order that significantly affect our risk evaluation are complete or covered by other requirements (emphasis supplied).

, In addition, the staff concluded that Zion's design has attributes i that directly counterbalance the relatively high population density I

surrounding the Zion Site. Again, quoting from reference (d);

The staff review of the Zion plant systems indicates that the Zion units have strengths in the area of the response of plant systems to transients and small-break loss-of-coolant accidents (LOCA). The staff has also determined that large, dry containment (such as Zion containment) are likely to contain most core melts, should they occur, resulting in a significant reduction in the magnitude of off-site consequences.

Mr. H. R. Denton July 21, 1986 The above discussion alone provides sufficient justification for the removal of the Zion confirmatory Order. Therefore, the information supplied in the attachment to this letter provides additional assurance that the recession of the 1980 Confirmatory Order will not adversely affect the continued safe operation of Zion Station.

If the NRC Staff feels as though additional discussion of this issue is warranted, commonwealth Edison personnel would be pleased to attend a meeting at your convenience.

Please address any additional questions regarding this matter to Commonwealth Edison's Department of Nuclaar Licensing.

Very truly yours,

, * = =-ln D. L. Farrar Director of Nuclear Licensing Im Attachment cc: Resident Inspector - Zion J. A. Norris - NRR i

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ATTACIGENT Reference (c) requested additional information on six specific Order items. The additional information for each of the items is listed separately below:

1. Item A.3-Low Pressure Gross Leak Test of Containment Prior to any Startup from Cold Shutdown Condition This Order item required that Commonwealth Edison perform two activities prior to any startup from cold shutdown condition. Those activities were; (a) ensure that the containment penetration and weld channel pressurization leakage is within technical specification limits.

(b) perform local leak tests on a specific set of containment isolation valves.

The first issue has been reviewed by the NRC subsequent to the issuance of reference (b). Specifically, the Zion Technical Specifications governing the operability, leakage rate, and surveillance periods for this containment leakage control system, have been reviewed and approved by the NRC. Reference (e) contains Zion License Amendment Nos. 79 and 69. The SER that approved these Technical Specifications specifically stated that there were no safety concerns associated with these revised Technical Specifications sections.

Thus, the imposition of an additional surveillance of the containment penetration and weld channel pressurization system has been shown to be unwarranted. In addition, the pertinent system pressures and flow rates are continuously monitored and will alarm in the main control room if system conditions degrade. This alarm capability provides supplemental assurance that the containment penetration and weld channel pressurization system will remain functional at all times.

The second issue required Commonwealth Edison to perform local leak

test on containment isolation valves that were not included in two

specified categories. Zion Station performed the required reviews in l 1980 to specifically identify the affected valves. This review resulted in the identification of only seven valves per unit that would require testing under Order Item A.3.

Four of the seven valves identified are normally open during accident conditions. These valves exist in the containment spray headers and in the containment air sampling return lines. Thus, leak testing these valves provides no useful information, since they have been designed to remain open following a postulated accident. '

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In addition, two of the seven valves have high pressure nitrogen available to be applied to them from the exterior of the containment.

This pressure is in excess of 100 psig and would force any potential ~

leakage back into the containment. l Finally, one valve is a check valve in the containment air sampling

'l return line. It is likely that this line would be in use following a loss-of-coolant accident. However, if this check valve should fail and containment air sampling not be in progress, then containment pressure would be applied back through the existing containment air rad monitors.

There is no direct release path to the environment.

All seven of the identified valves are also periodically tested in accordance with 10 CPR 50, Appendix J. This regulation requires that these seven valves be leak tested every refueling outage but in no case at intervals greater than 24 months. In addition, the existence of a mid-operating cycle cold shutdown'is a relatively rare occurrence. It is expected that each unit will experience a forced mid-cycle cold shutdown approximately once per year. Thus, the removal of Item A.3 will eliminate approximately one leak test of these valves per year.

However, the enforcement of 10 CPR 50, Appendix J will result in the continued testing of these valves.

In summary, the existing administative controls contained in the Zion Technical Specifications governing the surveillance and operability of the PP air system have been reviewed and approved by the NRC since the issuance of the Zion Confirmatory Order. In addition, there are only seven valves affected by Order Item A.3. The postulated leakage

- through these valves is not expected to play a role in containment performance following a postulated LOCA. The testing requirements contained in 10 CPR 50, Appendix J and the Zion Technical Specifications are adequate to ensure that the containment systems at Zion will perform their intended function.

2. Item B.1 - Vendor Representative to be Stationed on Site Zion Station and Commonwealth Edison have maintained a close working relationship with Westinghouse Electric Corporation for many years. This relationship has involved numerous and varied divisions within both Commonwealth Edison and Westinghouse. The existence of a full time vendor representative stationed at the Zion Nuclear Power Plant merely exemplifies this already close working relationship. Thus, 1 Commonwealth Edison sees no safety concern with deleting the requirement to utilize a full time vendor representative.

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. However, Zion Station's experience with this vendor representative over the last six years has been positive. This arrangement has allowed easy access to the appropriate Westinghouse personnel when required.

The specific technical expertise within Westinghouse has been more readily available through the use of the full time vendor

representative.

Commonwealth Edison Company believes that this arrangement has made the overall operation of Zion Station more efficient. It has allowed technical decisions and maintenance activities to be initiated more rapidly. Thus, commonwealth Edison expects to retain the Westinghouse representative following formal deletion of Item B.l.

3. Item C.5 - On-Site Nuclear Safety Review Committee Order Item C.5 requires the establishment of an onsite group whose function was to examine plant operating characteristics and various sources of technical information to improve plant safety. This on-site group was formed at Zion Station within the required 60-day time period j utilizing experienced plant personnel on a part-time basis.

I On August 11, 1980, General Company Order #43 was issued by Mr. J.

J. O'Connor, Chairman and President of Commonwealth Edison. GCO #43 created the Corporate Department of Nuclear Safety. This department was charged with reporting any unsafe conditions or practices directly to the Chairman of the Company. In addition, this department reviews nuclear operating experience both from within and outside of

. Commonwealth Edison to ensure that lessons learned are factored into Commonwealth Edison's nuclear power plant operations. An experienced individual familiar with Zion's design and operating characteristics is assigned to coordinate Zion's safety reviews on a full-time basis.

The Department of Nuclear Safety is a permanent feature of Commonwealth Edison's organizational structure. It is described within the Commonwealth Edison Company Quality Assurance Manual. This '

permanent offsite department is better equipped to accomplish the independent safety review goals outlined in Order Item C.5. Thus, the independent review function required of the on-site group are accomplished by the practices of the Corporate Department of Nuclear Safety. These corporate duties will continue following the removal of the Confirmatory order.

4. Item B.6 - Diesel Generator Surveillance Testing i

The NRC Staff expressed concern regarding the effect of unwarranted diesel generator testing on overall reliability in reference (f). The requirements of Order Item B.6 imposed unwarranted restrictions on surveillance test frequency and allowed outage times.

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Reference (g) demonstrated that diesel generators with a ninety-eight percent reliability could be subjected to both an increased test frequency and a reduced allowable outage time. This is detrimental from both the aspect of increased wear, as discussed in reference (f), and from the reduced time available fer diesel generator maintenance. Thus, the restrictions of order Item B.6 have been shown to be of little or no overall safety benefit.

We are not aware of any engineering or technical basis which justifies the confirmatory order restrictions on diesel generator testing. We believe the restrictions are an anachronistic, punitive requirement imposed upon Zion Station only among operating reactors.

5. Item F.4(b) - Implement an FMEA for Minor Procedural Departures.

Reference (h) provided the results of a FMEA of all active components on or within the reactor coolant boundary. The analysis presented in Table F.4-1 of reference (h) included postulated effects from maintenance and procedures.

1 Reference (1) submitted the Zion Probabilistic Safety Study (ZPSS) for NRC review. The ZPSS incorporated an explicit probability for the non-performance of major safety functions. This feature captures the consequences of major human failures and procedural violations.

Reference (j) submitted Zion's Procedure Generation Package for the -

development of the upgraded emergency procedures. These procedures contain guidance for operator action if an individual procedure step is not successfully completed. This guidance is contained in the right-hand column of every procedure page and is, entitled " Response Not ,

obtained". This feature provides detailed instructions in the event that the procedure step is not completed as intended.

Zion's upgraded emergency procedures are based upon the Emergency Response Guidelines (ERGS) developed by the Westinghouse Owner's Group.

The ERGS were developed by utilizing probabilistic evaluation techniques. ,

These techniques involved the identification of functions that are required to mitigate the consequences of postulated accidents. In addition, functional failures were defined for each of these identified functions. Thus, these ERGS have incorporated guidance for'an extremely large number of anticipated-abnormal conditions.

In summary, the effect of abnormal procedural or operational events have been thoroughly considered in references (h), (i), (j) and the WOG's development of the ERGS.

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6. Item F.4(c) - Explore Ways to Improve Components with High Failure Rates Reference (h) provided Commonwealth Edison Company's initial

. response to this order item. The LER review process described in reference (h) remains in effect. All equipment failures require the issuance of a Deviation Report (DVR). These DVRs are reviewed by both station personnel and the Nuclear Safety Department. The verification of the failure's root cause and proper corrective action are a part of these reviews.

In addition, Zion Station has formed the Recurring Station Problems Committee (RSPC) to specifically address the most frequent problems at Zion Station. This committee was formed in 1984 and has been effective in concentrating management attention on the components that are failing frequently.

The requirement to examine components with a "particularly high failure rate" has no significant meaning except in the context of system performance and overall plant risk. Thus, it is crucial to identify those components whose current failure rates result in a signficant addition to the risk at Zion Station. Once those components, systems, and accident sequences have been identified, the appropriate measures can be taken.

Reference (i) submitted the ZPSS for NRC review. This study I i'entified d the major contributors to risk at Zion Station. These failure sequences have identified the plant components that have a "high failure rate" relative to the additional risk generated by their failure.

commonwealth Edison Company, in conjunction with the NRC's review of the ZPSS (reference (d)), have produced the following list of plant l and component alterations specifically intended to reduce the overall risk.

a. The turbine-driven auxiliary feedwater pump has been modified so its

! operation is independent of A-C power. This modification was performed prior to the completion of the ZPSS.

b. The periodic testing of Low Pressure Injection Check Valves is being continued to reduce the probability of an interface LOCA.

. c. A periodic test of the Residual Heat Removal (RHR) System suction

( valves has been instituted to furtner reduce the chances of an interface LOCA.

d. A modification to the diesel-driven containment spray pumps to make l

their operation independent of A-C power is under consideration.

This modification would reduce the probahility of containment failure following a Loss of Coolant Accident.

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e. Numerous procedural changes were made as a result of the NRC's review of the ZPSS. Examples include the initiation of a periodic test of ECCS room coolers, providing emergency instruction for refilling the Refueling Water Storage Tank, and the development of an emergency procedure for the loss of D.C. bus.

In summary, commonwealth Edison Company is continually reviewing the observed failures through the DVR/LER review process. Zion Station is aggrescively pursuing solutions to the recurring failures through the RSPC.

The ZPSS has been instrumental in identifying the components whose postulated failure produces significant risk. Commonwealth Edison Company is utilizing this information to modify Zion Station to address these risks.

Thus, commonwealth Edison Company has been continually reviewing the effects of equipment failures and has been working towards minimizing the risk incurred.

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