RA24-023, Response to NRC LaSalle County Station, Units 1 and 2, Integrated Inspection Report 05000373/2024001 and 05000374/2024001
| ML24164A061 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 06/12/2024 |
| From: | Van Fleet J Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, NRC/RGN-III, Document Control Desk |
| References | |
| RA24-023 | |
| Download: ML24164A061 (1) | |
Text
Constellation RA24-023 June 12, 2024 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
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LaSalle County Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-374 LaSalle County Station 2601 North 21 " Road Marseilles. IL 61341 815-415-2000 Telephone
Subject:
Response to NRC LaSalle County Station, Units 1 and 2 Integrated Inspection Report 05000373/2024001 and 05000374/2024001
Reference:
Letter from Robert Ruiz (U.S. Nuclear Regulatory Commission) to David P.
Rhoades (Constellation Energy Generation, LLC), "LaSalle County Station -
Integrated Inspection Report 05000373/2024001 and 05000374/2024001,"
dated May 13, 2024 (ADAMS Accession No. ML24131A151)
The U.S. Nuclear Regulatory Commission (NRC) documented four Green findings and associated non-cited violations (NCVs) in the Integrated Inspection Report for the first quarter of 2024 for LaSalle County Station (LSCS).
The NCV and associated Green finding of note is associated with the Failure to Test Motor-Operated Valve in Accordance with the lnservice Test Program (NCV 05000374/2024001-02).
The NCV and finding was for LSCS's failure to meet the in-service testing requirements set forth in the American Society of Mechanical Engineers Operations and Maintenance Code and Addenda Code Case OMN-1 after performing maintenance that could affect motor-operated valve performance.
LSCS is respectfully contesting the finding and violation. The attached enclosure to this letter provides the response and basis for the contestation of the violation and finding referenced above.
There are no regulatory commitments contained in this letter.
Should you have any questions concerning this letter, please contact Ms. Laura Ekern, Regulatory Assurance Manager, at (815) 415-2800.
Respectfully, JJJ:::F~<f~
Site Vice President LaSalle County Station
RA24-023 June 12, 2024 Page 2 of 2
Enclosure:
Response to Non-Cited Violation 05000374/2024001-02 cc:
NRC Regional Administrator, Region Ill NRC Director, Office of Enforcement NRC Senior Resident Inspector - LaSalle County Station
Enclosure to RA24-023 Page 1 of 8 ENCLOSURE LaSalle County Station. Units 1 and 2 Response to Non-Cited Violation 05000374/2024001-02 On May 13, 2024, the U.S. Nuclear Regulatory Commission (NRC) issued LaSalle County Station - Integrated Inspection Report 05000373/2024001 and 05000374/2024001 (ADAMS Accession No. ML24131A151) (Reference 1). In Reference 1, the NRC issued a non-cited violation (NCV)05000374/2024001-02 of Title 10 of the Code of Federal Regulations (10 CFR)
Part 50.55a(f)(4)(ii) and associated Green finding to LaSalle County Station (LSCS) for the failure to meet in-service testing (1ST) requirements set forth in the American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code, Code Case OMN-1 after performing maintenance that could affect motor-operated valve (MOV) performance.
Specifically, LSCS failed to perform testing on primary containment isolation MOV 2821-F016, Main Steam Line Drain Header Inboard Isolation Valve, prior to returning the valve to service after electrically backseating the valve. The LSCS 1ST Program Plan -4th Ten-Year Interval (Reference 2) lists MOV 2821-F016 as an ASME Code Class 1, Category A, normally open, motor-operated, active valve with a safety function in the closed position.
LSCS has reviewed the details of the NCV provided in Reference 1 and disagrees with the NRC assessment and the conclusions related to the issue. LSCS has performed a detailed review of the applicable NRC regulations, ASME OM Code and Code Case, and NRC guidance related to post-maintenance testing (PMT) of an 1ST component. The applicable documents allow the licensee to define the level of testing that is required after replacement, repair, or maintenance of an 1ST component. LSCS asserts that an evaluation with stroke testing deferred to a more suitable plant condition can be used to meet the level of testing required to return a valve to service as long as appropriate justification is provided to support that conclusion. The following discussion demonstrates that this method meets the requirements of Code Case OMN-1.
LSCS Review of the NRC Inspection Report The Description section of the NCV 05000374/2024001-02 Inspection Results in Reference 1 provides the fundamental premise for issuing the NCV as follows:
Since both the valve and its control system underwent maintenance that could affect the MO V's performance, the inspectors determined the valve was required to be tested in accordance with Paragraph 3. 4 of Code Case OMN-1. The Code Case does not provide the allowance to perform an evaluation in lieu of the required inservice testing. Although this does not conform to the requirements, the licensee's evaluation and work results provided reasonable assurance the structural integrity of the MO V was not exceeded.
However, not performing any testing after maintenance prior to returning the valve to service did not maintain the requisite level of assurance for the valve. Considering operating experiences with backseating, the number of assumptions embedded in the evaluation, and the use of the new MOV BSRT, the inspectors noted there were several uncertainties associated with the engineering evaluation and its use to restore operability. Based on the inspectors' review of the /ST plan and procedures for the valve, the inspectors determined the licensee failed to ensure the testing required after maintenance under WO 5443427-01 was performed in accordance with Code Case
Enclosure to RA24-023 Page 2 of 8 OMN-1. In addition, the licensee did not request relief from the code via an ASME Code relief request to the NRG which, if approved, would have allowed the valve to be returned to service without performing the required testing.
Furthermore, the Performance Assessment section of the NCV 05000374/2024001-02 Inspection Results in Reference 1 provides additional clarity of the deficiency that led to the violation:
Performance Deficiency: The licensee's failure to perform required testing after maintenance for the primary containment isolation MOV 2B21-F016 in accordance with ASME OM Code-2004, 2006 Addenda, Code Case OMN-1, Paragraph 3.4, was a violation of 10 CFR 50.55a(f)(4)(ii) and a performance deficiency. Specifically, the licensee failed to perform required testing on the MOV prior to returning the valve to service after electrically backseating the valve, which was maintenance that could affect the valve's performance.
LSCS understands the NRC's position that Code Case OMN-1 requires some type of physical testing prior to returning the valve to service and the licensee cannot perform an evaluation as a PMT in lieu of testing without prior NRC approval through an ASME Code relief request. The inspection report does not reference any other NRC regulation or guidance to support this interpretation of the Code Case.
Code Requirements and Guidance A review of the applicable ASME OM Code requirements and NRC guidance was performed, with the relevant basis information summarized below:
ASME OM Code Case OMN-1, Alternative Rules for Preservice and lnservice Testing of Active Electric Motor-Operated Valve Assemblies in Light-Water Reactor Power Plants (Reference 3), states in Paragraph 3.4, Effect of MOV Replacement, Repair, or Maintenance:
When an MO V or its control system is replaced, repaired, or undergoes maintenance that could affect the valve's performance, new inservice test values shall be determined, or the previously established in service test values shall be confirmed before the MO V is re tu med to service... This testing is intended to demonstrate that performance parameters, which could have been affected by the replacement, repair, or maintenance, are within acceptable limits. The Owner's program shall define the level of testing required after replacement, repair, or maintenance.
NUREG-1482, Revision 3, Guidelines for lnservice Testing at Nuclear Power Plants (Reference 4), provides the following guidance in Section 4.4.2, Post-Maintenance Testing After Stem Packing Adjustments and Backseating of Valves to Prevent Packing Leakage:
Alternatively, backseating a valve may stop packing leakage without the need to take the valve out of service. Licensees should exercise caution when performing such maintenance, as improper backseating or adjustment of valve stem packing could adversely affect the valve's functional capability. Licensees will need to have justification
Enclosure to RA24-023 Page 3 of 8 that backseating or packing adjustments do not adverse [sic] impact the operational readiness of the valve.
The NRC Recommendation for Section 4.4.2 of Reference 4, states:
If it is necessary to adjust the stem packing or backseat a valve to stop packing leakage and if a required stroke test or leak rate test is not practical in the current plant mode, the licensee must, at a minimum, justify by analysis that... (2) the backseating does not deform the valve stem, and (3) the performance parameters of the valve are not adversely affected (including the stroke time of the valve). When intending to use backseating to stop a packing leak, the licensee will be expected to stroke the valve stem away from the backseat after the initial backseating operation to demonstrate that the valve stem will not become bound in the backseat by this temporary leakage mitigation method. In addition, the licensee must perform a confirmatory test at the first available opportunity when plant conditions allow testing....
Granting of relief under 10 CFR 50.SSa(f) is not necessary because this action is in accordance with the OM Code requirements if the licensee can demonstrate that the performance parameters will not be adversely affected.
To properly implement this guidance, licensees must perform a partial-stroke test, if practical, to obtain further assurance that the valve stem is free to move. At the first opportunity when the plant enters an operating mode in which testing is practical, the licensee must test all valves that have had packing adjustments or been backseated without post-maintenance testing.
The Basis for Recommendation for Section 4.4.2 of Reference 4, states:
The licensee would have to assess the effect of backseating on valve operation and determine whether post-maintenance testing is required.
Both the ASME OM Code Case and the applicable NRC NUREG guidance consistently state that post-maintenance testing is required after performing maintenance that could affect a valve's performance; however, both also state that the licensee determines the level of testing that is required following maintenance. Also, the guidance states that if the current plant conditions make testing not practical, an analysis can be performed to justify that the valve will still be able to perform its required function, and testing shall be performed at the first available opportunity when plant conditions allow.
LaSalle County Station Position It is the position of LSCS that the requirements of Code Case OMN-1 and the guidance in NUREG-1482 Section 4.4.2 were met by performing an analysis to defer post-maintenance testing to a more suitable plant condition. As explicitly stated in OMN-1 Paragraph 3.4, it is the licensee program that defines the level of testing required after replacement, repair, or maintenance.
MOV 2B21-F016, which is located in the Unit 2 drywell, was determined to be causing an increase in drywell unidentified leakage due to excessive packing leakage. The LSCS Unit 1
Enclosure to RA24-023 Page 4 of 8 and Unit 2 drywells are inerted with nitrogen during power operations and cannot be entered during power operations to perform repairs of equipment. Therefore, the only option to mitigate the excessive packing leakage and reduce drywell unidentified leakage while at power was to electrically backseat MOV 2821-F016. Since MOV 2821-F016 is located inside the drywell, there exists the risk that cycling of the valve could lead to unacceptable drywell leakage resulting in the unnecessary shutdown of LSCS Unit 2 to repair the packing. In 2009, a forced shutdown of Unit 2 was required due to elevated drywell leakage from a packing failure on this valve. Due to past operational experience (OE) with packing leakage causing a forced shutdown, a partial stroke off the backseat was deemed not practical while at power and it was deferred to a more suitable plant condition.
Application of the LSCS 1ST program, in accordance with Paragraph 3.4 of Reference 3, concluded that an evaluation based on past diagnostic testing and data provided justification for returning the valve to service. This evaluation (Reference 5) justified that the backseating performed did not adversely impact the operational readiness of the valve. The evaluation concluded that the backseating did not deform the valve stem and the performance parameters of the valve were not adversely affected, including the stroke time of the valve. The evaluation was reviewed by the NRC and their conclusion is documented in the Description section of the NCV 05000374/2024001-02 Inspection Results in Reference 1:
The licensee performed an engineering evaluation in support of backseating the valve under engineering change request (ECR) 461530. The inspectors reviewed the evaluation and noted there were two reasons for performing this evaluation. One aspect of the evaluation was to evaluate the backseating evolution, which was to be performed for the first time with a new MOV backseat relay tool (BSRT), under Work Order (WO) 5443427-01. This tool is installed at the MCC and bypasses the open limit switch to allow the stem to contact the backseat. The second purpose of the evaluation was to perform a formal technical evaluation to assess the limitation of the backseating, the potential effects on the MOV structural capability, and the valve requirements. The licensee evaluated the following three criteria: increased stroke time, thrust and torque loads applied during backseating of the valve compared to valve/actuator structural capability, and post-maintenance requirements/testing/evaluations. From the review, the inspectors noted the structural capabilities of the valve and actuator were calculated to be acceptable within design limits.
Therefore, the LSCS PMT process determined that a physical PMT was not required, and an evaluation was sufficient to support returning the valve to service while deferring stroking of the valve (i.e., stroking the valve stem away from the backseat after the initial backseating) to a more suitable plant condition.
This deferral of testing to a more suitable plant condition due to not being practical in the current plant condition is allowed by guidance provided in the NRC Recommendation for Section 4.4.2 of Reference 4:
If it is necessary to adjust the stem packing or backseat a valve to stop packing leakage and if a required stroke test or leak rate test is not practical in the current plant mode, the licensee must, at a minimum, justify by analysis that... (2) the backseating does not deform the valve stem, and (3) the performance parameters of the valve are not adversely affected (including the stroke time of the valve).... In addition, the licensee
Enclosure to RA24-023 Page 5 of 8 must perform a confirmatory test at the first available opportunity when plant conditions allow testing....
To properly implement this guidance, licensees must perform a partial-stroke test, if practical, to obtain further assurance that the valve stem is free to move. At the first opportunity when the plant enters an operating mode in which testing is practical, the licensee must test all valves that have had packing adjustments or been backseated without post-maintenance testing.
The deferral of testing does not require relief from the ASME OM Code requirements if it can be demonstrated that the performance parameters will not be adversely affected. As stated in the NRC Recommendation for Section 4.4.2 of Reference 4:
Granting of relief under 10 CFR 50.55a(f) is not necessary because this action is in accordance with the OM Code requirements if the licensee can demonstrate that the performance parameters will not be adversely affected.
The previously discussed evaluation provided the justification that backseating the valve would not adversely affect the performance parameters.
Per the evaluation (Reference 5), during plant shutdown (prior to plant cooldown to less than 250 degrees F), the valve is required to be moved off the backseat to prevent internal binding that could possibly damage the valve or actuator. The movement off the backseat would coincide with a closure stroke time test and meet the intent of a confirmatory test to verify freedom of movement of the valve stem. It also demonstrates that the valve would have closed in the required time, supporting the conclusions of the evaluation.
Due to LSCS Unit 2 being in Mode 1, Power Operation, when MOV 2821-F016 was electrically backseated, work order (WO) 05443427 was scheduled for the Unit 2 refueling outage, L2R20, in 2025 to test and repair MOV 2821-F016. Refueling outage L2R20 is the first scheduled opportunity that Unit 2 will be in a plant condition to allow testing of MOV 2821-F016 due to the drywell being deinerted for refueling and maintenance. Additionally, WO 05443427 was placed on the forced shutdown outage schedule to be completed if Unit 2 has a forced outage of sufficient scope and duration prior to the scheduled refueling outage in 2025.
To demonstrate that electrically backseating an MOV does not adversely affect the ability of the MOV to close from the backseated position an OE search was performed through the Institute of Nuclear Power Operations (INPO) using various terms and phrases such as:
backseat and "failure to close" backseat and closure backseat and "failure to stroke" backseat and bound "electrically backseat" "electrical backseat" The review of the INPO OE results produced one applicable result from April 18, 2005 at Brunswick, OE215560, (Reference 6) where a MOV that was not in the 1ST or MOV program was electrically backseated due to increased drywell leakage. At a later time, Operations
Enclosure to RA24-023 Page 6 of 8 attempted to close the MOV, and it failed to close, resulting in Operations having to use the handwheel to manually move the stem. The valve was then able to be operated electrically with no issue. Investigation of the issue determined binding was unlikely due to the backseat geometry. The cause of the Brunswick failure was indeterminate.
Other relevant OE identified was Information Notice (IN) 87-40, Backseating Valves Routinely to Prevent Packing Leaks (Reference 7). The IN identifies multiple instances of improperly electrically backseating MOVs by temporarily stalling the actuator during backseating, thus creating over torque / thrust conditions and a failed stroke time from the backseat. However, this IN does not identify any failures to stroke from the backseat due to binding. It should be noted that IN 87-40 predates the creation of the NRC required MOV program at commercial nuclear power plants in United States. Through the MOV Program, component weak link information, actuator capability assessments, stroke time computations, and performance trending have been implemented that address the issues identified in this IN.
Conclusion As explicitly stated in Code Case OMN-1, it is the licensee program that defines the level of testing required after replacement, repair, or maintenance. Due to MOV 2821-F016 being located in the drywell, cycling of the valve could have led to unacceptable drywell leakage resulting in a forced shutdown of Unit 2, similar to the event in 2009. Therefore, stroking of the valve at power was considered not practical and deferred to a more suitable plant condition.
The LSCS 1ST program and PMT process determined an evaluation was sufficient to justify returning the valve to service while deferring stroking of the valve to plant shutdown which is within the guidance provided in Section 4.4.2 of NUREG-1482. The valve is scheduled to be repaired during the Unit 2 refueling outage in 2025 and was placed on the forced shutdown outage schedule to be repaired if a forced outage of sufficient scope and duration occurs prior to the refueling outage. Per the evaluation, the valve is required to be moved off the backseat, during plant shutdown to prevent internal binding. This action will coincide with the closure stroke time test that will demonstrate the valve would have closed in the required time, supporting the evaluation conclusions.
Deferral of testing to a more suitable plant condition because testing is not practical in the current plant condition is within the guidance of Section 4.4.2 of NUREG-1482 and does not require relief from the ASME OM Code requirements if it can be demonstrated that the performance parameters are not adversely affected. The performance deficiency is predicated on an interpretation that a level of testing as described in the Code Case precludes an analysis justifying deferral even though the Code Case explicitly states the level of testing is determined by the licensee's program. The inspection report does not justify this interpretation or refute NUREG-1482's allowance for deferral. Therefore, the finding and violation for not meeting the requirements of ASME OM Code Case OMN-1, Paragraph 3.4 is unwarranted.
Enclosure to RA24-023 Page 7 of 8 Table 1 - Acronyms and Abbreviations Acronym/
Description Abbreviation ASME American Society of Mechanical Engineers BSRT backseat relay tool CFR Code of Federal Regulations ECR engineering change request IN Information Notice INPO Institute for Nuclear Power Operations 1ST in-service testing LSCS LaSalle County Station MOV motor-operated valve NCV non-cited violation NRC Nuclear Regulatory Commission OE operating experience OM Operations and Maintenance PMT post-maintenance testing WO work order
Enclosure to RA24-023 Page 8 of 8 References
- 1. Letter from Robert Ruiz (U.S. Nuclear Regulatory Commission) to David P. Rhoades (Constellation Energy Generation, LLC), "LaSalle County Station - Integrated Inspection Report 05000373/2024001 and 05000374/2024001," dated May 13, 2023 (ADAMS Accession No. ML24131A151).
- 2. LaSalle County Station Units 1 & 2, "lnservice Testing Program Plan, Fourth Ten-Year Interval," Revision 4, September 23, 2023.
- 3. American Society of Mechanical Engineers, Operations and Maintenance Code Case OMN-1, "Alternative Rules for Preservice and lnservice Testing of Active Electric Motor-Operated Valve Assemblies in Light-Water Reactor Power Plants."
- 4. United States Nuclear Regulatory Commission, "Guidelines for lnservice Testing at Nuclear Power Plants," NUREG-1482, Revision 3, July 2020 (ADAMS Accession No.
M L20202A4 73).
- 5. Constellation Energy Generation, LLC, "Programs Evaluate the Use Relay Tool for Backseating 2821-F016," ECR 461530, Revision 2, January 26, 2024.
- 6. Institute for Nuclear Power Operations, "Failure of *Rctr Rcirc Pump Suet Valvop that supports *Rctr Rcirc Pump Suet Valve 1-B32-F023B," OE 215560, April 18, 2015.
- 7. United States Nuclear Regulatory Commission, "Backseating Valves Routinely to Prevent Packing Leakage," Information Notice 87-40, August 31, 1987 (ADAMS Accession NO. ML031130374).