ML17055E306
| ML17055E306 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 10/31/1988 |
| From: | Varga S Office of Nuclear Reactor Regulation |
| To: | NIAGARA MOHAWK POWER CORP. |
| Shared Package | |
| ML17055E305 | List: |
| References | |
| NUDOCS 8811090443 | |
| Download: ML17055E306 (12) | |
Text
In the Hatter of UNITED STATES NUCLEAR REGULATORY COMMISSION NIAGARA MOMAWK POWER CORPORATION (Nine Mile Point Nuclear Station Unit No.
1)
EXEMPTION Docket No. 50-220 Niagara Mohawk Power Corporation {the licensee) is the holder of Facility Operating License No. DPR-63, which authorizes operation of the Nine Mile Point Nuclear Station Unit No.
1 (NMP-1 or the facility).
The license
- provides, among other things, that the facility is subject to all rules, regulations and Orders of the Nuclear Regulatory Comnission (the Commission) now or hereafter in effect.
The facility is a boiling water reactor located at the licensee's site in Oswego County, New York.
By letter dated September 14, 1988, the licensee requested an exemption from the requirements of 10 CFR Part 50.62(c)(4),
which establishes the minimum iniection flow rate and the boron concentration for the standby liquid control system (SCLCS).
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Specifically, 10 CFR Part 50.62(c)(4) requires that each boiling water reactor must have an SLCS with a minimum flow capacity and boron content equivalent in control capacity to 86 gallons per minute (gpm) of 13 weight percent sodium pentaborate solution.
The licensee requests an exemption from this requirement to permit use of an equivalency formula considering sodium pentaborate concentration, pump flow rate, boron enrichment and the requirements for the liquid poison system which performs the function of the SLCS.
The requirement established by the regulation was intended to provide for prompt injection of negative reactivity into a boiling water reactor pressure vessel in the event of an anticipated transient without scram (ATWS) event.
The reactor vessel size used to establish the required flow rate of 86 gpm and the sodium pentaborate concentration of 13 weight percent was the large 251-inch diameter vessel used in the BWR/5 and BWR/6 designs.
The NMP-I reactor has a much smaller, 213-inch diameter, vessel.
For the NMP-I reactor, a lesser rate of iniection of sodium pentaborate and/or a smaller concentration will provide adequate shutdown margin in an ATWS event, equivalent to that called for by the regulation for the larger 251-inch diameter boiling water reactor vessel.
Refer to Generic Letter 85-03, "Clarification of Equivalent Control Capacity for Standby Liquid Control Systems,"
January 28, 1985.
The purpose of the rule is to reduce the risk from ATWS events by ensuring adequate shutdown margin.
In this case, tHe injection flow rate, increased enrichment, and boron concentration will provide the equivalent level of control capacity for the smaller NMP-1 reactor pressure vessel as that called for by ATWS
rule based on larger reactor pressure vessels.
Requiring NMP-1 to provide the flow rate-boron concentration capacity specified by the rule would not, in these particular circumstances, serve the underlying purpose of the rule.
Thus, the Commission's staff finds that there are specia1 circumstances in this case which satisfy the standards of 10 CFR Part 50.12(a)(2)(ii>.
As set forth in the safety evaluation for Amendment No. lo 1, issued concurrently with this Exemption.
The licensee provided a determination that special circumstances exist under 10 CFR 50.12(a).
As discussed
- above, the underlying purpose of the requirements of paragraph (c)(4) of 10 CFR 50.62 is to ensure adequate shutdown margin in an ATMS event.
The underlying purpose is achieved and served by using the equivalency formula discussed in the licensee's application for a Technical Specification amendment concerning the liquid poison system dated March 7, 1988.
Accordingly, the Commission has determined that pursuant to 10 CFR Part 50.l2(a), the Exemption, as described in Section III, is authorized by law and will not present an undue risk to the public health and safety and is consistent with common defense and security, and special circumstances are present for the Exemption, in that application of the regulation in these particular circumstances is not necessary to achieve the underlying purposes of 10 CFR Part 50.62(c)(4}.
Therefore, the Commission hereby grants the Exemption from paragraph (c)(4) of 10 CFR Part 50.62 to allow the consideration of the smaller
vessel size in determining the equivalent control capacity of 13 weight percent sodium pentaborate at 86 gpm for the liquid poison system at NMP-l.
Pursuant to 10 CFR Part 51.32, the Commission has determined that the granting this Exemption will have no significant impact on the environment (53 FR 43297).
This Exemption is effective upon issuance.
Dated at Rockville, Maryland, this 31day of October 1988.;
FOR THE NUCLEAR REGULATORY COMMISSION Gus C. Lainas, Acting Director Division of Reactor Projects I/II Office of Nuclear Reactor Regulation
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vessel size in determining the equivalent control capacity of 13 weight percent sodium pentaborate at 86 gpm for the liquid poison system at NMP-1.
Pursuant to 10 CFR Part 51.32, the Commission has determined that the granting this Exemption will have no significant impact on the environment (53 FR 43297).
This Exemption is effective upon issuance.
Dated at Rockville, Maryland, this 31 day of october 1988.
FOR THE NUCLEAR REGULATORY COMMISSION Steven A. Varga, Director Division of Reactor Projects I/II Office of Nuclear Reactor Regulation LA:PDI-1 CVogan 9/30/88*
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vessel size in determining the equivalent control capacity of 13 weight percent sodium pentaborate at 86 gpm for the liquid poison system at NMP-l.
Pursuant to 10 CFR Part 51.32, the Commission&has determined that the granting this Exemption will have no significant impact on the environment (53 FR
).
This Exemption is effective upon issuance.
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