ML14183A355
| ML14183A355 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 09/11/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML14183A354 | List: |
| References | |
| NUDOCS 9609130195 | |
| Download: ML14183A355 (6) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 174 TO FACILITY OPERATING LICENSE NO. DPR-23 CAROLINA POWER & LIGHT COMPANY H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261
1.0 INTRODUCTION
By letter dated January 30, 1996, as supplemented May 20, 1996, the Carolina Power & Light Company (licensee) submitted a request for changes to the H. B.
Robinson Steam Electric Plant, Unit No. 2 (HBR), Technical Specifications (TS). The requested changes would add a 24-hour full-load emergency diesel generator (EDG) testing provision, which will be performed at a refueling interval. The proposed TS amendment also (1) revises the EDG (protective) trip bypass testing provision, which is usually performed at each refueling outage during unit shutdown, to separate it from the current TS section and incorporate it into the EDG inspection section and (2) modifies the frequency of the EDG trip bypass test and the EDG inspection so that they can be performed on-line at each refueling interval. The request to change a requirement to inspect the EDGs "at each refueling" to read "at least once every refueling interval" is still under review and will be addressed separately at a future date. The May 20, 1996, letter provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 EVALUATION Because EDGs provide the onsite AC standby power source to shutdown and maintain the reactor in a safe condition under a design basis accident (DBA),
that is, a loss of coolant accident (LOCA) coincident with a loss of offsite power (LOOP) event, the EDG is among the most risk significant components in a nuclear power plant that affect the core damage frequency (CDF). To achieve low CDF, EDGs must maintain adequate reliability and availability levels.
Each EDG at HBR consists of a 12-cylinder Fairbanks-Morse engine directly coupled to a Fairbanks-Morse 480-Vac generator. The EDGs are designed to start and attain rated speed (i.e., 900 rpm) and voltage within 10 seconds and assume the required loads automatically started during a safeguards actuation within 50 seconds.
The NRC staff has reviewed the proposed changes to TS Section 4.6.1. The evaluation of each of the proposed changes follows.
2.1 Revision of TS Section 4.6.1.2 Current TS Section 4.6.1.2 states:
9609130195 960911 1
PDR ADOCK 05000261 PPD
-2 Automatic start of each diesel generator, load shedding and restoration to operation of particular vital equipment, initiated by a simulated loss of all normal A-C station service power supplies together with a simulated safety injection signal.
This test will be conducted each refueling interval, to assure that the diesel generator will start and assume required load within 50 seconds after the initial starting signal. During this test, the diesel protective bypasses listed in Specification 3.7.1.d shall be demonstrated to be operable by simulating a trip signal to each of the trip devices that is bypassed and observing that the diesel does not trip.
The EDG (protective) trip bypass test and the EDG safety injection (SI)/LOOP test were performed at each refueling outage when the unit was shutdown. The licensee proposes that the EDG trip bypass testing requirement be moved from the current TS Section 4.6.1.2 to Section 4.6.1.3. The proposed change will allow the EDG trip bypass test to be performed during an EDG outage.
The NRC staff has reviewed the improved standard TS (STS), NUREG-1431, for Westinghouse plants to evaluate whether the EDG trip bypass test and the EDG SI/LOOP test should be performed together, thus requiring them to be in the same TS section. The NRC staff finds that there is no basis for requiring these two tests to be performed together and to be located in the same TS sections. Because moving the EDG trip bypass test from the SI/LOOP testing provision section would not affect the ability of the EDGs to mitigate an accident, the NRC staff concludes that the licensee's proposed request is acceptable.
2.2 Revision of TS Section 4.6.1.3 With incorporation of the EDG (protective) trip bypass test into the EDG inspection section (i.e., TS Section 4.6.1.3), the licensee proposes to modify how EDG trips would be observed by changing the last clause of the EDG trip bypass testing provision from "observing that the diesel does not trip" to "observing that the diesel does not receive a trip signal." Thus, the new TS Section 4.6.1.3 would read as follows:
Each diesel generator shall be inspected at each refueling.
During this test, the diesel protective bypasses listed in Specification 3.7.1.d shall be demonstrated to be operable by simulating a trip signal to each of the trip devices that is bypassed and observing that the diesel does not receive a trip signal.
The purpose of the EDG trip bypass test is to demonstrate that EDG non critical protective features listed in TS Section 3.7.1.d (i.e., low lube oil pressure, low coolant pressure, high coolant temperature, high crankcase pressure, and engine start failure) are bypassed during a DBA, but EDG critical protective features (such as engine overspeed and generator differential) would trip the EDG to avoid substantial damage to the EDG. The design is based on logic that the EDG's availability to mitigate the DBA is more critical than protecting the engine against minor problems that are not detrimental to emergency operation of the EDG. The non-critical trips are
-3 bypassed during DBAs, but provide an alarm on an abnormal engine condition.
The alarm provides the operator with sufficient time to react appropriately.
The testing of the EDG protective trip bypass is accomplished during an SI/LOOP test by a manual key-lock switch which is placed in "Trips Defeat" position to test the trip bypass feature. During monthly testing the switch is placed in "Trips in Service" position. When a jumper is placed across a set of contacts simulating a device actuation, the EDG shutdown relay should energize, but the EDG stopping relay should remain de-energized. The only difference between the proposed test and the testing during SI/LOOP test is an additional jumper, which is required across relay TD3 contacts 1/5 to simulate EDG operation. Therefore, with the requested TS change, the licensee will manually jumper TD3 Contacts 1/5 to simulate the EDG operation without actually running the EDG and observe that the EDG does not receive a trip signal when simulating each EDG protective trip device actuation. The NRC staff has reviewed the licensee's schematic diagram and its control logic for the EDG trip bypass test and finds that the proposed change will achieve the same result. Therefore, the NRC staff finds the proposed TS section 4.6.1.3 acceptable.
2.3 Addition of TS Section 4.6.1.5 The licensee proposes to add a new TS Section 4.6.1.5 for 24-hour full-load testing of the EDGs at a refueling interval, as no such requirement currently exists at HBR. The TS Section 4.6.1.5 states:
At each refueling interval, each diesel generator shall be tested by manually-initiated start, followed by manual synchronization with other power sources, and verification that each diesel generator is loaded and operates for > 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. During two hours of this test, the load shall be maintained between 2650 kW and 2750 kW.
During the remaining 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> of this test, the load shall be maintained between 2400 kW and 2500 kW'.
The power factor shall be maintained between 0.8 and 0.9 during the entire test.
The minimum and maximum kW values are included as guidance to avoid overloading of the engine. Loads in excess of this range for special testing under direct monitoring of the manufacturer or momentary variations due to changing bus loads shall not invalidate this test.
Section 2.2.9, "Endurance and Margin Test," of Regulatory Guide (RG) 1.9, "Selection, Design, Qualification, and Testing of Emergency Diesel Generator Units Used as Class lE Onsite Electric Power Systems at Nuclear Power Plants,"
requires demonstrating the full-load carrying capability of the EDG at a power factor between.8 and.9 for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> are at a load equal to 105 to 110 percent of the continuous rating of the EDG, and 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> are at a load equal to 90 to 100 percent of its continuous rating.
Although the licensee has not committed to RG 1.9 to perform 24-hour full-load testing of the EDGs at HBR, the licensee proposes to add 24-hour full-load testing to demonstrate reliability of the EDGs and to ensure that the EDGs can
-4 withstand accident loading conditions. In accordance with the latest EDG loading calculation, the maximum loading has been determined to be 2542 kW for EDG A and 2583 kW for EDG B. The NRC staff has reviewed the proposed TS Section 4.6.1.5 and its footnote and compared it with the improved STS. The NRC staff finds that it includes all the power factors and EDG loading conditions that are necessary to ensure that the EDG is tested under loading conditions that are as close to design conditions as possible and also includes the EDG loading ranges to avoid routine overloading of the EDG that could result in more frequent teardown inspections.
Since the proposed TS change is consistent with the recommendation provided in the RG and the improved STS, the proposed TS testing verifies the endurance of the EDGs and demonstrates its full-load carrying capability, and will not affect the ability of the EDG to perform its design function. On this basis, the NRC staff concludes that the proposed addition of TS Section 4.6.1.5 is acceptable.
2.4 Addition of Two Paraqraphs to Basis Section 4.6.1. "Diesel Generators" The licensee proposes to add paragraphs to the basis of TS Section 4.6.1.5 regarding the addition of the 24-hour full-load test and providing details of the EDG's loading values. The NRC staff has reviewed these paragraphs and finds that they provide an adequate basis for modifying TS 4.6.1.5. Thus, the NRC has no objection to the proposed TS basis change.
However, because the basis change to TS 4.6.1.2 involves a TS change still under active NRC review, it will be addressed separately.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the State of South Carolina official was notified of the proposed issuance of the amendment. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes the 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 (61 FR 7546). 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,
-5 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 Contributor:
P. Kang Date: September 11, 1996
AMENDMENT NO. 174 TO FACILITY OPERATING LICENSE NO. DPR H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DISTRIBUTION:
Docket File PUBLIC PD II-1 Reading File S. Varga J. Zwolinski OGC G. Hill (2)
C. Grimes - DOPS/OTSB P. Kang, EELB J. Calvo. EELB ACRS OPA OC/LFDCB E. Merschoff, R-II cc:
Robinson Service List