Nuclear Risk Research Center (NRRC)
Central Research Institute of Electric Power Industry
1-6-1 Otemachi, Chiyoda-ku, Tokyo, 100-8126, Japan

Dr. George Apostolakis
Head, NRRC
July 13, 2017
Mr. J.W. StetkarChairman
Technical Advisory Committee
Subject:

TAC Report titled “IMPLEMENTATION GUIDE ON HUMANRELIABILITY ANALYSIS (HRA) FOR PRA” dated May 27, 2017.

Dear Chairman Stetkar
NRRC will update the HRA guide continuously by incorporating the experience of thetrial case of HRA with the assistance of the utilities.
The NRRC reply to the TAC recommendation as follows.
CONCLUSIONS AND RECOMMENDATIONS (from TAC)
The following recommendations should be addressed before the guidance isissued for trial use:
•To the extent possible, these methods should be used to evaluate personnel
actions in the models that quantify PRA initiating event frequencies, in theLevel 1 plant response models, and in the Level 2 severe accident mitigation
models.

(NRRC Response)
The NRRC will respond to your comment in revision 1 (short term).
•The guidance should describe how to develop a realistic scenario timeline, thetypes of information that should be documented in the timeline, and how thetimeline is used in the qualitative assessment, operational narrative, andhuman error probability (HEP) quantification.

(NRRC Response)
The NRRC will respond to your comment in revision 1 (short term; see Figure 1).
This figure is consistent with the timeline presented in NEI 16-06 and the timeline
analysis in the HRA Calculator.

-1-

In our HRA guide example, the results of the time analysis are included in theinformation of Preliminary CRD (Crew Response Diagram) by using the results of thethermal hydraulic analysis contained in the installation permission application
document. Further modifications will be effected by realistic observations of training
and information obtained at the site.
•The guidance should describe how to perform a "time uncertainty analysis"
and how to account for that analysis during quantification of the scenariospecific HEPs.

(NRRC Response)
NRRC HRA team will consider the quantification method of time uncertainty analysis
this fiscal year.
•The guidance should be enhanced to place more emphasis on observationsof carefully selected simulator scenarios to supplement the informationobtained from the operator interviews. Simulator runs should also be
conducted for critical operator actions to confirm realistic scenario time
windows (e.g., delay time, time to perform an action, time to get to alocation, etc.).

(NRRC Response)
The NRRC will respond to your comment in revision 1 (short term).
As also shown in Appendix C ”F&B Evaluation Case (C.2.1.2 Questions about Plant
Data, System Data and Training Summary)”, actual observations of simulator
training was conducted first. An interview was held.
Corresponding to this recommendation, we emphasize the importance ofobservations of such simulator scenarios by appending it to Section "5.2 Narrative
discussion including operator interviews".
•Appendix G of the guide should include one or more instructional examples
that show how deviation scenarios are developed and applied in a practicalHRA.

(NRRC Response)
We will consider rational ways of implementation in future HRA research byacquiring detailed knowledge and increasing the number of cases.
THERP's method of decomposing actions of personnel into elemental acts andapplying error rates to each one of them led to excessive HEP that did not match theactual condition. For this reason, we will also consider the application of task
analyses and quantification methods that do not break human behavior into
individual actions like IDHEAS.

Sincerely,

George Apostolakis-2-TSw
TAvailable
TExecute

TDelay
TCog

T0
Cue
Event
received
Start (indication)

TDeploy

TInstallｙｙ

Crewcognitive/diagnosis
Complete

DeployComplete

TOperate

Install
Complete

T0 =Event Start
Tsw : system time window
Tdelay : time elapsed before the indication occurs
Tavail : Time available for action＝(Tsw - Tdelay)
Tcog : Time required for cognitive, diagnosis, decision making
Texe : Time for execution = (Tdeploy + Tinstall +Toperate)
Tdeploy : Deployment time
Tinstall : Install time
Toperate : Operation time
Treqd : Minimum time required to achieve operation = (Tcog + Texe)

Fig1. Timeline concept for HRA guide-3-Time
MarginOperate
Complete

Action nolonger
beneficial