ML20210A362
| ML20210A362 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 01/29/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20210A248 | List: |
| References | |
| NUDOCS 8702060462 | |
| Download: ML20210A362 (6) | |
Text
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- p* Krog'o, UNITED STATES l'
7,n NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 1 TO FACILITY OPERATING LICENSE N0. DPR-21 NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION, UNIT NO. 1 DOCKET NO. 50-245
1.0 INTRODUCTION
By letter dated January 28, 1986, the Northeast Nuclear Energy Company (NNECO) submitted a request for changes to the Millstone Nuclear Power
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Station, Unit No. 1.
On April 15, 1986, the licensee provided revisions for the technical specification pages in the submittal to correct minor errors and omissions, and to withdraw the request to change the 27.5 kv offsite power line rating to 23.ky.
This portion of the amendment would change the existing technical specifications by:
removing the underlined words in the section 3.9.B.2 as follows:
"3.9.B.2.
From and after the date that incoming power is not available from any 345 kv line, reactor operation shall be permitted provided both emergency power sources are operating and the isolation condenser system is operable. The NRC shall be notified, within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the precautions to be taken during this situation and the plans for restoration of incoming power. The minimum fuel supply for the gas turbine during this situation shall be maintained above 20,000 gallons."
8702060462 870129 PDR ADOCK 05000245 P
inserting a new limiting condition of operation as follows in section 3.9.B.3.
"3.9.B.3 From and after the date that power cannot be made available from the RSST, the plant shall be isolated from the grid within the next 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after which time reactor operation is permissible according to specification 3.9.B.2.
During the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period, both emergency power sources shall be operable. The minimum fuel supply for the gas turbine during this situation shall be maintained above 20,000 gallons.
If during the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> period it is determined that the plant cannot be operated isolated from the grid, be in at least HOT STANDBY within the next six (6) hours and in COLD SHUTDOWN within the following thirty (30) hours."
renumbering section 3.9 B.3 to 3.9.8.4 and section 3.9.B.4 to 3.9.8.5.
removing the underlined words in the bases section B.3.9.B as follows:
"B.3.9.B.
Normally, three 345 kv lines will be available to provide emergency power to the plant when the reactor is operating. However, adequate power is available with only one 345 kv line in service.
Therefore, reactor operation is permitted for up to seven days with only one 345 kv line in service to accommodate necessary maintenance, etc.
In the event that all 345 kv lines are out of service, continued reactor operation is permitted provided both onsite emergency power sources are operating with an adequate fuel supply. Two operational power sources provide an adequate assurance of emergency power availability under these circumstances.
In addition, the isolation condenser system is required to be operable as a standby heat removal system.
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Normally both the gas turbine-generator and diesel generator are required to be operable to assure adequate emergency power with no offsite power sources. However, due to the redundancy and reliability of offsite power, one of the two emergency onsite power sources may be out of service for limited periods of time providing two offsite power sources are available during these periods."
and adding the following new paragraph in bases section B.3.9.B.
"In the event that power cannot be made available from the RSST, continued reactor operation is permitted for the succeeding 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> provided both onsite emergency power sources are available with an adequate supply of fuel. Seventy-two hours of reactor operation provides adequate time for repairs of a reasonable nature or to isolate from the grid. When isolated from the grid, the plant is not susceptible to offsite induced transients.
If neither repair nor isolation is possible, an additional 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> is allowed for an orderly shutdown. Two operable emergency power sources provide adequate assurance of emergency power availability under these circumstances."
A Notice of Consideration of Issuance of Amendment to License and Proposed No Significant Hazards Consideration Determination and Opportunity for Hearing related to the requested action was published in the Federal Register on April 23, 1986 (51 FR 15404).
No comments or requests for hearing were received.
2.0 EVALUATION Each of the changes identified is addressed below:
3.9.B.2 The requested changes relate to the actions required upon a loss of 345 kv power. The Millstone Unit 1 plant is relatively unique in that it is designed to accomodate load rejections up to the full rating of the main generator without a turbine trip or reacto'r scram.
In the unlikely event of a complete loss of the offsite power grid, the main generator automatically disconnects from the grid and reduces output to supply the._
plant auxiliary load. The turbine bypass valves open to discharge reactor steam in excess of the auxiliary load requirements directly to the main con-denser. The loss of electrical load also causes automatic insertion of a pre-selected group of control rods (i.e., rod select insert feature) to compensate for the negative reactivity resulting from colder feedwater produced by the load rejection, so as to avoid a reactor trip. Load rejection will also automatically reduce core inlet recirculation flow until the system stabilizes (about 50 percent flow). Under these con-ditions, the reactor produces only that electrical power required to support plant operation.
Under the existing technical specifications, such a complete load rejec-tion (loss of all 345 kv lines) would require that the operators manually startup, synchronize, and load the emergency diesel generator and emergency gas turbine generator, provided the isolation condenser is operable.
If the isolation condenser is not operable or both emergency power sources are not operable the reactor must be shutdown and cooled by emergency safety features.
The lice 1see has requested that the technical specification requirements be changed to permit continued operation utilizing the nonnal heat sink, i.e., the main condenser, to avoid unnecessary challenge to the emergency power sources and safety features.
Deletion of the requirement for isolation condenser operability with no offsite power available will allow the main condenser to be used as the heat sink with the main generator supplying the house loads while repairs are being made to restore the isolation condenser and offsite 345 kv power operability, thereby reducing dependence on emergency power sources.
The staff agrees that continued reactor operation using the normal heat sink is the preferred mode of operation following load rejection events, primarily because this avoids an unnecessary challenge to the engineered safety features for emergency core cooling. Moreover, in the recent past, the staff has reconsnended several changes to avoid unnecessary fast starts of the emergency power sources, (e.g., IE Bulletin 85-15). Under the pro-posed change, the licensee would only be required to verify that the emergency diesel and gas turbine are operable and notify the NRC of the planned corrective actions based on the specific circumstances in-volved.
In the event of a planned reactor shutdown, the staff would expect the emergency power systems to be started, synchronized and loaded pre-ceding an orderly shutdown of the plant to avoid an unnecessary automatic quick start of the emergency diesel and turbine generators.
3.9.B.3 The licensee has proposed to add a new requirement for the loss of the reserve station service transformers (RSST), which can fail for reasons other than a loss of all 345 kv main transmission lines to the switchyard.
The RSST steps-down power from the main switchyard to supply power for the plant auxiliary equipment in the event of a loss of power from the main generator.
If the RSST is out of service, reactor trips would directly demand emergency power. Consequently, the licensee has proposed to initiate an orderly shutdown if the RSST cannot be restarted in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in hot standby within six (6) hours and cold shutdown within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> if it is determined that the plant cannot operate separated from the grid. This action is consistent with Regulatory Guide 1.93, " Availability of Electric Power Supplies," and is, therefore, acceptable.
B.3.9.B Removal of the requirement for the isolation condenser is accep-table for the reasons listed above under section 3.9.B.2.
The proposed paragraph to be added to this section provides an acceptable basis for the new limiting conditions of operation in section 3.9.B.3 above. On this basis, the proposed changes to Basis section 3.9.B are acceptable.
Subsequent to the January 28, 1986 proposed change, the licensee requested that the change from 27.6 kv to 23 ky, for the alternate offsite power line, be postponed. Therefore, no action is required for this request.
Based on the foregoing discussion, the staff concludes that the proposed changes will, overall, enhance the availability of electric power for the plant auxiliary needs and are, therefore, acceptable.
3.0 ENVIRONMENTAL CONSIDERATION
This amendment involves a change to a requirement with respect to the installation or use of facility components located within the restricted area as defined in 10 CFR Part 20. The 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 this amendment involves no significant hazards consideration and there has been no public coment on such finding. Accordingly, this 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 this amendment.
4.0 CONCLUSION
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, and (2) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: James J. Shea Dated:
January 29, 1987