IR 05000346/1999005
| ML20206B826 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 04/27/1999 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20206B820 | List: |
| References | |
| 50-346-99-05, 50-346-99-5, NUDOCS 9904300093 | |
| Download: ML20206B826 (7) | |
Text
, - - -
,
.
U. S. NUCLEAR REGULATORY COMMISSION REGION lli Docket No.:
50-346 License No.:
NPF'3 Report No.:
50-346/99005(DRS)
- Licensee:
Toledo Edison Company Facility:
Davis-Besse Nuclear Power Station Location:
5501 N. State Route 2 Oak Harbor, OH 43449 Dates:
April 5 - 9,1999 Inspector:
S. Burgess, Senior Reactor Analyst Approved by:
Steven A. Reynolds, Deputy Director Division of Reactor Safety 9904300093 990427 F
{DR ADOCK 05000346
=
.
r
.
.
EXECUTIVE SUMMARY l
l Davis-Besse Nuclear Power Station
'
NRC inspection Report 50-346/99005(DRS)
.This was a routine inspection to review aspects of the licensee's on-line maintenance risk assessment program. Risk assessments performed for the last outage and other engineering issues were also reviewed. No violations of NRC requirements were identified during this inspection.
Maintenanco Plant risk and configuration during maintenance activities were appropriately controlled
.
using risk ir. sights to minimize plant's aggregate risk.
Although stili in the initial implementation stages, the new on-line maintenance risk
.
program was a significant improvement from what the plant had used in the past and appeared to be working well.
The on-line maintenance risk program had the necessary steps to demonstrate that
.
emergent activities were adequately planned and controlled to avoid causing initiating events to occur or affect the functional capability of mitigating systems.
Enaineerina The updated Individual Plant Evaluation coupled with a plant specific on-line risk
.
assessment computer program, provided the Probabilistic Safety Assessment (PSA)
engineers the necessary tools to implement the Weekly Maintenance Risk Summary.
The Weekly Maintenance Risk Summary and the revised Maintenance Matrix were
.
considered to be a usable, scrutable, and repeatable product.
The risk categorization of surveillance tests and increasing initiating event frequencies to
.
account for surveillance testing in the computer-based risk program was considered to be a strength.
PSA risk evaluations performed to support engineering issues were thorough, of good
.
,
quality, and resulted in keeping the plant's aggregate risk at a minimum.
Davis-Besse's use of deterministic risk tools during outages appropriately maintained a
.
defense-in-depth philosophy, and contrclled key safety functions related to shutdown conditions. The last outage safety review clearly identified higher risk evolutions in the schedule and contingency plans when appropriate.
l l
l
l l
p
+
e:
)
II. Maintenance MI Conduct of Maintenance
- Ml.1 On-Line Maintenance Work Prioritization and Control a.
Insoection Scope (93702)
The inspector reviewed the licensee's process for planning and controlling maintenance j
activities to determine if the plant's aggregate risk was appropriately considered.
b.-
Observations and Findinas The licensee's maintenance risk assessment program had recently undergone
.j significant changes as part of an ongoing process to apply risk insights more effectively in maintenance scheduling. Previously, planners used a two-by-two risk Maintenance Matrix tool, developed for the purposes of the maintenance rule, to limit the number of
'
systems undergoing maintenance simultaneously. This matrix was considered to be a weak risk-assessment tool as previously documented in NRC maintenance rule inspection report 346/97002.
The proposed planned maintenance and surveillance testing schedule was provided to the Probabilistic Safety Assessment (PSA) engineers two weeks prior to the work week.
The PSA engineers would then input the equipment out-of-service data and th3 surveillance testing into the computer orogram to assess the daily plant risk due to the activities. Once the proposed plan was inputted into the computer program and the risk evaluation was complete, changes to the plan could be made to further reduce the risk profile for the day or the week. The results were then higb!!ghted in a Weekly.
Maintenance Risk Summary and discussed during the Piv.-of-the-Day meeting. The summary provided risk assessments into the daily and weekly on-line maintenance work activities with core damage frequency (CDF) insights. The risk summary also provided the plant with a risk " color" that was a visual correlation to a spec lfic CDF value and gave the plant risk profile for the v/sek. The Maintenance Matrix was also revised and color-coded to reflect the risk and CDF values to the maintenance combinations. The Weekly Maintenance Risk Summary and the revised Maintenance Matrix were considered to be a usable, scrutable, and repeatable product.
The Weekly Maintenance Risk Summary also provided an excellent vehicle to disseminate risk information during the Plan-of-the-Day meeting and served as a good mechanism for ingraining risk-insights thinking into the maintenance planners,
,
maintenance staN, and other plant personnel. Davis-Besse also disseminated risk information to the plant personnel through the use of an intemal web site arxl through PSA risk summary posters.
Although still in the initial implementation stages, the new program was a significant improvement from what the plant had used in the past and appep:ed to be working well.
The process also had the necessary steps to demonstrate that emergent activities were
)
4
E
.
adequately planned and controlled to avoid causing initiating events to occur or affect the functional capability of mitigating systems. Overall, the control of plant risk and
{
configuration were appropriately controlled using risk insights to minimize the plant's aggregate risk.
c.
. Conclusions Plant risk and configuration durint maintenance activities were appropriately controlled using risk insights to minimize plant's aggregate risk. Although still in the initial implementation stages, the new program was a significant improvement from what the plant had used in the past and appeared to be working well. The process had the necessary steps to demonstrate that emergent activities were adequately planned and controlled to avoid causing initiating events to occur or affect the functional capability of mitigating systems.
Ill. Enaineerina E1 Conduct of Engineering E1.1 Risk Assessment Proaram a.
inspection Scope (37551)
The inspector reviewed the licensee's on-line maintenance risk assessment process and engineering's use of risk insights in day-to-day problem solving.
b.
Observations and Findinas Computer-Based Fault Tree Analysis Proaram To perform the weekly on-line maintenance risk evaluations, the PSA engineers utilized
)
a microcomputer-based fault tree analysis workstation. An Individual Plant Evaluation (IPE) update (completed in late 1998) coupled with a plant specific on-line risk assessment computer program, provided the licensee the necessary tools to implement the Weekly Maintenance Risk Summary. The revised IPE established a solid foundation for a risk-informed program and gave the engineering staff the necessary plant-specific risk insights. The changes seen from the revision also emphasized the need for the PSA
'
to be a living document that should be maintained to continue providing meaningful risk j
insights, The inspector noted that the PSA engineers placed emphasis on the impact that -
surveillance testing had on the risk profile. Although the system was considered to be in service during the testing, performing the test did pose a potential increase in certain initiating event frequencies. The PSA engineers accounted for this additional risk by increasing the applicable initiating event frequencies when running the computer-based risk analysis. An existing risk ranking of surveillance testing (performed as part of the maintenance rule program) was used when determining the surveillance's risk level of
~
i
>
high, medium, low, or none. The risk categorization of surveillances and the use of increased initiating event frequencies in the computer-based risk program was considered to be a strength.
Risk insichts in Evalutina Enaineerina issues With the updated IPE and the cornputer-based risk analysis tool, the licensee was also capable of eyaluating other engineering issues. The inspector reviewed PSA risk evaluations performed to support engineering issues, such as, risk insights for performing system outages during a plant outage wrsus on-line, installation of temporary modifications, and conditions identified in Condition Reports. The inspector determined that the risk evaluations were thorough, of good quality, and resulted in keeping the plant's aggregate risk at a minimum.
c.
Conclusions The updated IPE coupled with a plant specific on-line risk assessment computer program, provided the PSA engineers the necessary tools to produce tha Weekly
. Maintenance Risk Summaty. The risk categorizction of surveillances and the use of increased initiating event frequencies in the computer-based risk program was considered to be a strength. PSA risk evaluations performed to support engineering issues were thorough, of good quality, and resulted in keeping the plant's aggregate risk at a minimum.
E1.2 Risk insiahts in Outaae Plannina a.
Inspection Scope (37551)
The inspector reviewed the licensee's process for ensuring that risk insights were integrated into outage schedules and that risk reduction methodologies were developed to control plant configuration.
b.
Observations and Findinas The licensee used deterministic risk assessment tools since Davis-Besse did not have a shutdown risk model. However, in using the deterministic risk tools, the outage planning program appropriately maintained a defense-in-depth philosophy, and controlled key J
safety functions related to shutdown conditions,'such as, decay heat removal, inventory control, power availability, reactivity control, and containment control.
The inspoctor reviewed the last outage safety review, and determined that higher risk
,
evolutions were clearly identified in the schedule and contingency plans were developed
)
when appropriate.
The inspector was informed that the B&W Owner's Group did have plans to work on a generic shutdown PSA and Davis-Besse would benefit from its risk insights and potentially perform a site-specific shutdown PSA in the future.
,
s
&
c.
' Conclusions Davis-Besse's use of deterministic risk tools during outages appropriately maintained a defense-in-depth philosophy, and controlled key safety functions related to shutdown conditions. The last outage safety review clearly identified higher risk evolutione in the schedule and contingency plans when appropriate.
.
\\.
I
.
- .
PARTIAL LIST OF PERSONS CONTACTED Licensee W. J. Bentley, Supervisor, On-Line Work Control S. A. Brinkman, PSA Engineer K. W. Byrd, PSA Engineer G. G. Campbell, Vice President Nuclear S. A. Coakley, Manager, Work Management D. L. Eshel man, Manager, Operations J. L. Freels, Manager, Regulatory Affairs J. J. Johnson, Supervisor, Independent Safety Engineering J. H. Lash, General Manager, Plant Operations A. L. McA!!ister, Supervisor, Test & Performance
.
J. L. Michaelis, Manager Maintenance R. l. Rishel, Maintenance Rule Coordinator F. L. Swanger, Manager, Design Basis Engineering G. M. Wolf, Engineer, Regulatory Affairs L. W. Worley, Director, Nuclear Assurance NRC S. Campbell, Senior Resident inspector, Ferml INSPECTION PROCEDURES USED IP 37551 Onsite Engineering IP 62700 Maintenance Program implementation LIST OF ACRONYMS USED B&W Babcock & Wilcox CDF Core Damage Frequency CR Condition Report IPE Individual Plant Evaluation l
PSA Probability Safety Assessment PDR Public Document Room
l l
!