ML20072J117
| ML20072J117 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 08/22/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20072J110 | List: |
| References | |
| NUDOCS 9408260203 | |
| Download: ML20072J117 (8) | |
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[fec_k UNITED STATES NUCLEAR REGULATORY COMMISS!ON o
If WASHINGTON, D.C, 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0. 62 TO FACILITY OPERATING LICENSE NO. NPF-73 i
DUOVESNE LIGHT COMPANY OHIO EDIS0N COMPANY THE CLEVELAND ELECTRIC ILLUMINATING COMPANY l
THE TOLEDO EDIS0N COMPANY BEAVER VALLEY POWER STATION. UNIT 2 DOCKET N0. 50-412
1.0 INTRODUCTION
i On August 15, 1994, Duquesne Light Company, the licensee for Beaver Valley Power Station, Unit No. 2, requested and received enforcement discretion from meeting the requirements of Technical Specification Limiting Condition for 1
Operation (LCO) 3.6.2.2, action statement "a."
The staff confirmed that the enforcement discretion had been granted in a letter dated August 17, 1994.
i The licens'ee submitted an application for amendment dated August 17, 1994.
l The action statement requires that with one containment recirculation spray subsystem inoperable, both spray subsystems must be restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the plant must be in Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
If both spray subsystems are not restored to operable status within the next 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the plant must be placed in Cold Shutdown within the next 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Recirculation spray system (RSS) pump 2RSS*P21A was declared inoperable at 3:15 p.m. on August 12, 1994, because it was determined that the pump could not meet the requirements of SR 4.6.2.2.d.
This surveillance requires that the pump develop on recirculation flow a differential pressure of equal to or greater than 112 psid at a flow of equal to or greater than 3500 gpm.
The inability of the 2RSS*P21A pump to meet SR 4.6.3.3.d was discovered during the process of evaluating the past RSS pump performance.
It was observed that the 2RSS*P21A pump flow element 2RSS*FE157A certified calibration report predicted a flow of 3850 gpm at 100 inches of water column (wc) differential while the flow transmitter 2RSS*FT157A was calibrated to indicate 4000 gpm at 100 inches wc.
This calibration mismatch is unaccounted for in the test loop analysis. The result is that flows recorded during surveillance testing would be non-conservatively measured.
Correction of the calibration mismatch has resulted in a revised predicted flow of approximately 3388 gpm at 112.8 psid for 2RSS*P21A pump, which, when compared to the pump performance curve, was determined to be less than the technical specification required. flow.
The function of the RSS pumps is to take suction from the containment sump and discharge to the spray rings located in the containment dome during a Design Basis Accident (DBA). This provides cooling inside containment and will 9408260203 940822 PDR ADOCK 05000412 P
. maintain a subatmospheric containment for the duration of the accident.
The containment is initially brought to a subatmospheric condition using the quench spray system and the recirculation spray system following transfer to recirculation; the recirculation spray system will then maintain the containment subatmospheric.
In order to test the recirculation spray pumps, a temporary dike must be installed in the lowest floor elevation of containment around the safeguards sump area, which contains the suction piping for all four RSS pumps, to ensure adequate net positive suction head (NPSH) for each pump.
A test loop is provided from the discharge of each pump back to the sump area in containment.
This alignment is accomplished by placing the four RSS header spectacle flanges into the "no flow" position, and by removing blind flanges and installing temporary strainer spoolpiece housings into the recirculation test i
loop flow path to divert flow back to the containment sump.
The licensee proposes to revise Surveillance Requirement (SR) 4.6.2.2.d of Limiting Condition For Operation (LCO) 3.6.2.2 titled, " Containment Recirculation Spray System." The specific revision would be to add a new footnote which would state the following:
"Until the beginning of the fifth refueling outage (Mode 5) or until an outage of an expected duration of 30 days or greater, whichever occurs first, 2RSS-P21A recirculation spray pump is only required to develop a differential pressure of 2110 psid at a flow of 2 3275 gpm."
i In addition, SR 4.6.2.2.e.2 would be revised by deleting a footnote denoted by a single asterisk.
This footnote pertains to an extension to the 18 month surveillance interval for the first fuel cycle.
Since Beaver Valley Unit 2 is currently in the fifth fuel cycle, this footnote is no longer applicable.
2.0 EVALUATION 2.1 RSS Pump The proposed change to SR 4.6.2.2.d is necessary since the 2RSS*P21A pump cannot be tested or repaired, if necessary, during plant operation.
It is impractical to install the temporary dike in the containment sump, which is necessary to run the RSS pumps on recirculation flow.
If the temporary dike were installed, it would obstruct the containment sump inventory during a DBA j
from reaching the suction of the pumps, thus rendering all RSS pumps incapable 1
of fulfilling their safety function.
This concern of testing the RSS pumps at power is reflected in the existing IST Pump Relief Request No. 2.
Following testing, any necessary repairs that might be required which could involve removing the pump rotating element, would be highly involved.
The pump is a deep draft vertical design and its removal would require use of a crane located outside of the safeguards building. The approximate length of the pump from the impeller to the centerline of the discharge flange is 68 ft.
Therefore, it is impracticable to restore 2RSS*P21A pump performance to meet the current surveillance requirement values until the plant is shut down for a refueling outage or for some other outage of sufficient duration.
1
. The containment peak pressure occurs prior to the initiation of quench spray.
Since recirculation spray is initiated after quench spray, changing its performance requirements will not affect containment peak pressure.
Recirculation spray performance does, however, affect the capability to depressurize the containment following an accident.
Specifically, the time to
)
obtain a subatmospheric condition and the subatmospheric peak pressure are directly affected due to changes in recirculation spray system performance.
The proposed reduction in the required performance for 2RSS*P21A pump and its effect on the recirculation spray system's performance has been evaluated using the LOCTIC computer code. This analysis was performed using the proposed performance requirements for the 2RSS*P21A pump on recirculation flow I
as an input.
The results of this analysis demonstrated that the design basis requirement for the containment depressurization system continues to be met with the proposed performance requirements for the 2RSS*P21A pump and the maximum SWS temperature of 87" F.
This analysis also assumes the current plugging level of 28 tubes in "A" RSS heat exchanger.
With the above mentioned analysis inputs, the containment depressurization system continues i
to be capable of reducing the containment pressure to a subatmospheric condition within one hour following a LOCA and maintaining the containment pressure subatmospheric for the long term. The current analysis requirements of a containment depressurization time of less than 3600 seconds and a subatmospheric peak pressure of less than 0.0 psig continue to be met.
The containment depressurization time increased by approximately 10 seconds (3440 seconds to 3450 seconds) as a result of the revised inputs.
The subatmospheric peak pressure decreased by approximately.04 psig (~.03 psig to
~.07 psig) 1 In the revised containment analysis, there exist additional conservative margins.
These margins include:
The use of the minimum sump temperature for the RSS heat exchanger inlet temperature which results in a minimum overall heat transfer coefficient i
(Vo).
This is only done for the heat exchanger performance evaluation.
Then this artificially lower Uo is used as an input to LOCTIC which then maximizes RSS spray temperature.
The sump elevation is also taken at the minimum level, rather than taking credit for the sump volume build-up as the transient progresses.
This reduces the NPSH available and hence the RSS pump flow.
The design fouling (0.0003) is utilized for the RSS heat exchanger performance evaluation as an input to the analysis.
The Service Water System (SWS) flow for the tube side of the RSS heat exchanger is taken at the minimum requirement of 5500 gpm per heat exchanger.
Plant testing has shown that the actual flows are higher than these flows.
1 t.
. The revised analysis assumes that the river water does not exceed 87* F.
The actual recorded river water temperature during the week of August 15, 1994, was approximately 75* F and has been trending downward due to cooler average daily temperatures and recent precipitation. The river water temperature reached a maximum value of 83* F in 1994, and the site maximum temperature of 86" F was recorded in 1988.
The river water temperature is currently verified acceptable as less than 87* F per Log L-5 Item #89.
Technical Specification 4.7.5.1 requires verifying an average river water temperature of less than blow 89* F once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Log L-5 has been revised to include a note that would require containment temperature to be maintained equal to or greater than 100* F at a service water temperature of 2 86* F and the 2RSS*P21A pump to be declared inoperable should the river water temperature exceed 87* F.
Therefore, the proposed change to SR 4.6.2.2.d for RSS pump 2RSS*P21A is justified for the period until the fifth refueling outage, due to the special test configuration required to perform SR 4.6.2.2.d, the pump design, and special considerations to perform any necessary repairs, if required, which prohibit returning the 2RSS*P21A pump performance back to current technical specification limits, without incurring an outage of significant duration.
Since the acceptance criteria for the containment depressurization system continue to be met and the containment peak pressure remains unchanged, the ability of the containment structure to restrict the release of fission products to the environment following a LOCA remains unchanged.
The increased containment depressurization time does not affect the calculated offsite dose consequences, since the release is assumed to occur for one hour following a LOCA.
The revised depressurization time of 3450 seconds is less than the assumed 3600 second depressurization time.
In addition, the revised pump performance parameters for the 2RSS*P21A pump used in the new analysis provides a margin between actual pump performance and assumed pump performance, i.e., 3388 gpm at 110 psid.
The remaining three RSS pumps currently meet the required technical specification performance parameters.
Four separate and independent RSS subsystems will continue to be available to mitigate the consequences of a DBA.
Therefore, the proposed change is acceptable based on the fact that the containment depressurization system will continue to meet its design basis requirements. The proposed change will not impose additional challenges to the containment structure in terms of peak pressure.
The calculated offsite dose consequences of a DBA will remain unchanged since the assumed one hour release duration remains unchanged. There is a margin between actual pump performance and assumed pump performance which adds conservatism to the calculated containment depressurization performance.
2.2 Editorial Removal of Footnote The proposed deletion of the footnote pertaining to extending the 18 month surveillance interval for the first fuel cycle is editorial in nature and does not affect plant safety.
Beaver Valley, Unit 2 is currently in its fifth fuel cycle. Therefore, this footnote is no longer applicable and should be removed.
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e 3.0 EMERGENCY CIRCUMSTANCES In accordance with the technical specification action statements, the plant would be required to shutdown to Hot Standby conditions within 78 hours9.027778e-4 days <br />0.0217 hours <br />1.289683e-4 weeks <br />2.9679e-5 months <br /> of declaring the "A" recirculation spray subsystem inoperable.
Permission was requested to continue plant operation with a reduced recirculation spray flow and not initiate a shutdown of Beaver Valley Unit No. 2 at 3:15 p.m.,
August 15, 1994, and be in Mode 3 by 9:15 p.m. the same day.
During the process of evaluating the past recirculation spray system pump performance, it was observed that the "A" recirculation spray system pump flow element 2RSS*FE-157A certified calibration report predicts a flow of 3850 gpm at 100 inches of water column (wc) differential while the flow transmitter 2RSS*FT-1574 was calibrated to indicate 4000 gpm at 100 inches wc.
This calibration mismatch is unaccounted for in the test loop analysis.
The result is that flow recorded during surveillance testing would be non-conservatively measured.
Corrections of the calibration mismatch has resulted in a revised predicted flow of approximately 3388 gpm at 112 psid which is less than the technical specification required flow.
The licensee could not have anticipated these circumstances.
We agree with the licensee's view that continued operation would not adversely affect the health and safety of the public and that an unscheduled plant shutdown to immediately resolve the issue is inappropriate. We conclude that a license amendment pursuant to 10 CFR 50.91(a)(5) should be processed.
4.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility in accordance with the amendment would not:
(1) involve a significant increase in the probability or consequences of an accident previously evaluated, or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.
The licensee proposed that the subject change to the Technical Specifications did not involve a significant hazards consideration, stating as follows:
1.
Does this change involve a significant increase in the probability or consequences of an accident previously evaluated?
The proposed change will revise the operability criteria for recirculation spray pump 2RSS*P21A.
The differential pressure and flow requirements are being revised to account for a change in pump performance.
The recirculation spray system (RSS) is designed to assist the quench spray system in returning the containment to subatmospheric conditions following a Design Basis Accident (DBA) and then maintaining a subatmospheric containment for the duration of accident mitigation and recovery.
's
. The change in operability criteria does not result in a modification to plant equipment nor does it affect the manner in which the plant is operated. The change establishes new acceptance criteria for determining pump operability. This equipment is normally in a standby condition and only operates during accident mitigation.
Since the physical plant equipment and operating practices are not changed, and this equipment is normally in a standby configuration, there is no change in the probability of an accident previously evaluated.
Changing the operating criteria was evaluated against the DBA safety analysis.
The 2RS*P21A recirculation spray pump will provide less flow than previously analyzed. This pump characteristic was evaluated by examining the LOCTIC containment analysis to determine if sufficient cooling would still be provided to demonstrate that previous accident consequences remain unchanged. Actual heat exchanger tube plugging levels versus assumed end of life conditions were utilized and the evaluation demonstrated that the containment returns to subatmospheric pressure following a DBA within previously approved analysis results.
This continues to demonstrate that the consequences of an accident are unchanged since any potential release from containment is terminated within existing accident analysis assumptions.
In order to provide additional pump operating margin, the evaluation was redohe assuming a lower flow and a reduced river water temperature.
River water provides the ultimate heat sink source at Beaver Valley.
The design basis river water temperature was reduced for the evaluation; however, the temperature assumed remains above the highest river water temperature recorded at the site. The results of this evaluation demonstrate that at actual heat exchanger conditions, reduced river water flow through the recirculation spray heat exchanger and at a slightly reduced river water temperature, the containment returns to subatmospheric pressure within the current accident analysis assumptions of one hour.
This again demonstrates that the consequences of an accident previously evaluated remains unchanged since there is no change to assumptions regarding releases from containment.
One editorial change is also included which deletes a footnote which provided a schedule extension for completing a specific refueling frequency surveillance during the first refueling outage.
Since this has been completed, this footnote is no longer needed.
Based on the above discussion, it is concluded that this change will not increase the probability or consequences of an accident previously avaluated due to revising the 2RSS*P21A recirculation spray pump performance criteria.
2.
Does the change create the possibility of a new or different kind of accident from any previously evaluated?
The proposed change does not alter the method operating the plant.
The recirculation spray system is an accident mitigation system and is normally in standby.
System operation would be initiated following a
. containment pressure increase resulting from DBA.
A revision to the 2RSS*P21A pump operating criteria has been shown to continue to provide sufficient flow to mitigate the consequences of a DBA.
RSS operation continues to fulfill the safety function for which it was designed and no changes to plant equipment or operating procedures will occur. As a result, an accident which is different than any already evaluated in the Updated Final Safety Analysis Report will not be created due to this change.
The removal of the footnote is editorial and eliminates a previously granted schedular extension which is no longer applicable.
Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.
3.
Does the change involve a significant reduction in a margin of safety?
It has been demonstrated that the proposed change will not affect the ability of the RSS from performing its safety function.
This proposed change to reduce the flow requirements associated with the "A" train recirculation spray subsystem inherently results in some reduction in system performance.
However, overall plant safety margin is not affected.
The evaluation shows that the return to subatmospheric pressure will take approximately 10 seconds longer than previously demonstrated.
The design bases for the containment depressurization system is for containment to be restored to subatmospheric conditions within one hour following a DBA.
This design requirement is still being satisfied. There is no resultant change in dose consequences related to the increased time to reach subatmospheric pressure.
The surveillance requirements for demonstrating the RSS is operable will continue to assure the ability of the system to satisfy its design function.
Daily monitoring of river water temperatures, as currently done, assures the evaluation assumptions will continue to be met while the plant is operating.
The assumed river water temperature is greater than the highest recorded temperature at Beaver Valley; therefore, margin to design basis conditions is not affected.
The removal of the schedular extension from the surveillance requirement is editorial since it is no longer applicable.
Therefore, based on the above discussion, it can be concluded that the proposed change does not involve a significant reduction in a margin of safety.
Based on the above discussion, with which the staff concurs, the staff concludes that this amendment meets the criteria and, therefore, does not involve a significant hazards consideration.
9
5.0 STATE CONSULTATION
i In accordance with the Commission's regulations, the Pennsylvania State official was notified of the proposed-issuance of the amendment. The State official had no comments,
6.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase-in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure.
The Commission has made a final no significant hazards consideration finding with respect to this amendment, Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the-issuance of the amendment.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that: (1) the amendment does not (a) significantly increase the probability or consequences of an accident previously evaluated, (b) increase the possibility of a new or different kind of accident from any previously evaluated or (c) significantly reduce a safety margin and, therefore, the amendment does not involve a significant hazards consideration; (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (3) such activities will be conducted in compliance with the Commission's regulations, and (4) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
Jim Pulsipher Date: August 22, 1994
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