ML14206A206

July 2, 2014 Summary of Meeting with Exelon Generation Company, LLC to Continue Discussions on the Proposed Risk-Informed Approach to the Resolution of Generic Letter 2004-02

ML14206A206
Person / Time
Site:	Calvert Cliffs
Issue date:	11/07/2014
From:	Nadiyah Morgan Plant Licensing Branch 1
To:	Exelon Generation Co
Morgan N
References
TAC MC4672, TAC MC4673
Download: ML14206A206 (5)

Text

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LICENSEE: Exelon Generation Company, LLC FACILITY: Calvert Cliffs Nuclear Power Plant, Unit Nos. 1 and 2

SUMMARY

OF JULY 2, 2014, MEETING WITH EXELON GENERATION COMPANY, LLC, TO CONTINUE DISCUSSIONS ON THE PROPOSED RISK-INFORMED APPROACH TO THE RESOLUTION OF GENERIC LETTER 2004-02, "POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED-WATER REACTORS" WITH A FOCUS ON ONGOING CHEMICAL EFFECTS TESTING AND EARLY RESULTS (TAC NOS. MC4672 AND MC4673)

On July 2, 2014, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Exelon Generation Company, LLC, the licensee, at NRC Headquarters, Three White Flint North, 11601 Landsdown Street, Rockville, Maryland.

The purpose of the meeting was to discuss the licensee's proposed risk-informed approach to the resolution of Generic Letter (GL) 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized-Water Reactors" with a focus on ongoing chemical effects testing and early results for Calvert Cliffs Nuclear Power Plant (Calvert Cliffs), Unit Nos. 1 and 2. The meeting notice and agenda, dated June 17, 2014, is available in the Agencywide Documents Access and Management System (ADAMS) at Accession No. ML14168A246. A list of attendees is provided in the Enclosure, but may not be all inclusive.

The licensee (1) summarized the Calvert Cliffs Risk-Informed GL 2004-02 Program; (2) discussed the Autoclave Chemical Effects Test Results; (3) discussed the Option 2a Refined Closure Plan; and (4) scheduled future periodic meetings (See ADAMS Accession No. ML14142A323).

The information exchanged during the meeting is summarized below.

• Calvert Cliffs' representatives provided a summary of the plant specific actions that have been made to support GL 2004-02 resolution, including removal of some plant hardware that contained aluminum, removal or double banding of deleterious insulation material, a change in the post loss-of-coolant accident (LOCA) buffer chemical, and installation of a large 6000 square foot pocket design strainer. The licensee also described chemical effects related testing that has been performed to date.

• The licensee discussed the deterministic and risk informed parallel paths they are pursuing to resolve GL 2004-02. Although the test results, thus far suggest that the licensee will be able to achieve closure of the issue using a deterministic path, the licensee indicated that they will continue development of a "simplified" risk-informed evaluation since that analysis may help address questions that arise in the future after issue closure.

• The licensee discussed the results from autoclave test series that evaluated: (1) the initial highest temperature post-LOCA conditions; (2) the potential contributions from alkyd coatings; and (3) chemical contributions from integrated tests to support decisions on the length of a larger scale test. In total, the licensee performed more than 50 autoclave tests.

• The licensee described their treatment of inorganic zinc (IOZ) coatings in the chemical effects testing. All IOZ in the pipe break zone of influence and all unqualified IOZ will be modeled with double the surface area for testing. One half the zinc surface area will be submerged during the test as it is assumed to fall into the sump pool. The remaining IOZ will be treated as staying on the wall such that it will be submerged in the test, only if it is below the post-LOCA flood plane. This approach is acceptable to the NRC staff.

• Autoclave testing was performed on two alkyd coatings typical of the alkyds used at Calvert Cliffs. Comparison of the chemical analyses from tests with and without coatings showed potential chemical effects contributions from these two coatings was insignificant. The licensee stated that post-test visual observations showed no disbanded coatings. Based on these results, the NRC staff agreed that alkyd coatings would not need to be included in a larger scale, integrated plant-specific test.

• The NRC staff suggested that the licensee skip over the five slides related to previous Phenomenon Identification and Ranking Table (PIRT) issues. The NRC staff made this recommendation since it appears the licensee has a high probability of resolving GL 2004-02 with a deterministic approach. For licensees with previously NRC accepted deterministic chemical effects evaluations, the NRC staff has balanced remaining uncertainties against conservative evaluation methods instead of having the licensee address remaining PIRT issues. Therefore, the NRC staff expects the licensee to show some margin to account for uncertainties with a deterministic resolution. The licensee accepted the NRC staff's suggestion to skip the portion of their presentation related to PIRT issues.

• The licensee provided a plot of strainer plant-specific net positive suction head (NPSH) margin as a function of time after a LOCA that showed a rapidly increasing allowable head loss from debris. The NRC staff recognized that the plot shows that NPSH margin quickly increases, but noted that other considerations (e.g., deaeration, flashing) would become more limiting than NPSH margin.

• The licensee discussed a refined closure plan that relies on the testing performed to date to achieve closure in a deterministic manner. Although the NRC staff agreed that the test results to date warrant reducing the scope and potentially the length of a larger

scale integrated test, the NRC staff stated that such a test would be important for the following reasons:

- The larger scale tests has some important features not evident in the autoclave tests such as continuous flow past the materials, recirculation of fluid through a fiber bed and larger size samples for heterogeneous materials; Consistency with previous limited time delayed precipitation credit NRC has given to licensees based on smaller scale tests; and NRC Staff has observed testing where a larger scale test revealed some chemical precipitation that was not predicted by smaller scale tests. For example, see the information contained in ADAMS Accession No. ML083650005.

• The licensee has performed additional plant-specific strainer tests with chemical precipitate that the NRC staff has not seen. The licensee agreed to provide that information to the NRC staff, as it will provide the NRC staff with a better basis to judge any head loss margin used by the licensee in a deterministic resolution of GL 2004-02.

Members of the public were in attendance. Public Meeting Feedback forms were not received.

Please direct any inquiries to me at 301-415-1016, or Nadiyah.Morgan@nrc.gov.

Nadiyah S. Morgan, Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket Nos. 50-317 and 50-318

Enclosure:

List of Attendees cc w/encl: Distribution via Listserv

LIST OF ATTENDEES JULY 2. 2014, MEETING WITH EXELON GENERATION GL 2004-02 RISK-INFORMED RESOLUTION CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS. 1 AND 2 J NAME

! NRC Marioly Diaz-Colon /NRC

--~-- -MYHM -~------- -***********************

1 Gloria Kulesa NRC Vic Cusumano I Greg Makar *****************************************

Greene Tom Konerth I Ben Scott r**---~~- -~--*~* *---~***-****-~-*-

1 Steve Kinsey

-~-~------~*-----~~********

Eric Federline Associates, Inc.

I Josh Wargo I MPR Associates, Inc.

I Helmut Kopke Sargent & Lundy, LLC Sargent & Lundy, LLC j*Exelon Enercon Services, Inc.

Blake Stair I Enercon Services, Inc.

I Ron Ho**u***o****w--a****Y******** / Wolf Creek Nuclear Generating Corporation

• ---------- r-c:-:*--:----~--~*---.:_-----*-**----*---!1 I Marvin Lewis Member of the public Ruth Thomas of the public Enclosure

ML083650005.

• The licensee has performed additional plant-specific strainer tests with chemical precipitate that the NRC staff has not seen. The licensee agreed to provide that information to the NRC staff, as it will provide the NRC staff with a better basis to judge any head loss margin used by the licensee in a deterministic resolution of GL 2004-02.

Members of the public were in attendance. Public Meeting Feedback forms were not received.

Please direct any inquiries to me at 301-415-1016, or Nadiyah.Morgan@nrc.gov.

IRA/

Nadiyah S. Morgan, Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket Nos. 50-317 and 50-318

Enclosure:

List of Attendees cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC RidsNrrLAKGoldstein T. Wertz, NRR LPLI-1 R/F RidsRgn1 MaiiCenter T. Bowers, EDO Region I RidsAcrsAcnw_MaiiCTR RidsNrrDeEsgb M. Diaz-Colon, NRR RidsNrrDorl P. Klein, NRR S. Smith, NRR RidsNrrDorllpli-1 M. Yoder, NRR RidsNrrDssSsib RidsNrrPMCalvertCiiffs ADAMS Accession No.: ML14206A206 OFFICE DORL/LPLI-1 /PM DORLILPLI-1 /LA DE/ESGB/BC DSS/SSIB/BC DORL/LPLI-1 /BC NAME NMorgan KGoldstein GKulesa VCusumano BBeasley DATE 8/12/2014 08/07/2014 10/15/2014 10/16/2014 11/07/2014