ML14178B038

Discusses 10CFR50.46 Large Break loss-of-coolant Evaluation Model for Plant

ML14178B038
Person / Time
Site:	Robinson
Issue date:	04/21/1997
From:	Mozafari B NRC (Affiliation Not Assigned)
To:	Hinnant C CAROLINA POWER & LIGHT CO.
References
TAC-M97759, NUDOCS 9704240211
Download: ML14178B038 (3)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-4001 April 21, 1997 Mr. C. S. Hinnant, Vice President Carolina Power & Light Company H. B. Robinson Steam Electric Plant, Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550

SUBJECT:

10 CFR 50.46 LARGE BREAK LOSS-OF-COOLANT EVALUATION MODEL FOR H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 (TAC M97759)

Dear Mr. Hinnant:

In our letter of October 11, 1996, we informed you about the problems that we had identified concerning changes in the large break loss-of-coolant accident (LBLOCA) evaluation model developed by Siemens Power Corporation (SPC) for pressurized water reactors (PWRs) to comply with 10 CFR 50.46. The changes to the 1986 approved LBLOCA evaluation model were proposed to correct an error of nonphysical behavior in the prediction of heat transfer coefficients during core reflood. We indicated in the letter of October 11, 1996, that the 1986 model had an unacceptable error and we requested, in accordance with 10 CFR 50.46(a)(3)(ii), that you assess the impact of the model error and changes, and take whatever actions are required to assure compliance with 10 CFR 50.46 for the H. B. Robinson Steam Electric Plant, Unit No. 2 (HBR).

At a meeting with other affected licensees on October 16, 1996, you were asked to report to the NRC regarding your assessment of the peak cladding temperature (PCT) for the LBLOCA and the corrective actions and compensatory measures that have been undertaken, both short-term and long-term for HBR.

A new estimated PCT of 2114 oF was reported in your letter of January 17, 1997. You state that the new PCT estimate:

...utilized a measured resinter density from a randomly selected sample from each lot of the cycle 18 reload fuel pellets as an input to the RODEX2 Fuel Rod Thermal-Mechanical Response EM [Evaluation Model] in place of the density change specified in the manufacture of the cycle 18 reload fuel.

The manufacturing specifications for the cycle 18 reload fuel resinter density required a 95% Upper Confidence Limit (UCL) on the mean resinter density change of 1.4%. The actual measured UCL resinter density change based on random samples of each lot was 0.87%.

The measured resinter density change data was sent to the NRC on March 12, 1997.

Further evaluation of this concern was conducted by the NRC inspection team during its inspection activities at SPC. On the basis of unresolved concerns raised by the NRC inspection team at SPC, the NRC staff requests that you provide the following information to address an inconsistency in the SPC analysis. Reg Guide 1.126 states that when applying the 95% UCL statistical 9704240211 970421 PDR ADOCK 05000261 P

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-2 Mr. C. S. Hinnant method, the largest mean Ao densification value (i.e., 1.11% theoretical density (TD) from lot 709-0r from Table 1) shall be used; as opposed to the 0.87% TD (also from Table 1) average mean Ao s densification value used by SPC.

Provide a discussion on why the SPC anatysis (SPC Topical XN-NF-81 58(P)(A), "RODEX2 Fuel Rod Thermal-Mechanical Response Evaluation Model") uses the average mean Apsntr densification value instead of the largest mean 0sntr densification value.required by the Reg Guide when applying the 95% UCL.

You are requested to provide the response to this RAI within 21 days of the receipt of this letter.

Sincerely, (Original Signed By)

Brenda Mozafari, Project Manager Project Directorate II-1 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-261 Distribution PUBLIC PDII-1 RF S. Varga J. Zwolinski EKendrick J. Johnson SMatthews OGC RGallo ACRS AAttard DOCUMENT NAME: G:\\Robinson\\ROB97759.RAI 4

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Mr. C. S. Hinnant H. B. Robinson Steam Electric Carolina Power & Light Company Plant, Unit No. 2 cc:

Mr. William D. Johnson Mr. Mel Fry, Acting Director Vice President and Senior Counsel N.C. Department of Environment, Carolina Power & Light Company Health and Natural Resources Post Office Box 1551 Division of Radiation Protection Raleigh, North Carolina 27602 3825 Barrett Dr.

Raleigh, North Carolina 27609-7721 Ms. Karen E. Long Assistant Attorney General Mr. Robert P. Gruber State of North Carolina Executive Director Post Office Box 629 Public Staff -

NCUC Raleigh, North Carolina 27602 Post Office Box 29520 Raleigh, North Carolina 27626-0520 U.S. Nuclear Regulatory Commission Resident Inspector's Office Mr. Max Batavia, Chief H. B. Robinson Steam Electric Plant South Carolina Department of Health 2112 Old Camden Road Bureau of Radiological Health Hartsville, South Carolina 29550 and Environmental Control 2600 Bull Street Regional Administrator, Region II Columbia, South Carolina 29201 U.S. Nuclear Regulatory Commission 101 Marietta St., N.W., Ste. 2900 Mr. T. D..Walt Atlanta, Georgia 30323 Director Operations & Environmental Mr. Dale E. Young Support Department Plant General Manager Carolina Power & Light Company Carolina Power & Light Company 412 S. Wilmington Street H. B. Robinson Steam Electric Plant Raleigh, North Carolina 27601 Unit No. 2 3581 West Entrance Road Hartsville, South Carolina 29550 Mr. Milton Shymlock U. S. Nuclear Regulatory. C ommission Public Service Commission 101 Marietta Street, N.W. Suite 2900 State of South Carolina Atlanta, Ga. 3023-0199 Post Office Drawer 11649 Columbia, South Carolina 29211 Mr. T. M. Wilkerson Manager -

Regulatory Affairs Mr. H. K. Chernoff Carolina Power & Light Company Supervisor, Licensing/Regulatory Programs H. B. Robinson Steam Electric Plant, Carolina Power & Light Company Unit No. 2 H. B. Robinson Steam Electric Plant, 3581 West Entrance Road Unit No. 2 Hartsville, South Carolina 29550-0790 3581 West Entrance Road Hartsville, South Carolina 29550