ML20082T891
| ML20082T891 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/01/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20082T883 | List: |
| References | |
| NUDOCS 9505040222 | |
| Download: ML20082T891 (4) | |
Text
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A UNITED STATES f
S NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 20555 4001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.110 TO FACILITY OPERATING LICENSE NO. NPF-49 NORTHEAST NUCLEAR ENERGY COMPANY. ET AL.
MILLSTONE NUCLEAR POWER STATION. UNIT NO. 3 DOCKET NO. 50-423
1.0 INTRODUCTION
By [[letter::B15067, Application for Amend to License NPF-49,modifying SR 4.8.1.1.2.g.3 That Will Permit DG Full Load Rejection Tests to Be Performed at Realistic Plant Conditions Using Power Factor to Envelope Calculated Power Factor|letter dated December 23, 1994]], the Northeast Nuclear Energy Company (the licensee), submitted a request for changes to the Millstone Nuclear Power Station, Unit No. 3 Technical Specifications (TSs). The requested changes would change the acceptance criteria for the peak transient generator voltage from 4784 volts to 5000 volts during full load rejection tests of the diesel generator (DG), and also delete the 10-year surveillac:e requirement to perform a 110% pressure test of the DG fuel oil system.
2.0 EVALUATION Diesel Generator Full Load Rejection Test -
The proposed change to TS surveillance requirement (SR) involves using a power factor (PF) that will envelope the calculated PF during worst case loading conditions. To accommodate this test, the voltage limit for TS SR 4.8.1.1.2.g.3 is being revised. The proposed change to TS surveillance j
requirement 4.8.1.1.2.g.3 would permit the emergency diesel generator (EDG) full load rejection test to be performed at more realistic plant conditions.
i A full load rejection test demonstrates that the EDG has the capability to reject the total connected load without overspeed tripping or exceeding predetermined voltage limits. An EDG full load rejection may occur because of a system fault or inadvertent breaker tripping. TS Surveillance Requirement 4.8.1.1.2.g.3 at Millstone 3 requires verification that the EDG has the i
capability to reject a load of 4784 kW at unity PF without tripping or exceeding specified voltage limits. The proposed change in SR 4.8.1.1.2.g.3 of Millstone Unit 3 TS would change the acceptable peak transient voltage and PF. This change would permit the EDG full load rejection test to be performed at more realistic plant conditions using a PF that would envelope the calculated PF during worst case loading conditions.
Presently, the EDG full i
load rejection test at the Millstone 3 requires that the test be performed at i
unity PF and a peak voltage limit of 4784 volts during snd following a full load rejection test. The present load rejection test ! eing performed is 9505040222 950501 PDR ADOCK 05000423 P
1 i consistent with the current TS at Millstone 3 but is not considered to be a true representation of the EDG's ability to properly respond to an actual full load rejection.
The issue of performing the EDG full load rejection test has been raised in f
the past in NRC Information Notice (IN) 91-13, " Inadequate Testing of Emergency Diesel Generators (EDGs)."
It was determined that Vermont Yankee Generating Station was inadequately testing the EDG by using a unity PF.
Specifically, the plant surveillance test required that the EDGs maintain a load of 2500 to 2750 kW which is equivalent to 2500 to 2750 kVA'at a PF at i
unity (equal to 1). The licensee considered this limit sufficient to meet the maximum load of 2471 kW specified in the final safety analysis report (FSAR).
However, during subsequent analysis the licensee determined that the worst case EDG loading could actually reach 2751 kW.
In addition, the EDG would realistically experience an electrical PF of 0.85, causing the actual generator output current to be significantly higher. Therefore, it was determined that the original surveillance test did not adequately demonstrate I
the capability of the EDG to carry its worst case accident kW and inductive i
loading. As a result, the licensee modified its EDG testing requirements to ensure that both engine and generator is appropriately tested.
In addition, i
the Westinghouse Improved TS requires that the full load rejection test for the EDGs be performed at a voltage and power factor that is as close as possible to actual worst case loading.
Therefore, to ensure that the EDGs at Millstone 3 are tested under conditions that are as close as possible to worst case loading conditions, the licensee l
intends to perform the subject surveillance with a PF between.84 and.86.
However, this PF will result in a higher transient voltage during the full load rejection test. Thus, the licensee is proposing to revise the acceptance criterion regarding transient voltage limits. Currently, the voltage limit is j
4784 volts during and following a load rejection. The licensee's proposal i
changes the acceptance criterion to:
"The generator voltage shall not exceed 5000 volts during and 4784 volts following the load rejection." The licensee has determined that the peak transient voltage of 5000 volts experienced during the revised testing will be of a very short duration and will not j
exceed the design limits of the EDGs.
The staff agrees that the proposed change to the load rejection test at Millstone 3 is more representative of worst case loading conditions during an actual full load rejection. Additionally, the changes adequately address the concerns expressed by the staff in NRC IN 91-13 and the revised voltage limits do not exceed the design limits of the EDGs during the load rejection test.
Therefore, the staff concludes that the above changes will more accurately demonstrate the capability of the EDGs to perform their safety function and are acceptable.
Emergency Diesel Oil System Pressure Test -
The proposed amendment deletes the surveillance requirement of TS 4.8.1.1.2.1.2 which involves performing a pressure test of portions of the emergency diesel fuel oil system. Alternative testing for the tanks and
. piping would include leak testing at hydrostatic head pressure with the tanks filled to design capacity and would be governed by TS 4.0.5.
The existing Technical Specification 4.8.1.1.2.1.2 requires a pressure test of those portions of the diesel fuel oil system designed to Section III, subsection ND of the ASME Boiler and Pressure Vessel Code. This pressure test is required to be performed at 110 percent of the system design pressure.
This test is consistent with the acceptable method which is presented in NRC Regulatory Guide 1.137, " Fuel-011 Systems for Standby Diesel Generators."
Regulatory Guide 1.137 adopts Section 7.3 of ANSI N195-1976, " Fuel Oil Systems for Standby Diesel Generators" which specifies testing in accordance with Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," of the ASME Code.Section XI Article IWD-5000 in turn requires testing of components at 1.10 times the system pressure for systems with design temperatures loss than 200*F or in the case of atmospheric storage tanks, the hydrostatic head, developed with the tank filled to its design capacity, is considered to be an acceptable test pressure.
The licensee has requested the proposed change due to the diesel fuel oil system's incompatibility with the requirements of the performance of a pressure test at 110 percent of system pressure. The diesel fuel oil tank is vented to atmosphere without an existing ability to isolate and pressurize the tank in order to perform the pressure test. The fulfillment of ASME Code requirements is achieved by the performance of the alternate testing i
consisting of leak testing with the associated atmospheric tanks filled to design capacity. The alternate test is considered to provide equivalent assurance of the tank and piping integrity in that filling the tank to design capacity and verifying that no loss of inventory occurs is comparable to 1
pressurizing the system and monitoring for any decrease in pressure. The diesel fuel oil system is classified as ASME Code Class 3 in accordance with the guidance of Regulatory Guide 1.26, " Quality Group Classifications and Standarde for Water, Steam, and Radioactive-Waste-Containing Components of Nuclear Power Plants." Technical Specification 4.0.5 requires testing of ASME Code Class 1, 2, and 3 components in accordance with Section XI of the ASME Code. The existing TS 4.8.1.1.2.1.2 is, therefore, seen as redundant to the requirements of TS 4.0.5 in that ASME Section XI testing is required, but the specific testing methodology of TS 4.8.1.1.2.1.2 is not practical for the current design of the diesel fuel oil system.
Upon review of the licensee's submittal, the staff concludes that the alternative testing allowed by Section XI of the ASME Code is an adequate inservice testing methodology and that the performance of the inservice testing is required by TS 4.0.5.
Therefore, the deletion of TS 4.8.1.1.2.1.2 is deemed acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.
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4.0 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 previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (60 FR 8751). 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.
5.0 CONCLUSION
The Commission 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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributors: MD Pratt VL Rooney Date: May 1, 1995