ML19085A385
| ML19085A385 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 03/26/2019 |
| From: | David Helker Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML19085A385 (10) | |
Text
200 Exelon Way Exelon Generation ~ Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.90 March 26, 2019 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278
Subject:
Response to Second Request for Additional Information - License Amendment Request to Reduce High Pressure Service Water System Design Pressure and Revise Technical Specifications 3.6.2.3, 3.6.2.4, 3.6.2.5, and 3.7.1 for Temporary Extension of Completion Times
References:
- 1. Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission - "License Amendment Request to Reduce High Pressure Service Water System Design Pressure and Revise Technical Specifications 3.6.2.3, 3.6.2.4, 3.6.2.5, and 3. 7.1 for Temporary Extension of Completion Times," dated September 28, 2018 (ADAMS Accession No. ML18275A023)
- 2. Electronic mail message from Jennifer Tobin (U.S. Nuclear Regulatory Commission) to David Helker, Exelon Generation Company, LLC - "Peach Bottom Units 2 and 3 -
Request for Additional Information - High Pressure Service Water One Time TS Change (EPID L-2018-LLA-0265)," dated January 16, 2019 (ADAMS Accession No. ML19017A047)
- 3. Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission - "Response to Request for Additional Information - License Amendment Request to Reduce High Pressure Service Water System Design Pressure and Revise Technical Specifications 3.6.2.3, 3.6.2.4, 3.6.2.5, and 3. 7.1 for Temporary Extension of Completion Times," dated February 15, 2019 (ADAMS Accession No. ML19046A129)
- 4. Electronic mail message from Jennifer Tobin (U.S. Nuclear Regulatory Commission) to David Helker, Exelon Generation Company, LLC - "Peach Bottom Units 2 and 3 -
Request for Additional Information - High Pressure Service Water One Time TS Change (EPID L-2018-LLA-0265), "dated February 27, 2019 (ADAMS Accession No ML19058A290)
By letter dated September 28, 2018 (Reference 1), Exelon Generation Company, LLC (Exelon) requested amendments to Renewed Facility Operating License Nos. DPR-44 and DPR-56 for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3, respectively. The proposed changes would revise the PBAPS, Units 2 and 3, design and licensing basis
U.S. Nuclear Regulatory Commission Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 March 26, 2019 Page 2 described in the Updated Final Safety Analysis Report (UFSAR) to reduce the design pressure rating of the High Pressure Service Water (HPSW) system. The proposed changes will provide additional corrosion margin in the HPSW system pipe wall thickness, increasing the margin of safety for the existing piping. The proposed changes will also temporarily revise the PBAPS, Units 2 and 3, Technical Specifications (TS) Sections 3.6.2.3, "Residual Heat Removal (RHR) Suppression Pool Cooling," TS 3.6.2.4, "Residual Heat Removal (RHR) Suppression Pool Spray," TS 3.6.2.5, "Residual Heat Removal (RHR) Drywell Spray,"
and TS 3. 7 .1, "High Pressure Service Water (HPSW) System," to allow sufficient time to perform physical modifications of the PBAPS, Units 2 and 3, HPSW systems and other supporting plant equipment.
Exelon responded to an earlier NRC Request for Additional Information (RAI) (Reference 2) concerning this license amendment request by letter dated February 15, 2019 (Reference 3).
The NRC has been continuing its review of the information provided in Reference 1 and indicated the need for additional information in support of completing its review and evaluation of the proposed changes. In an electronic mail message dated February 19, 2019, the NRC issued a draft RAI. This draft RAI was the subject of further discussions during a teleconference on February 27, 2019, between Exelon and NRC representatives.
The NRC then formally issued the RAI on February 27, 2019 (Reference 4) and requested that Exelon respond to the RAI by March 27, 2019.
The Attachment to this letter provides a restatement of the RAI questions cited in Reference 4 followed by Exelon's responses.
Exelon has reviewed the information supporting a finding of no significant hazards consideration, and the environmental consideration, that were previously provided to the NRC in the Reference 1 letter. Exelon has concluded that the information provided in this response does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92. In addition, Exelon has concluded that the information 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 new regulatory commitments in this response.
In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"
paragraph (b), Exelon is notifying the Commonwealth of Pennsylvania of this RAI response by transmitting a copy of this letter and its attachments to the designated State Official.
If you have any questions or require additional information, please contact Richard Gropp at 610-765-5557.
U.S. Nuclear Regulatory Commission Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 March 26, 2019 Page 3 I declare under penalty of perjury that the foregoing is true and correct. Executed on the 26th day of March 2019.
Respectfully, David P. Helker Manager, Licensing and Regulatory Affairs Exelon Generation Company, LLC
Attachment:
Response to Request for Additional Information (RAl-2) - License Amendment Request for High Pressure Service Water System Design Change and One-Time Technical Specifications Changes cc: w/ Attachment Regional Administrator - NRC Region I U.S. NRC Senior Resident Inspector - Peach Bottom Atomic Power Station U.S. NRC Project Manager, NRR- Peach Bottom Atomic Power Station Director, Bureau of Radiation Protection - Pennsylvania Department of Environmental Protection R. R. Janati, Pennsylvania Bureau of Radiation Protection D. A Tancabel, State of Maryland
ATTACHMENT License Amendment Request Peach Bottom Atomic Power Station, Units 2 and 3 Docket Nos. 50-277 and 50-278 Response to Request for Additional Information (RAl-2) - License Amendment Request for High Pressure Service Water System Design Change and One-Time Technical Specifications Changes
Attachment Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 Page 1of6 Attachment Response to Request for Additional Information (RAl-2) - License Amendment Request for High Pressure Service System Design Change and One-Time Technical Specifications Changes By letter dated September 28, 2018 (Reference 1), Exelon Generation Company, LLC (Exelon) requested amendments to Renewed Facility Operating License Nos. DPR-44 and DPR-56 for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3, respectively. The proposed changes would revise the PBAPS, Units 2 and 3, design and licensing basis described in the Updated Final Safety Analysis Report (UFSAR) to reduce the design pressure rating of the High Pressure Service Water (HPSW) system. The proposed changes will provide additional corrosion margin in the HPSW system pipe wall thickness, increasing the margin of safety for the existing piping. The proposed changes will also temporarily revise the PBAPS, Units 2 and 3, Technical Specifications (TS) Sections 3.6.2.3, "Residual Heat Removal (RHR)
Suppression Pool Cooling," TS 3.6.2.4, "Residual Heat Removal (RHR) Suppression Pool Spray," TS 3.6.2.5, "Residual Heat Removal (RHR) Drywell Spray," and TS 3. 7.1, "High Pressure Service Water (HPSW) System," to allow sufficient time to perform physical modifications of the PBAPS, Units 2 and 3, HPSW systems and other supporting plant equipment.
Exelon responded to an earlier NRC Request for Additional Information (RAI) (Reference 2) concerning this license amendment request by letter dated February 15, 2019 (Reference 3).
The NRC has been continuing its review of the information provided in Reference 1 and indicated the need for additional information in support of completing its review and evaluation of the proposed changes. In an electronic mail message dated February 19, 2019, the NRC issued a draft RAI. This draft RAI was the subject of further discussions during a teleconference on February 27, 2019, between Exelon and NRC representatives. The NRC then formally issued the RAI on February 27, 2019 (Reference 4) and requested that Exelon respond to the RAI by March 27, 2019.
Below is a restatement of the questions cited in the Reference 4 RAI followed by Exelon's response to each of the questions. The numbering sequence for the questions continues from the previous Reference 2 RAI.
Issue: In Section 2. 2 of the license amendment request, last paragraph, the licensee stated that
"... The proposed reduction in design pressure will provide for additional corrosion margin in pipe wall thickness, increasing the margin of safety for the existing piping ... " It is not evident that the submittal included the corrosion margin calculations, pipe diameter and wall thickness.
Request: Provide the following: (1) Pipe nominal pipe size (NPS), (2) Pipe nominal wall thickness, (3) the corrosion margin (allowance) after proposed modification, (4) the existing corrosion margin (allowance) with the current pressure inside the pipe, and (5) corrosion calculations and associated references.
Attachment Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 Page 2 of 6
Response
Table 1, "Corrosion Data at Various Design Pressures," of this attachment includes information requested in response to items 1 through 4, noted above, for two different maximum design pressure scenarios at seven representative locations in the HPSW system piping. The current maximum design pressure for the HPSW system is 450 psig. The final maximum design pressure, following implementation of modifications enabled by this License Amendment Request (LAR) once approved, is expected to be within the range of 200 - 230 psig. The two maximum design pressures presented in Table 1 are 450 psig and 230 psig.
The design pressures for some portions of the HPSW system, such as that associated with the sixth entry in Table 1, are lower than the maximum system design pressure. The design pressures of these portions of the HPSW system piping will be unaffected by implementation of the modifications supporting the HPSW system changes. For the first entry in Table 1, the pertinent portion of piping is currently subject to the system maximum design pressure.
Following implementation of planned modifications, this portion of piping will have a design pressure less than the system maximum design pressure.
Table 1 is presented as representative of current input parameter values and the station standard methodology for determining code minimum required wall thickness values. Minimum required wall thickness is computed based on code requirement limits for pressure (hoop) stress and actual piping design stresses due to system applicable design load cases versus code equation limits at the location of interest. Therefore, the computation that determines the minimum required wall thickness may change as the local system design pressure decreases.
The values shown in Table 1 may vary in the future from those shown because of input parameter value changes and/or due to altered loading associated with modification of the piping configuration.
The corrosion rates used in projecting the remaining life of the piping for the various maximum design pressure scenarios are also shown in Table 1. In response to the requested item 5, cited above, the corrosion rate is calculated using the measured wall thickness value from two successive examinations of a particular location divided by the length of time between those examinations, while applying a 10% safety factor. The calculations are procedurally governed and requires a documented engineering evaluation for future reference.
Issue: In Section 2. 2 of the license amendment request, first paragraph, the licensee stated that
" ... [the system pressure] will be reduced from the current rating of 450 psig to a design pressure rating of approximately 200 psig. The final value is expected to fall between 190 psig and 230 psig in the detailed design with final vendor inputs ... "
In Section 3.1, page 3, fourth paragraph, the licensee stated, " ... At maximum expected RHR system pressures, a pressure of 233 psig at the HPSW pump discharge is required to ensure HPSW side pressure exceeds RHR system pressure at the RHR heat exchanger .. . "
Attachment Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 Page 3of6 In Attachment 4, Peach Bottom UFSAR, Table 10. 7.1, page 33 of the pdf file, the proposed pump shut off head is changed to 240 psig.
As shown above, the licensee mentioned various pressures--190, 200, 230, 233, and 240 psig.
It is not clear the exact design pressure and maximum operating pressure in HPSW piping after modification. The NRG staff notes that there should be only one design pressure value, not a range of design pressure.
Request: (1) Provide the exact design pressure and maximum operating pressure in the HPSW piping system after the proposed modification. (2) Discuss the pressure that is used to calculate the corrosion margin.
Response
As noted in the response to RAI 3 above, the HPSW system has piping regions with different design pressures, which are reflective of the local operating conditions. However, there will be one (1) HPSW system maximum design pressure, which is expected to be within the range of 200 - 230 psig, following implementation of modifications supported by the LAR. At the time the LAR was submitted (Reference 1), a range of pressures was discussed in the LAR because the specific final design characteristics for the new Low Head Pumps and the new valves downstream of the RHR Heat Exchangers had not yet been established. One specific design characteristic that will contribute to the exact maximum design pressure is the pump shutoff head. The final design documents and supporting calculations will establish the exact design pressure. This selected design pressure will be used to calculate the corrosion margin. Results are shown in Table 1 for 230 psig. Minimum required wall thicknesses at 200 psig would be slightly lower than, or possibly the same as, those for 230 psig, depending upon the type of stress (pressure-related or non-pressure-related) that sets the minimum required wall thickness.
Issue: In Attachment 5, page 6, of the license amendment request, the licensee discussed the replacement of existing valves and orifices. However, it is not evident that the licensee discussed an examination that will be performed prior to installation/replacement to determine the condition of the HPSW piping.
Request: Discuss if inspections will be performed on the HPSW piping prior to hardware modifications to determine the general condition of the piping. If not, discuss whether the existing piping condition would support the replacement activities.
Response
PBAPS will perform necessary inspections of existing piping in areas affected by the installation activities associated with the HPSW project. The areas affected by the modification will include valve, pump, and orifice replacement work. Inspections are required as part of the station's normal maintenance procedures and specifications related to piping replacement and Nondestructive Examination (NOE).
Attachment Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 Page 4 of 6 Issue: In the license amendment request, it is not evident that the licensee discussed (1) the examinations to accept the modification/installation, (2) the pressure test to demonstrate any potential leakage, and (3) functionality test to demonstrate the modified HPSW system will perform its intended function.
Request: (1) Discuss the acceptance examination that will be performed immediately after the hardware modification to demonstrate the structural integrity and leak tightness of the modified HPSW piping. If leakage occurs, discuss the acceptance criteria and how the leakage will be dispositioned. (2) Discuss whether the hardware modification will be performed based on the provisions of article IWA-4000 of the ASME Code,Section XI. If not, discuss the industry guidance that will be used as part of the hardware modifications. (3) Discuss if a system leakage test will be performed in accordance with the ASME Code,Section XI, IWA-5000 and IWD-5000.
If yes, discuss what would be the pressure used for the system leakage test. If a system leakage test will not be performed, provide justification. (4) Discuss whether a functionality or operability test will be performed to demonstrate that the proposed pressure reduction will achieve the intended function of the HPSW system.
Response
PBAPS will perform applicable required Code Inspections, and examination and testing as part of the HPSW modification installation work. The pump and valve replacement meets the provisions of article IWA-4000, Repair and Replacement activities for Code Class 1, 2,3 and associated supports; therefore, they will be subject to lnservice Inspection (ISi) which include system leakage, pressure, and VT-2 testing as required in accordance with the ASME Code,Section XI, IWA-5000 and IWD-5000. The pressure test will be performed at the system operating pressure. The acceptance criteria will be based on the new design parameters. The new pump will be tested for flow and pressure, and the valves will be tested for stroke time.
These tests will be performed in accordance to the lnservice Testing (IST) requirement to demonstrate operability. Applicable station Surveillance Tests (STs) will be revised, as appropriate, based on the new system design pressure and new valve stroke times. These revised STs will be used in the future to demonstrate the system operability to satisfy applicable TS Surveillance Requirements (SRs).
Issue The NRG staff finds that with the proposed pressure reduction, the pipe stresses will be different from the original design basis for the HPSW piping. The license amendment request did not appear to discuss the reanalysis of the existing pipe stress analysis of HPSW piping based on the original construction Code, USAS 831.1-1967 edition, as a result of proposed pressure reduction in HPSW piping.
Attachment Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 Page 5 of 6 Request Because of the proposed pressure reduction, discuss if a reanalysis is needed to evaluate pipe stresses for the HPSW piping in accordance with the original construction code, USAS B31.1-1967 edition.
Response
The Engineering design process will analyze pipe stress at locations impacted by physical changes associated with the project. The re-analyses will be performed in accordance with 1967 or 1973 (with Addenda thru Summer 1973) of ANSI 831.1 Code, as approved by PBAPS specification NE-00104, to ensure compliance with code requirements. In addition, revisions to calculations for HPSW system piping sections not physically changed by this project will be made to note the new system design pressure and its effect on system piping stresses.
References:
- 1. Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission - "License Amendment Request to Reduce High Pressure Service Water System Design Pressure and Revise Technical Specifications 3.6.2.3, 3.6.2.4, 3.6.2.5, and
- 3. 7. 1 for Temporary Extension of Completion Times," dated September 28, 2018 (ADAMS Accession No. ML18275A023)
- 2. Electronic mail mes$age from Jennifer Tobin (U.S. Nuclear Regulatory Commission) to David Helker, Exelon Generation Company, LLC - "Peach Bottom Units 2 and 3 - Request for Additional Information - High Pressure Service Water License Amendment One Time TS Change (EPID L-201 B-LLA-0265), "dated January 16, 2019 (ADAMS Accession No. ML19017A047)
- 3. Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission - "Response to Request for Additional Information - License Amendment Request to Reduce High Pressure Service Water System Design Pressure and Revise Technical Specifications 3.6.2.3, 3.6.2.4, 3.6.2.5, and 3. 7.1 for Temporary Extension of Completion Times," dated February 15, 2019 (ADAMS Accession No. ML19046A129)
- 4. Electronic mail message from Jennifer Tobin (U.S. Nuclear Regulatory Commission) to David Helker, Exelon Generation Company, LLC- "Peach Bottom Units 2 and 3- Request for Additional Information - High Pressure Service Water One Time TS Change (EPID L-2018-LLA-0265), "dated February 27, 2019 (ADAMS Accession No. ML19058A290)
Attachment Response to Request for Additional Information (RAl-2)
HPSW System License Amendment Request Docket Nos. 50-277 and 50-278 Page 6of6 Table 1 Corrosion Data at Various Design Pressures Remaining Nominal Eva I Remaining Life from Pipe Design End of Wall Last Last Corr Tm1n Wall t0Tm1n Last Component Location Size Press Life Thickness Exam T1ow Rate (Inch) (Inch - Inspection (Inch) (psig) (831.1)
(inches) (mpy) 831.1) (months-831.1) 2-32G8-14-11-8-4 450 0.182 0.026 45 11/2021 U2 B RHR 14 0.375 2/2018 0.208 7 (IS0-2-32-4-F04 U/S) 150 0.140 0.068 117 11/2027 3-32GB-14-04-A-1 450 0.232 0.062 149 7/2030 U3 B RHR 14 0.375 2/2018 0.294 5 (IS0-3-32-5-TOl BR) 230 0.198 0.096 230 4/2037 3-32GB-14-05-A-1 450 0.182 0.092 158 4/2031 U3 B RHR 14 0.375 2/2018 0.274 7 (IS0-3-32-5-ROl D/S) 230 0.110 0.164 281 7/2041 3-32GB-18-17-A-2 450 0.234 0.062 106 12/2026 U3 B RHR 18 0.375 2/2018 0.296 7 (IS0-3-32-5-TOl D/S) 230 0.120 0.176 302 4/2043 3-32GB-18-17-A-3 450 0.234 0.031 74 4/2024 U3 B RHR 18 0.375 2/2018 0.265 5 (IS0-3-32-5-TOl U/S) 230 0.120 0.145 348 2/2047 3-32GB-18-19-A-1 U3 C RHR 18 0.375 2/2018 0.166 7 150 0.119 0.047 81 11/2024 (IS0-3-32-7-TOl BR)
U3 HPSW 450 0.182 0.095 380 10/2049 3-32GBD-14-01-A-5 Pump 14 0.375 2/2018 0.277 3 (IS0-3-32-10-E05) 230 0.110 0.167 668 10/2073 Room Corrosion Rate = (Tmeasl - Tmeas2) x SF I time Tmeas1 =The minimum measured value from the first examination (mils)
Tmeas2 =The minimum measured value from the second examination (mils)
SF= Safety Factor of 10% is used = 1.10 Time =The length of time between inspections (years)
Note: Values reflected in the table are due to pressure reduction only.