ML20140C993
| ML20140C993 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 01/17/1986 |
| From: | Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Partlow J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| References | |
| NUDOCS 8601290047 | |
| Download: ML20140C993 (4) | |
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[ * - %d JAN 17 isss p-MEMORANDUM FOR:
James G. Partlow, Director, Division of Inspection Programs, IE FROM:
Richard W. Starostecki, Director, Division of Reactor Projects
SUBJECT:
COMMENTS ON DRAFT ANNUAL REPORT TO ED0 ON USE OF PRA IN INSPECTION PROGRAM The following comments are offered on the proposed memorandum which was forwarded to us for comments by Leon Whitney.
Five contributing factors are cited in paragraph 2 as ressons for PRA results not being easily applied by inspectors. Only one of these appears to us to be relevant, i.e., the inspector must draw conclusions from the results of a product with which he is not familiar. The remaining factors appear to us to be either irrelevant or of minor significance. of the proposed memorandum describes one of the programs that is being developed by DRP in Region I.
We offer the attached summary as a more complete description of that program.
The memorandum does not discuss another major Region I initiative dealing with emergency risk projection. A summary of that program also is attached.
As we briefly discussed, I propose that a revised draft be the vehicle for further discussions.
Stu and I will be happy to work with you and your staff to assure that the report properly integrates and reflects the various successes and accomplishments to date.
A Richard W. Starostecki, Director Division of Reactor Projects
Enclosures:
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ENCLOSURE 1 REGION I PROBABILISTIC RISK BASED INSPECTION GUIDANCE FOR INDIVIDUAL PLANTS During 1985, Region I completed development work on a program for presenting plant-specific PRA information in a form useful for inspections by both resident and region-based inspectors.
The information is presented in an appendix for each plant.
The first two of these appendices were prepared for the Indian Point 2 and 3 plants.
Four others are planned for FY-86.
Following that, Region I plans to determine whether generic appendices can be developed based on the results of the plant-specific work.
l The purpose of the appendices is to provide guidance for inspections that is based on the results of plant-specific probabilistic risk assessments.
PRA-4 based inspections using the appendices as guidance permit the focusing of the inspector's resources on those systems that make up at least 95% of the risk and components that are the significant contributors to the failure of those i
systems.
j An assessment of the plant-specific risk provides both a measure of potential accident risk to the public and insights into the adequacy of plant design and operation. This assessment is achieved by identifying those sequences of potential events that contribute to risk and by establishing which features of the plant contribute most to the frequency of such sequences. These plant features may be influenced by hardware failures, tests and maintenance during operations, or human errors resulting from tests, maintenance, or operational activities. Thus, a probabilistic analysis reveals the features of a plant that merit close attention and provides a focus for improving safety.
Infor-mation developed in the assessments will be used to make decisions about the allocation of inspection resources by directing attention to the factors and failure modes that contribute most to plant risk.
A typical plant-specific appendix consists of three principal products. The first, in the form of a table, provides for each system, the inspection modules that are relevant to the important systems and components.
For a system-based inspection a module is not expected to be performed in its entirety, since each module usually requires a look at more than one system. However, all of the requirements in each module typically will be applied to the components or activities that are described in the table.
For a module-based inspection, this table can be used, along with the corresponding tables for the other important systems, to compile a complete list of components on which to focus the inspection.
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The failure modes are also identified in a table to describe the way in which each component failure contributes to risk.
By understanding the failures that are significant, the 'ospector can focus on particular subcomponents, operations, tests, etc.
For evenple, while the premature transfer of a power supply will not usually be a feiture mode, the failure to transfer usually is. By under-l standing that this is an important failure mode, the inspector can then review or observe those tests that are relevant to the transfer function.
l Finally, a modified checkoff list is provided in tabular form.
It contains only those components that contribute significantly to system failure.
It is a i
good tool for a quick look at a system, covering those components that con-tribute at least 95% to a system's failure probability, but it will usually cover less than 20% of the components in a system. For this reason, while a full checkoff list may be used for most applications, the abbreviated checkoff list may be used for quick, frequent walkdowns.
The important features of the program are:
It is consistent with and constructed around the current IE modules.
1 It is structured for use by resident as well as region-based inspectors.
It covers approximately all of the components and activities that affect public risk.
An appendix can be scaerated for any facility for which a PRA has been developed.
An appendix can be implemented by NRC inspectors without the need to j
conduct a review of the PRA.
It provides a clear definition to inspectors of the dominant contributors to risk without requiring PRA expertise.
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ENCLOSURE 2 REGION I l
EMERGENCY RISK PROJECTION Region I has completed a prelimi7ary evaluation of a related application of PRA for use in responding to emergency situations. The same program that is f
used to develop the inspection appendices (discussed earlier) also can be used to recompute risk values to reflect degraded plant status.
Changes in plant risk are then used to determine those events for which the plant is most vulnerable based on its degraded state.
Another output of the program will be the change in importance rankings of the individual plant systems based on the degraded state of the plant. These rankings can vary significantly depending upon the degraded state of the plant.
This information can be used by resident inspectors on a day-to-day basis but its primary application is in prioritizing emergency response actions by NRC emergency response teams. The program will be developed for use by NRC emergency response personnel and by resident inspectors and can be used on the IBM PC at the resident inspector offices.
In FY-86, Region I plans to complete development of the program for Indian Point Units 2 and 3, and two other plants.
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