ML20086M397

Responds to Recommendation in NRC SER on Station Blackout Rule (10CFR50.63) Transmitted Via NRC . Commitments Discussed in Encl Will Be Implemented by Nov 1993,as Permitted by Station Blackout Rule

ML20086M397
Person / Time
Site:	Fort Calhoun
Issue date:	12/11/1991
From:	Gates W OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LIC-91-325R, NUDOCS 9112170411
Download: ML20086M397 (8)

Text

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Omaha Public Power District 444 South 16th Street Mall i Omaha, Net >raska 68102-2247 402/636-2000 December 11, 1991 LIC-91-325R U. S. Nuclear Regulatory Commission Attn Document Control Desk Mail Station Pl-137 Washington. DC 20555

References:

1. Docke' a

2. Letter 4  % & Wigginton) to OPPD (W.

G. Gates ,

hr 1, 1991 Gentlemen:

SUBJECT:

OPPD Response to .- w *J ons in the Stati on Blackout Rule (10 CFR bt' .3 ) Safety Evaluation Report The NRC Safety Evaluation Report (SER) on Station Blackout (SBO) for the Fort Calhoun Station (Reference 2) was based on previous Omaha.Public Power District (OPPD) submittals in response to the SBO Rule. The SER contained several recommendations which require OPPD resolution before the NRC concludes that Fort Calhoun Station is in compliance with the SBO Rule.

The SER recommendations are restated and OPPD recponses are i provided in the attachment to this letter. Commitments provided as part of the response to each recommendation will be implemented by November, 1993 as allowed by the SBO Rule.

If you should have any questions. please contact me.

1 Sincerely, V, b. /h l

W. G. Gates l Division Manager Nuclear Operations WGG/sel Attachment l

c: LeBoeuf, Lamb, Leiby & MacRae i R. D. Martin, NRC Regional Administrator, Region IV D. L. Wigginton, NRC Senior Project Manager l R. P. Mullikin, NRC Senior Resident Inspector p

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LIC-91-325R-e , Attachment-OPPD Response to Safety Evaluation Report Recommendations Regarding FCS' Station Blackout MRC RECOMMENDhTION MO. 1 After analysing all the data in the Licensee's submittal, the staff finds that the Licensee should evaluate the plant for an -

8-hour copingLduration, or lower the minimum required: coping i duration froe 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.to 4-hours by selecting an EDG target reliability of-0.975.instead of 0.95. .If the EDG reliability selected is 0.975,: confirmation of this should be provided to the1 NRC > and included in the documentation supporting . the .

-response -to .the 880~ rule. Retention- of the 0.95 EDG

-reliability would result in a conclusion of nonconformance to-the SBO rule'and-would require that the Licensee revise and resubmit--its SBO response based on a plant coping capability analysis lfor 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

1 OPPD RESPONSES The NRC concluded that:by using The Logarithmic' Law in determining the Extreme Severe Weather-(ESW) category, the Fort Calhoun Station i twould fall in the 4-hour,LO.975 EDG reliability category.

There:are two. equations available to determine the ESW category. -

They are equations 2.4.1, 'lhe Logarithmic Law, and 2.4.2, The Power Law,.of Reference 1. OPPD utilized.-equation 2.4.2 to originally ,

determine the ESW category. Use of equation 2.4.2 yields _a wind-speed . of ' 111.1 - miles per hour -(MPH)' at 10. meters.

The NRC

. consultant,-' Science: Applications International Corporation (SAIC),

utilized. equation. 2.4.1: in determining the ESW category for Fort Calhoun. .Use of equation 2.4.1-yields a' wind speed of 107.67 MPH ate 10 meters.-

The"use of equation 2.4.2 is recognized by The'American Society of Civil Engineers and is utilized by_ the _ utility industries 'ini calculation: of transmission line_ design as- outlined in: The-Guidelines for Transmission Line Structural Loadino (Reference.3) .

Although neither., calculation ~ appears in ASCE 7-88-(formerly ANS__I-A58 il W ' Minimum Desion ' Loads for - Buildino and Other , Structures

. (Reference _4 ), the publication. does imply that OPPD's original' evaluationLin determining' terrain'and selection =of~equat)on 2.4.2 is; appropriate.

During-a phone conversation-between OPPD:and the NRC on November

-26, 1991',. a discussion o_f the proper use of Zo (roughness length) was conducted. The NRC consultant, SAIC, utilized e Zo of 0.05 -

i meter .in calculation of the wind speed using equation 2.4.1 of-

-Reference 1.. The NRC staff questioned if 0.05 meter was an

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LIC-91-325R Attachment appropriate value for Zo. OPPD had subsequent conversations with the author of References 1 and 2, Mr. Emil Simiu, and he stated that the industry used 0.05 meters because it was " average". He further stated that the industry typically used equation 2.4.2 because it was more simple to use and that the margin for error was approximately 1% to 2% between the two equations. This margin is also noted in Reference 1. After a description of the terrain at Fort Calhoun Station, Mr. Simiu suggested that an appropriate value for Zo would be approximately 0.03 meters if using equation 2.4.1.

The terrain around Fort Calhoun Station varies from snowy surface during the winter to low grass and/or f allow-like fields during the other seasons (the tallest field crop, located approximately one mile from the plant site, is corn), According to Reference 2, table 2.2.1, page 42, the surface roughness length (Zn) for terrains similar to Fort Calhoun vary from 0.01 meters to 0.04 meters. This is validated using similar analogies in References 3 and 4. Therefore, the value of Zo = 0.05 meters is conservative for Fort Calhoun Station.

Based on the above discussinn, results of the OPPD calculation, validated by the author of References 1 and 2, are still valid and yield a wind speed of 111.1 MPH. SAIC'c calculations, utilizing a different equation, yields a wind speed of 107.67 MPH. Utilizing Reference 1, use of either approach yields a return period between 1000 and 2000 years. SAIC's calculation yields a return period of 1052 years. This value is clearly between 1000 and 2000. Using the SAIC methodology, which is conservative, coupled with Table 8 of Regulatory Guide 1.155, the correct ESW category for Fort Calhoun is 2.

OPPD concludes that even using the more restrictive and conservative calculational method endorsed by SAIC, the correct ESW category is 2. Selecting a diesel generator target reliability of 0.95 and a ESW category 2, correctly places Port Calhoun Station in the four hour coping duration for a Station Blackout event.

4 NRC RECOMMENDATION NO. 2:

The Licensee needs to consider an aging factor of 1.25 in its battery capacity calculations, and verify that the batteries will have sufficient capacity for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to power the required SBO loads. The Licensee also needs to verify that Appendix R Lighting adequately replaces the emergency Lighting. All information resulting from the above actions should be included in the documentation supporting the SBO submittal that is to be maintained by the Licensee.

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e LIC-91-325R Attachment

.QPPD RESPONSE:

The Station Batteries will be replaced during the 1992 refueling outage. Therefore, the_ - battery - capacity calculations will be revised to ' include the 1.25 aging f actor and the new battery characteristics.

In 1989,- a plant walkdown was performed to determine if existing DC emergency lighting is sufficient to allow operations personnel to bring _the plant to_a safe _ hot shutdown condition in the event of a Control Room fire (Appendix R, Section J). Another walkdown in 1990 was performed by plant operations and training personnel to.

identify the areas which need to be illuminated -in case of a Station Blackout. The recommendations resulting from both walkdowns were incorporated into modification MR-FC-89-061.

This modification, which was implemented in 1990, upgraded the DC emergency lighting throughout the-plant. OPPD will reverify that emergency _ lighting that will be available during a SBO event is adequate to perform required actions. The above information will be included-in documentation maintained by 09PD in support of the SBO submittals.

NRC. REC 0)QE!LimT10M_MQ. . 3:

1._ The Licenses should verify that the locations from which the AFW-flow valves and-the ADV valves that are to be locally operated are habitable during 8B0 conditions, and should include the relevant information in the "

documentation to be maintained by the Licensee in support of the SBO submittals.

2 .- The Licensee needs-to perform a heat-up calculation to verify habitability for the operator to modulate the ADV-while maintaining cosaunication with the control room during an SBO event. _ The relevant information should be-included with the documentation to be maintained by the Licensee in support of the SBO submittals.

OPPD RESPON.SE:

The'ADV'and AFW flow control valves are located in the same room (Room 81) in close proximity-to each other. OPPD believes that, in spite of this,. habitability is not an issue. Heat-up calculations will-be completed and maintained to verify the habitability of the areas where the ADV and AFW flowcontrol valves are located. The above information will be included in documentation maintained by OPPD in support of the SBO submittals.

4 LIC-91-325R Attachment EBC_RCDt01ERQhTIQ]t NO. 4:

The Licensee should use an initial temperature for SBO control-room heat-up calculation no lower than that allowed by the TS or the administrative procedures. Also, the Licensee needs to verify the Control room heat generation rate includes the heat loads generated by the operators. The relevant information should be included with the documentation to be maintained by the Licensee in support of the SBO submittals.

OPPD RESPONSE:

As discussed in the November 26, 1991 telephone conversation

- between OPPD and the NRC, administrative controls will be implemented to ensure corrective actions are taken if the Control Room initial - temperature used in the heat-up calculation is exceeded. The Control Room heat generation rate used in the calculation does include the heat loads generated by the Control Room Operators. This information will be included with the documentation maintained by OPPD in support of the SBO submittals.

NRC RECOMMENDATION NO. 5:

1. The Licensee should verify by calculation and confirm to the NRC Staff, that there is sufficient RCS inventory to maintain the core covered during a 4-hour SBO event. The calculation should be included with the other documentation that is to be retained by Licensee in support of the GBO submittals.

2. The Licensee should verify that the resolution of this issue (RCS _ inventory) does not entail plant modifications, or provide the appropriate information on

, required modification.

OPPD RESPONSE:

OPPD has reviewed the calculations that were performed to calculste the RCS inventory at the end of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> coping period and finds the results consistent with the previously reported data. The calcu3ations were performed on a "best estimate" basis, consistent with the Regulatory Guide 1.155 requirements, using the CENTS computer code. The CENTS code is the latest in reactor system simulation codes developed by Combustion Engineering. Tne CENTS code incorporates a flexible nodal arrangement with state of the art algorithms for two phase media.

LIC-91-325R-

- Attachment The code accounts for downcomer of facts and pump seal leakage effects. The downcomer (cold log) volume varies due to elevation and pressure effects from the steam generator and pump loop seal.

The dynamic ef fects are calculated by CENTS which indicates sufficient inventory at the end of the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> coping period to maintain the core covered with water.

Leakage rates for the reactor coolant pump seals were conservatively assumed to be 25 gpm which is very high for the Combustion Engineering / Byron Jackson seal design. The final resolution of Generic Issue 23, " Reactor Coolant Pump Seal Failure" is being jointly resolved by the Combustion Engineering Owners Group, of which OPPD is a task participant.

Therefore, af ter review of the RCS coping calculations it is OPPD's conclusion that - suf ficient inventory exists to ensure the core remains covered during a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> Station Blackout event. Based on tbs above, no modifications are required.

HBNDATLQE NO. 6:

The Licensee should verify that the SBO equipment is covered by an appropriate QA program consistent with the guidance of RG.1.155, Appendix A. Confirmation that such a program-is in place or will be implemented should be included as part of the documentation supporting the SBO response.

OPPD RESEQRSAL A majority of the SB0 equipmer*J is currently in the Fort Calhoun -

-Station (FCS) QA Program. Utilizing the guidance of RG. 1.155 an evaluation will be performed to ensure SBO equipment is includod in the FCS QA Program, as appropriate. This information will be included with the documentation maintained by OPPD in support of the SBO Rule.

ERC RECOMMENDATION NO. 7:

It is the staff's-position that an EDG reliability program should 'be developed in accordance- with the guidance of RG.

1.155, Section 1.2. Confirmation that such a program is in place or will be implemented should be included in - the documentation that is to be maintained by the Licensee - in support of the SBO submittals.

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LIC-91-325R-Attachment i OPPD RESPONSE:

An EDG reliability program is being developed ~and- will be '

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. implemented to- meet the requirements of RG. 1.155, Section --1. 2.

- This program _will be included in the documentation maintained by '

. OPPD_-in support of the SBO submittals.

7tifBR_lSSERS._

Other NRC issues which were discussed in the Safety Evaluation but no specific recomunendations were made:

-1. Procedures

2. -Training OPPD RESPONSES

- 1. A . Station Blackout coping- procedure (EOP-07) was implemented in 1990._ Other applicable plant procedures will- be reviewed and revisions will be made (if

-necessary) to comply with the SBO Rule. '

2. . - Tho - operators - have been trained on proceduro EOP-07.

Additional training will be provided -if other plant procedures are revised to comply with the SBO Rule.

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LIC-91-325R Attachment

}tEFEREJQES,L

1. NBS Building Science Series 118

2. Wind Effects on Structures, Second Edition, 1986, authored by Emil Simiu and Robert H. Scanlan, and published by John .;iley & Sons, ISBN 0-471-86613-X.

3. Guidelines for Transmission Line Structural Loading, American Society of Civil Engineers, ISBN 0-87262-425-0.

4. ASCE 7-88 (Formerly ANSI A58.1), Minimum Design Loads for Buildings and Other Structures, 1990. American Society of Civil Engineers, ISBN 0-87262-742-X.

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