NMP2L2713, Response to Request for Additional Information by the Office of Nuclear Reactor Regulation to Support Review of Nine Mile Point Nuclear Station, Unit 2, License Amendment Request to Increase Allowable MSIV Leakage Rates

Response to Request for Additional Information by the Office of Nuclear Reactor Regulation to Support Review of Nine Mile Point Nuclear Station, Unit 2, License Amendment Request to Increase Allowable MSIV Leakage Rates

ML19325D201
Person / Time
Site:	Nine Mile Point
Issue date:	11/21/2019
From:	David Gudger Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NMP2L2713
Download: ML19325D201 (9)

Text

Exelon Generation .

200 Exelon Way Kennett Square. PA 19348 www.exeloncorp.com 10 CFR 5090 NMP2L2713 November 21, 2019 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington. DC 20555-0001 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410

Subject:

Response to Request for Additional Information by the Office of Nuclear Reactor Regulation to Support Review of Nine Mile Point Nuclear Station, Unit 2, License Amendment Request to Increase Allowable MSIV Leakage Rates

References:

1. Letter from J. Barstow (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "License Amendment Request to Revise Technical Specifications Main Steam Isolation Valve Leak Rate," dated May 31, 2019

2. Letter from M. Marshall (Senior Project Manager, U.S. Nuclear Regulatory Commission) to R. Reynolds (Exelon),"Nine Mile Point Nuclear Station, Unit 2-Request for Additional Information Regarding License Amendment Request to Increase Allowable MSIV Leakage Rates (L-2019-LLA-0115),"

dated October 23, 2019 By letter dated May 31, 2019, (Reference 1) Exelon Generation Company, LLC (Exelon) requested to change the Nine Mile Point Unit 2 (NMP2) Technical Specifications (TS). The proposed amendment request would modify NMP2 TS License Amendment Request to increase allowable MSIV leakage rates.

On October 3, 2019, the U.S. Nuclear Regulatory Commission (NRC) identified a draft request for additional information necessary to complete the review. On October 22, 2019, a clarification teleconference was held between NRC and Exelon personnel. On October 23, 2019 (Reference 2), the NRC issued to Exelon a formal request for additional information.

Attachment 1 to this letter contains the NRC's request for additional information immediately followed by Exelon's response.

U.S. Nuclear Regulatory Commission Response to Request for Additional Information Increase Allowable MSIV Leakage Rates Docket No. 50-410 November 21, 2019 Page 2 Exelon has reviewed the information supporting a finding of no significant hazards consideration and the environmental consideration provided to the NRC in Reference 1. The additional information provided in this response does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. Furthermore, the additional information provided in this response does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.

There are no commitments contained in this response.

If you should have any questions regarding this submittal, please contact Ron Reynolds at 610-765-524 7.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 21 51 day of November 2019.

Respectfully, David T. Gudger Senior Manager - Licensing Exelon Generation Company, LLC Attachment 1: Response to Request for Additional Information cc: USNRC Region I Regional Administrator w/attachments II USN RC Senior Resident Inspector - NMP II USNRC Project Manager, NRR - NMP II A. L. Peterson, NYSERDA

ATTACHMENT 1 Response to Request for Additional Information

Response to Request for Additional Information Attachment 1 Increase Allowable MSIV Leakage Rates Page 1 of 6 Docket No. 50-410 REQUEST FOR ADDITIONAL INFORMATION Regulatory Criteria:

Section 50.49(e)(1) of Title 10 of the Code of Federal Regulations (10 CFR) requires that the time-dependent temperature and pressure at the location of the electric equipment important to safety must be established for the most severe design basis accident during and following which this equipment is required to remain functional.

Section 50.49(e)(2) of 10 CFR requires that humidity during design basis accidents must be considered .

Section 50.49(e)(4) of 10 CFR requires that the radiation environment must be based on the type of radiation, the total dose expected during normal operation over the installed life of the equipment, and the radiation environment associated with the most severe design basis accident during or following which the equipment is required to remain functional.

Section 50.49(b)(2) of 10 CFR requires qualification of nonsafety-related electric equipment whose failure under postulated environmental conditions could prevent satisfactory accomplishment of safety functions specified in subparagraphs (b)(1) (i) (A) through (C) of paragraph (b)(1) of 10 CFR 50.49 by the safety-related equipment.

Issue:

Exelon provided an evaluation on the radiological impact on the environmental qualification of electrical equipment due to the proposed increased leakage rate of MSIVs. However, it did not provide an evaluation of the impact of the MSIV increased leakage rate on temperature, pressure, or humidity of electrical equipment in those zones of impact. Exelon did not address whether, considering the total dose expected (total integrated dose (TIO) analysis of record), the change could result in electrical equipment currently classified as non-environmentally qualified now being subject to the requirements of 10 CFR 50.49 (i.e., transition from a Mild area to Harsh). It is also unclear as to whether the licensee considered the impact of the proposed change on non-safety related equipment whose failure under postulated environmental conditions could prevent satisfactory accomplishments of safety functions by the safety-related equipment.

Request:

RAI 1

Provide a description of the evaluation that shows that the revised temperatures, pressures, and humidity remain bounded by the existing environmental qualification for equipment in zones impacted by the proposed change.

Response to Request for Additional Information Attachment 1 Increase Allowable MSIV Leakage Rates Page 2of6 Docket No. 50-410 Exelon Response to RAI 1 As documented in the Nine Mile Point Nuclear Station Unit 2 Environmental Qualification Program Basis Document (2EQPBD), for equipment located outside containment, harsh humidity, temperature, and/or pressure conditions will only exist in those plant areas affected by High Energy Line Breaks (HELB), Moderate Energy Line Cracks (MELC), or Design Basis Accidents (OBA). Outside containment, the LOCA only results in increased gamma and beta radiation doses from various contributions depending on location in the plant (e.g., shine from containment, shine from recirculating fluids, leakage from containment including MSIV leakage, and shine from buildup on the standby gas treatment system (SGTS) or control building filters).

The various post-LOCA leakage pathways from containment, including MSIV leakage, are postulated as releases directly to the environment from appropriate release points. The releases are transported to various areas outside containment via atmospheric dispersion, rather than being released directly into plant areas outside containment as in the case of a HELB. The release and transport through the atmosphere preclude any temperature, pressure, or humidity effects in EQ zones outside containment.

The proposed change does not make any physical modifications to the plant. Rather, it proposes an increase in allowable leakage through an existing leakage path (MSIVs). As such, there is no change to the MSIV release pathway other than the allowable flow rate and the only potential impacts to the EQ program from the proposed change are to radiation in zones outside containment due to atmospheric dispersion.

The temperatures, pressures, and humidity remain bounded by the existing environmental qualification for equipment in zones impacted by the proposed change. The MSIV leakage is assumed to be released directly to the environment and impacts areas outside of containment through atmospheric dispersion. Therefore, there is no impact on temperatures, pressures, and humidity by the proposed increase in MSIV leakage.

RAl2:

Provide information that shows that the proposed TIO bounds the current TIO for each environmental qualification (EQ) zone outside the secondary containment. This information is needed to confirm Exelon's conclusion that no EQ zones transition from Mild to Mild Except for Electronics (ME), and that no zones transition from ME to Harsh.

Exelon Response to RAI 2 Reference 1 (pg. 16 of Attachment 1) states, "The evaluation of EQ impacts outside SC [Secondary Containment] included updating the EQ dose analyses with revised airborne doses resulting from increased MSIV leakage. Revising total integrated doses (TIO) for all EQ zones outside of SC were determined using updated post LOCA and 60-year normal doses. The revised EQ zone Tl Os were compared to the current zone doses and the EQ zone classification thresholds [Mild: TIO < 1.0E+3 rads; Mild Except for Electronics (ME): 1.0E+3 <TIO <

1.0E+4 rads; Harsh: TIO > 1.0E+4 rads]. The analyses and evaluation confirmed that no EQ zones transition from Mild to ME, and that no zones transition from ME to Harsh.

Based on no zones transitioning there is no new equipment that needs to be evaluated for inclusion in the EQ Program."

Response to Request for Additional Information Attachment 1 Increase Allowable MSIV Leakage Rates Page 3of6 Docket No. 50-410 The evaluation performed for the proposed activity, which summarizes the revised EQ radiological analyses, demonstrates that no zones transition by presenting the current and revised TIDs for every zone outside containment (see Table 1). The zone designators reflect the building/structure (letters), the elevation (first three numbers), and the room/zone identifier (remaining numbers). The structure codes are as follows:

• ASB - Auxiliary Service Building

• CB - Control Building

• DG - Diesel Generator Building

• ET - Electrical & Piping Tunnel

• ITK - Intake Structure

• MS - Main Stack

• MST - Main Steam Tunnel

• SA - Screenwell Area

• SG - Standby Gas Treatment Building

• SW - Service Water Area

• TB - Turbine Building

• YD-Yard The evaluation summarized in Table 1 includes 60-year normal doses, though the period of extended operation does not begin until 2026. The proposed change only impacts the post-LOCA dose, which is broken out in Table 1 in the current LOCA dose and updated LOCA dose columns.

The MST zones are not listed in the table because those zones are conservatively assumed to experience post-LOCA doses corresponding to the environment inside secondary containment.

Therefore, there is no impact to the doses in these zones from an increase in MSIV leakage.

The impact of the increase in MSIV leakage on the total post-LOCA doses in zones outside containment is dependent on what other dose contributors are present in a given zone post-accident (e.g., containment shine, non-MSIV airborne activity, filter shine, piping containing post-LOCA fluids, etc.). For example, zones near the SGTS filters (e.g., SG261355 &

SG261356) show no change in dose due to the increase in MSIV leakage because the shine dose from the SGTS filters is several orders of magnitude higher than the airborne dose from MSIV leakage.

Some EQ zones show a lower updated TID compared to the current TID. In analyzing the impact of increased MSIV leakage on these zones, other areas of margin were adjusted such that existing zone classifications were maintained. The resulting updated EQ doses remain conservative through the use of bounding inputs, assumptions, and methodology as documented in the supporting calculations.

As discussed in Reference 1 (pg. 17 of Attachment 1), equipment in zones outside containment that experienced an increase in dose and were already subject to a ME or Harsh radiation environment were investigated. It was determined that all EQ equipment in these affected outside containment zones was qualified in areas of the plant that are exposed to significantly higher doses post-accident (e.g., inside containment). Therefore, all EQ equipment affected by the increase in MSIV leakage remains qualified.

Response to Request for Additional Information Attachment 1 Increase Allowable MSIV Leakage Rates Page 4 of 6 Docket No. 50-410 Table 1 - EQ Zone TIO Changes Due to MSIV Leakage Increases Current Updated Zone EQZone Normal Dose Current TIO Updated LOCA Dose LOCA Dose Classification (rads) 1 (rads) TIO (rads)

Grouping (rads) 2 (rads) 3 Based on TIO ASB24053 9.66E+02 3.98E+03 4.36E+03 4.95E+03 ME 5.33E+03 ASB24054 9.66E+02 3.98E+03 4.36E+03 4.95E+03 ME 5.33E+03 ASB24055 9.66E+02 3.98E+03 4.36E+03 4.95E+03 ME 5.33E+03 EQ Zones Beginning with CB215, CB237, 9.66E+01 7.57E+02 6.20E+02 8.54E+02 M 7.17E+02 CB261, and CB274 EQ Zones Beginning with CB289 and 9.66E+01 3.17E+02 3.53E+02 4.14E+02 M 4.50E+02 CB306 (Not Including Filter Cubicle)

CB289392 9.66E+01 3.19E+04 3.34E+04 3.20E+04 H 3.35E+04 CB289393 9.66E+01 1.55E+04 1.63E+04 1.56E+04 H 1.64E+04 CB289395 9.66E+01 1.99E+03 2.11E+03 2.09E+03 ME 2.21E+03 CB306321 9.66E+01 1.99E+03 2.11E+03 2.09E+03 ME 2.21E+03 CB306325 9.66E+01 1.55E+04 1.63E+04 1.56E+04 H 1.64E+04 CB306326 9.66E+01 3.19E+04 3.34E+04 3.20E+04 H 3.35E+04 Diesel Generator 9.66E+01 7.59E+02 6.75E+02 8.56E+02 M 7.72E+02 Bldg .

Electrical &

Piping Tunnel (Except 9.66E+01 9.02E+02 6.01E+02 9.99E+02 M 6.98E+02 ET215241 &

ET240248)

ET215241 &

9.66E+02 9.02E+02 6.01 E+02 1.87E+03 ME 1.57E+03 ET240248 ITK23490 &

9.66E+01 8.62E+02 4.40E+02 9.59E+02 M 5.37E+02 ITK28591 MS261750 9.88E+01 1.77E+04 1.77E+04 1.78E+04 H 1.78E+04 MS289751 4.36E+04 3.32E+06 3.32E+06 3.36E+06 H 3.36E+06

Response to Request for Additional Information Attachment 1 Increase Allowable MSIV Leakage Rates Page 5 of 6 Docket No. 50-41 O Current Updated Zone EQZone Normal Dose Current TIO Updated LOCA Dose LOCA Dose Classification (rads) 1 (rads) TIO (rads)

Grouping (rads) 2 (rads) 3 Based on TIO SA261369 &

9.66E+01 2.23E+04 2.26E+04 2.24E+04 H 2.27E+04 SA289370 SG261355 2.44E+06 8.32E+08 8.32E+08 8.34E+08 H 8.34E+08 SG261356 2.44E+06 8.32E+08 8.32E+08 8.34E+08 H 8.34E+08 SG261357 9.66E+02 2.81E+04 2.85E+04 2.94E+04 H 2.95E+04 SG261358 9.66E+01 2.81E+04 2.85E+04 2.82E+04 H 2.86E+04 SG289359 1.09E+01 2.20E+04 2.24E+04 2.20E+04 H 2.24E+04 SG289360 1.09E+01 2.36E+04 2.40E+04 2.36E+04 H 2.40E+04 Service Water 9.66E+01 8.83E+02 7.88E+02 9.80E+02 M 8.85E+02 Pump Rooms SW250364 9.66E+01 8.56E+02 7.63E+02 9.53E+02 M 8.60E+02 TB289761 4.83E+03 3.93E+03 4.32E+03 8.76E+03 ME 9.15E+03 TB306780 4.83E+04 4.38E+04 4.42E+04 9.21E+04 H 9.25E+04 TB306782 9.66E+01 4.97E+03 5.34E+03 5.07E+03 ME 5.44E+03 TB306783 9.66E+01 2.88E+03 3.24E+03 2.98E+03 ME 3.34E+03 YD261790 9.66E+01 5.78E+05 5.79E+05 5.78E+05 H 5.79E+05 YD261792 9.66E+01 8.51 E+03 8.89E+03 8.61E+03 ME 8.99E+03 YD409793 &

9.94E+01 2.70E+03 3.09E+03 2.80E+03 ME 3.19E+03 YD440794 1 - H21C-110 Revision 0, "Equipment Qualification 60 Year Normal Dose."

2 - H21C-108 Revision 1, "Post Accident Radiation Doses for Equipment Qualification in Selected Radiation Zones and Specific Locations."

3 - ECP-18-000616-CN-013 H21C-108-01.00 Revision 0, "Post Accident Radiation Doses for Equipment Qualification in Selected Radiation Zones and Specific Locations."

Response to Request for Additional Information Attachment 1 Increase Allowable MSIV Leakage Rates Page 6 of 6 Docket No. 50-410 RAil:

Explain how the impact of the proposed change was assessed on non-safety related equipment whose failure under postulated environmental conditions could prevent satisfactory accomplishments of safety functions by the safety-related equipment.

Exelon Response to RAI 3 As documented in the Nine Mile Point Nuclear Station Unit 2 Environmental Qualification Program Basis Document (2EQPBD), the following categories of electrical equipment were considered for inclusion within the scope of the EQ Program:

1. Safety-related (Class 1E) electric equipment.

2. Non-safety-related electric equipment whose failure under postulated environmental conditions could prevent satisfactory accomplishment of safety functions by the safety-related equipment.

3. Post-accident monitoring equipment designated as Category 1 or 2 in Revision 2 of Regulatory Guide 1.97.

The impact of the proposed activity on non-safety-related equipment whose failure under postulated environmental conditions could prevent satisfactory accomplishment of safety functions by the safety-related equipment was evaluated in the same way as safety-related electric equipment. The evaluation performed is described in Reference 1 (pgs. 16-17 of ) and the responses to questions 1 and 2 above. Specifically, this important to safety electrical equipment is already included in the EQ Program, per 2EQPBD, and was therefore reviewed as part of the evaluation of potential impacts to the EQ Program. The evaluation of the radiological impacts of the proposed change determined that no zones transitioned to a harsher classification and that all equipment currently in the EQ Program remains qualified for the expected post-accident environment. As such, there is no new equipment, including non-safety-related equipment, that needs to be considered for inclusion in the EQ Program and there are no impacts to the qualified status of equipment already in the EQ Program.