ML25261A338
| ML25261A338 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 09/25/2025 |
| From: | Markley M Plant Licensing Branch II |
| To: | Coleman J Southern Nuclear Operating Co |
| Kalathiveettil, D | |
| References | |
| EPID L-2025-LLR-0012 | |
| Download: ML25261A338 (1) | |
Text
September 25, 2025 Ms. Jamie M. Coleman Regulatory Affairs Director Southern Nuclear Operating Co., Inc.
3535 Colonnade Parkway Birmingham, AL 35243
SUBJECT:
EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1 AND 2 - AUTHORIZATION OF ALTERNATIVE REQUEST RR-P SIXTH INSERVICE TESTING INTERVAL (EPID L-2025-LLR-0012)
Dear Ms. Coleman:
By letter dated January 30, 2025, and as supplemented by letter dated May 15, 2025, Southern Nuclear Operating Company (SNC, the licensee) submitted Alternative Request RR-P-8 for specific pumps during its Sixth Inservice Testing (IST) interval at the Edwin I. Hatch Nuclear Plant (Hatch), Units 1 and 2, which is scheduled to begin on January 1, 2026.
The licensee requested Alternative Request RR-P-8 for Hatch, Units 1 and 2, on the basis that compliance with the testing requirements in the 2022 Edition of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code) for the pumps affected would result in hardship without a compensating increase in the level of quality and safety. The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review and determined that Alternative Request RR-P-8, provides reasonable assurance that the affected components are operationally ready to perform their safety functions. The NRC staff concludes that SNC has adequately addressed the regulatory requirements set forth in Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.55a, Codes and standards, paragraph (z)(2) for this proposed alternative.
Therefore, pursuant to 10 CFR 50.55a(z)(2), the NRC staff authorizes the use of this alternative to the 2022 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, for the Code of Record interval, as defined in 10 CFR 50.55a(y), Definitions, that implements the 2022 Edition of the ASME OM Code, for Hatch, Units 1 and 2. Use of this alternative with other Codes of Record is not authorized.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
J. Coleman If you have any questions, please contact the Project Manager, Dawnmathews Kalathiveettil at Dawnmathews.Kalathiveettil@nrc.gov or 301-415-5905.
Sincerely, Michael Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2025.09.25 11:51:12 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION AUTHORIZATION OF PUMP ALTERNATIVE REQUEST RR-P-8 SIXTH INSERVICE TESTING INTERVAL SOUTHERN NUCLEAR OPERATING COMPANY EDWIN I. HATCH NUCLEAR PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-321 AND 50-366
1.0 INTRODUCTION
By letter dated January 30, 2025 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25030A363), and supplemented by letter dated May 15, 2025 (ML25135A409), Southern Nuclear Operating Company (SNC, the licensee) submitted RR-P-8 to the U.S. Nuclear Regulatory Commission (NRC) requesting authorization for a proposed alternative for specific affected pumps in lieu of certain inservice testing (IST) requirements of the 2022 Edition of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, OM Code: Section IST (OM Code), as incorporated by reference in Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.55a, Codes and standards, for the Sixth Inservice Testing (IST) interval at the Edwin I. Hatch Nuclear Plant (Hatch), Units 1 and 2.
The licensee submitted Alternative Request RR-P-8 pursuant to 10 CFR 50.55a(z)(2), Hardship without a compensating increase in quality and safety, on the basis that compliance with the specified ASME OM Code requirements would result in a hardship without a compensating increase in the level of quality and safety for IST activities applied to the specific affected pumps within the scope of this request.
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(f)(4), Inservice testing standards requirement for operating plants, state, in part, that:
Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice test requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in paragraphs (f)(2) and (3) of this section [10 CFR 50.55a] and that are incorporated by reference in paragraph (a)(1)(iv) of this section [10 CFR 50.55a], to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The regulations in 10 CFR 50.55a(z), Alternative to codes and standards requirements, state, in part, that alternatives to the requirements of paragraphs (b) through (h) of 10 CFR 50.55a or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation.
The applicant or licensee must demonstrate that:
(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
NUREG/CR-6396, Examples, Clarifications, and Guidance on Preparing Requests for Relief from Pump and Valve Inservice Testing Requirements (ML19275F829), February 1996.
3.0 TECHNICAL EVALUATION
The applicable Code of Record for the Hatch, Units 1 and 2, Sixth IST interval is the 2022 Edition of the ASME OM Code. The Hatch, Units 1 and 2, Sixth IST interval is scheduled to begin on January 1, 2026.
3.1 Licensees Alternative Request RR-P-8 3.1.1 Applicable ASME OM Code Requirements The requirements in the ASME OM Code, Subsection ISTB, Inservice Testing of Pumps in Water-Cooled Reactor Nuclear Power Plants - Pre-2000 Plants, as incorporated by reference in 10 CFR 50.55a, related to Alternative Request RR-P-8 are as follows:
Paragraph ISTB-3520, Pressure, (b), Differential Pressure, states, in part, that:
When determining differential pressure across a pump, a differential pressure gauge or a differential pressure transmitter that provides direct measurement of the pressure difference or the difference between the pressure at a point in the inlet and the pressure at a point in the discharge pipe shall be used.
3.1.2 Components for Which Alternative is Requested The alternative was proposed for the following components:
Component ID Pump Description / Pump Type ASME Code Class ASME OM Code Category 1E11-C002A Unit 1 Residual Heat Removal Pump A /Centrifugal 2
Group A 1E11-C002B Unit 1 Residual Heat Removal Pump B /Centrifugal 2
Group A 1E11-C002C Unit 1 Residual Heat Removal Pump C /Centrifugal 2
Group A 1E11-C002D Unit 1 Residual Heat Removal Pump D /Centrifugal 2
Group A 1E21-C001B Unit 1 Core Spray Pump B /
Centrifugal 2
Group B 2E11-C002A Unit 2 Residual Heat Removal Pump A / Vertical Line Shaft 2
Group A 2E11-C002B Unit 2 Residual Heat Removal Pump B / Vertical Line Shaft 2
Group A 2E11-C002C Unit 2 Residual Heat Removal Pump C / Vertical Line Shaft 2
Group A 2E11-C002D Unit 2 Residual Heat Removal Pump D / Vertical Line Shaft 2
Group A 3.1.3 Licensees Proposed Alternative and Basis for Use In its letter dated May 15, 2025, the licensee states, in part, that:
Pump suction pressure will be assumed to be 5 psig [pounds per square inch gauge]
based on the review of several years of IST data which support suction pressure being virtually constant when performing Group A and B testing. During these tests pump differential pressure will be calculated by measuring pump discharge pressure and subtracting 5 psig. This value will then be compared to the corresponding reference value. The acceptance criteria of Table ISTB-5121-1 and ISTB-5221-1 will be applied for assessing pump operational readiness and for monitoring potential pump degradation during the applicable Group A or Group B pump test. This testing method meets the intent of the Code for monitoring pump operational readiness and degradation and relieves the Licensee of the burden associated with the use of temporary test gauges.
This request is not applicable to Comprehensive Pump or Baseline Testing. The above proposed alternative provides an acceptable means of evaluating pump performance without a substantial decrease in the ability to monitor operational readiness. Based on the determination that compliance with the Code requirements, results in a hardship or unusual difficulty without a compensating increase in the level of quality and safety, this proposed alternative should be authorized pursuant to 10 CFR 50.55a(z)(2).
By letter dated December 30, 2015 (ML15310A406), a similar alternative request was authorized for Hatch, Units 1 and 2.
In its supplemental letter dated May 15, 2025, the licensee confirmed that Pump Periodic Verification Tests are not within the scope of this alternative request.
3.1.4 Licensees Reason for its Request In its letter dated May 15, 2025, the licensee states, in part, that:
Pursuant to 10 CFR 50.55a(z)(2), relief is requested from the requirements of the ASME OM Code, 2022 Edition, Subsection ISTB-3520(b) which requires differential pressure be determined by the difference between the pressure at a point in the inlet pipe and the pressure at a point in the discharge pipe if a direct indicating instrument is not provided.
This alternative request is a re-submittal of NRC approved 4th and 5th Interval(s) Relief Request RR-P-11, previously submitted and approved for use for these instruments.
There have been no substantive changes to this alternative or to the basis for use, which would alter the previous NRC Safety Evaluation conclusions for previous IST Intervals for Plant Hatch. (See Precedents for [safety evaluation reports] SERs)
The Residual Heat Removal (RHR) and Core Spray (CS) pumps are aligned to the suppression pool (torus) during all modes of normal plant operation. The installed suction pressure gauges do not meet Code requirements. Suction pressure to these pumps is primarily a function of suppression pool level, which is controlled within a 4-inch range, and this results in a virtually constant suction pressure. IST is performed utilizing a full flow test line which circulates water to and from the suppression pool.
The Plants Technical Specifications require that the suppression pool be maintained within a narrow range of level, temperature, and internal pressure during plant operation which results in a suction pressure of approximately 5 psig. The Unit 1 and 2 Technical Specification operability limits for the suppression pool are itemized below.
Level 146 & 150 Internal Pressure 1.75 psig Water Temperature 100° F These Technical Specification operability limits for the suppression pool result in a maximum difference in calculated pump suction pressure of < 2 psig. This 2 psig variance (Pi) is insignificant in relation to nominal discharge pressure and the calculation of differential pressure (P = Po-Pi) when considering the Group A pump test acceptable operating range (i.e., 95 - 110% for vertical line shaft pumps from Table ISTB-5221-1 and 90-110% for centrifugal pumps from Table ISTB-5121-1) and the allowable +/- 2% instrument accuracy from Table ISTB-3510-1; or when considering the Group B pump test acceptable operating range (i.e., 90-110% for centrifugal and vertical line shaft pumps from Table ISTB-5121-1 and Table ISTB-5221-1) and the allowable
+/- 2% instrument accuracy from Table ISTB-3510-1. Therefore, direct suction pressure measurement for differential pressure derivation provides no added benefit for determining pump operational readiness or for monitoring pump degradation.
PUMP LOWEST REFERENCE DISCHARGE PRESSURE (Po)
MAXIMUM VARIANCE (Pi/Po)
Unit 1 RHR 171 psig 1.17% max Unit 1 CS 273 psig 0.73% max Unit 2 RHR 180 psig 1.11% max The following table summarizes several years worth of IST pump suction pressure data. This summary confirms that the RHR and CS pumps suction pressures are consistent and are relatively insignificant in comparison with the pumps discharge pressure. Applying an average suction pressure of 5 psig, when calculating differential pressure, will provide data that is meaningful for assessing operational readiness and for monitoring pump degradation.
Pump MPL No.
Minimum Pressure (psig)
Maximum Pressure (psig)
Average Pressure Note 1 (psig)
Reference Values 1E11-C002A 4.5 5.0 4.9 (31)
Qr = 8000 gpm, Pr = 166 psid 1E11-C002B 4.9 5.6 5.0 (33)
Qr = 7700 gpm, Pr = 175 psid 1E11-C002C 4.9 5.2 5.0 (31)
Qr = 7700 gpm, Pr = 176 psid 1E11-C002D 4.7 5.2 4.9 (33)
Qr = 7700 gpm, Pr = 180 psid 1E21-C001B 1.7 Note 2 5.0 4.8 (33)
Qr = 4300 gpm, Pr = 268 psid 2E11-C002A 5.0 5.8 5.0 (32)
Qr = 7700 gpm, Pr = 184.6 psid 2E11-C002B 4.3 5.0 4.9 (36)
Qr = 7700 gpm, Pr = 184.9 psid 2E11-C002C 5.0 5.7 5.0 (32)
Qr = 7700 gpm, Pr = 184.9 psid 2E11-C002D 4.2 5.0 4.9 (35)
Qr = 7700 gpm, Pr = 175 psid AVERAGE 4.3 5.3 4.9 N/A Notes :
- 1. Number in parenthesis ( ) indicates the number of test values averaged to get the indicated value.
- 2. One time occurrence only.
[psid = pounds per square inch differential]
The permanently installed pump suction pressure gauges encompass a wider range of pressures than does IST and thus exceed the OM Code allowable range limit (3 times the reference value). The installed RHR pump gauges must account for the pressure experienced with the RHR loop in the shutdown cooling mode of operation. The installed CS pump gauges must account for the pressure experienced with the CS suction aligned to the Condensate Storage Tank. Therefore, a temporary test gauge which satisfies the Code range limits would have to be installed each time the IST test is required.
Applying a constant pump suction pressure, when calculating differential pressure, will allow the Group A and B testing to be performed with the installed pressure gauges, thus lessening the burden on operations personnel responsible for the testing. Since temporary test gauges are required to be calibrated both prior to and after usage, it also eliminates the possibility of invalidating test data due to a gauge being damaged during transportation, installation or removal.
Mechanical degradation of centrifugal pumps which experience significant differences in suction (inlet) pressure would be indicated by changes in the differential pressure.
However, for these pumps, the suction pressure variance is insignificant in comparison to the developed head (pressure).
Therefore, monitoring discharge pressure and calculating differential pressure assuming a constant 5 psig suction pressure provides an adequate method to determine operational readiness and detect potential degradation.
3.2
NRC Staff Evaluation
In RR-P-8, the licensee has proposed an alternative approach to the instrumentation requirements of ASME OM Code, Subsection ISTB, paragraph ISTB-3520(b), for differential pressure measurement for the pumps listed above. ISTB-3520(b) requires that differential pressure be determined by the difference between the pressure at a point in the inlet pipe and the pressure at a point in the discharge pipe if a direct indicating instrument is not provided. The licensee proposes to measure the discharge pressure and calculate the differential pressure by assuming a constant suction pressure of 5 psig (based on historical data). The range of the permanently installed pressure gauges at the pumps inlet exceed the OM Code allowable range limit (3 times the reference valve), and so temporary gauges would need to be installed for each test. Accordingly, these temporary gauges would need to be calibrated both prior to and after usage. These extra steps, which are necessary for compliance with the requirements of ISTB-3520(b), create a hardship for the licensee without a compensating increase in the level of quality and safety.
Discharge pressure can be used in lieu of differential pressure for evaluating pump hydraulic performance if variations in pump suction (inlet) pressure are small. NUREG/CR-6396, Examples, Clarifications, and Guidance on Preparing Requests for Relief from Pump and Valve Inservice Testing Requirements, Section 3.3.2 provides the following five considerations for justifying the use of discharge pressure instead of differential pressure.
- 1. The inlet pressure is small in comparison with the discharge pressure (maximum deviation of 2 percent).
- 2. The maximum expected variation in inlet pressure from test to test is relatively small as determined by control procedures and TS limits and as verified by historical data.
- 4. Even though some uncertainty is introduced by this method, applying the ASME OM Code acceptance criteria for differential pressure to discharge pressure for this application adds conservatism.
- 5. If a significant blockage occurs at the pump suction, this condition would affect the discharge pressure and/or flow rate measurement and would be detected.
The licensees proposed alternative meets the above considerations. The licensee proposes to measure the discharge pressure and calculate the differential pressure by assuming a constant suction pressure of 5 psig (based on historical data). The maximum difference in calculated pump suction pressure is less than 2 psig. This 2 psig maximum difference is insignificant when performing quarterly Group A or Group B tests considering the normal discharge pressure range (maximum variation 1.17 percent) of the RHR and CS pumps.
The 2 psig variance is insignificant in the calculation of differential pressure (Po-Pi) when considering the Group A pump test ASME OM Code acceptable operating range (95 to 110 percent for vertical line shaft pumps from Table ISTB-5221-1 and 90 to 110 percent for centrifugal pumps from Table ISTB-5121-1) and the allowable +/-2 percent instrument accuracy from Table ISTB-3510-1; or when considering the Group B pump test acceptable operating range (i.e., 90 to 110 percent for centrifugal and vertical line shaft pumps from Table ISTB-5121-1 and Table ISTB-5221-1) and the allowable +/-2 percent instrument accuracy from Table ISTB-3510-1.
Based on the above, the NRC staff has determined that requiring the licensee to meet the requirements for differential pressure for these specific pumps at Hatch, Units 1 and 2, required by the ASME OM Code would result in a hardship without a compensating increase in the level of quality and safety. The NRC staff finds that the proposed alternative provides reasonable assurance of the operational readiness of these pumps. Therefore, the NRC staff finds that RR-P-8 may be authorized in accordance with 10 CFR 50.55a(z)(2) for the applicable pumps at Hatch, Units 1 and 2.
The NRC staff notes that the applicable Code of Record for the Hatch Units 1 and 2, Sixth IST interval, is the 2022 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a. The Hatch, Units 1 and 2, Sixth IST interval, is scheduled to begin on January 1, 2026.
The ASME OM Code (2022 Edition), Subsection ISTA, General Requirements, paragraph ISTA-3120, Inservice Examination and Test Interval, as incorporated by reference in 10 CFR 50.55a, requires that licensees implement 10-year intervals for their IST programs. Although not requested, the NRC regulations in 10 CFR 50.55a allow licensees to implement the same ASME OM Code as their Code of Record for two consecutive IST program intervals.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that proposed alternative numbered RR-P-8 for Hatch, Units 1 and 2, provides reasonable assurance that the affected pumps are operationally ready. The NRC staff has also determined that the licensee has justified that compliance with the testing requirements in the ASME OM Code for the pumps within the scope of this request would result in hardship without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(2) for this proposed alternative.
Therefore, pursuant to 10 CFR 50.55a(z)(2), the NRC staff authorizes the use of Alternative Request RR-P-8 for the Sixth IST Interval for the specified pumps in lieu of the IST requirements of the 2022 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a, for Hatch, Units 1 and 2, for the Code of Record interval, as defined in 10 CFR 50.55a(y), Definitions, that implements the 2022 Edition of the ASME OM Code. Use of this alternative with other codes of record is not authorized.
All other ASME OM Code requirements as incorporated by reference in 10 CFR 50.55a for which relief or an alternative was not specifically requested, and granted or authorized (as appropriate), in the subject request remain applicable.
Principal Contributors: N. Hansing, NRR T. Scarbrough, NRR G. Bedi, NRR Date: September 25, 2025
ML25261A338 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DEX/EMIB/BC NAME DKalathiveettil KZeleznock SBailey DATE 09/18/2025 09/22/2025 08/19/2025 OFFICE NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME MMarkley DKalathiveettil DATE 09/25/2025 09/25/2025