ML20245E457

Draft Preface

ML20245E457
Person / Time
Issue date:	09/01/2020
From:	Office of Nuclear Regulatory Research
To:
Carmen Franklin, Susan Cooper
Shared Package
ML20245E456	List: ML20245E457 ML20245E458 ML20245E459
References
Download: ML20245E457 (2)

Text

DRAFT PREFACE This body of work illustrates the NRCs effort to appropriately credit human actions within flexible coping strategies (FLEX) using a systematic, qualitative approach to produce human error probability (HEP) estimates. Volume 1 of this report, Utilization of Expert Judgment to Support Human Reliability Analysis of Flexible Coping Strategies (FLEX), was completed in 2018 as an assessment of FLEX action feasibility using data collected by the NRC staff. This information was used to inform the development of the NRCs Integrated Human Event Analysis System for Event and Condition Assessment (IDHEAS-ECA). IDHEAS-ECA is a human reliability analysis (HRA) method that can be used for FLEX and Non-FLEX actions. Upon completion of the method, in 2019, the NRC and industry further explored the feasibility of FLEX actions using IDHEAS-ECA. This work is documented in Volume 2 of this report, Flexible Coping Strategies (FLEX) HRA Using IDHEAS-ECA. The two reports demonstrate how the teams of experts were used and describe how each project was introduced into the NRCs framework for FLEX. Both projects capture the state of knowledge and uncertainties of the technical issues within FLEX and non-FLEX scenarios, however, there are several differences between each project.

In Volume 1, the staff performed an expert elicitation to obtain benchmark human error probabilities (HEPs) of FLEX actions and to understand the performance influencing factors associated with the use of portable FLEX equipment. This information was then used to benchmark IDHEAS-ECA. The expert elicitation project scope was developed to capture the variation of FLEX and non-FLEX scenarios and estimate the HEP ranges of the five FLEX actions. In particular, the project captured which performance influencing factors might drive the HEPs up or down.

Volume 2, on the other hand, describes FLEX scenario evaluation using a new HRA method built specifically to handle FLEX actions: IDHEAS-ECA. Along with the method, the staff developed a software tool to take the qualitative analysis of FLEX actions and produce quantitative results, HEP values.

The technical approaches and scenario context were slightly different among the two projects.

Volume 1 Implemented principles and processes of the NRCs Expert Elicitation Guidance, ML16287A734, and included an expert panel with experience in PRA/HRA, auditing FLEX strategies, and understanding maintenance practices in nuclear power plants. The NRC provided the expert panel with the scenario limitations and human failure events to analyze for the scenarios. Since FLEX varies from plant to plant, there were challenges to create base, generic scenarios due to limited FLEX information. Therefore, the NRC project leads first developed a skeleton of the scenarios prior to the workshop, then had the expert panel develop the details of the scenarios.

Volume 2 used a similar framework as the expert elicitation with a larger set of participants and resources to implement data collection. To the extent possible, scenarios were based on relevant previous efforts to develop HRA/PRA scenarios for FLEX (e.g., EPRIs November 2018 report and Volume 1 of this report). However, when performing this work (Volume 2), the HRA analysts evaluated scenarios and HFEs for specific nuclear power plants. The analysis approach allowed HRA analyst to attend a boiling water reactor (BWR) and a pressurized water reactor (PWR) site visit. The plant visits were the predominant sources of detailed HRA-relevant FLEX information for the HRA analyst to reference. Lastly, information from a small

group of PWR Owners Group and BWR Owners Group representatives, and FLEX experts (both NRC and industry) supplemented the plant-specific information from the two sites to provide a more generic operational understanding of FLEX strategies and equipment analyzed in the scenarios.

Because of the plant visits coupled with the input from FLEX and operational experts throughout the project, the second project team (Volume 2) developed more credible and detailed HRA/PRA scenarios than those for the expert elicitation (Volume 1). Also, because of the time gap between the two efforts, Volume 2 captures the increased reliability of operator actions due to industry improvements to their FLEX programs from 2018 to 2019.

In conclusion, both projects serve as a bases to explore the data and knowledge of FLEX within HRA. They demonstrate a cohesive effort to address the challenges identified in existing HRA methods and create solutions to bridge the gaps of understanding. Previous methods used by the NRC assumed that FLEX actions were not feasible. However, these two-projects provide evidence of feasibility. Both efforts increased the understanding of operator actions using FLEX equipment and developed estimates of their feasibility to inform and improve analysis, methodologies, and quantification tools.