ML080880012

Request for Additional Information Related to LAR to Revise TS 3.7.8, Essential Service Water System, and TS 3.8.1, AC Sources - Operating, for One-time Completion Time Extension Re Underground Piping

ML080880012
Person / Time
Site:	Callaway
Issue date:	03/31/2008
From:	Thadani M C NRC/NRR/ADRO/DORL/LPLIV
To:	Naslund C D Union Electric Co
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MD7252
Download: ML080880012 (7)

Text

March 31, 2008

Mr. Charles D. Naslund

Senior Vice President and Chief Nuclear Officer

Union Electric Company

Post Office Box 620

Fulton, MO 65251

SUBJECT:

CALLAWAY PLANT, UNIT 1 - REQUEST FOR ADDITIONAL INFORMATION RELATED TO LICENSE AMENDMENT REQUEST FOR ONE-TIME EXTENSION OF COMPLETION TIME FOR INOPERABLE ESSENTIAL

SERVICE WATER SYSTEM (TAC NO. MD7252)

Dear Mr. Naslund:

By application dated October 31, 2007, as supplemented by letter dated February 21, 2008, Union Electric Company (the licensee) requested the U.S. Nuclear Regulatory Commission (NRC) staff approval of a one-time change to the Technical Specifications (TS) for its Callaway

Plant.

The proposed change would revise the TS to extend the completion time (CT) associated with

an inoperable Essential Cooling Water train from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 14 days, applicable once per train, and to be implemented prior to December 31, 2008. The licensee also proposed to eliminate

the second CT applicable to TS 3.8.1, Condition B in accordance with the NRC staff-approved

TS Task Force (TSTF) traveler TSTF-439.

The NRC staff has reviewed the information provided in your submittal and determined that

additional information is required in order to complete its review. Please provide a response to

the enclosed questions by May 15, 2008, to facilitate the continuation of the review by the NRC

staff. In the absence of your response by the requested date, the NRC staff may proceed to

deny your request pursuant to Title 10 of the Code of Federal Regulations, Part 2, Section 108, for not responding to this request within the time specified by the NRC staff.

If there are any questions, please contact me at (301) 415-1476, or e-mail mct@nrc.gov.

Sincerely,

/RA/ Mohan C. Thadani, Senior Project Manager

Plant Licensing Branch IV

Division of Operating Reactor Licensing

Office of Nuclear Reactor Regulation

Docket No. 50-483

Enclosure:

As stated

cc w/encl: See next page

ML (*) memo dated OFFICE NRR/LPL4/PM NRR/LPL4/LA DSS/APLA/BC NRR/LPL4/BC NAME MThadani, JBurkhardt MRubin (*) THiltz DATE 3/31/08 3/31/08 3/24/08 3/31/08 Callaway Plant, Unit 1 (November 2007)

cc:

John O'Neill, Esq.

Pillsbury Winthrop Shaw Pittman LLP

2300 N. Street, N.W.

Washington, D.C. 20037

Mr. Tom Elwood, Supervising Engineer

Regulatory Affairs and Licensing

AmerenUE P.O. Box 620

Fulton, MO 65251

Mr. Les H. Kanuckel, Manager

Quality Assurance

AmerenUE P.O. Box 620

Fulton, MO 65251

Mr. Luke Graessle, Manager

Regulatory Affairs

AmerenUE P.O. Box 620

Fulton, MO 65251

Mr. Scott Maglio

Assistant Manager, Regulatory Affairs

AmerenUE P.O. Box 620

Fulton, MO 65251

U.S. Nuclear Regulatory Commission

Resident Inspector Office

8201 NRC Road

Steedman, MO 65077-1302

Missouri Public Service Commission

Governor Office Building

200 Madison Street

P.O. Box 360

Jefferson City, MO 65102-0360

Regional Administrator, Region IV

U.S. Nuclear Regulatory Commission

611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005

Mr. H. Floyd Gilzow Deputy Director for Policy

Department of Natural Resources

P.O. Box 176

Jefferson City, MO 65102-0176

Mr. Rick A. Muench, President and CEO

Wolf Creek Nuclear Operating Corporation

P.O. Box 411

Burlington, KA 66839

Certrec Corporation

4200 South Hulen, Suite 422 Fort Worth, TX 76109

Technical Services Branch Chief

FEMA Region VII

2323 Grand Boulevard, Suite 900

Kansas City, MO 64108-2670

Kathleen Logan Smith, Executive Director

and Kay Drey, Representative, Board of

Directors

Missouri Coalition for the Environment

6267 Delmar Blvd., Suite 2E

St. Louis, City, MO 63130

Mr. Lee Fritz, Presiding Commissioner

Callaway County Courthouse

10 East Fifth Street

Fulton, MO 65251

Mr. Keith G. Henke, Planner III

Division of Community and Public Health

Office of Emergency Coordination

Missouri Department of Health and

Senior Services

930 Wildwood Drive

P.O. Box 570

Jefferson City, MO 65102

Mr. Scott Clardy, Director

Section for Environmental Public Health

Missouri Department of Health and

Senior Services

930 Wildwood Drive

P.O. Box 570

Jefferson City, MO 65102 Director, Missouri State Emergency

Management Agency P.O. Box 116 Jefferson City, MO 65102-0116 OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR ADDITIONAL INFORMATION RELATED TO ESSENTIAL SERVICE WATER UNION ELECTRIC COMPANY CALLAWAY PLANT DOCKET NO. 50-483 By application dated October 31, 2007, as supplemented by letter dated February 21, 2008, Union Electric Company (the licensee) requested the U.S. Nuclear Regulatory Commission (NRC) staff approval of a one-time change to the Technical Specifications (TS) for its Callaway

Plant. The NRC staff has reviewed the information provided in your submittal and determined

that additional information is required in order to complete its review. Please provide a

response to the following request for additional information (RAI) questions by May 15, 2008, to

facilitate the continuation of the review by the NRC staff:

1. The NRC staff asked for substantive justification that the known deficiencies in the probabilistic risk assessment (PRA) model, identified from peer reviews and identified to

the NRC staff in the submittal, would not significantly impact the application. In

response, to address the Scientech gap assessment against the American Society of

Mechanical Engineers internal events standard, the licensee restated that it "believed" these gaps would not invalidate the risk insights for this application, then argued that

since the existing PRA results were already greater than the Regulatory Guide 1.177

guidelines for permanent changes, the gaps would not result in any further significant

increase in the risk.

Please submit specific information which qualitatively discusses the substance of the

deficient items and adequately justifies that these deficiencies or gaps do not impact the

risk results of this application.

2. The NRC staff asked for discussion and justification of the truncation level for this application. The licensee's response identified the use of pre-solved cutsets to generate

the application risk results. The staff is concerned that the use of pre-solved cutsets for

this application may not be adequate to obtain an accurate assessment of the

configuration-specific risk level. Specific ally, the service water unavailability and random failure probability, coincident with the unavailability or failure of the backup normal

service water system (identified in other RAI responses as credited in the model),

represents a very unlikely failure mode, which may not appear in many cutsets above

truncation. Regenerating the cutsets with the service water train out-of-service to reflect

the actual configuration during the proposed extended completion time (CT) could result

in many more cutsets generated above the nominal truncation level, resulting in an

increase in the configuration-specific risk. This can be an especially significant problem

if the nominal unavailability and random failure probability result in large numbers of

cutsets just below the truncation level. In addition, initiating events, such as

loss-of-service water, are more likely to occur when one of the two trains is out-of-service. This frequency increase may not be reflected in the pre-solved cutsets, and, therefore, the risk contribution from such initiators would not be reflected in the

results.

Please provide risk results which avoid this potential non-conservatism by regenerating

cutsets for the specific configuration(s) expected as result of the changes requested and

addressing the increased likelihood of the loss-of-service water initiating event.

3. The NRC staff requested the licensee to address initiating events not included in its risk assessment model, including fires, floods, seis mic events, and other external events.

The licensee identified proposed compensatory measures, to include walkdowns of the

operable service water train, fire and flood watches in rooms identified as risk important

in the licensee's internal flooding, seismic margin, and fire protection evaluations, and

evaluation of transient combustibles within 20 feet of the operable service water train.

The staff is unable to conclude that these sources of risk will not be potentially significant

while the plant configuration has one service water header unavailable.

(a) With regard to seismic risk, there is no risk mitigation provided by the compensatory measure of walkdowns of rooms identified as risk-important in a

seismic margins analysis. Please provide a summary of the relationship between

the results of the seismic margins analyses which it identified in its response with

the specific configuration of the plant when it is reliant upon a single service

water header. The seismic ruggedness of the remaining operable service water

system should be addressed to justify that a seismic event is not likely to cause

damage to this system. The qualitative information should be adequate for the

NRC staff to conclude that seismic risk is not significant for this application.

Otherwise, additional quantified estimates should be provided to characterize the

risk impact.

(b) With regard to internal flooding, the NRC staff agrees that the compensatory measure of verifying the availability of flood mitigation equipment for the

protected train is beneficial. However, the NRC staff needs to understand the

significant contributors to internal flooding risk, how these could potentially

impact the remaining operable protected train of equipment, or otherwise result in

increased reliance upon that equipment, and either conclude that the risk of

these scenarios is not significant or that compensatory measures are in place to

mitigate these events. Please provide adequate qualitative information for the

NRC staff to determine whether the internal flooding risk is not significant for this

application. Otherwise, please provide additional quantified estimates enable the

NRC staff to characterize the risk impact.

(c) Similar to internal fires, the compensatory measures identified for walkdowns and monitoring of transient combustibles is a benefit. The staff must understand the

significant contributors to fire risk, how these could potentially impact the

remaining operable protected train of equipment or otherwise result in increased

reliance upon that equipment, and either conclude that the risk of these

scenarios is not significant or that compensatory measures are in place to

mitigate these events. Please provide adequate qualitative information for the

NRC staff to determine whether the fire risk is not significant for this application.

Otherwise, provide additional quantified estimates to characterize the risk impact.

(d) Please discuss the impact of this proposed TS change on other external events (i.e., hazardous material leaks, transportation events, high winds and tornadoes, etc.). Although weather-related loss-of-offsite power was addressed (and

credited in the risk analyses), there is no discussion of high winds with regard to

any unique vulnerabilities during the time the service water header is out of

service, the vulnerability of the backup normal service water system to high

winds, or other discussion to characterize the site with regard to this source of

risk. Other external events were not discussed at all.

4. The NRC staff previously requested the licensee to address sources of uncertainty in the risk analyses which may be significant for this application. In response, the licensee

stated, without justification or basis, that the assumptions applied and the use of point

estimates of mean values would not invalidate the risk analyses. For the specific areas

identified by the NRC staff as examples of key assumptions, the licensee identified the

methodologies used in the risk analyses, but did not provide any assessment as to the

impact of uncertainties associated with these assumptions on the application.

The purpose of this RAI was to request the licensee to review the important PRA

assumptions and elements of the model which are especially relevant to the risk of the

plant configuration with one service water header unavailable, to characterize the impact

of these uncertainties, and to develop and present its basis as to why these sources of

uncertainty do not adversely impact the result s of the risk analyses relevant to the NRC staff decision to accept a 14-day extended CT. Please provide a more specific technical

justification for your conclusions that the uncertainties do not affect the risk analyses.

With regard specifically to equipment repair credit, please identify what equipment

repairs are credited, the numerical value and basis for such credit, and the specific

impact to the risk metrics for this application. (Note that the NRC staff position does not

permit PRA credit for repair and restoration of any equipment subject to the extended CT

to be used in the calculation of the risk metrics.)