ML20029D061
| ML20029D061 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 04/20/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20029D059 | List: |
| References | |
| NUDOCS 9405030358 | |
| Download: ML20029D061 (6) | |
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UNITED STATES
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j NUCLEAR REGULATORY COMMISSION
- %g WA$HINGTON, D.C 20666-0001
%f..u., j 1AFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NCS 147 AND 151 TO FACILITY OPERATING LICENSE N05. DPR-24 AND DPR-27 WISCONSIN ELECTP.1C F0WER COMPANY PolNT BEACH NUCLEAR PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50-266 AND 50-301
1.0 INTRODUCTION
By letter dated February 26, 1993, Wisconsin Electric Power Company (Wisconsin Electric or the licensee) requested amendments to the steam and power conversion system Technical Specifications (TSs) for th9 Point Beach Nuclear Plant, Unit Nos. I and 2.
The proposed amendments would revise TS section 15.3.4 by adding operating conditions and limiting conditions for operation for the atmospheric steam dump valves, the crossover steam dump system, the turbine overspeed protection features, and the turbine stop and governor valves.
The request also proposes to. revise the surveillance requirements of TS section 15.4.8 (Auxiliary Feedwater System).
The bases for these TS sections are also being revised to support the proposed changes.
The proposed amendments resulted from a review of the safety analyses in the Point Beach Nuclear Plant's Final Safety Analysis. Report (FSAR) against the Limiting Condition for Operation and Surveillance sections of the TSs.
Wisconsin Electric committed to conduct this review in a letter that was submitted to the NRC on December 3, 1991.
The review identified several systems, components, and functions credited in the safety analyses which the licenseo concluded should be added to the TSs.
This request includes the changes and additions identified in the review that are associated with the steam and power conversion systems.
2.0 BACKGROUND
2.1 Current License Condition The current license condition as stated in the TSs is applicable for both Units 1 and 2 as follows:
(1)
Section 15.3.4, " Steam and Power Conversion System," describes the operating conditions and limiting conditions for operation for the main steam safety valves and the auxiliary feedwater system.
This section also. prescribes the limits for Iodine-131 activity on the secondary side of a steam generator.
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Section 15.4.8, "Auxiiiary Feedwater System," describes the surveillances required to be performed on the auxiliary feedwater pumps and associated support equipment.
2.2 Proposed Changes The proposed revisions will add operating conditions and limiting conditions for operation for the atmospheric steam dump valves, crossover steam dump slystem, turbine stop and governor valves, and the various turbine over-speed protection features. Additionally, the changes will revise the surveillance requirements for the auxiliary feedwater system and add explanatory text to the bases for Section 15.3.4 (Steam and Power Conversion System) and Section 15.4.8 (Auxiliary Feedwater System).
The changes include:
(1)
Add limiting conditions to the atmospheric steam dump lines by placing a limit on the time that a steam dump line is allowed to be inoperable.
(2)
Add a limiting condition to the crossover steam dump system; an inoperable crossover steam dump system will require a reduction in power.
(3)
Add specifications to the Turbine Overspeed Protection System and the Turbine Stop and Governor Valves.
The change would require that at least one Turbine Overspeed Protection System be operable during power operation.
In addition, all Turbine Stop Valves and Governor valves must be operable.
(4)
Revise the Turbine-Driven Auxiliary Feedwater Pumps surveillance requirements (TS 15.4.8.1.b).
The modification will contain a clarifying statement that states the surveillance requirements in the event steam is unavailable.
(5)
Modify the Auxiliary Feedwater Pump Discharge Valves and Suction Side Service Water Supply Valves surveillance requirements (TS 15.4.8.1.c).
The test interval will be consistent with the existing surveillance requirements for the Motor and Turbine-Driven Auxiliary Feedwater Pumps.
(6)
Revise the basis for TS 15.3.4 (Steam and Power Conversion System) and 15.4.8 (Auxiliary Feedwater System) to support the changes.
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3.0 EVALUATION 3.1 Atmospheric Steam Dump Lines in the event the main condenser is unavailable, the atmospheric steam dump lines, in conjunction with the Auxiliary Feedwater System (AFW) and Condensate Storage Tank (CST), act to initially cool the Reactor Coolant System (RCS).
In the case of the Point Beach Nuclear Plant (a 2-Loop Westinghouse design),
there are two atmospheric steam dump lines per unit, one line per steam generator. Af ter the RCS has been initially cooled and depressurized to a specified temperature and pressure, the Residual Heat Removal System (RHR) is placed in operation, further reducing the temperature of the core.
Although RCS cooldown to RHR entry conditions using the atmospheric steam dump lines may be necessary following several classes of accidents involving a loss of the main condenser, the performance of the atmospheric steam dump lines in attaining subcooled conditions in the RCS to terminate primary to secondary flow following a steam generator tube rupture is most limiting.
The acceptability of the Point Beach Nuclear Plant FSAR analysis of a steam generator tube rupture with a loss of power to plant auxiliaries is based on the use of an atmospheric steam dump line to cool down the RCS.
Based on this accident analysis, an atmospheric steam dump line is considered operable when the RCS is capable of being cooled to RHR entry conditions through local manual or remote operation of the associated atmospheric steam dump valve within the time period assumed in the FSAR accident analysis for a steam generator tube rupture.
The licensee proposes adding the fol. lowing specification for the atmospheric steam dump lines as TS 15.3.4. A.5:
Both atmospheric steam dump lines shall be operable.
If either of the atmospheric steam dump lines is determined to be inoperable, restore the inoperable line to an operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
If operability cannot be restored, be in hot shutdown within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and cold shutdown within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Both lines are required to be operable due to the lack of redundancy for the limiting steam generator tube rupture event.
The proposed action times are acceptable based on the likely availability of the steam dump system and the main condenser, and the low probability of an event requiring use of the atmospheric steam dump lines during that period of time. The required action places the plant in cold shutdown if both atmospheric steam dump lines are not returned to an operable status in the allowed time because the atmospheric steam dump lines are not needed to perform a necessary function in that mode.
The proposed additional specification is acceptable because it is conservative in placing new operability requirements on the atmospheric steam dump system.
3.2 Crossover Steam Dump and Turbine Overspeed Protection Systems The crossover steam dump system is designed to vent the steam stored in the high pressure turbine and the moisture separator /rehea,ters (MSRs) to '
atmosphere following a unit trip in order to prevent the turbine from exceeding its design overspeed of 132 percent of: rated speed.
The crossover steam dump system is armed at a generator output above approximately 430 MWe.
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. A In addition to the crossover steam dump system, the turbine is provided with three different turbine overspeed protection systems which control steam-supply to the high pressure turbine. The mechanical overspeed trip mechanism and the Independent Overspeed Protection System (10PS) prevent an overspeed condition by rapidly closing the turbine stop and governor valves using independent trip mechanisms when an overspeed condition is sensed.
The auxiliary governor uses solenoid operated hydraulic dump valves to rapidly close the turbine governor valves when an overspeed condition or a mismatch between MSR pressure and generator output is sensed.
Each turbine governor valve must be operable or closed in order for the auxiliary governor overspeed protection function to be operable. Each of the systems described above reduce the probability of generation of a turbine missile with sufficient energy to damage safety-related structures, systems, or components.
The licensee proposes adding the following specification for the crossover steam dump system as TS 15.3.4.D:
The crossover steam dump system shall be operable.
If the crossover steam dump system is determined to be inoperable, reduce power to less than 480 MWe (gross) within three hours.
The crossover steam dump system is required to be operable since there is no redundant system which performs its function.
The licensee has determined that the turbine will not exceed 132 percent of rated speed following a unit trip when initially operating at less than 480-MWe (gross) regardless of the status of the crossover steam dump system.
Therefore, the proposed action is acceptable because it places the plant in a condition where the function of the crossover steam dump'is not required.
The required time to complete the action is acceptable based on the low probability of a unit trip requiring operation of the crossover steam dump system during that time.
The licensee proposes adding the following specification for the turbine overspeed protection systems as TS 15.3.4.E:
During power operation, at least one of the turbine overspeed protection systems that trips the turbine stop valves or shuts the turbine governor valves shall be operable.
If all three systems are determined to be inoperable, isolate the turbine from the steam supply within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
The licensee also proposed adding the following specification for the turbine stop and governor valves as TS 15.3.4.F:
Should one of the turbine stop valves or governor valves be declared inoperable, restore the inoperable valve to an operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
If operability cannot be restored, perform one of the following actions:
1.
Shut the affected valve within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
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Isolate the turbine from the steam supply within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
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,. The proposed additions of turbine overspeed protection system and turbine stop and governor valve specifications are acceptable because they are conservative-in placing new operability requirements on the turt,ine overspeed protection systems and the turbine stop and governor valves.
3.3 Auxiliary feedwater System Surveillance Requirements.
The licensee proposes adding a statement to TS 15.4.8.1.b which would require that a quarterly operability test of the turbine-driven AFW pump which comes due when not at power operation be performed during the subsequent startup within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of entering power operation.
The existing TS 15.3.4.A states that when the reactor coolant is heated above 350 *F, the reactor shall not be taken critical unless the turbine-driven AFW pump, together with its associated flowpath and essential instrumentation, is operable.
However, the reactor coolant pumps are not capable of maintaining the RCS at the necessary temperature for performance of the turbine-driven AFW pump operability test with its associated steam demand unless core heat generation is occurring.
The proposed addition to TS 15.3.4.A is acceptable due to the low probability of the turbine-driven AFW pump being inoperable when required to function during the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after entering power operation, due to the availability of the motor-operated AFW pumps, and because it is consistent with the requirements of the ASME Boiler and Pressure Vessel Code,Section XI,
" Rules for Inservice Inspection of Nuclear Power Plant Components," as implemented by 10 CFR 50.55a The licensee also proposes changing the frequency of the full stroke and valve position indication tests required by TS 15.4.8.1.c from monthly to quarterly.
This change would require testing of the AFW pump discharge valves and suction side service water supply valves at the same frequency as the motor-operated and turbine driven AFW pumps.
This proposed test interval is acceptable since it corresponds to the requirements of the ASME Boiler and Pressure Vessel Code,Section XI, " Rules for Inservice inspection of Nuclear Power Plant Components."
3.4 Technical Specification Bases The licensee submitted proposed bases changes for TS Section 15.3.4, " Steam and Power Conversion System," and TS Section 15.4.8, " Auxiliary feedwater System." These changes reflect the proposed TS changes to these two sections, and are explanatory only.
The staff has reviewed the revised bases submitted by the licensee, and found the revised bases to be consistent with the revised TSs, the system description, and the safety function presented in the FSAR.
H 3.5 Concluding Remarks l
lhe staff found the proposed TS additions to be acceptable.
The additions were conservative in that operability restrictions weie proposed for systems and components which currently have no TS operability requirements.
The revisions to the AFW system surveillance requirements were found to be i
acceptable based on the physical constraints and regulatory' requirements associated with the testing.
The bases revisions were found to be acceptable as they are administrative only.
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4.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Wisconsin State official
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was notified of the proposed issuance of the amendments.
The State official had no comments.
5.0 ENVIRONMENTAL CONSIDERATION
These amendments change 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 change a surveillance requirement.
The staff has determined' that the amendments involve 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 radi4 tion exposure..The Commission has previously published a 4
proposed finding that these amendments involve no significant hazards consi-deration and there has been no public comment on such finding (58 FR 43939).
Accordingly, these amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 651.22(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 these amendments.
6.0 CONCLUSION
i 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 the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
S. Jones Date:
April 20, 1994 I
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