ML20128B398
| ML20128B398 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 05/14/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20128B394 | List: |
| References | |
| TAC-57643, NUDOCS 8505240516 | |
| Download: ML20128B398 (5) | |
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UNITED STATES
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' NUCLEAR REGULATORY COMMISSION r, '
- j WASHWGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION.
SUPPORTING AMENDMENT NO. 46 TO FACILITY OPERATING LICENSE NO NPF-5 GEORGIA POWER COMPANY OGLETHORPE POWER CORPORATION MUNICIPAL ELECTRIC AUTHORITY OF GEORGIA CITY OF DALTON, GEORGIA EDWIN I. HATCH NUCLEAR PLANT, UNIT NO. 2 DOCKET NO. 50-366 Introduction g
-By letter dated May 9, 1985, Georgia Power Company (the licensee) requested an emergency change to Edwin I. Hatch Nuclear Plant, Unit No. 2, Technical Specification (TS).3.8.2.6 dealing with setpoints for overcurrent protective i
devices for electrical penetrations installed in the primary containment.
The licensee is requesting approval of either of two separate proposed revisions to the TSs. The licensee's preferred revision would remove all
'setpoints from Table 3.8.2.6-1, " Primary Containment Penetration Conductor Overcurrent Protective Devices." The alternate revision would modify the setpoints of four specific breakers serving the drywell cooling unit and the drywell cooling return air fans. Two additional changes, of an administrative nature, were requested. These changes are common to either proposed revision. One administrative change corrects a-typographical error in the parts listing for a component. The other administrative change revises motor control center frame identifications for two breakers for circuits which have been moved. According to the licensee, these administrative changes would not affect unit operation but are necessary to maintain the technical accuracy of the table. During the review, questions were raised concerning the surveillance requirements of TS 4.8.2.6.1.a.2.
Removal of all setpoints from Table 3.8.2.6-1 was not evaluated, as this did l
not appear appropriate in the context of an Emergency TS review.
l Additionally, two changes of an administrative nature, as proposed by the licensee, were not addressed.
Background
1 During scheduled surveillance testing, four breakers were discovered, which must have their trip setpoints set at values higher than those currently specified in Table 3.8.2.6-1, in order for their associated circuits to i
function properly. TS Table 3.8.2.6-1 lists trip setpoints (in amperes) for circuit breakers which provide overcurrent protection for electrical l'
penetrations through the primary containment. The basis for the trip setpoint specification is the protection of the electrical penetration from 8505240516 850514 PDR ADOCK 05000366 P
PDR l
the effects of overcurrent. However, the values listed in the table correspond to the current at which damage to the connected load.or associated cables could occur. This amount of current is generally much lower than that at which damage to the penetration itself would occur.
The four breakers not in conformance with Table 3.8.2.6-1 are associated with the drywell cooling unit and the drywell cooling return air fans. The drywell coolers consist of a fan and cooler arrangement and are used to provide temperature control within the drywell. TS 3.8.2.6 allows the plant to startup and continue operation when the trip setpoints are not met, provided that the associated equipment (in this case the drywell cooling unit
. and'the drywell cooling return air fans) be de-energized. The drywell coolers are normally in continuous operation when the plant is at nomal operating temperature.
Failure to grant the emergency change in TSs would
. prevent the unit from restarting due to the increased drywell temperatures-that would~ result if these fans were de-energized. The unit is currently shutdown for refueling with restart scheduled for May 12, 1985.
This request for an emergency change to TS 3.8.2.6 is similar to a previous emergency request filed by the licensee (submittals of August 27, 1984, and September 20,1984) and granted by the NRC on September 28, 1984. Apparently the need to change the setpoints in Table 3.8.2.6-1 for the drywell cooling unit and the drywell cooling return air fans was not recognized at that time. The licensee states in their submittal of May 9,1985, that a review has been conducted to assure that no other breakers listed in Table 3.8.2.6-1 require a similar modification of their setpoints.
Evaluation
-Electrical overload protection for containment penetrations is essential to protect the integrity of the reactor. containment structure.. Technical guidance is provided in NRC Regulatory Guide 1.63, " Electric-Penetration Assemblies in Containment Structures for Water-Cooled Nuclear Power Plants,"
l dated October 1973. This guide basically endorses IEEE Standard 317-1972 as an acceptable method of complying with the regulations. The licensee l
committed to conform to Regulatory Guide 1.63, as stated on page 8.3-21 of the Hatch Unit 2 Updated Final Safety Analysis Report. A major feature of L
these documents is to specify redundant (single-failure proof) overload protection at current-time values below the damage threshold for the penetration' assembly.
The licensee has stated that two of the penetration assemb1 as involved (Items g.2 and g.3, on Table 3.8.2.6-1) are General Electric 100-Series penetrations using #8 wire size and are capable of withstanding the following current conditions:
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1.
Steady state current rating - 50 amps 2.
Startup current rating (30 seconds) - 350 amps 3.
Short circuit current rating (8 cycles or 0.133 seconds) - 3300 amps RMS asymmetrical or 2350 amps symmetrical I
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v LThe other two affected penetrations (Items f.10 and f.13, on Table 3.8.2.6-1) are General Electric'100 Series Electric Penetration Assemblies using #6 size
- wire. Reviews of the specifications for this type penetration assembly indicate the following current versus time ratings for each circuit in the
._ penetration:
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- 1. -
Steady state current rating - 70 am
~5tartup current rating (30 seconds)ps 2.
- 490 am Snort circuit current rating.(0.133 seconds)ps 3.
5200 amps RMS-asymetrical or 3850 amps symetrical The circuit. breakers-involved are Westinghouse Mark 75 HFB type molded case magnetic only (providing short circuit protection only) breakers. Reviews of manufacturer's specification sheets and characteristics trip curves for this type breaker indicate an interrupt time of approximately 0.016 seconds (one cycle). Backup protection,-assuming single failures of these breakers, as.
F
. required by Regulatory Guide 1.63, is provided by fuses located in the motor 4
l control centers.
As noted above, the trip setpoints presently listed in TS Table 3.8.2.6-1 are not based solely on protection of containment penetrations. The trip setpoints of the affected breakers are based on general guidelines designed to protect cables inside containment, assuming a ground fault in the load.
The Georgia Power Company procedure for determination of the setpoints recommends that the setpoint be 200% of locked rotor amperage (LRA), if known,'or otherwise be set at 12 times full load amperage. On the other hand,.the vendor recommends setting the setpoint at 160% of LRA. Since the function of the motor is lost before the breaker opens, the protection of the
. cables.is an economic censideration rather than a safety consideration.
Therefore, changes to the trip setpoints do not affect plant safety as long as they provide protection for the penetration by remaining within the current versus time limits and allow sufficient current to be supplied to the i
loads.
'We have determined that to protect the integrity of.the penetration and to comply with Regulatory Guide 1.63, any setting between the 160% LRA value and the 30 second startup current limit (350 amps for penetrations using #8 wire, 490 amps for penetrations using #6-wire) is acceptable. This is based, in part, upon the large margin afforded by the breaker, which has a fast response time compared to 30 seconds. Since the setpoint values proposed by the licensee'are within the 30-second startup current limit, they also are acceptable.
.Although we find the new setpoints proposed by the licensee to be acceptable, we have certain concerns which need to be addres'.4 by the utility. Backup i
protection assuming single failures of these breakers, as requi' red by y
Regulatory Guide 1.63 (October 1973), is provided by fuses located in the motor control centers. The licensee has agreed to verify before startup that these fuses are properly sized to provide backup protection should the breakers fail.
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i During the course of our review of this matter, a question arose regarding the surveillance testing of the protection devices, prescribed by Section 4.8.2.6.1.a.2 of the Hatch Unit 2 TSs.
If a test current approximately equal to the trip setpoint is used, the breaker may or may not trip.
Since our basis for the acceptability of the setpoint value itself is the 30-second
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rating of the penetration, we find a test current at any value above the setpoint bu.t not to exceed the value of the 30-second rating'to be an adequate test to satisfy TS Section 4.8.2.6.1.a.2 for this plant.
In a telecon on May 10, 1985, between Mr. Ray Baker of Georgia Power Company and Mr. J. T. Beard, Mr. John Stolz, and Mr. George Rivenbark, the licensee committed to conduct such tests as defined above. NRC Region II (Mr. Roger Walker) has also agreed to this interpretation.
The NRC staff discussed the proposed revision of Table 3.8.2.6-1 which would delete all setpoints from the table and the two administrative changes with the licensee. These items will be reviewed by the NRC staff as part of a routine Technical Specification change request.
Emergency Circumstances The emergency circumstances result from the licensee's late discovery (during recent surveillance tests performed during the current refueling outage) that the trip setpoints for the breakers that provide overcurrent protection for some of the containment electrical penetrations, as specified by the TSs, are too low for startup of the equipment powered by these conductors. These setpoints must be changed in order to startup and operate the plant. The TS values for these setpoints must be changed in order to allow operation at the changed setpoints. The licensee infonned us in its letter of May 9, 1985, requesting the TS change that the unit would be ready to startup by May 12, 1985.
Final No Significant Hazards Consideration Determination The Comission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards consideration if operation of the facility in accordance with the amendment would not:
(1)
Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3)
Involve a significant reduction in a margin of safety.
The requested change is a minor change in the overcurrent protection setpoints for four circuit breakers protecting four containment penetration electrical conductors. As noted above in this Safety Evaluation, we have concluded that this change is acceptable. The change does not affect the manner in which the plant is operated or the design bases for the plant.
.o Therefore, we conclude that :
(1) Operation of the facility in accordance with the amendment would not significantly increase the probability or consequences of an accident previously evaluated.
(2) Operation of the facility in accordance with the amendment would not create the possibility of a new or different kind of accident from any accident previously evaluated.
(3) Operation of the facility in accordance with the amendment would not involve a significant reduction in a margin of safety.
Accordingly, we conclude that the amendment to Facility Operating License NPF-5 revising the overcurrent protection setpoints of the four circuit breakers involves no significant hazards considerations.
The State of Georgia was consulted on this matter and had no comments on the determination.
Environmental Considerations The amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
We have 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 made a final no significant hazards consideration finding with respect to this amendment. Accordingly, the emendment meets the eli for categorical exclusion set forth in 10 CFR 51.22(c)(9)gibility criteria 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.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the Consnission's regulations, and the issuance of the amendment will not be inimical to the coninon defense and security or to the health and safety of the public.
Dated: May 14, 1985 Principal Contributor:
W. Swenson, J. T. Beard, G. Rivenbark
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