ML20073E201
| ML20073E201 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 09/23/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073E196 | List: |
| References | |
| NUDOCS 9409280295 | |
| Download: ML20073E201 (11) | |
Text
l l* "% k UNITED STATES 8
) '^
E NUCLEAR REGULATORY COMMISSION WASHINGTON. D.C. 20555-0001 g..... /
SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION j
RELATE 9 TO AMENDMENT NOS.153 AND 157 TO FACILITY OPERATING LICENSE NOS. DPR-24 AND DPR-27 WISCONSIN ELECTRIC POWER COMPA_N_1 POINT BEACH NUCLEAR PLANT. UNIT NOS. 1 AND 2 DOCKET N05. 50-266 AND 50-301
1.0 INTRODUCTION
By letter dated August 9, 1994, as supplemented August 19, 1994, Wisconsin Electric Power Company (WEPCo), the licensee, proposed to modify the Point Beach Nuclear Plant (PBNP), Units 1 and 2, Technical Specifications (TS) by increasing the allowed outage times for one motor driven auxiliary feedwater pump and for the standby emergency power for the Unit 1 Train B 4160 Volt safeguards bus (A06) from 7 to 12 days.
The proposed amendments modify TS 15.3.4, " Steam and Power Conversion System," and TS 15.3.7, " Auxiliary Electrical Systems," to provide the one-time extensions of the specific allowed outage times.
The proposed amendments also modify TS 15.3.3,
" Emergency Core Cooling System, Auxiliary Cooling Systems, Air Recirculation Fan Coolers, and Containment Spray," to provide the clarification that the service water pump (P-32E) operating with power supplied by the Alternate Shutdown System is operable from offsite power.
2.0 BACKGROUND
WEPCo is adding two EDGs to Point Beach Nuclear Plant, Units 1 and 2, and reconfiguring portions of the 4160-Volt emergency electrical power system.
The first connection of the output of one of the additional emergency diesel generators into the existing electrical system is expected to take place during the fall,1994 Unit 2 refueling outage, which is presently scheduled to start on September 24, 1994.
During the connection process, Unit 2 will be defueled; however, some shared equipment that supports the operation of Unit I could be out-of-service for longer than the present Technical Specification allowed outage time (A0T).
This license amendment request is necessary to allow the safe continued operation of Unit I while the connection of the first additional EDG (G-04) is taking place.
9409280295 940923 PDR ADOCK 05000266 P
l l The major steps of the connection process are:
1.
Changing the power source of the Unit 2 Train B 480 Volt safeguards bus (2804) from the existing Unit 2 Train B 4160 Volt safeguards bus (2A06) to the new 2A06.
2.
Installation of a new supply breaker from the Unit 2 Train B 4160 Volt supply bus (2A04) to the new 2A06.
3.
Connection of 2A04 to the new 2A06.
4.
The final step will be to establish operability of the new EDG G-04 as a standby emergency power supply for the new 2A06.
With respect to Unit 1, operability of the safeguards buses is based on maintaining at least one on-site AC power source and associated distribution system operable during accident conditions coincident with an assumed loss of off-site power and a single failure in the other on-site AC source.
To cope with the loss of all AC power (station blackout), Point Beach Gas Turbine G-05 is used as an alternate AC power source to comply with the blackout rule.
Core cooling and appropriate containment integrity can be maintained by using the Gas Turbine G-05 as the alternate AC power source if a station blackout occurs during the connection process. Verification of G-05 operability prior to beginning the connection process is one of the compensatory measures.
3.0 EVALUATION 3.1 TS 15.3.4.C.2 and TS 15.3.7.B.I.h Current TS 15.3.4, " Steam and Power Conversion System," specifies the limiting conditions for operation for the auxiliary feedwater system and service' water system.
TS 15.3.4.C.2 states thet either of the two motor driven auxiliary feedwater pumps may be out-of-service for up to 7 days.
The proposed amendment adds a footnote to the TS 15.3.4.C.2.
It revises the A0T for the motor driven auxiliary feedwater pump from 7 to 12 days, and states:
During the Unit 2 1994 refueling outage, P-38B, the Train B motor driven auxiliary feedwater pump, may be out-of-service for up to 12 days."
i The motor driven auxiliary feedwater pump (powered from Unit 2 B04), P-38B, will be removed from service to prevent potential overload of the associated (Train A, EDG G-01) emergency diesel generator during the connection process and'thus will enter into the LC0 in TS 15.3.4.C.2.
The loss of the one auxiliary feedwater pump (Train B, P-388) does not compromise the safety of plant due to the sufficient capabilities of the remaining motor driven auxiliary feedwater pump and the turbine driven auxiliary feedwater pump.
i
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- The most limiting single-failure for the auxiliary feedwater system with the
.one motor driven auxiliary feedwater pump out-of-service would be the loss of the Unit I turbine driven auxiliary feedwater pump.
In this case, only the one Train A electric motor driven auxiliary feedwater pump would be available.
The Train A motor driven auxiliary feedwater pump can provide sufficient flow to mitigate accidents that require auxiliary feedwater, except it normally provides feedwater to the Loop A Steam Generator. Accidents that require isolation of the Loop A Steam Generator could be mitigated by realignment of
. electrical systems to power the other motor driven auxiliary feedwater pump (P-38) or by manual cross-connection of the Train A and Train B auxiliary feedwater flow lines, if the turbine driven auxiliary feedwater pump has failed.
The possible cross-connection or switching the power supply provides an additior.al benefit along with the compensatory measures (listed below in the safety evaluation section 3.3) not recognized in the original A0T.
Present TS 15.3.7, " Auxiliary Electrical Systems," specifies the limiting conditions for operation for the standby emergency power supplies for the engineered safeguards buses. TS 15.3.7.B.I.h states that the standby emergency power supply to Unit 1 A06/B04 and Unit 2 A06/B04 may be out of service for a period not exceeding 7 days provided the redundant engineered safety features are operable and the required redundant standby emergency power supplies are started within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> before or after entry into this LC0 and every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> thereafter.
The proposed amendment adds a footnote to the TS 15.3.7.B.I.h.
It revises the A0T for the Train B standby emergency power supply from 7 to 12 days, and J
states:
During the Unit 2 1994 refueling outage, standby emergency power to Unit 1 A06/B04 and Unit 2 ^06/B04 may be out-of-service for up to 12 days."
The basis for the request to extend the A0T from 7 to 12 days is that the connection of one of the new emergency diesel generators during the Unit 2 refueling outage will require that the Train B safeguards buses in Unit 2 be significantly reconfigured.
During the reconfiguration, power will be i
supplied to the Unit 2 Train B 480 Volt safeguards bus (B04) by a tie-breaker from the Unit 2 Train A 480 Volt safeguards bus (803).
The use of the tie-breaker for the installation of the new emergency diesel generators is limited by TS 15.3.7.B.I.e, which states:
With a unit defueled, one pair of buses for the defueled unit, A05 and A06 or 803 and.B04, may be tied together through their common tie-breaker in excess of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> provided:
1.
An evaluation is performed to show that the loads that remain or can be energized by the buses will not cause a potential overload of the associated EDG.
The applicable Limiting Conditions for Operation of l
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- the equipment removed from service shall be entered for the operating unit.
2.
A single train of spent fuel cooling is adequate to cool the spent fuel pool.
3.
The required redundant shared engineered safety features for the other unit are operable.
Unit 2 will be defueled during the connection process.
The standby emergency power LCO will be entered for Unit 1 A06 and Unit 2 A06 (TS 15.3.7.B.I.h.)-
because Train B emergency diesel generator G-02 will not be able to provide power to at least two service water pumps.
The estimated time for completion of the activities to restore the standby emergency power, auxiliary feedwater, and service water system to normal is 12 days.
The A0Ts for the applicable LCOs in the Point Beach Technical Specifications are 7 days.
The justification for these changes include the compensatory measures, the contingency actions, and the probabilistic safety assessment that follows.
3.2 TS 15.3.3.D.l.a Current TS 15.3.3.D.1.a specifies that four service water pumps must be e
operable for the reactor to be made or maintained critical.
The proposed amendment adds a footnote to the TS 15.3.3.D.1.a:
During the Unit 2 1994 refueling outage, one train B service water pump operating with power supplied by the Alternate Shutdown System, 808/B09 480 volt buses, may be considered operable from a normal (offsite) power supply, under the provisions of Technical Specification 15.3.0.C.
Three Train A service water pumps powered by the 1803 and 2B03 buses will remain unaffected by the reconfiguration and bus-tie work.
The one service water pump powered from 1804 bus will be unaffected except that the standby emergency power source will be considered inoperable.
One of the two service water pumps powered from 2B04 will be removed from service to prevent potential overload and the other will be powered by the Alternate Shutdown System buses. The footnote added to TS 15.3.3.D.1.a is only for clarification to the existing TS, since the service water pump supplied by the Alternate Shutdown System would be considered operable under existing TS 15.3.0.C.
TS 15.3.0.C states the component is " considered operable for the purpose of r
satisfying the requirements of the applicable Limiting Conditions of Operation, provided...the alternate power source (normal or emergency) is operable."
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3.3 Comoensatory Measures The following compensatory measures will be invoked to establish appropriate assurance that the required equipment will remain operable during the connection process:
1.
The gas turbine generator (G05), which is the alternate AC power source for Point Beach, will be verified operable by a start and load-run test within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> prior to entry into the standby emergency power LCO.
The gas turbine generator will continue to be verified operable by completion of an operational readiness check every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the initial test, until the standby emergency power LC0 is exited.-
2.
Other maintenance and test activities that could cause inoperability of required equipment, a loss of off-site power, or shutdown of the operating unit will not be scheduled during the period of these LCOs.
The outage planning committee and safety evaluation group will implement this compensatory measure by evaluating specific work activities in a thorough refueling outage safety review process and by maintaining an appropriate outage schedule.
3.
At least three of the four off-site power 345 kV transmission lines will be in-service during the connection process.
4.
The Train A EDG (G01) will be tested within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of entry into the standby emergency power LC0 and every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> thereafter, until the LC0 is exited.
i 5.
Train B EDG (G02) will be maintained in the maximum possible state of operational readiness during the connection process.
6.
A twice per shift (approximately every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) firewatch in the auxiliary feedwater pump room will be instituted as a compensatory measure for the inoperability of the Train B auxiliary feedwater pump (P-38B) as required by the Point Beach Appendix R fire protection program.
7.
All Senior Reactor Operators and Reactor Operators will be trained on the Technical Specifications for the allowed outage time extension and the procedures that will be used for the connection process.
The connection process procedures, called installation work plans (IWPs),
contain the appropriate compensatory measures and contingency actions.
8.
Continuous technical support for the operating crews will be provided by-an on-call Senior Reactor Operator with detailed knowledge of the connection process.
In addition, there will be an IWP coordinator on site at all times during the connection process.
The IWP coordinators will be technically qualified personnel with detailed knowledge of the
~.
. connection process. The IWP coordinators will be responsible for the following:
a.
Monitoring the status of the connection process and completion of the procedural steps that are being performed.
b.
Periodically updating the operating crew regarding the status of the connection process.
c.
Providing updates to the refueling outaae planning committee to coordinate the connection process with refueling outage activities.
3.4 Contingency Actions The emergency response organization (ERO), the emergency operating procedures (EOPs), and the shutdown emergency procedures (SEPs) for Point Beach are established and are sufficient to protect the health and safety of the public during anticipated emergencies.
No changes to the ERO, E0Ps, or SEPs are necessary for emergency response during the connection process.
The following contingency actions will be invoked as necessary to recover from possible failures or malfunctions during the connection process:
1.
Alternative methods of restoring power to the safeguards buses will be identified in the procedures used to perform the connection process.
2.
The PBNP System Control Center will have guidance in place that will provide the actions that are necessary to ensure grid stability and off-site power to Point Beach.
This includes the loss of any single transmission element for all combinations of off-site power lines that can be expected during the connection process.
3.
The work will be performed in such a manner during the connection process to allow restoration of the electrical system to the state it was in prior to the connection process, if completion of the connection process becomes unworkable.
4.
Guidance for contingency actions to maintain service water system operability will be provided in the procedures used to perform the connection process.
3.5 Probabilistic Safety Assessment i
The installation of the third emergency diesel generator will require that diesel generator G02 be unavailable for one day, and that certain equipment that would normally be powered from the Unit I train B 4160 volt safeguards bus A06 be placed in " pull-to-lock" position or provided with alternative, non-redundant or non-safety grade power supplies for the next 11 days.
The current technical specifications allow a 7-day outage time for one auxiliary
i feedwater pump and one standby emergency power source, and prohibit operation of either unit unless there are 4 operable service water pumps.
During the last 11 days of the connection process, EDG B will be considered inoperable, but will be functionally available and will autostart on demand.
Buses IA06 and 2A06 will be tagged out of service, which will isolate bus 2B04 from EDG B.
Therefore, bus 2B04 will be cross-tied to bus 2B03 to provide emergency power from EDG A.
However, to avoid overloading EDG A, the two service water pumps normally on bus 2B04 will be eliminated from these loads by placing P-32E on the Alternate Shutdown System buses and taking P-32D out of automatic start mode.
The six service water pumps will temporarily be
't powered as follows:
Power Source Bus SWS Pumo EDG A (G-01) 1B03 P-32A P-32B 2B03 P-32F 2B04 X-tied P-32D (not in auto)
EDG B (G-02) 1804 P-32C Alt Shutdown Sys B08/B09 P-32E This creates a vulnerability to loss of offsite power with failure of EDG A, which would leave only the single SWS pump powered by EDG B to supply all service water system loads. The licensee's request states that the single SWS pump would be sufficient for the loads of a LOSP, provided that the spent fuel i
pool cooling load is isolated from the SWS within a half-hour.
However, this configuration would not provide adequate service water under the design basis condition of a LOCA with LOSP.
(The risk implications of the LOCA with LOSP were evaluated by the staff and the results are presented later.)
i The licensee used the Point Beach Nuclear Plant (PBNP) Individual Plant Examination (IPE) model to calculate the risk increment associated with the equipment unavailability created by the 12-day connection process. They
.i modified the IPE to represent the following conditions-1 Train B EDG (G-02) completely out-of-service for the first day, then available' with operator action for the remaining Il days.
The train B auxiliary feedwater pump (P-388) not available for-12 days, i
The Unit 2 train B 4160 volt safeguards bus and supply bus both being out-of-service for 12 days.
l i
The Unit 2 train B 480 volt bus (2B04) powered from the train A 480 volt safeguards bus (2803).
\\
1 One train B service water pump (P-32D) not in automatic, and one train B
-service water pump (P-32E) powered from the alternate shutdown system.
l i
Their results indicated that the increase in core damage probability during the first day is 8.4x10'7 and the increase over each of the next 11 days is 4
4.14x10~8/ day, for a total increment of 1.30x10 over the 12-day connection process. The steam generator tube rupture sequences were the dominant contributors to their total, and the station blackout sequences were the dominant difference between the first day and the other days of the outage.'
As a check on the licensee's conclusions, the NRC staff used a simplified Point Beach model, previously developed for the Accident Sequence Precursor _
(ASP) Program, to estimate the incremental core damage probability associated with the 12-day connection process.
Input assumptions included:
EDG 2 inoperable for 1 day AFW pump B inoperable for 12 days Gas Turbine available to power emergency buses with failure probability of 0.10/ demand (assumes no maintenance during connection period)
Steam generator tube rupture frequency in generator normally fed by the remaining operable AFW pump = 1x10-2/ year.
AFW to ruptured steam generator available as an operator recovery action, only.
The resulting incremental core damage probability for the 12-day connection process was estimated at 4.7x10, with LOOP sequences dominating. These results are presented in Table 3.5.
The results of the licensee's and staff's analyses are comparable, considering the level of accuracy associated with the probabilistic models.
In addition, the staff evaluated the issue (discussed above) concerning the adequacy of the service water supply to EDG B when LOCA loads are added under conditions of LOSP and failure of EDG A.
The frequency of the joint occurrence of LOSP and LOCA is too small to contribute significantly to the probability of core damage. However, analysis of Licensee Event Report (LER) i dataindicatesthatabout16%pfLOSPeventsinvolvespuriousemergencycore cooling system (SI) actuations.
This would increase the demand on the SWS until the reactor operators could follow their procedures to the point of
)
terminating the SI function.
If the LOSP event is accompanied by failure of EDG A, then EDG B would not have sufficient cooling from the one remaining SWS l
'Information about relative-contributions of accident sequences was provided during a telephone conversation on August 12, 1994, between Tom Malinowski and Scott Hoggatt at Wisconsin Electric Power Company and Steve Long and Allen Hansen at NRC.
2" Loss of Offsite Power Search (SMTP Id#: 6221)," Internet message from Andrea Cross, ORNL to Thomas Koshy, NRC, March 25, 1994, 4:27 p.m.
-g pump until SI is terminated. The probability of EDG B damage prior to SI termination and isolation of SI associated SWS loads has not been evaluated.
To investigate the sensitivity of the core damage probability estimate to this issue, the incremental probability of core damage was estimated for the 12-day connection process, assuming that LOSP with failure of EDG A would always cause failure of EDG B.
Again, the gas turbine was credited with a failure probability of 0.1/ demand.
The resulting additional core damage probability was estimated as 5.8 x 10'7 This value would be reduced by any probability of recovering sufficient service water flow to EDG B before the diesel was destroyed, but this reduction was not quantified.
Thus, the total risk increment estimated by the staff is s 1.0x10'6, and the inclusion of this issue does not significantly alter the conclusions.
On the basis of these evaluations, it is concluded that the probability of core damage associated with the 12-day connection process is on the order of 10~6 The increase in probability of creating a bypass release due to core damage following steam generator tube rupture is estimated to be in the mid-10 range.
These values are low compared to annual core damage and bypass release frequency values previously found to be acceptable by NRC in its own PRAs and the IPEs.
Therefore, the risk associated with the technical specification modifications requested to facilitate connection of the third emergency diesel generator is found to be acceptably low.
No evaluations were conducted to estimate the risk associated with alternatives, such as requiring the operating unit to shut down during the connection process.
Because there is an increase in the level of risk associated with the early phases of shutdown, it is not clear that there would be an alternative with less associated i n..
However, it is clear that the potential risk savings are too small to make such analysis worthwhile, due to the low value associated with the proposed actions.
Table 3.5 Staff Estimate of Core Damage Probability Increase Period Condition Probability 1st dav EDG B and MDAFW train B inoperable 2.4x10'7 4
2nd - 12th day HDAFW train B inoperable 7.0x10 (LOCA, LOSP and Transient initiators)
All 12 days Tube rupture in SG A with 2.2x10'7 MDAFW train B inoperable 4.7x10'7 2nd - 12th days Sensitivity to spurious SI s 5.8x10~7 Core Damage Probability Increase s 1.0x10~6
. Event Identifier:
Point Beach 12-day ESF bus outage for adding 3rd EDG Event
Description:
Sensitivity to potential dependent failure of EDG B given LOSP and failure of EDG A Station Blackout Probability:
LOSP frequency
= 1.4x10/ day (from 1-day ASP run) duration
-11 days EDG A failure probability
- 5x10' Probability of SI signal, given LOSP = 1.6x10
Probability of EDG B failure, given EDG A failure and SI signal = 1.0
- 1x10(assumed)
Probability of gas turbine failure product:
1.23x10'6 Conditional Probability of Core Damage, given Station Blackout:
nonrecovery probability for offsite power - 4.5x10
probability of TDAFW failure
- 1. 7 x 10-2
=
sum:
4.7x10
Probability of core damage:
station blackout probability 1.23x10~6 conditional core damage probability 4,7x10
product:
5.8x10'7 3.6 Summary Based on our review of compensatory measures, the contingency actions, and probabilistic safety analysis, the staff concludes that a one-time extension of the 7-day A0T to 12-day A0T period for the motor driven feedwater pump and the standby emergency power would not have an unacceptable effect on the overall safety of Point Beach Nuclear Plant. On this basis, we find that a one-time extension of an additional 5 days during the upcoming refueling outage is acceptable. Also, the added footnote for the service water pumps is for clarification only. Therefore, the staff finds the addition acceptable.
4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Wisconsin State official was notified of the proposed issuance of the amendment.
The State official had no comments.
_ 11 _
5.0 ENVIRONMENTAL CONSIDERATION
This amendment changes a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or changes a surveillance requirement. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluent that may be released offsite and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment on such finding (59 FR 42870).
Accordingly, this amendment meets the eligibility criteria for categcrical 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 this amendment.
6.0 CONCLUSION
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
SLong SSaba GDentel Date: September 23, 1994
,