ML14162A261

Additional Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding - Flood Hazard Reevaluation

ML14162A261
Person / Time
Site:	Calvert Cliffs
Issue date:	03/07/2014
From:	Korsnick M Constellation Energy Nuclear Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML14162A261 (4)

Text

Office 410-470-613,3 f ý; Chief E(2'ct iv Offier Fax 44~3-213-6739

..nWia: Marja.Korsnick@cengj~c~com CENG..

a joint venture of Aft onaeltaion 4 OE.tkr -eDF March 7, 2014 U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant, Units I and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 Docket Nos. 50-317 and 50-318 Additional Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding - Flood Hazard Reevaluation

REFERENCES:

(a) Email from M. Thadani (NRC) to E. Tyler (CENG), "Calvert Cliffs R2.1 flooding reevaluations: RAIs," dated January 9, 2014 (ML14010A015)

(b) Letter from J. A. Spina (CENG) to Document Control Desk (NRC), Calvert Cliffs Nuclear Power Plant, Units I and 2, Flood Hazard Reevaluation Report, dated March 12, 2013 (ML13078A010)

(c) Letter from M. G. Korsnick (CENG) to Document Control Desk (NRC),

Calvert Cliffs Nuclear Power Plant, Units I and 2, Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding - Flood Hazard Reevaluation, dated February 10, 2014 On January 9, 2014 (Reference a), the Nuclear Regulatory Commission (NRC) issued a Request for Additional Information (RAI) to Constellation Energy Nuclear Group, LLC (CENG) regarding the Calvert Cliffs Nuclear Power Plant, LLC (CCNPP) Flood Hazard Reevaluation Report submitted on March 12, 2013 (Reference b). Reference (c) provided partial responses to Reference (a) and an explanation for the delay in submitting the CENG response to the NRC's RAI 3. The response to RAI 3 has now been prepared and is provided in Attachment (1).

This letter contains no new regulatory commitments.

If there are any questions regarding this submittal, please contact Bruce Montgomery, Manager-Nuclear Safety and Security, at 443-532-6533.

Constellation Energy Nuclear Group, LLC 100 Constellation Way, Suite 200C, Baltimore, MD 21202 AD0o

Document Control Desk March 7, 2014 Page 2 1declare under penalty of perjury that the foregoing is true and correct. Executed on March 7, 2014.

Sincerely, or snický MGK/GGM/EMT

Attachment:

(1) Calvert Cliffs Nuclear Power Plant Response to Request for Additional Information (RA! 3) cc: NRC Project Manager, Calvert Cliffs Resident Inspector, Calvert Cliffs NRC Project Manager, Ginna Resident Inspector, Ginna NRC Project Manager, Nine Mile Point Resident Inspector, Nine Mile Point Regional Administrator, NRC Regioný I S. Gray, DNR

ATTACHMENT (1)

CALVERT CLIFFS NUCLEAR POWER PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (RAI 3)

Constellation Energy Nuclear Group, LLC March 7, 2014

ATTACHMENT (1)

CALVERT CLIFFS NUCLEAR POWER PLANT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (RAI 3)

NRC RAI 3 - Local Intense Precipitation Flooding The licensee is requested to provide a description of the methods used to incorporate elevation measurements in the flood analysis and the likely magnitude of the errors associated with these elevations. Elevation measurement and conversion is crucial in defining flow parameters such as slope and flowpaths. Staff are also requesting a discussion of the methods used to incorporate elevation measurements in the flood analyses performed using HEC-RAS and HEC-HMS.

CCNPP Response Ground elevations within the Calvert Cliffs Nuclear Power Plant (CCNPP) property boundary were obtained from an aerial photogrammetric survey conducted in 2007. The survey specification requires that at least 90 percent of all elevations on the I-foot contours are accurate within one-half the contour interval (0.5 foot), and the remaining 10 percent are accurate within one contour interval (1.0 foot). For spot elevations, the specification requires that at least 90 percent of the elevations shown on the maps are accurate within one-fourth of the contour interval (0.25 foot), and the remaining 10 percent are accurate within one-half of the contour interval (0.5 foot). The local intense precipitation flood evaluation in the Flooding Hazard Reevaluation Report (FHRR) used ground elevation data only within the CCNPP property boundary as the contributing sub-basins and schematized flow channels are entirely located within the property. The topographic data, as obtained from the aerial survey, were used to develop the HEC-RAS cross-sections as shown in Figures 2. 1-7a, 2.1-7b, and 2.1-8 of the FHRR. The cross-sections include the effects of structures that are blocking flows in the overbanks and were represented in HEC-RAS as an obstruction. Also, the cross-section areas where there is no flow conveyance were modeled as ineffective flow areas in HEC-RAS.

In addition to using the recent surveyed ground elevation data to develop the local intense precipitation flood model, the HEC-HMS and HEC-RAS models incorporated highly conservative assumptions, including conservative Manning's roughness coefficients and reduced time of concentration values. In addition, the entire site was considered impervious and modeled with a curve number of 98, and all storm drains were considered to be non-operational.

The combined effect of these conservative assumptions is expected to adequately compensate for any small uncertainty in the ground elevation measurements. Therefore, the estimated flood levels can be considered as the maximum possible flood levels due to the local intense precipitation over the site.

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