ML20202J065
| ML20202J065 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 12/01/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20202J059 | List: |
| References | |
| NUDOCS 9712110031 | |
| Download: ML20202J065 (4) | |
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NUCLEAR REGULATORY COMMISSION 2
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WASHINGTON, D.C. 30n864001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED FINAL SAFETY ANALYSIS REPORT CHANGES AMENDMENT NO. 159 TO FACILITY OPERATING LICENSE NO. DPR-72 FLORIDA POWER CORPORATION. ET Al.
CRYSTAL RIVER UNIT NO. 3 NUCLEAR GENERATING PLANT DOCKET NO. 50-302
1.0 BACKGROUND
In NRC Inspection Report 50-302/97-09. dated July 14. 1997. the Nuclear Regulatory Commission (NRC or the staff) stated that the modifications made to l
the emergency diesel penerator (EDG) relaying scheme during the implementation of Modification 80-09 13-01 constituted an Unreviewed Safety Question (USQ) and that the modifications should be reviewed and approved by the NRC.
In its response dated August 11. 1997. Florida Power Corporation (FPC or the licensee) agreed that a USQ existed, and accordingly, by letter dated Seatemoer 12. 1997, submitted proposed modifications to the EDG relaying scieme for NRC review and approval. By letter dated November 7. 1997, the licensee provided additional information which did not affect the original no significant hazards consideration (62 FR 51165. September 30, 1997).
Modification 80-09-13-01 involved adding protective relaying to each EDG and rewiring some of the existing relaying. The modifications were intended to add more fault protection for each EDG and improve the availability of the EDG after fault conditions. The licensee is proposing Modification 97-08-01-01 to revise the EDG relay scheme to add more complete EDG and 4160V ES bus protection. However, the benefit of preventing damage to the EDG also has created the negative impact of increasing the )robability of a spurious operation of the aoded relays which could disaale the on-site emerCency AC Th? licensee is requesting a license amendment to reflect the changes source.
to the EDG protective scheme at Crystal River Unit 3 (CR-3) in the next revision to the Final Safety Analysis Report (FSAR),
2.0 EVALUATION The hcensee determined that the pre-modification relay configuration at CR-3 had some protective relaying for the EDG. However, the pre-modification relay protection scheme did not provide sufficient protection for the EDG during fault or overcurrent conditims. This created the potential of damaging the EDG and affecting the EDG's wailability for long-term accident mitigation.
Modifications 80-09-13-01 and 97-08 01-01 add new releying to each EDG and rewire some of the existing relay configurations to provide sufficient EDG relay protection at CR-3.
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2 Comoleted Modification 80-09-13-01 Modification 80 09-13 01 added the following protective relaying for each EDG at CR-3:
Device-51V AC time overcurrent relays with voltage restraint was added. Toese relays protect the EDG from damage by tripping the EDG engine device-86 lock-out relay if a fault or prolonged overcurrent condition is detected.
These relays provide new protection for 4160V ES bus phase-to-phase and three phase faults and backup arotection to the device-87 generator differential relaying for faults in the EDG generator or in the power cables between the generator and EDG breaker.
The voltage restraint feature of these relays prevents the EDG from tripping during overcurrent excursions resulting from block loading.
The device-51v AC time overcurrent relays are electromechanical induction disk relays.
Device-32 directional power relays were added.
These relays prevent an EDG from being overloaded when the EDG and 4160V ES bus are paralleled with the offsite power sources.
This relay sends a trip signal to e'.ch of the three tu offsite power source breakers if the EDG is called upon to deliver real power greater than 3498 kW to the 4160V Es bas.
There is one device-32 directional power relay for each EDG.
are solid state and require DC power to operate.The device-32 directional power relays i
This modification installed additional device 86B1 lock-out relays from two of three 4160V bus offsite power source breakers (230 kV switchyard) AC time overcurrent relaying (device-51B and device-51BN).
The two new device-86B1 lock-out relays were installed on the 4160V ES bus enclosure for use after control was transferred to the Remote Shutdown Panel.The two new device-86B1 lock-out relays are only functional after control is transferred to the Remote Shutdown Panel.
This circuit configuration maintains the function of the 4160V ES bus offsite power source breaker device-86B lock-out relay trips to the EDG engine device-86DG lock-out relay for Main Control Room or Remote Shutdown Panel operation.
Additionally. Modification 80-09-13 01 wired each of the three previously to the EDG engine device-86DG lock-out relays. existing 4160V ES bus o This relaying prevents the EDG from running and attempting to energize the associated 4160V ES bus after the 4160V bus has been de-energized due to an overcurrent or fault condition.
This modification also wired the previously existing device-64DG generator ground relay to the EDG engine device-86DG lock-out relay. The purpose of the device-64DG generator ground relay was to protect the EDG from a 4160V ES bus ground fault.
Another reason Modification 80-09-13-01 moved the device-64DG generator ground relay to the EDG engine device-86DG lock-out relay was to act as a backu) for the device-870G generator differential relaying for a ground fault in tae EDG generator or on the power cables between the EDG generator and the EDG breaker.
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Procosed Modification 97-08-01-01 Modification 97-08-01-01 changes the relay scheme to add the following protective relaying for each of the EDGs at CR3:
Modification 97-08-01-01 is adding more com)lete protection for each EDG and 4160V ES bus by installing a new device-86 EDG breaker lock-out relay for each EDG.
The device-86 EDG breaker lock-out relay trips and prevents subsequent closure of the EDG output breaker onto a bus during overcurrent or fault conditions. The previous modification would trip the EDG on these conditions but there was no relaying to keep the EDG from closing on the bus if the overcurrent condition still existed.
The tripping of the new breaker device-86B will also initiate an alarm on the Main Control Board.
A power available light will be located adjacent to the new EDG breaker device-86B to indicate that the lockout circuit has power available and is not actuated.
This modification will also return each EDG engine device-86DG lock-out relay circuits to the pre modification 80-09-13-01 configuration by moving the l
overcurrent relaying from the EDG engine device-86 lock-out relay to the new device-86B EDG breaker lock-out relay.
Returning some of the EDG relaying to the are-modification configuration will reduce the potential number of times the EDG is shut down unnecessarily.
The EDG will be allowed to operate in stand-by for fault or overcurrent conditions caused by a 4160V ES bus problem or for a false protective relay actuation.
The 870G relaying will still remain in ) lace to shut down the EDG upon receipt of a differential relay signal.
T11s is acceptable because the device-870G differential relaying can be depended upon to protect the EDG and the associated cabling.
The device-51V AC time overcurrent relaying with voltage restraint and device 64DG generator ground relay will be wired to the new 86B relay.
This configuration will 1. rip the EDG output breaker on overcurrent or ground fault conditions. Additionally, device-46DG negative sequence relay will be moved from the EDG breaker trip circuit to the new EDG breaker device-86B lock-out relay.
The device-46DG negative sequence relay is being connected to the new EDG breaker device-86B lock-out relay to prevent EDG output breaker cycling i
due to any unsymmetrical operating condition.
The two device-86B1 lock-out relays that were installed in Modification 80 13-01 for Remote Shutdown Panel operation will also be connected to the new EDG breaker device-86B lock-out relay.
If a Main Control Room fire / Cable Spreading Room fire occurred shorting out the conductors to the device 86B lock-out relay, an operator verification action to reset the EDG breaker device-86 lock-out relay is required.
This ;s considered acceptable since the new EDG breaker device-86B lock-out relay is located in the 4160V ES Switchgear Room with the associated Remote Shutdown Panel transfer switches.
Therefore, the operator can take appropriate actions within a reasonable. time.
Additionally, the need to check / reset the EDG breaker device 86B lock-out will be a planned verification action per plant procedure AP-990 for a Main Control Room / Cable Spreading Room fire.
This modification will not change the operation of the device-32 directional power relaying which was installed by Modification 80-09-13-01.
3.0
SUMMARY
The pre-modification EDG protective relay configuration at CR-3 was determined by the licensee to be inadequate to protect the EDG and 4160V ES bus from fault or overcurrent conditions. Modification 80-09-13 10 and Modification 97-08-01-01 involved adding more protective relaying to each EDG and 4160V ES bus. Protecting the EDG and 1-imiting the damage to the 4160V ES bus improves the probability of having the ED3 and 4160V ES bus available given a fault or overcurrent condition.
The introduction of additional relay protection may increase the 3robab'llity of a spurious relay operation impacting the availability of the E E.
However.
historical protective relay operation at CR-3 has been demonstrated to be l
relioble and spurious relay operation has been rare.
The staff concludes that the benefits of protecting the EDG and 4160V ES bus outweigh the slight increase in the probability of saurious relay operation. Therefore, the staff finds the modifications to the EE and 4160V ES bus protection scheme at CR-3 to be acceptable.
4.0 STATE CONSULTATIOy Based u on written notice of the proposed amendment, the Florida State officia had no comments.
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5.0 ENVIRONMENTAL CONSIDERATION
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The amendment changes reqcirements with respect to installation or use of a facility component locateo within the restricted area as defined in 10 CFR Part 20. The NRC 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 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 (62 FR 51165). 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 imaact statement or envi.onmental assessraent need be prepared in connection wit 1 the issuance of the amendment.
6.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safet public will not be endangered by operation in the proposed manner.y of the (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 Contributor: Mark Patt Date: December 1, 1997
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