ML18304A150
| ML18304A150 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 10/31/2018 |
| From: | Libra R Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Material Safety and Safeguards, Office of Nuclear Reactor Regulation |
| References | |
| LG-18-117 | |
| Download: ML18304A150 (7) | |
Text
Exelon Generation 10 CFR 50.59(d)(2) 10 CFR 72.48(d)(2)
LG-18-117 October 31, 2018 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352, 50-353 and 07200065
Subject:
10 CFR 50.59 and 10 CFR 72.48 Evaluation 24-Month Summary Report for the Period July 1, 2016 through June 30, 2018 Attached is the 24-Month 10 CFR 50.59 and 10 CFR 72.48 Evaluation Summary Report for Limerick Units 1 and 2 for the period of July 1, 2016 through June 30, 2018, forwarded pursuant to 10 CFR 50.59(d)(2) and 10 CFR 72.48(d)(2). The report includes brief descriptions of any changes, tests and experiments, including a summary of the evaluation of each.
Four plant changes were approved and/or implemented using 10 CFR 50.59 Evaluations during this 24-month period.
There were no plant changes implemented using 10 CFR 72.48 Evaluations during this 24-month period.
There are no regulatory commitments contained in this letter.
If you have any questions, please contact Robert B. Dickinson at (610) 718-3400.
Respectfully, Richard W. Libra Vice President - Limerick Generating Station Exelon Generation Company, LLC
Attachment:
Limerick Generating Station 10 CFR 50.59 Evaluation and 10 CFR 72.48 Evaluation 24-Month Summary Report, 2018 cc: NRC Regional Administrator - Region I NRC Senior Resident Inspector- Limerick Generating Station
ATTACHMENT Limerick Generating Station 10 CFR 50.59 Evaluation and 1 O CFR 72.48 Evaluation 24-Month Summary Report 2018 Note: This report summarizes 10 CFR 50.59 and 10CFR72.48 Evaluations that were approved between July 1, 2016 and June 30, 2018.
Attachment:
Limerick Generating Station 10 CFR 50.59 Evaluation and 10 CFR 72.48 Evaluation 24-Month Summary Report, 2018
Title:
Limerick Non Class 1E Offiste Power System Open Phase Detection System Trip Activation on the 10, 101, 20 and 201 Transformers Unit Affected: Units 1 and 2 Year Implemented: Approved not implemented Brief
Description:
The Limerick open phase detection (OPD) project is a three-step project. This activity is for the final (third) step. It will enable the Limerick open phase detection relaying trip function on both independent sources of offsite power.
The original design of the non-class IE offsite power 5y.>tem protective schemes and its associated path to the onsite safety related distribution buses is that it can be isolated if an electrical fault occurs so that the other independent offsite oource or standby diesel generators can be reestablished to the onsite class IE buses. The OPD modification maintains this design by adding protective relaying capable of detecting an open phase condition to the existing non-class IE offsite source electrical protective relaying schemes.
Summary of Evaluation:
This activity supplements the existing non-class IE offsite source protective relaying schemes with the addition of open phase detection (OPD) relays in each of the Limerick independent offsite power sources to mitigate a newly identified malfunction that is beyond the approved Limerick design and licensing basis of the plant.
The original design of the non-class IE offsite power system protective schemes and its associated path to the onsite safety related distribution buses is that it can be isolated if an electrical fault occurs so that the other offsite saJrce or standby diesel generators can be reestablished to the onsite class IE buses. The OPD modification maintains this design by adding protective relaying capable of detecting an open phase condition to the existing electrical protective relaying schemes.
The reliability of the OPD relaying installed by this activity is comparable to the existing protection relays and other 500kV/220kV system offsite source components, so the magnitude of impact on the likelihood of malfunctions is not discernible. Therefore, the increase in likelihood of evaluated malfunctions, consequences, or frequency of evaluated design basis events is not more than minimal and is acceptable.
The OPD relays will be periodically tested to verify alarm and trip functions to ensure continued reliability. This maintains compliance with GDC 18 to periodically test offsite source protective relaying as described in the UFSAR.
Therefore, this activity maintains compliance with GDC 17 and GDC 18as documented in the UFSAR by installing the Exelon/NE! industry preferred voluntary open phase detection system to maximize offsite saJrce reliability and minimize the probability of losing offsite power.
Page 1 of 5
Attachment : Limerick Generating Station 10 CFR 50.59 Evaluation and 10 CFR 72.48 Evaluation 24-Month Summary Report, 2018
Title:
TRM Shutdown Statement Removal and Standalone TRM Applicability Section Creation Unit Affected: Units 1 and 2 Year Implemented: 2017 Brief
Description:
This activity will perform a 50.59 evaluation to change TRM shutdown statements and other unnecessary restrictions and create a standalone TRM Applicability Section instead of referencing the Technical Specification Applicability Section.
These changes are being made to prevent unnecessary plant shutdonws and action statement induced plant transients. These changes are being performed, because the current TRM requirements are unnecessarily restrictive based upon the impacted TRM component functions, safety significance, and risk significance that supported their removal from Technical Specifications per 10 CFR 50.36. It is unreasonable to require a plant shutdown when a subject component/system function is lost if it:
- Is not credited in the accident analysis
- Is not a risk significant SSC
- Does not create an unanalyzed condition The shutdown actions are being replaced with an action to initate and perform a prompt assessment to determine the impact of continued plant operation while TRM related equipment remains out of service. The conclusions of the assessment may be based on risk insights (qualitative or quantitative or both), other required equipment simultaneously removed from service, alternate means of achieving the support function, compensatory measures to offset the effect of the out of service equipment, etc.
This provides the benefit of evaluating each particular situation and making an informed nuclear safety biased decision based on the conditions. The assessment may conclude that a shutdown is appropriate based on accrued risk or the aggregate safety significance of several required components being out of service simultaneously.
Summary of Evaluation:
These changes are commensurate with the non-critical function and lower safety significance of TRM SSCs. This will prevent unnecessary plant shutdowns and action statement induced plant transients. These changes provide the ability ard benefit of evaluating each particular TRM SSC inoperability situation to make an informed nuclear safety biased decision based on existing plant conditions. These changes could potentially avoid an unnecessary plant shutdown, but do not necessarily prevent all plant shutdowns.
The 50.59 evaluation determined that there were no impacts to the probability or consequences of accidents or malfunctions of equipment important to safety. Also, there were no accidents of a different type or malfunctions of equipment with a different result involved. The design basis limits for a fission product barrier were not exceeded or altered.
Page 2 of 5
Attachment:
Limerick Generating Station 10 CFR 50.59 Evaluation and 10 CFR 72.48 Evaluation 24-Month Summary Report, 2018
Title:
Turbine Overspeed Protection System 3.3.8 TAM Required End StateAction Relaxation Unit Affected: Units 1 and 2 Year Implemented: 2017 Brief
Description:
This activity wil perform a 50.59 evaluation that involves relaxation of Technical Requirements Manual (TRM) 3.3.8 Turbine Overspeed Protection System required end state actions that require isolation of the affected inoperable stop or control or intermediate valve and complete turbine isolation if the turbine overspeed protection 5)'Stem is inoperable.
To justify this change, when a turbine stop or control or intermediate valve or turbine overspeed trip system becomes inoperable, detail is being added to the TRM 3.3.8 actions and TRM Bases 3.3.8 to require a review to ensure the assumptions and results of the turbine missile generation probability discussion in UFSAR Section 3.5.1.3 remain valid and within the acceptable probability limit.
It also changes the end state actions to enter the actions of TRM TLCO 3.0.3 instead of removing turbine valves or the turbine from service if the action cannot be completed.
Summary of Evaluation:
A thorough Limerick Licensing Basis and commitment documents search did not reveal a documented basis for the TRM Turbine Overspeed Protection System 72-hour or 6-hour completion time to isolate a turbine steam valve or the turbine listed in TRM 3.3.8.
The changed TRM 3.3.8 requirements will require a review to ensure the assumptions and results of the turbine missile generation probability discussion in UFSAR Section 3.5.1.3 remain valid and within the acceptable calculated probability limits and entry into TLCO 3.0.3. These combined actions will prevent an adverse impact and ensure safe plant operation. The addition of detail to TRM Bases 3.3.8 provides clear direction to prompt a review of the turbine missile analysis information in the UFSAR instead of just providing a reference to UFSAR 3.5.1.3.
These changes are commensurate with TRM Turbine Overspeed Protection System function. The current TAM requirements are unnecessarily restrictive based upon the impacted TRM component functions, safety significance, and risk significance that supported their removal from Technical Specifications per 10 CFR 50.36.
Page 3 of 5
Attachment : Limerick Generating Station 10 CFR 50.59 Evaluation and 10 CFR 72.48 Evaluation 24-Month Summary Report, 2018
Title:
Reactor Coolant System Chemistry 3.4.4 TRM Shutdown Statement and Surveillance Requirements Change Unit Affected: Units 1 and 2 Year Implemented: 2017 Brief
Description:
This activity removes the Regulatory Guide (RG) 1.56 reactor coolant system chemistry shutdown action statement and associated surveillance requirements and instead refers the operator to comply with the requirements of the EPRI BWR plant water chemistry guidelines (BWRVIP-190). This is a Limerick license renewal committed program as documented in UFSAR Pppendix A. The current EPRI BWR Water Chemistry Guidelines provide direction to reduce the applicable chemistry parameter below limits, assess the impact on long term plant reliability, and in oome cases, require plant shutdown.
Summary of Evaluation:
These changes provide the ability and benefit to promptly evaluate and address the actual impact of a poor reactor water chemistry condition on plant operation and the RCPB to make an informed nuclear safety biased decision based on existing plant conditons instead of mandating a plant shutdown that can initiate a plant transient that can impact nuclear safety. The evaluation may conclude that a plant shutdown is approporate based upon reactor chemistry conditons. Therefore, these changes may not necessarily prevent a plant shutdown.
The existing TRM limits and associated surveillance requirements are the guideline limits established in Regulatory Guide (RG) 1.56. This change removes the existing TRM shutdown action statement and surveillance requirements and instead refers the operator to comply with the requirements of the EPRI BWR plant water chemistry guidelines (BWRVIP-190). This is a Limerick license renewal committed program as documented in the UFSAR.
The current EPRI BWR Water Chemistry Guidelines provides direction to reduce the applicable chemistry parameter below limits, assess the impact on long term plant reliability, and in some cases, requires plant shutdown. The Exelon/Limerick BWR plant water chemistry program that complies with the BWRVIP-190 has action levels that meet, or are conservative with respect to, the limits specified in existing TRM Table 3.4.4-1 that are based upon RG 1.56. The BWRVIP-190 program has shutdown requirements based upon those action levels. The same justification and rationale also applies to the surveillance requirements.
These changes will continue to provide adequate assurance that reactor coolant system conductivity limits, chloride concentration and pH will continue to be met, monitored, and controlled as appropriate. This ensures that degradation of the reactor coolant pressure boundary is not exacerbated by poor reactor water chemistry conditions or the inability to obtain a sample. Chemistry induced degradation of the reactor coolant pressure boundary is a long-term process and the requirements related to the chemistry program are an operational concern. They do not constitute initial conditions that are assumed in any design basis accident or transient related to reactor coolant !¥Stem integrity.
Page 4 of 5
Attachment:
Limerick Generating Station 10 CFR 50.59 Evaluation and 10 CFR 72.48 Evaluation 24-Month Summary Report, 2018 The 10 CFR 50.59 evaluation determined that there were no impacts to the probability or consequences of accidents or malfunctions of equipment important to safety. Also, there were no accidents of a different type or malfunctions of equipment with a different result irwolved. The design basis limits for a fission product barrier was not exceeded or altered.
Page 5 of 5