ML14353A051

Request for Additional Information, Request to Revise Updated Safety Analysis Report, Design and Evaluation of Seismic Class I Structures Using Ascm (Alternate Seismic Criteria and Methodologies) Developed Floor Response Spectra

ML14353A051
Person / Time
Site:	Fort Calhoun
Issue date:	12/22/2014
From:	Lyon C Plant Licensing Branch IV
To:	Cortopassi L Omaha Public Power District
Lyon C
References
TAC MF4016
Download: ML14353A051 (4)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 22, 2014 Mr. Louis P. Cortopassi Site Vice President and Chief Nuclear Officer Omaha Public Power District Fort Calhoun Station 9610 Power Lane, Mail Stop FC-2-4 Omaha, NE 68008

SUBJECT:

FORT CALHOUN STATION, UNIT NO. 1 -REQUEST FOR ADDITIONAL INFORMATION RE: LICENSE AMENDMENT REQUEST TO USE ASCM-DEVELOPED FLOOR RESPONSE SPECTRA IN THE DESIGN AND EVALUATION OF SEISMIC CLASS I STRUCTURES (TAC NO. MF4016)

Dear Mr. Cortopassi:

By letter dated April 25, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14118A435), Omaha Public Power District submitted a license amendment request to permit the use at Fort Calhoun Station, Unit No. 1 of alternate seismic criteria and methodologies (ASCM)-developed seismic floor response spectra in the design and evaluation of seismic Class I structures and structural elements attached to structures.

The U.S. Nuclear Regulatory Commission staff has reviewed the information provided in your application and determined that additional information is required in order to complete its formal review. The enclosed questions were provided to B. Hansher of your staff on December 18, 2014. Please provide a response to the enclosed questions within 30 days of the date of this letter. If you have any questions, please contact me at 301-415-2296 or via e-mail at Fred.Lyon@nrc.gov.

Sincerely, Carl F. Lyon, Project Manager Plant Licensing Branch IV-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-285

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST TO USE ASCM-DEVELOPED FLOOR RESPONSE SPECTRA IN THE DESIGN AND EVALUATION OF SEISMIC CLASS I STRUCTURES OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION. UNIT NO. 1 DOCKET NO. 50-285 By letter dated April 25, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14118A435), Omaha Public Power District (OPPD, the licensee) submitted a license amendment request (LAR) to permit the use at Fort Calhoun Station, Unit No. 1 (FCS) of alternate seismic criteria and methodologies (ASCM) developed seismic floor response spectra in the design and evaluation of seismic Class I structures and structural elements attached to structures.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in the LAR and determined that the additional information below is required in order to complete its formal review.

1. Section 2.0 of the LAR states, in part, that Reference 3.6 as identified in USAR [updated safety analysis report],

Appendix F is engineering analysis EA-FC-94-003, "Alternate Seismic Criteria and Methodologies," Revision 0, which has since been updated and is now Revision 1.

a) Please describe the content of engineering analysis EA-FC-94-003, "Alternate Seismic Criteria and Methodologies," and clarify its association with the information provided to the NRC staff at the time of review of FCS ASCM and preparation of the NRC's safety evaluation dated April 16, 1993.

b) Please discuss whether the updates to EA-FC-94-003 affect any technical information that was provided to the NRC staff at the time of review of FCS ASCM and preparation of the NRC's safety evaluation dated April 16, 1993.

2. Regarding the proposed revision to the USAR, Section 5.11.3 and Appendix F, Section 2.1.4, included in Attachment 1 to the LAR:

Enclosure

b. Figures F-1 and F-2 shown in Appendix F of the FCS USAR are design basis ground response spectra for FCS. The two proposed alternatives, to determine

• seismic loading, one using ground response spectra and the other using ASCM floor response spectra are not consistent. In addition, the existing wording of the USAR, Section 5.11.3 refers to Appendix F where FCS seismic criteria are outlined. The proposed revision to Section 5.11.3 of the FCS USAR appears to be redundant.

Please provide a discussion relative to the proposed revision of the FCS USAR, Section 5.11.3 and reconcile the apparent inconsistency between the two proposed alternatives.

c. The proposed revision to Appendix F, Section 2.1.4 of the FCS USAR states that:

An alternative method of determining the seismic loads for a Class 1 structure and structural elements attached to structures is available using the ASCM floor response spectra provided in Reference 3.6. The maximum "g" value from the curve for the building floor at which the structure is anchored is to be used.

The second sentence "The maximum 'g' value from the curve for the building floor at which the structure is anchored is to be used." is not consistent with the seismic analysis methods for piping and heating, ventilation, and air conditioning systems described in the NRC's staff safety evaluation dated April 16, 1993.

Please provide further discussion and reconcile this apparent inconsistency.

3. The OPPD July 31, 1992, letter to the NRC included FCS, Unit 1 in-structure response spectra (ISRS) for the Auxiliary building, Containment building, and containment internal structures. Specifically, the ASCM ISRS in the vertical direction depicts a pronounced second peak at the frequency range of approximately 12 Hertz to 18 Hertz.

The design basis vertical floor response spectra for the Reactor and Auxiliary buildings are shown in Figures F-22 through F-27 of Appendix F of the FCS USAR. There are several indications in Appendix F of the FCS USAR that for equipment, piping, and electrical raceways, the spacing of restraints and support system was controlled to maintain the lowest vertical and horizontal natural frequencies of the component equal to or greater than 18 Hertz and 6 Hertz, respectively. Thus, limiting the acceleration used for the analysis to approximately zero period acceleration of the floor response spectra.

OPPD has indicated that the ASCM ISRS represent an updated and a more refined version of the FCS original design basis spectra. Please provide information to reconcile the effects of the ASCM ISRS on the existing Class I systems and components, located in Class I structures.

• .. ML14353A051 *memo dated OFFICE NRRIDORULPL4-1/PM NRR/DORLILPL4-1/LA NRR/DE/EMCB/BC(A)* NRR/DORL/LPL4-1/BC(A) NRR/DORLILPL4-1/PM NAME FLyon JBurkhardt YLi EOesterle FLyon DATE 12/22/14 12/19/14 12/16/14 12/22/14 12/22/14