ML24078A275
| ML24078A275 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 03/18/2024 |
| From: | David Helker Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| Download: ML24078A275 (1) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.ConstellationEnergy.com
March 18, 2024
U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTN: Document Control Desk
Limerick Generating Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353
Subject:
Response to Requests for Additional Information (RAIs 5, 6, 7, and 8) for License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety -Related Analog Control Systems with a Single Digital Plant Protection System (PPS)
References:
- 1. Constellation Energy Generation, LLC (CEG) letter to the U.S. Nuclear Regulatory Commission (NRC), "License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS)," dated September 26, 2022 (NRC Agencywide Documents Access and Management System (ADAMS) Accession No. ML22269A569).
- 2. Constellation Energy Generation, LLC (CEG) letter to the U.S. Nuclear Regulatory Commission (NRC), "Resubmittal of License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS) - To Address Proprietary Issues with INL HFE Reports," dated September 12, 2023 (ADAMS Accession No. ML23255A095)
- 3. Email from Michael Marshall, U.S. Nuclear Regulatory Commission to Francis Mascitelli, Constellation Energy Generation, LLC, Limerick Generating Station, Units 1 and 2 - Request for Additional Information Regarding Limerick Digital Instrumentation and Controls License Amendment Request (EPID L-2022-LLA-0140), dated February 16, 2024 (ADAMS Accession No. ML24051A065)
In accordance with 10 CFR 50.90, Constellation Energy Generation, LLC (CEG) requested a License Amendment Request (LAR) to replace the Limerick Generating Station, Units 1 and 2 existing safety-related analog control systems with a single digital Plant Protection System (PPS) (Reference 1).
Limerick DMP LAR RAIs 5, 6, 7, and 8 Response Docket Nos. 50-352 and 50- 353 March 18, 2024 Page 2
In Reference 2, CEG submitted a LAR supplement that replaced in its entirety the original license amendment request, dated September 26, 2022. CEG replaced the original submittal to address issues associated with proprietary/non-proprietary information.
In Reference 3, the NRC notified CEG that additional information is needed to complete its review of the Reference 2 submittal.
The Attachment to this letter provides the response to request for additional information for RAIs 5, 6, 7, and 8.
CEG has reviewed the information supporting a finding of no significant hazards consideration, and the environmental consideration, which was previously provided to the NRC in the Reference 2 letter. CEG has concluded that the information provided in this RAI response does not affect the bases for concluding that the proposed license amendments do not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92. In addition, CEG has concluded that the information in this RAI response letter 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 amendments.
This RAI response letter contains no regulatory commitments.
In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"
paragraph (b), CEG is notifying the Commonwealth of Pennsylvania of this supplemental letter by transmitting a copy of this letter to the designated State Official.
If you have any questions regarding this submittal, then please contact Frank Mascitelli at 267-533-5677 or Ashley Rickey at 267-533-1427.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 18th day of March 2024.
Respectfully,
David P. Helker Sr. Manager - Licensing Constellation Energy Generation, LLC
Attachment:
Response to Requests for Additional Information (RAIs 5, 6, 7, and 8) for License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS)
Limerick DMP LAR RAIs 5, 6, 7, and 8 Response Docket Nos. 50-352 and 50- 353 March 18, 2024 Page 3
cc: USNRC Region I, Regional Administrator w/ attachment USNRC Project Manager, LGS "
USNRC Senior Resident Inspector, LGS "
Director, Bureau of Radiation Protection - Pennsylvania Department "
of Environmental Protection Attachment
License Amendment Request Supplement
Limerick Generating Station, Units 1 and 2 Docket Nos. 50- 352 and 50- 353
Response to Requests for Additional Information (RAIs 5, 6, 7, and 8) for License Amendment Request to Revise the Licensing and Design Basis to Incorporate the Replacement of Existing Safety-Related Analog Control Systems with a Single Digital Plant Protection System (PPS)
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By letter dated September 26, 2022 (Agencywide Documents Access and Management System Accession No. ML22269A569; non-public), as supplemented by letters dated August 12, 2022 (ML22224A149), November 29, 2022 (ML22333A817), February 8, 2023 (ML23039A141), February 15, 2023 (ML23046A266), March 30, 2023 (ML23089A324),
April 5, 2023 (ML23095A223), June 26, 2023 (ML23177A224), July 31, 2023 (ML23212B236), September 12, 2023 (ML23255A095), October 30, 2023 (ML23303A223),
November 21, 2023 (ML23325A206), and January 26, 2024 (ML24026A296), Constellation Energy Generation, LLC (Constellation; the licensee) (CEG) submitted license amendment requests to replace the Limerick Generating Station, Units 1 and 2 (Limerick) existing safety-related analog control systems with a single digital control system called plant protection system. The supplement dated September 12, 2023 replaced in its entirety the original license amendment requests dated September 26, 2022. The licensee replaced the original submittal, because it had mistakenly included proprietary information in the non-proprietary parts of the requests. The U.S. Nuclear Regulatory Commission (NRC) staff made all of the original submittal non-public. With the exceptions noted by the licensee in its letter dated September 26, 2023, the content of the replacement and the original are the same.
The proposed amendment requests would change both the design and technical specifications to permit the use of a new single digital instrumentation and controls system to replace analog instrumentation of reactor protection system, analog nuclear steam supply shutoff system, emergency core cooling system, reactor core isolation cooling system, and end-of-cycle recirculation pump trip at Limerick. In addition, the proposed amendments would change the classification of the redundant reactivity control system from safety-related to non-safety-related, eliminate the automatic redundant reactivity control system feedwater runback function, eliminate the automatic isolation function for the turbine enclosure main steam line tunnel temperature high indication, eliminate several surveillance requirements, and allow the use of automated operator aids (or automated controls) from main control room.
The NRC staff has reviewed the information provided in the license amendment request and has determined that additional information is needed to complete our review. This request for additional information (RAI) was discussed with Constellation on February 15, 2024. It was agreed that CEG would provide a response within 30 days of the final RAI email (by March 18, 2024).
NRC RAI 5
- 5) In response to the requirements in Three Mile Island (TMI) Action Item I.D.1, the licensee for Limerick reviewed the plants control room design with consideration of human factors engineering (HFE) principles. The review of the control room was required to include the use of task analysis (i.e., TMI I.D.1.5.1.b(ii)). A task analysis should identify important human actions (IHAs).
In Section 6.8 of the HFE Program Plan, which was included with Constellations letters dated September 26, 2022 and September 12, 2023, the licensee states that the human reliability analysis (HRA) identifies IHAs that are within the scope of the analog to digital upgrade. Also, the licensee states that risk -IHAs were identified in Chapter 19 of the final safety analysis report. The licensee stated that it used the screening analysis described in NUREG-1764, Guidance for the Review of Changes to Human Actions, and considered the guidance in NUREG-0711, Human Factors Engineering Program
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Review Model, in the identification of IHAs. In Sections 2.0 and 5.4 of the Combined Results Summary Report (RSR), which was included in Constellations letters dated September 26, 2022 and September 12, 2023, the licensee stated that IHA considered in a manner consistent with the guidance in NUREG-0711, where applicable. NUREG-0711 Section 7.1 indicates applicants should identify those human actions most important to safety via a combination of probabilistic and deterministic analyses, and then address them when conducting the HFE. The specific guidance used from NUREG-0711 is not specified.
The HFE Conceptual Verification RSR, which was included with Constellations letters dated February 9, 2023 and April 5, 2023, contains a list of manual operator actions impacted by the modification and included in the current licensing basis in Section 4.3.2.1 Table 3. Section 4.3.2.2 Table 4 provides a list of additional manual actions considered, but that were not part of the licensing basis. These actions in Table 4 were identified as time sensitive actions. However, neither of these sections discusses whether there were any IHAs identified using probabilistic analyses. Additionally, Sections 4.3.2.1 and 4.3.2.2 do not state whether these manual actions met the criteria to be considered an IHA.
a) Please clarify which of the manual actions described in Sections 4.3.2.1 and 4.3.2.2 of the HFE Conceptual Verification RSR are identified as an important IHAs per the HFE Program Plan.
CEG 5a Response
The Important Human Actions (IHAs) include timebased Credited Manual Actions -
(CMAs) and other actions with no specified time constraint. The manual actions described in Table 3 of Section 4.3.2.1 and Table 4 of Section 4.3.2.2 of the HFE Conceptual Verification RSR are the time-based CMAs required to be completed as part of the associated IHAs. The manual actions described in the text following Table 4 of Section 4.3.2.2 of the HFE Conceptual Verification RSR are nontime-based -
CMAs required to be evaluated as part of the associated IHAs.
Table 3 of Section 4.3.2.1 and Table 4 of Section 4.3.2.2 of the HFE Conceptual Verification RSR (CV RSR) lists the CMAs along with their unique CMA number. The actions are identified as CV1 through CV7. In the final column of these tables are the IHAs associated with each CMA. These IHAs are described in Table 4 of Section 5.1.2.2 of the Combined Results Summary Report (RSR), the text immediately following Table 4, and in Table 2 of Section 4.3.1 of the CV RSR.
The process used to develop the IHAs and CMAs is described in RAI 5b response below.
Because of the direct correlation between the IHAs and the CMAs, the decision was made to evaluate the IHAs using the CMAs during CV and PV. This was done since the CMAs allowed for discrete evaluations of the time constraints for all but two of those actions. This decision is noted at the end of Section 4.3.2 in the HFE Conceptual Verification RSR. Section 4.3.2 states:
a more focused evaluation LGS documentation by the HSI Design and Procedure Modification Team was made to identify manual actions of interest
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for CV and PV. The results of this effort are captured in the subsections below.
The actions identified in the subsections below [CMAs] supplant those identified in Table 2 [IHAs] and were used for CV. These will also be used for PV.
As described in Section 4.3.2.2 of the HFE Conceptual Verification RSR, the methodology for determining the IHAs was refined between the time the Combined Results Summary Report (RSR) and the HFE Conceptual Verification RSR. That refinement led to the incorporation of the required times to perform IHAs during the performance of CV and PV. That focus led to the development of more refined actions which have a time measured element and are the time-based evaluated elements from CV and PV. Two additional untimed CMAs were evaluated as part of the associated IHAs (Residual Heat Removal Shutdown Cooling Operation and the Common Cause Failure of the PPS system). These are described in the text immediately following Table 4, and in Table 2 of Section 4.3.1 of the CV RSR. Although untimed these CMAs were added to ensure thorough coverage of the original IHAs and understanding of the new failure modes requi red to be evaluated because of the Defense-in-Depth and Diversity ( D3) analysis. Other non-time-based aspects of the IHAs and other unrelated operator actions were evaluated as part of the dynamic simulation scenarios described in Section 5.3 of the CV and PV RSRs.
Evaluation of the CMAs in both CV and PV resulted in successful completion of all time-based and untimed elements of the CMAs, as documented in Section 5.3.1 and 5.3.2 of the CV and PV RSRs, as well as the maintenance of acceptable operator burden as noted in the RAI 8.b response below.
b) Please, identify the specific guidance (i.e., methods) used to identify the IHAs, including whether any probabilistic analyses were used. For example, if specific guidance from NUREG-0711 was used, please provide the sections of the document that were used.
CEG 5b Response
As described in RAI 5.a response above, the CMAs are decomposed elements of the IHAs which were developed for the execution of CV and PV. As such, the IHAs bound the tasks determined to be the time evaluated elements (i.e., CMAs) for CV and PV.
Section 5.1.2.2 of the Combined Results RSR provides the general method for identifying IHAs. This method is summarized below.
The methodology used to select the IHAs was implemented by subject matter experts from the Operations department reviewing the scope and associated impacts of the digital modernization project. That group of SMEs then identified those tasks that were impacted by the modification. This part of the evaluation used the operator training task list. The operator training task list contains all the current activities trained on for both licensed and non-licensed operators in both initial and requalification settings.
The list includes a combined rating (DIF), which is a weighted measure of the relative difficulty, importance, and frequency of occurrence of each task. Although the DIF score was reviewed as part of the original task analysis, it did not serve as a direct differentiating factor.
The impacted tasks were then reviewed against the USFAR and the current Limerick
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PRA, as described in Section 5.1.2.2 of the Combined Results Summary Report (RSR). The impact of the modification on the task and the presence of that task in either the licensing bases, D3 or PRA served as the screening to which tasks would be included for further evaluation. During that evaluation several tasks had the same actions / operator response even though they have discrete task identifiers in Table 4 of Section 5.1.2.2 of the Combined Workshop Report. In those cases, the actions taken by the one of the selected IHAs was determined to be representative of the operator impact and every impacted task was not added for further evaluation in CV and PV. This evaluation is described in Section 5.1.2.3 of the Combined Results Summary Report (RSR) following Table 6.
As noted in RAI 5.a response above, the CMAs were then decomposed from the IHAs for the execution of CV and PV. This again involved the Operations SMEs reviewing the modification impacts against the existing Limerick Generating Station Operator Response Time Program. The following is the background of this program based on text from the Limerick Generating Station Operator Response Time Program:
The Limerick Generating Station Operator Response Time Program is an industry wide process which provides governance on the identification, control, validation, and documentation requirements for specific operator actions.
Each plant has a number of actions that are to be accomplished in a specified time. Completion of these actions assures the plant complies with the assumptions made during the analysis of design basis events, regulatory committed design events, events with high PRA significance and tasks, manual actions and decisions for beyond design bases events. These actions are referred to as Time Critical Actions (TCA), Time Sensitive Actions (TSA) as well as FLEX time constrained actions. Each site maintains a site-specific procedure where the identified TCA and TSA actions are listed, and the bases are documented.
Time Critical Actions (TCAs) are time constrained manual actions which are credited in the safety analyses as part of the primary success path for mitigating design basis accidents. Manual operator actions required to support the credited strategy in the safety analysis (both implicitly and explicitly) are also TCAs. Only operator action(s) that are performed within a specified time, which are credited in the plants design are considered time critical.
Time Sensitive Actions (TSAs) are time-constrained manual actions or series of actions that are not credited in the plant Design Basis, but which must be completed within a specified time to meet requirements in programs, procedures, and documents. These include actions from the peer reviewed PRA model (internal events including internal floods, fire, and if applicable other hazards) modeled actions, beyond design basis actions, items such as fire safe shutdown, execution of B.5.b mitigation actions and other items that are not credited in the plants design basis.
The results of the Operations SMEs review of the modification impacts against the existing Limerick Generating Station Operator Response Time Program and the specific impacted TCAs and TSA are as follows:
- The list of CMAs impacted by the modification which are described as Time
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Critical Actions are listed in Section 4.3.2.1 of the CV and PV RSRs and are part of the current Limerick licensing bases.
- The list of CMAs impacted by the modification which are described as Time Sensitive Actions are listed in Section 4.3.2.2 of the CV and PV RSRs and are part of the current Limerick PRA analysis.
- Additionally, the team added two items which are not described in the Operator Response Time Program. These were (1) the operation of RHR in Shutdown Cooling and (2) a Common Cause Failure of the PPS system.
These items, although not time based, were incorporated to ensure important actions in multiple operating modes and D3-related actions, respectively, were evaluated. These items are described in the text immediately following Table 4, and in Table 2 of Section 4.3.1 of the CV RSR.
This methodology incorporated aspects of NUREG-0711 Section 7 philosophy in ensuring the list of evaluated actions included risk important human actions from the PRA and deterministically important actions from both Chapter 15 as well as the D3 analysis. The use of the of TCAs and TSAs as described above aligned with the definitions for deterministically identified important human actions and risk-important human actions from the glossary of NUREG-0711.
This methodology also identifies specific times associated with accomplishing these IHAs. This allowed for the identification and use of a timeline analysis method for CV and PV leveraging the timing guidance contained in the Guidelines for Using Timelines to Demonstrate Sufficient Time to Perform the Actions, provided in Appendix A of NUREG -1852, Demonstrating the Feasibility and Reliability of Operator Manual Actions in Response to Fire. This method is captured in Section 4.4.3 of the CV RSR and PV RSR.
NRC RAI 6
- 6) In response to the requirements in TMI Action Item I.D.1, the licensee for Limerick reviewed the plants control room design considering HFE principles. The review of the control room was required to include the use of task analysis (i.e., TMI I.D.1.5.1.b(ii)). A task analysis should identify IHAs. The Limerick Detailed Control Room Design Review (DCRDR) Program Plan (comparable to the Limerick HFE Program Plan) that was developed by the licensee in response to TMI I.D.1 included an operating experience review (OER) intended to discover human engineering shortcomings that have caused actual operating problems.
In Section 6.8 of the HFE Program Plan, the licensee states that the HRA identifies IHAs that are within the scope of the analog to digital upgrade. The licensee stated that it used the screening analysis described in NUREG-1764 and considered the guidance in NUREG-0711 in the identification of IHAs. In Sections 2.0 and 5.4 of the Combined RSR, which was included in Constellations letters dated September 26, 2022, and September 12, 2023, the licensee stated that IHA considered in a manner consistent with the guidance in NUREG-0711, where applicable. NUREG-0711, Section 7.1 indicates applicants should identify those human actions most important to safety via a combination of probabilistic and deterministic analyses, and then address them when
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conducting the HFE. The specific guidance used from NUREG-0711 is not specified.
In Section 6.4 of the HFE Program Plan, the licensee states that its OER methodology is based on review criteria in NUREG-0711 and guidance in Electric Power Research Institute (EPRI) Report 3002004310, Human Factors Guidance for Control Room and Digital Human-System Interface Design and Modification. The specific guidance used from NUREG- 0711 and EPRI Report 3002004310 is not specified.
In the Limerick Safety-Related Instrumentation and Control Upgrade HFE Preliminary Validation (PV) RSR, which was included in Constellations letters dated March 30, 2023, and June 26, 2023, the licensee states that there are deterministic actions that are identified as impacted or affected by the modification. Specifically, some actions that were performed locally in the plant are now performed through the upgraded system from digital controls in the control room. In Section 1 of the PV RSR, the licensee states that Constellation personnel identified credited manual operator actions (CMAs) in the Limerick licensing basis that are impacted the analog to digital upgrade at Limerick.
Section 7.1 of NUREG-0711 states, in part, applicants identify those human actions most important to safety via a combination of probabilistic and deterministic analyses, and then address them when conducting the HFE. NUREG-0711, Section 7.4 states that applicants should identify deterministic IHAs from operator actions credited in the Limerick Final Safety Analysis Report and operator actions identified in the diversity and defense-in-depth coping analyses.
Section 3.4.1(5) of NUREG-0711 states, in part, that the applicants OER should identify IHAs in the predecessor plants or systems and determine whether they remain important in the applicants design.
a) Please clarify as to whether the CMAs are required as a part of any identified IHAs identified deterministically which are affected by the modification.
CEG 6a Response
As noted in RAI 5.a response, the CMAs identified in the CV and PV RSRs are time-based IHAs. As further clarified in the RAI 5.b response, the CMAs identified in Section 4.3.2.1 of the CV and PV RSRs were identified deterministically using existing station programs. The CMAs are documented in Section 4.3.2.1 Table 3 in the CV RSR and Section 4.3.2.1 Table 1 in the PV RSR.
b) If there are, please describe the methodology used to screen the existing impacted actions as IHAs.
CEG 6b Response
The method used to screen actions as IHAs and CMAs is described in the RAI 5.b response above.
c) Please provide a discussion on how operating experience affected the relevance of IHA and the proposed modifications.
CEG 6c Response
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The operating experience reviewed and documented in INL/RPT 68703, Human Factors Engineering Operating Experience Review of the Constellation Limerick Control Room Upgrade: Results Summary Report did not identify any CMAs / IHAs beyond those evaluated using the methods described in the response to RAI 5.b above. The report confirmed the relative difficulty of certain tasks taken by the Operations staff during transient situations using the existing Human-System Interface (HSI) design; however, this determination did not elevate the relative importance of those tasks in relation to PRA nor did it change the timeliness required for their execution in the licensing basis. As such, these activities did not elevate to CMAs / IHAs with their identification in the referenced Operating Experience Review ( OER).
The insights from the OE review did, however, serve as a feeder into the design of the new system and the operator interface through the HSIs to simplify the response as much as achievable given the scope of the project and the current accident analyses being unchanged for this modification.
The movement of temperature monitoring into the Main Control Room and requests for automation to simplify operator responses in transient conditions are examples of items identified during the OE review and incorporated into the final design.
NRC RAI 7
- 7) In response to the requirements in TMI Action Item I.D.1, the licensee for Limerick reviewed the plants control room design considering HFE principles. The review of the control room was required to include the use of function analysis (i.e., TMI I.D.1.5.1.b(ii)). The Limerick DCRDR Program Plan (comparable to Limerick HFE Program Plan) that was developed by the licensee in response to TMI I.D.1 included a function analysis that examined the required functions and functional sequences with respect to available staffing, technology, and other resources to determine how the functions may be executed.
In Section 4 of the Combined RSR and in Section 6.5 of the HFE Program Plan, the licensee states that an functional requirements analysis (FRA) and function allocation (FA) were performed and that the facilitys FRA and FA methodology was based upon principles described in NUREG-0711, EPRI report providing HFE guidance for control room design and modification, IEEE-1023, Recommended Practice for the Application of Human Factors Engineering to Systems, Equipment, and Facilities of Nuclear Power Generating Stations and Other Nuclear Facilities, providing recommendations for applying HFE, and an EPRI HFE training course. The specific guidance used from NUREG-0711 and the other documents is not specified.
In Section 4.1.2 of the Combined RSR, the licensee describes the methodology used for the FRA. This includes taking the current list of control room tasks and using subject matter experts to review and identify all tasks that will be impacted by the modification.
This section of the document does not specify what changes were made for the high-level functions, nor did the document discuss what the specific changes were made to
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impacted tasks.
Section 4.4 of NUREG-0711 describes use of a structured, documented methodology reflecting HFE principles to perform FRA and FA, including describing the plants functional hierarchy, including, as appropriate: goals, functions, processes, and systems.
Based on the information provided by Section 4.1.2 of the Combined RSR, a task analysis was performed to determine changes to the current list of control room tasks.
There was no discussion about the plants functional hierarchy.
a) Please clarify if there are no changes to the plants functional hierarchy or requirements for high-level functions due to the proposed modification. If there are changes, please provide the following details regarding the task analysis:
i) Please describe the functional hierarchy, such as determining goals, functions, processes, or systems.
ii) Please clarify whether high-level functions remain unchanged and if they are, please provide the technical basis for modifications.
iii) Please describe which functions differed for the new design or clarify that there are no differences.
iv) Please provide a list of requirements that should be identified for each high-level function that will be affected by the proposed modification, if applicable.
CEG 7a Response
The design of the digital upgrade at Limerick Generating Station did not change the functional hierarchy or the high-level functions for the facility. The new interface for the safety systems was designed to maintain the current licensing basis response and timing of required operator responses. Because there were no changes to the fundamental plant response or the required operator interactions with the plant there were no changes in the functional hierarchy.
As also noted in RAI 5.b response, the task analysis performed for the modification was therefore performed by SMEs evaluating the current task list for the licensed and non-licensed operators and identifying those tasks which were impacted by the change in the design and / or operator interface. This analysis was performed in this manner due to the scope and implementation of the modification not impacting the high-level functions as noted above.
NRC RAI 8
- 8) In response to the requirements in TMI Action Item I.D.1, the licensee for Limerick reviewed the plants control room design considering HFE principles. The review of the control room was required to include the use of function and task analysis (i.e., TMI I.D.1.5.1.b(ii)). The DCRDR Program Plan (comparable to HFE Program Plan) that was developed by the licensee in response to TMI I.D.1 included a function analysis that examined the required functions and functional sequences with respect to available staffing, technology, and other resources to determine how the functions may be
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executed and a task analysis that delineated system functions and the specific actions that needed to be taken to accomplish those functions.
For manual actions that the operator must perform correctly to safely operate the unit or maintain it in a safe condition, the necessary cognitive and physical needs of the operator should be met, including an evaluation of the overall cognitive and physical load on the operator during performance of these actions. This includes consideration of other operator responsibilities and their impact on operator performance. Part of HFE includes determining if the overall cognitive and physical load on the operator will impact their ability to take the necessary manual actions to safely operate the unit or maintain it in a safe condition.
The function analysis is performed to review the new reassignments since existing functions were reassigned as part of the modification. In Section 4 and Appendix A of the Combined RSR, there is no discussion of the acceptability of the aggregate of all functions allocated to the control room staff, nor on whether the functions interfered with each other. Section 4 of the Combined RSR and Section 6.5 of the HFE Program Plan, the licensee states that the FRA and FA methodology was based on the principles in NUREG-0711, EPRI report providing HFE guidance for control room design and modification, IEEE-1023 providing recommendations for applying HFE, and an EPRI HFE training course. The specific guidance used from NUREG-0711 is not specified.
One of the principles of NUREG-0711 relates to ensuring that the overall role of personnel is evaluated by considering all personnel allocated functions in the aggregate to ensure that the operator is able to perform all required duties.
a) Please describe how the new or changed operator tasks resulting from the modification were considered in conjunction with existing tasks such that the complete set of operator tasks were considered in aggregate for their appropriateness.
CEG 8a Response
The task analysis performed for the modification was performed by first having a group of SMEs evaluate the current task list for the licensed and non -licensed operators and identify those tasks which were impacted by the change in the design and / or operator interface. The current task list is a controlled list used for the conduct of qualification and training of operators and is aligned with the tasks described previously in the Operator Response Time program and PRA analysis at Limerick Generating Station.
Next, the same team of SMEs reviewed the modification scope and impacts as well as the D3 analysis to determine if any new tasks had been created as part of the modification. In that review, the response to a Common Cause Failure was determined to be a new task which was required to be performed by the MCR operators.
Because the existing task list addresses actions which cover all operating conditions and both design bases and beyond design bases required actions, the review of the current task list plus the addition of specific items from the modification and D3 analyses were comprehensive and covered all aspects of operator response.
These tasks were aggregated in their dynamic performance in the PV activity to
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validate that the ability to perform both new and existing tasks and CMAs was still achievable with the modified operator interface. As noted in Section 4.1 of the PV RSR:
"Finally, as described in Section 4.4.1, SEGs were developed to envelope the manual actions under study from both Section 4.3.2.1 and Section 4.3.2.2 in a way that was consistent with how operators are trained and evaluated. Efforts were made to make the scenarios described in the SEGs more challenging. This was done to better represent situations that operators are presented with during training and evaluation simulator drills where multiple, unlikely, and potentially challenging failures occur. This was done to more generally evaluate whether the HSIs created for and procedures modified by the upgrade supported these operational ac tivities.
This was also done as good engineering practice."
This dynamic evaluation involved multiple failures and or conditions to evaluate the operators in a realistic representation where multiple tasks and events would be dealt with by the operators concurrently or in close sequence. These combined scenarios evaluated the operator performance and burden in such a manner as to ensure that the combinations of time-based CMAs along with other concurrent operator tasks does not adversely impact the performance of either the time based or non-time-based actions.
b) Please describe how the new or changed aggregate tasks affects the overall role of personnel.
CEG 8b Response
Though improvements were made to how operators interface with the plant, the overall role of each of the MCR operators is unchanged with the incorporation of the new design.
Operator actions and the details of their implementation have been changed in a tactical way in the new operator interface. The fundamental actions being taken by the Reactor Operators, Senior Reactor Operators, and field operators are fundamentally the same as in the current design. Since the required actions to be taken by the operators and their required responses during design bases and beyond design bases events is effectively unchanged from the current requirements, their role and the number of operators required to respond to these events is unchanged from the current design. This was validated during PV when a minimum complement crew executed nine different design basis and beyond design basis scenarios with minimal preparation and were successful in completing all the CMAs / IHAs in the required time limits.
The design did result in the general relaxation of workload for the operators in the MCR which resulted in them having greater ability to monitor equipment status and respond with simplified and less repetitive actions. These insights are documented in the scenario summaries in Sections 5.3.3 of the Preliminary Validation RSR. This reduction in overall burden also resulted in satisfactory performance of all CMAs during the PV as documented in Table 3 of Section 5.3.1 and Table 4 of Section 5.3.2 of the PV RSR.