ML040410657
| ML040410657 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 02/18/2004 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Webb M, NRR/DLPM, 415-1347 | |
| Shared Package | |
| ML040560491 | List: |
| References | |
| DG-1122 | |
| Download: ML040410657 (3) | |
Text
INITIAL STAFF IMPRESSIONS OF THE STP LAR TO BECOME THE RMTS INITIATIVE 4b, FLEXIBLE COMPLETION TIMES, FULL PLANT PILOT, AND DG-1 122 PRA QUALITY PILOT
- 1. The submittal does not provide sufficient information to determine the acceptability of the STP PRA. It only provides a commitment to provide the necessary information at a future time. Justification that the licensees PRA model is adequate to support the determination of completion times is needed.
STPNOC has committed to be a DG-1 122 PRA Quality Pilot. Additional information regarding the STP PRA Quality will be provided after initial issues are resolved regarding the scope of the application.
- 2. No risk assessments were included in the information provided to support the proposed changes to the technical specifications described in Table 2.
These assessments are needed to make a determination about the acceptability of the proposed changes. The staff expects such risk assessments to be submitted for staff review.
STPNOC included general risk insights in Table 2. The level of detail required for this application needs to be resolved in a meeting with the NRC. Although some additional detail may be required, STPNOC does not believe the level of detail provided in the CE application for their HPSI system is needed for each of the changes proposed by STPNOC. In addition, the PRA quality evaluation is expected to provide a substantial level of confidence in the risk assessments.
3.a. The submittal does not provide sufficient information to determine the acceptability of the proposed process to establish a risk informed technical specification required action completion time. The licensee's process is embodied in his configuration risk management program (CRMP); a detailed description of the CRMP is needed. Documentation regarding this program, associated procedures and analysis methods needs to be provided for review; a description of the licensees risk assessment methods for determining appropriate completion times is needed.
STPNOC agrees that a detailed description of the CRMP is required. The examples provided in the application were intended to demonstrate how the CRMP would be applied in "real world" situations. Again, a meeting with the NRC staff will facilitate the level of detail needed.
3.b. Two CRMP "risk thresholds' are mentioned (on page 2). A Non-Risk Threshold" of 1 E-6 CDP and a "Potentially Risk-Significant Threshold" of I E-5 CDP. It is stated that "The allowed outage time would be calculated as the time required for the cumulative risk associated with a plant configuration to cross the threshold [of CDP equal to I E-5]." This Fnn1nsiirP a
statement may not be in agreement with industry's Risk Management Guide (Draft M) where a target and a maximum risk-informed completion time (RICT)" are defined to distinguish between voluntary and involuntary (emergent) entries. The staff believes this is an important distinction.
STPNOC's thresholds were selected to be consistent with the EPRI Maintenance Rule guidelines. STPNOC believes that establishing separate TS criteria for emergent and planned conditions would be counterproductive and administratively burdensome. In addition, there are a number of disincentives for operators to unnecessarily extend outage times, including impact on equipment and plant availability and reliability. STP's operating history with extensive ability for on-line maintenance demonstrates that the extended threshold would seldom, if ever, be approached for planned maintenance. However, there is no reason the TS should prohibit planned entry into the condition.
- 4. It is stated (on page 2) that STP is proposing the establishment of a new TS 3.13 to determine risk-informed allowed outage times applicable to a number of identified LCOs (listed in Table 2). How were these LCOs selected? Why is the proposed change limited to these LCOs? TS 3.13 does not appear consistent with the Risk Management Guide proposed TS.
STPNOC chose the LCOs because they were systems modeled in the STOP PRA and consequently lent themselves to a quantified assessment. STPNOC does not have new "Improved" Technical Specification format. TS 3.13 was chosen as an administratively effective way to impose the risk-informed allowed outage times on the affected Technical Specifications. STPNOC does not believe there is any difference in the application.
- 5. STP is proposing the incorporation of RITS Initiative 6 into Initiative 4b. The staff believes that any completion time (CT) extensions associated with complete loss of a system's function (all three trains inoperable) should be allowed only for emergent (involuntary) conditions and should be based on analyses approved by the staff (such as those reported in CE NPSD-1208 being reviewed by the staff for CEOG plants). Since STP is a special case (three redundant trains instead of the two usually present In other plants),
the case with two trains inoperable could be incorporated in Initiative 4b provided STP performs analyses showing that the availability of one train of a specific system is capable of performing the function of that system. If more than one train is needed for certain accident conditions, then these conditions will need to be identified and analyzed. Analyses, such as the ones mentioned in Table 3, should be submitted for the staffs review.
Except for Control Room HVAC and FHB HVAC where STP already has a 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> allowed outage time and where certain infrequent maintenance activities require all trains to be inoperable for a brief time, STPNOC does not foresee any normal maintenance activities where all three trains of a system would be
intentionally removed from service. Situations where two of three trains would be removed from service would not be common, but activities such as filling one ECW train from another ECW train could be performed. However, provided the risk assessments provide adequate justification, there is no technical reason that there should not be an allowed outage time for a loss of function.
The information provided in Table 3 was also part of the justification for the 14 day allowed outage time justified for the SDGs in 1996.
- 6. It is stated (on page 1) that STP may consider the Incorporation of RITS Initiative 7 into Initiative 4b. It appears that this proposal is a departure from the industry's approach (e.g., TSTF-427 and TSTF-372) regarding support system inoperability. Since there is no discussion of an approach, the staff cannot make any comments about this issue at this time.
Incorporation of Initiative 7 into Initiative 4b needs to de discussed and justified.
STP believes application of the CRMP considers the inoperability of the affected systems, regardless of the cause. Consequently, it appears that Initiative 7 would be subsumed by this initiative.