ML20245D212

Forwards Addl Info to Suppl 890414 Application for Amend to License DPR-61,per NRC Request

ML20245D212
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	06/16/1989
From:	Mroczka E, Sears C CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST NUCLEAR ENERGY CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20245D215	List: ML20245D212 ML20245D228
References
GL-84-04, GL-84-4, NUDOCS 8906270017
Download: ML20245D212 (5)

Text

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.airar ma.ewanwco (203) 665-5000 June 16, 1989 Docket No. 50-213 B13276 Re: Cycle 15 Coastdown GL 84-04 SEP Topic III-6 ISAP Topic 1.08 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Gentlemen:

Haddam Neck Plant Cycle 15 Coastdown Asymmetric LOCA Loads on Reactor Vessel Internals In a letter dated April 14,1989,II) Connecticut Yankee Atomic Power Company (CYAPCO) proposed to amend Operating License DPR-61 by incorporating certain changes into the technical specifications for the Haddam Neck Plant. These proposed changes were being submitted to support coastdown operation of the Haddam Neck Plant at the end of Cycle 15, the current cycle. The purpose of this letter is to provide the NRC Staff with additional information to supple-ment the April 14, 1989, letter and support the Staff's review of that license amendment request. This letter documents discussions that CYAPCO has had I recently with the Staff on two issues:

1.

The impact on the Cycle 15 coastdown analysis gee the April 14, 1989,  !

letter) from a recent reportable occurrence documenting a model discrepancy with the Haddam Neck Plant large-break loss-of-coolant accident (LOCA) analysis.

2. The impact of " asymmetric LOCA loads" on the reactor coolant system (RCS) and reactor vessel internals for Cycle 15 coastdown operation.  ;

1 (1) E. J. Mroczka letter to the U.S. Nuclear Regulatory Commission, "Haddam 1 Neck Pl ant, Cycle 15 Coastdown, Proposed Changes to Technical  ;

Specifications," dated April 14, 1989. l l

(2) D. B. Miller letter to the U.S. Nuclear Regulatory Commission,

" Reportable Occurrence LER 50-213/89-006-00," dated May 23, 1989.

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U.S. Nuclear Rcgulatory Commission B13276/Page 2 June 16, 1989 This letter summarizes how both of these issues have been addressed for the Haddam Neck Plant in general and for Cycle 15 coastdown operation in particu-lar.

Revised LOCA Analysis During CYAPCO's large-break LOCA model development activities, a modeling discrepancy was noted in the Westinghouse Interim Acceptance Criteria (IAC) evaluation model. The Westinghouse model used a nonconservative distribution of the downcomer/ lower plenum nodal volumes based on RCS nodalization data provided to Westinghouse by CYAPC0 in 1985. The CYAPC0 data was based on the assumption that the downcomer region within the reactor vessel extended to the bottom of the core barrel, thus minimizing the lower plenum volume. The IAC evaluation model assumes that the downcomer extends only to the bottom of the active fuel, which yields a larger lower plenum volume. The larger lower plenum volume yields a longer adiabatic fuel rod heat-up period, and therefore a higher peak cladding temperature (PCT). The NRC problem in accordance with 10CFR50.73(a)(2)(v)(D).ytaff was notified of this The impact of this modeling discrepancy was assessed by redistributing the volume between the downcomer and the lower plenum and requalifying the limit-ing break for Cycle 15 full power and coastdown operation. The results of the reanalysis show the following:

For Full Power Operation:

1. The current limiting linear heat generation rate (LHGR) must be reduced from 14.6 to 13.7 kW/ft in order to maintain the PCT less than the IAC limit af 2300'F.

2. The current 100 percent power axial offset alarm set point must be reduccd from -15 to -14 percent in order to assura that the core is operated at a peak LHGR less than 13.7 kW/ft.

For Coastdown Operation:

3. The coastdown PCT increased from 2213' to 2269'F at the LHGR limit proposed iri CYAPC0's letter dated April 14, 1989.

On April 25, 1989, CYAPC0 initiated administrative controls to limit the LHGR and axial offset to the values outlined above to address full power operation i' for the rest of the current cycle. These values are more restrictive than the current technical specifications and ensure that the IAC limit of 2300*F for PCT is not exceeded. As discussed with the NRC Staff, CYAPC0 will not be (3) Ibid.

U.S. Nuclear Regulatory Commission 813276/Page 3 June 16, 1989 proposing and submitting a license amendment request since by the time it was processed by CYAPC0 and the NRC Staff, the end of full power core life for Cycle 15 would have been achieved.

The LOCA reanalysis for Cycle 15 coastdown conditions shows an increase in PCT from 2213' to 2269'F. Since these results continue to meet the IAC limit of 2300*F, the proposed license amendment submitted on April 14, 1989, remains valid. A revision to page 7-2 of the " Technical Report Supporting Cycle 15 Operation--Coastdown Addendum," submitted with CYAPC0's April 14,19f,9, letter is provided as an attachment to this letter. This revised page reflects the updated analysis results.

Asymmetric LOCA Loads In recent telephone conversations regarding the Cycle 15 coastdown, the NRC Staff questioned whether CYAPC0 had examined the impact of " asymmetric LOCA loads" on the RCS and reactor vessel internals for Cycle 15 coastdown opera-tion. This in turn led to questions as to where the g

with respect to the NRC 5taff's Generic Letter 84-04gddam andNeck Plant stood the leak-before-break issue. In summary CYAPC0 has fully addressed Generic Letter 84-04 for the Haddam Neck Plant ar d demonstrated that the leak-before-break philosophy as presented in Westing'iouse WCAP-9558, is applicable to Haddam Neck. This conclusion is based on the following.

There were two conditions identified in Generic Letter 84-04 for applying the leak-before-break philosophy to those plants, which include Haddam Neck, with Systematic Evaluation Program (SEP) seismic spectra. Condition No. 1, regard-ing the maximum bending moments for the highest stressed vessel nozzi location, was addressed by CYAPC0 in a lettg) dated Aprilas11, (1g6,gipe supplemented by letters dated August 26, 1986, and May 1, 1987. Therein (4) D. G. Eisenhut letter to All Operating PWR Licensees, Construction Permit Holders, and Applicants for Construction Permits, " Safety Evaluation of Westinghouse Topical Reports Dealing with Elimination of Postulated Pipe Breaks in PWR Primary Main Loops (Generic Letter 84-04)," dated February 1, 1584.

(5) J. F. Opeka letter to C. I. Grimes, " Response to Request for Additional Information on Generic Letter 84-04," dated April 11, 1986.

(6) J. F. Opeka letter to C. 1. Grimes, " Reactor Coolant System Seismic Recalculations," dated August 26, 1986.

l (7) E. J. Mroczka letter to the U.S. Nuclear Regulatory Commission, " Reactor Coolant System Seismic Reevaluation and Final Plans for Modifications,"

dated May 1, 1987.

U.S. Nuclear Regulatory Commission B13276/Page 4 June 16, 1989 CYAPC0 confirmed seismic analyses show that for Haddam Neck the maximum bending moments do not exceed the allowable limit specified in Generic Let-ter 84-04. It was also stated that these seismic analyses identified certain RCS modifications necessary to ensure that WCAP-9558 was applicable. In CYAPCO's Inte Safety Assessment Program (ISAP) update report dated March 2,1989,grgted it was reported under ISAP Topic No. 1.08, " Seismic Modifi-cations to Reactor Coolant System," that the subject RCS modifications were completed during the 1987-1988 refueling outage. Condition No. 2 regarding the sufficiency of RCS leakage detection systems to detect an RCS leak of 1 gpm in 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 5 1986,ggyas as addressed superseded byby CYAPC0 in a license a subsequent amendment request dated Mayrequest 30, dated April QI 1989.5 The NRC Staff issued License Amendment No.116, dated May 31, 1989,(11) to Operating License DPR-61 for the Haddam Neck Plant, approving technical specifications that govern the operability of systems that are able to detect an RCS leak of 1 gpm for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Having satisfactorily addressed both conditions of Generic Letter 84-04, CYAPC0 has demonstrated that the leak-before-break philosophy is applicable to the Haddam Neck Plant. CYAPC0 has concluded that all outstanding issues with respect to the RCS portion of SEP Topic III-6 are resolved.

CYAPCO also considered the impact of the Cycle 15 coastdown operation on LOCA loads for the RCS and reactor vessel internals. In a recent telephone conver-sation with the NRC Staff, CYAPC0 stated that for LOCA loads on RCS components outside the reactor vessel, the design basis was not affected by coastdown.

In a separate telephone conversation discussing LOCA loads on reactor vessel internals, CYAPC0 informed the NRC Staff that Westinghouse typically qualifies reactor vessel internals for loads associated with pipe breaks on the order of 100 square inches in area. An analysis performed for the Haddam Neck Plant showed that a through-wall crack in the most highly stressed location in the primary coolant loop would yield a crack opening of less than I square inch in area; therefore, the projected loads on the Haddam Neck Plant reactor vessel internals are bounded by the typical Westinghouse design.

(8) E. J. Mroczka letter to the U.S. Nuclear Regulatory Commission,

" Integrated Safety Assessment Program (ISAP)," dated March 2, 1989.

(9) J. F. Opeka letter to C. 1. Grimes, " Proposed Revision to Technical  ;

Specifications--Leakage Detection Systems," dated April 25, 1986.  !

(10) E. J. Mroczka letter to the U.S. Nuclear Regulatory Commission, i

" Supplement to License Amendment Request, Response to Request for Adaitional Information (TAC No. 61329)," dated May 30, 1989.

(11) A. B. Wang to E. J. Mroczka, " Issuance of Amendment (TAC No. 61329),"

dated May 31, 1989.

U.S. Nuclear Regulatory Commission B13276/Page 5 June 16, 1989 In addition to the above, the change in density of the primary coolant (due to decreasing average RCS temperature) is so small (< 5 percent) as to result in an insignificant increase in loads on the reactor vessel internals.

i We trust that the above information supports the review of the April 14, 1989, license amendment request. Please contact us if you have any questions.

Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY D . b, b E. J. Mroczka "

Senior Vice President b

By: C. F. Sears Vice President Attachment cc: W. T. Russell, Region I Administrator A. B. Wang, NRC Project Manager, Haddam Neck Plant J. T. Shedlosky, Senior Resident Inspector, Haddam Neck Plant l

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