ML19261B220
| ML19261B220 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 09/18/2019 |
| From: | Marshall M Plant Licensing Branch 1 |
| To: | Enrique Villar Exelon Generation Co |
| Marshall M, NRR/DORL/LPLI, 415-2871 | |
| References | |
| EPID L-2018-LLA-0222 | |
| Download: ML19261B220 (2) | |
Text
From:
Marshall, Michael To:
Villar, Enrique:(GenCo-Nuc) (Enrique.Villar@exeloncorp.com)
Cc:
James Danna (James.Danna@nrc.gov)
Subject:
CALVERT CLIFFS NUCLEAR POWER PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING FINAL RESPONSE TO GENERIC LETTER 2004-02 (EPID L-2018-LLA-0222)
Date:
Wednesday, September 18, 2019 1:06:00 PM Hello Rick,
By letter dated August 13, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18226A189) as supplemented by letters dated October 10, 2018 and June 7, 2019 (ADAMS Accession Nos. ML18283A034, and ML19158A075, respectively), Exelon Generation Company, LLC (Exelon) submitted license amendment requests (LARs) for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (Calvert Cliffs). The proposed amendments would change the Calvert Cliffs licensing bases, including the affected portions of the Technical Specifications and Updated Final Safety Analysis Report. The methodologies in the submittal describe the use of a risk-informed approach to address safety issues discussed in Generic Safety Issue -191, Assessment of Debris Accumulation on Pressurized-Water Reactor Sump Performance and close out generic letter 200402, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors (ADAMS Accession No. ML042360586).
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided in the LAR and has determined that additional information is needed to complete its review. Below is the NRC staffs request for additional information. The information being requested is needed to determine inputs to the licensees methodologies assure compliance with Section 50.46(b)(5) of Title 10 of the Code of Federal Regulations. The request for additional information was discussed with you on September 18, 2019, and it was agreed that your response would be provided within 30 days of the date of this email.
REQUEST FOR ADDITIONAL INFORMATION
- 1. Attachment 1-2, Deterministic (Approved Methodologies) Bases, (Page 88) of the letter dated June 7, 2019 states the largest quantity of NaAlSi3O8 predicted from all breaks analyzed is 115.9 pounds mass (lbm). Attachment 1-2 (page 92) states that the break that produces the largest quantity of chemical precipitates (117.21 lbm) of sodium aluminum silicate is a longitudinal break. The aluminum concentration for that break is 3.64 ppm. Attachment 1-4 (page 14), however, indicates the maximum aluminum concentration in the Calvert Cliffs sump pool for the break that produces the largest quantity of precipitate is 3.39 ppm. Please discuss which values of maximum precipitate quantity and maximum aluminum concentration are appropriate.
- 2. The values in data columns of Table 2, Description of Operating Margins," in Attachment 1-4, "Defense in Depth and Safety Margin," (Page 21) appear to be inconsistent.
- a. The aluminum surface area in the actual value column appears to be the value used in the analysis. However, the difference between the "actual value" column and "maximum value used in the analysis" do not sum to the value in the operating
margin column. Confirm that the values for aluminum surface area shown in -4, Table 2 are correct. If the values are correct, explain why the maximum value used in the analyses is greater than the sum of the actual value and operating margin.
- b. The fiber values in the actual value and maximum value columns do not appear to correspond to values provided elsewhere in the submittal. For example, the values used in the analysis would likely be consistent with Attachment 1-3, Table 4.
Confirm that the values for fiber shown in Attachment 1-4, Table 2 are correct. If the values are correct, please explain the apparent discrepancies.
- c. The maximum coating values correspond to values in Table 7a of attachment 1-2, but the origin of the actual values for coatings was not apparent. Unqualifed and degraded qualified coatings are assumed to fail independent of break location.
Identify the sources for each value in the "actual value" and "maximum values used in the analysis" columns. How are other sources of particulate evaluated?
Should particulate be evaluated including all potential sources since that is how the analysis models particulate? If the values in the table are not taken from the submittal provide the bases for the values.
- d. If relevant to the method for establishing margin, describe how the amount of debris considered to be margin is assessed in combination with other types of debris from potential breaks. Describe the most limiting combinations of debris that could occur (including the margin amounts of debris).
- 3. Attachment 1-2, response to issues 3b1 and 3b2 (Page 9) includes a zone of influence of 4 diameters for welded stainless steel cassettes containing mineral wool. During the regulatory audit on January 29-31, 2019, Exelon stated that some of their cassettes were modified to use rivets. Testing has identified that riveted cassettes are much less robust than welded cassettes. Discuss whether any field modifications or repairs made to the cassettes using rivets within potential zones of influence at Calvert Cliffs do or do not result in non-conservative debris generation values for mineral wool.
Best Regards, Michael L. Marshall, Jr.
Senior Project Manager
Plant Licensing Branch I Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
301-415-2871
Docket No. 50-317 and 50-318