ML14328A426
| ML14328A426 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 06/28/2012 |
| From: | Excel Services Corp |
| To: | Beckner W Office of Nuclear Reactor Regulation |
| honcharik, michelle415-1774 | |
| Shared Package | |
| ML14328A412 | List: |
| References | |
| Download: ML14328A426 (5) | |
Text
June 28, 2012 Response to NRC Concerns Regarding TSTF-412, Revision 3, "Provide Actions for One Steam Supply to Turbine Driven AFW/EFW Pump Inoperable"
Background
At the May 8, 2012 TSTF/NRC Public Meeting, the TSTF and NRC discussed NRC concerns with TSTF-412-A, Rev. 3, "Provide Actions for One Steam Supply to Turbine Driven AFW/EFW Pump Inoperable," which was approved on July 17, 2007.
Prior to the meeting, the NRC provided an internal memo requesting that the Traveler be withdrawn. The TSTF provided a white paper in response to the memo on April 27.
At the May 8 meeting, the NRC did not object to the responses in the TSTF white paper but raised a new reason why they believed that portions of TSTF-412 are not acceptable. The NRC's model Safety Evaluation, Section 3.0, states:
"Motor driven AFW/EFW pumps are typically powered from an independent Class 1E power supply and each pump train typically feeds half of the steam generators, although each pump has the capability to be realigned from the control room to feed other steam generators." (Emphasis added.)
This was not identified as a condition of approval in the model SE and was not captured in the model application as a requirement. However, the technical staff now believes that the ability to realign an AFW/EFW pump train to another steam generator from the control room is a requirement to adopt the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time in TSTF-412. The NRC acknowledged this is a change in the staff's position, as the TSTF-412 approval accepted the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time without such a limitation.
Response
The NRC position that adoption of the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is only appropriate if a pump train can be realigned to another steam generator from the control room is not supported. The Traveler justification and the NRC Safety Evaluation do not credit realignment of AFW/EFW flow. In fact, the Traveler and SE do not take credit for any mitigating actions and the Completion Time is based solely on available equipment and the low probability of the occurrence of an accident.
The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is appropriate for conditions in which the accident analysis assumptions can be met for some, but not all, accident scenarios. The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is used in this manner in several other existing Technical Specifications, such as:
- LCO 3.0.9 for inoperable barriers allows 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> even though the protected equipment may be rendered inoperable during a LOCA, HELB, flood, tornado missile, etc.
- LCO 3.5.1, Accumulators, Condition B for one accumulator inoperable - The Completion Time is appropriate because the accumulators can respond to many events, but the contents of remaining accumulators cannot be assumed to reach the core during a LOCA depending on the location of the pipe break.
Page 1 EXCEL Services Corporation
Response to NRC Concerns Regarding TSTF-412, Revision 3, "Provide Actions for One Steam Supply to Turbine Driven AFW/EFW Pump Inoperable"
- LCO 3.6.8, Shield Building, Condition A for an inoperable shield building. The Completion Time is appropriate because the shield building is only needed following a LOCA and is not needed for other events.
- LCO 3.7.4, Atmospheric Dump Valves (ADVs), Condition B for two or more ADVs inoperable. The Completion Time is appropriate based on the availability of the Steam Bypass System and MSSVs (which cannot respond to all accident scenarios), and the low probability of an event occurring during this period that would require the ADV lines.
In summary, the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time in TSTF-412 is appropriate for the condition, is consistent with similar conditions in the Technical Specifications, and is supported by the TSTF justification and NRC model Safety Evaluation.
Discussion Section 3.0, "Background," of the Traveler justification states:
"Each motor driven AFW pump is powered from an independent Class 1E power supply and feeds [two] steam generators (SGs), although each pump has the capability to be realigned to feed other SGs." This is taken from the NUREG-1431, "Standard Technical Specifications - Westinghouse Plants," Technical Specification Bases, "Background" section, of LCO 3.7.5, "Auxiliary Feedwater System."
This is the only mention of realignment of the AFW/EFW pump trains in the Traveler justification. Note that the Traveler and the Standard Technical Specifications do not state the pump can be realigned from the control room.
Section 4.0, "Technical Analysis," of the Traveler justification states:
"This [24 hour] Completion Time is reasonable based on the remaining OPERABLE motor driven AFW train, the remaining OPERABLE steam supply to the turbine driven AFW pump, the turbine driven AFW pump still being capable of performing its specified function, and the low probability of an event that would result in the inability of the AFW system to provide 100% of the required flow. A 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Completion Time is proposed for this condition when plant design still provides for 100% of the AFW flow requirements regardless of this scenario. This Completion Time is reasonable since the consequences of this configuration are less severe, but the configuration represents a higher level of degradation than one inoperable AFW train, which can exist for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> per Condition B."
The Traveler justification for the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is based on the remaining Operable equipment and the low probability of an event. The justification takes no credit for the ability to realign a pump train to another steam generator. This is reiterated in the Reviewer's Note in the TS Bases:
Page 2 EXCEL Services Corporation
Response to NRC Concerns Regarding TSTF-412, Revision 3, "Provide Actions for One Steam Supply to Turbine Driven AFW/EFW Pump Inoperable" "Licensees should adopt the appropriate Completion Time based on their plant design.
The 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is applicable to plants that can no longer meet the safety analysis requirement of 100% EFW flow to the SG(s) assuming no single active failure and a FLB or MSLB resulting in the loss of the remaining steam supply to the inoperable turbine driven EFW pump." (Emphasis added.)
The NRC model Safety Evaluation makes similar arguments and makes no mention of realignment of an AFW/EFW pump train to another steam generator:
"A proposed 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is applicable to plants that may provide insufficient flow to the steam generators (SGs) in accordance with accident analyses assumptions if a main steam line break (MSLB) or feedwater line break (FLB) were to occur that renders the remaining steam supply to the turbine driven AFW/EFW pump inoperable (a concurrent single failure is not assumed). Insufficient feedwater flow could result, for example, if a single motor driven AFW/EFW train does not have sufficient capacity to satisfy accident analyses assumptions, or if the operable pump is feeding the faulted SG (i.e. the SG that is aligned to the operable steam supply for the turbine driven AFW/EFW pump). [This would typically apply to plants with each AFW/EFW motor driven pump having less than 100% of the required flow.] Likewise, a proposed 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Completion Time is applicable when the remaining operable motor driven AFW/EFW train is capable of providing sufficient feedwater flow in accordance with accident analyses assumptions. [This would typically apply to plants with each AFW/EFW motor driven pump having greater than or equal to 100% of the required flow.]"
"In this particular case, a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is proposed for the situation where the AFW/EFW system would be able to perform its function for most postulated events, and would only be challenged by a MSLB or FLB that renders the remaining operable steam supply to the turbine driven AFW/EFW pump inoperable. Additionally, depending on the capacity of the operable motor driven AFW/EFW pump, it may be able to mitigate MSLB and FLB accidents during those instances when it is not aligned to the faulted SG.
The selection of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for the Completion Time is based on the remaining operable steam supply to the turbine driven AFW/EFW pump and the continued functionality of the turbine driven AFW/EFW train, the remaining operable motor driven AFW/EFW train, and the low likelihood of an event occurring during this 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period that would challenge the capability of the AFW/EFW system to provide feedwater to the SGs. The proposed Completion Time for this particular situation is consistent with what was approved for Waterford 3 by License Amendment 173 for a similar Condition (ADAMS Accession No. ML012840538), and it is commensurate with the STS in that the proposed Completion Time is much less than the 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> that is allowed for the situation where accident mitigation capability is maintained. Therefore, the NRC staff agrees that the proposed 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Completion Time is acceptable for this particular situation." (Emphasis added.)
Page 3 EXCEL Services Corporation
July 12, 2002 Mr. Anthony R. Pietrangelo, Director Risk & Performance-Based Regulation Nuclear Generation Nuclear Energy Institute 1776 I Street, N.W.
Suite 400 Washington, DC 20006-3708
Dear Mr. Pietrangelo:
This is to inform you of the disposition for traveler TSTF-412 containing proposed changes to the improved Standard Technical Specifications (iSTS), initiated by the NEI Technical Specification Task Force (TSTF). TSTF-412 will require modification.
The staff has reviewed traveler TSTF-412 which proposed adding a new Required Action with a Completion Time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for the Condition of one motor driven auxiliary feedwater (AFW) pump inoperable concurrent with one inoperable steam supply to the turbine driven AFW pump, in NUREGs 1430, 1431, and 1432, Specification 3.7.5. Comments that may be useful for possible modification of TSTF-412 are enclosed.
Please contact me at (301) 415-1161 or email wdb@nrc.gov if you have any questions or need further information on these dispositions.
Sincerely,
/RA/
William D. Beckner, Program Director Operating Reactor Improvements Program Division of Regulatory Improvement Programs Office of Nuclear Reactor Regulation
Enclosures:
As stated cc: J. Arbuckle, BWROG D. Bice, CEOG N. Clarkson, BWOG S. Wideman, WOG D. Hoffman, EXCEL
- 1. The auxiliary or emergency feedwater (AFW or EFW) system designs tend to vary from one plant to another. Some plants have two turbine-driven pumps and one motor-driven pump, but most have two motor-driven pumps and one turbine-driven pump. Some of the motor-driven pumps can feed all of the steam generators while some can not. Some of the motor-driven pumps are 100% capacity, and some are less than 100% capacity. These design elements are further complicated by the various situations that can arise, such as an inoperable steam supply valve for the turbine-driven pump coincident with an inoperable motor driven pump that is (a) associated with the same electrical division as the inoperable valve, or (b) associated with the opposite electrical division. TSTF-412 could be significantly improved by establishing a function-based TS that takes these differences in design and possible situations into consideration. An example of this approach can be found in Waterford Unit 3 Technical Specification (TS) 3.7.1.2, which was issued by Amendment No. 173 to the Waterford Unit 3 license on October 4, 2001 (ADAMS Accession No. ML012840538). The following guidance may be of particular interest in pursuing this approach:
- The first sentence of the reviewers note for Action C of TSTF-412 satisfies the criteria for a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time (AOT). In general, a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> AOT is appropriate if a system is able to perform its safety function, excluding consideration of a postulated single active failure. If excess capability exists, (e.g., one steam supply to the turbine-driven pump inoperable), a 7-day AOT might be appropriate.
- If the EFW system is able to mitigate most events with limited vulnerability, excluding consideration of a postulated single active failure (e.g., vulnerable to a main steam line or main feedwater line break event 50% of the time), a 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> AOT might be appropriate for 100% capacity motor-driven pumps, whereas a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> AOT might be appropriate for 50%
capacity motor-driven pumps.
- If the EFW system is in a condition where it does not have sufficient capability to remove all of the reactor decay heat, action should be taken immediately to restore this capability.
During this condition, LCO 3.0.3 and other LCOs requiring Mode changes should be suspended until the EFW system is capable of removing 100% of the reactor decay heat.
- 2. The proposed Required Action C.1, which states Restore affected equipment to OPERABLE status, could be misconstrued to require restoring both the motor driven train and the steam supply to the turbine driven train within the specified Completion Time. It would be clearer to state this action as two options. It could be stated this way, for example: C.1 Restore the motor driven train to OPERABLE status. OR C.2 Restore the steam supply to the turbine driven train to OPERABLE status.
Enclosure