ML17333A578

Discusses Resolution of Spent Fuel Storage Pool Safety Issue & Issuance of Final Staff Rept & Notification of Staff Plans to Perform plant-specific,safety Enhancement Backfit Analysis

ML17333A578
Person / Time
Site:	Cook
Issue date:	09/26/1996
From:	John Hickman NRC (Affiliation Not Assigned)
To:	Fitzpatrick E INDIANA MICHIGAN POWER CO. (FORMERLY INDIANA & MICHIG
References
TAC-M88094, NUDOCS 9610010059
Download: ML17333A578 (7)

Text

~+A g/g p,R REG UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 September 26, 1996

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Nr. E.

E. Fitzpatrick, Vice President Indiana Michigan Power Nuclear Generation Group 500 Circle Drive

Buchanan, MI 49107

SUBJECT:

RESOLUTION OF SPENT FUEL STORAGE POOL SAFETY ISSUES:

ISSUANCE OF FINAL STAFF REPORT AND NOTIFICATION OF STAFF PLANS TO PERFORM PLANT-

SPECIFIC, SAFETY ENHANCEMENT BACKFIT ANALYSES, DONALD C.

COOK NUCLEAR PLANT, (TAC NO. 88094)

Dear Nr. Fitzpatrick:

The Nuclear Regulatory Commission staff recently completed a detailed review of spent fuel storage pool safety issues.

The results of the staff's review are documented in a report to the Commission which is enclosed for your information.

In the report, the staff concludes that existing structures,

systems, and components related to the storage of irradiated fuel provide adequate protection of public health and safety.

Notwithstanding this finding, the staff has also identified certain design features that reduce the reliability of spent fuel pool decay heat removal, increase the potential for loss of spent fuel coolant inventory, or increase the potential for consequential loss of essential safety functions at an operating reactor.

The staff intends to conduct plant-specific regulatory analyses to evaluate potential safety enhancement backfits pursuant to 10 CFR

50. 109(a)(3) at a number of operating plants that possess one or more of these design features.

The staff observed that the absence of isolation capability for leakage identification systems could allow water to leak at a rate in excess of make-up capability for certain events that cause failure of the SFP liner.

The staff identified four operating reactors, including D.C. Cook, with this characteristic, but this, item was not included in our previous information collection efforts.

However, the staff also has not collected the information necessary to evaluate makeup capability relative to credible leakage through the leakage detection channels.

To address this omission, the staff will examine previous licensing reviews to determine if the staff had previously evaluated makeup capability relative to credible coolant inventory loss through the leakage detection channels.

Because the four plants identified with this characteristic, including D.C. Cook, were not evaluated for inventory control using the SRP guidance, the staff believes that the depth of review for these plants would be indicative of the depth of review at other gy operating reactors.

If this issue has not been previously addressed by the staff at the four operating reactors, the staff will initiate additional information collection activities for this design characteristic and conduct a

regulatory analysis to determine if modification to the leakage detection system is justified.

Through the extensive evaluation of loss of spent fuel pool cooling concerns at, the Susquehanna Steam Electric Station, the NRC staff identified certain design characteristics that increase the probability that an elevated SFP temnerature will interfere with the safe operation of a reactor either at 9610010059 960926 PDR ADOCK 05000315 P

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E. Fitzpatrick September 26, 1996 power or shutdown.

The first characteristic is an open path from the area around the SFP to areas housing safety systems.

This path may be through personnel or equipment access ports, ventilation system ducting, or condensate drain paths.

Without an open path, the large surface area of the enclosure around an SFP would allow water vapor to condense and return to the SFP and allow heat to be rejected through the enclosure to the environment without affecting reactor safety systems.

The second characteristic is a short time for the SFP to reach elevated temperatures.

The time for the SFP to reach an elevated temperature is affected by initial temperature, coolant inventory, and the decay heat rate of irradiated fuel.

On the basis of operating practices and administrative limits on SFP temperature, the NRC staff has determined that short times to reach elevated temperatures are credible only when nearly the entire core fuel assembly inventory has been transferred to the SFP and the reactor has been shut down for a short period after extended operation at power.

These conditions establish the third design characteristic, which is a reactor site with multiple operating units sharing structures and systems related to the SFP.

At a single-unit site, large coolant inventories in the SFP and in the reactor cavity act as a large passive heat sink for irradiated fuel during fuel transfer.

When the entire core fuel assembly inventory has been transferred to the SFP at a single-unit site, safety systems associated with the reactor are not essential because no fuel remains in the reactor vessel.

Multi-unit sites with no shared structures can be treated as a single-unit site.

At a multi-unit site with shared structures, a short time to reach an elevated temperature can exist in the SFP associated with a reactor in refueling while safety systems in communication with the area around that SFP are supporting operation of another reactor at power.

When these three design characteristics coexist at a single site, one SFP could reach an elevated temperature in a short time (i.e.,

between 4 and 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />) after a sustained loss of cooling, the heat and water vapor could propagate to systems necessary for shutdown of an operating reactor, and these systems could subsequently fail while needed to support shutdown.

The staff has determined through its survey of SFP design features that these three design characteristics coexist at no more than seven operating reactor sites in addition to Susquehanna.

D.

C.

Cook was one of the plants identified.

The staff determined through its review of design information and operational controls that immediate regulatory action is not warranted on the basis of the capability of available cooling systems, the passive heat capacity of the

SFP, and the operational limits imposed by administrative controls at these seven sites.

In making this determination, the.staff considered the findings from its review of this issue at Susquehanna.

Nevertheless, the staff will conduct detailed reviews to identify enhancements to refueling procedures or cooling system reliability that are justified based on the reduced potential for SFP conditions to impact safety systems supporting an operating reactor at these seven sites, including D.

C. Cook.

If you wish to comment on the accuracy of the staff's understanding of the plant design, the safety significance of the above design features, the cost

E.

E. Fitzpatrick September 26, 1996 of potential modifications to.address the above design features, or the existing protection from the above design concerns which may be provided by administrative controls or other means, comments received before November 15, 1996, will be considered in developing plans for inspections and other activities associated with the planned regulatory analysis. If you have any questions regarding this matter, please do not hesitate to contact John Hickman at (301) 415-3017,.

Sincerely, x,

Original signed by:

\\

,John B. Hickman, Project Hanager Project Directorate III-l Division of Reactor Projects III/IV Office, of Nuclear Reactor Regulation Docket Nos.

50-315 and 50-316

Enclosure:

Memo,to the Commission, from J.'aylor, "Resolution of Spent Fuel Storage Pool Action Plan Issues,"

dated July 26, 1996 cc w/encl:

See next page ISTRIBUTION w encl:...

Docket: Fi.l e". (50-315..and '.50-'316)

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E. Fitzpatrick Indiana Michigan Power Company CC; Regional Administrator, Region III U.S. Nuclear Regulatory Commission 801 Warrenville Road Lisle, Illinois 60532-4351 Attorney General Department of Attorney General 525 West Ottawa Street Lansing, Michigan 48913 Township Supervisor Lake Township Hall P.O.

Box 818 Bridgman, Michigan 49106 Al Blind, Site Vice President Donald C.

Cook Nuclear Plant 1 Cook Place Bridgman, Michigan 49106 U.S. Nuclear Regulatory Commission Resident Inspector's Office 7700 Red Arrow Highway Stevensville, Michigan 49127 Gerald Charnoff, Esquire

Shaw, Pittman, Potts and Trowbridge 2300 N Street, N.

W.

Washington, DC 20037 Mayor, City of Bridgman Post Office Box 366 Bridgman, Michigan 49106 Special Assistant to the Governor Room 1 - State Capitol Lansing, Michigan 48909 Drinking Water and Radiological Protectio~ Division Michigan Department of Environmental guality 3423 N. Hartin Luther King Jr Blvd P. 0.

Box 30630 CPH Hailroom Lansing, Michigan 48909-8130 Donald C.

Cook Nuclear Plant Hr. Steve J.

Brewer Indiana Michigan Power Nuclear Generation Group 500 Circle Drive

Buchanan, Michigan 49107 Augural 1 996

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