ML17054B608
| ML17054B608 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 04/29/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17054B607 | List: |
| References | |
| GL-84-09, GL-84-9, NUDOCS 8505090138 | |
| Download: ML17054B608 (8) | |
Text
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/y kak*y4 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION NIAGARA MOHAWK POWER CORPORATION NINE MILE POINT, UNIT NO.
1 RECOMBINER CAPABILITY RE UIREMENTS OF 10 CFR 50.44(c)(3)(ii)
~Back round On December 2, 1981, the NRC amended 10 CFR 50;44 of its regulations by addition of the provisions in 10 CFR 50.44(c)(3).
One of these provisions requires licensees of LWRs, that rely upon purge/repressurization systems as the primary means of hydrogen control, to provide a recombiner capability by the end of the first scheduled outage after July 5, 1982, of sufficient duration to permit the required modifications.
Those plants for which notices of hearing on applications for construction permits were published on or after November 5, 1970, are not permitted by 10 CFR 50.44(e) to rely on purge/repressurization systems as the primary means for hydrogen control.
Therefore, these plants are not affected by the requirement for recombiner capability.
However, Nine Mile Point, Unit No.
1 is affected by the new requirement.
As a result of the new inerting requirements in 10 CFR 50.44(c)(3),
the BWR Mark I Owners Group undertook a substantial program to demonstrate that the Mark I plants potentially affected by the recombiner capability requirements of the rule do not need to rely on the safety grade purge/repressurization system required by the original 10 CFR 50.44 rule as the primary means of hydrogen control.
Extensive review and independent studies by the NRC staff generally supported the findings of the Mark I Owners Group program.
The Commission has determined that a Mark I BWR plant will be found to not rely on purge/repressurization systems as the primary means of hydrogen control, if certain technical criteria are satisfied.
These criteria were provided in the Generic Letter 84-09 (Reference 1), dated May 8, 1984, which was sent to all licensees of operating reactors.
Therefore, the recombiner capability defined in 10 CFR 50.44(c)(3)(ii) need not be furnished for those inerted Mark I BWR containments where the licensees are able to demonstrate that the Generic Study (Reference
- 2) is applicable to the licensee's plant and that the following three criteria are met:
(1) the plant has Technical Specifications requiring that, when the containment is required to be
- inerted, the containment atmosphere be less than four percent oxygen; (2) the plant has only nitrogen or recycled containment atmosphere for use in all pneumatic control systems within containment; and (3) there are no potential sources of oxygen in containment other than that resulting from radiolysis of the reactor coolant.
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E Most of the affected Mark I BWR plants have Containment Atmosphere Dilution (CAD) Systems utilizing either nitrogen or air.
In order to clarify the staff's position regarding these
- systems, Generic Letter 84-09 stated that a plant that has a "safety grade" purge/repressurization system designed to conform with the general requirements of Criteria 41, 42 and 43 of Appendix A of 10 CFR Part 50 and installed in accordance with 10 CFR 50.44(f) or 10 CFR 50.44(g) must continue to have that system, even though it may be determined with respect to 10 CFR 50.44(c)(3) that the plant does not rely on that system as the primary means for hydrogen control; thus, a decision on recombiner capability does not affect the requirements of 10 CFR 50.44(f) and 10 CFR 50.44(g) for the "safety grade" purge/repressurization system.
Evaluation In a letter dated June 8, 1984, (Reference 3), the licensee for Nine Mile Point, Unit No. 1, the Niagara Mohawk Power Corporation, submitted a partial response to the staff's Generic Letter 84-09.
The licensee stated that the criteria presented in Generic Letter 84-09 are satisfied for Nine Mile Point, Unit 1 and therefore, a recombiner capability is not required.
The licensee completed its response concerning the applicability of the generic study (Reference
- 3) to Nine Mile Point, Unit No.
1 with two further submittals, dated June 29 and July 31, 1984 (References 4 and 5).
The staff has reviewed the compliance of Nine Mile Point, Unit No.
1 with the criteria presented in Generic Letter 84-09.
We have found that the licensee has participated in the generic study (Reference
- 2) made by the BWR Owners Group.
The main parameter regarding the applicability of the study was found to be the ratio of the core thermal power to the free drywell volume.
The applicability of the study to Nine Mile Point, Unit No.
1 was addressed in Chapter 1.3 of the study.
We agree that the conclusions of the generic study are applicable to Nine Mile Point, Unit No. 1, and that the following three criteria of Generic Letter 84-09 are satisfied:
( 1)
Nine Mile Point, Unit 1 Technical Specification 3.3. 1 requires that when the containment is inerted, the containment atmosphere is to include less than four percent oxygen.
This satisfies the first of the three criteria of Generic Letter 84-09.
(2)
Nine Mile Point, Unit 1 does not have any pneumatic controls inside the containment.
The power operated valves located inside containment are motor operated.
The relief valves are actuated by electrical solenoids.
The CAD system at Nine Mile Point, Unit 1 uses nitrogen as its working f1 ui d.
Based on the above discussion, we find that Nine Mile Point, Unit 1
meets the second of the three criteria of Generic Letter 84-09.
/
(3)
The licensee performed an engineering study to identify the potential sources of oxygen in the containment.
The only source of oxygen found was the radiolysis of the reactor coolant.
The instrument and service air supplies to the containment are disconnected prior to plant startup.
The plant does not utilize MSIV leakage control systems and the containment access openings rely on compression fittings.
Nitrogen is used, where necessary, to pressurize containment penetrations.
Air in any leakage past the purge valves is not expected since the containment would be at a higher pressure relative to atmosphere following onset of an accident.
Accordingly, we find that Nine Mile Point, Unit No.
1 satisfies the third of the three criteria of Generic Letter 84-09.
Conclusions We conclude that a recombiner capability for Nine Mile Point, Unit No.
1 is not required since the criteria defined in Generic Letter 84-09 have been satisfied.
Principal Contributor:
P.
Salminen Dated:
1
4
References:
( 1)
Letter from D. G. Eisenhut to All Licensees dated May 8, 1984, "Recombiner Capability Requirements of 10 CFR 50.44(c)(3)(ii)"
(2)
"Gener ation and Mitigation of Combustible Gas Mixtures in Inerted BWR Mark I Containments,"
by F.
R. Hayes, L. B. Nesbitt and P.
P. Stancavage.
Technical Report NEDO-22155/82-NEDO-69/CLASS 1/June 1982.
(3)
Letter from C. V. Mangan, NM, to D. B. Vassallo, NRC, dated June 8, 1984, "Recombiner Capability Requirements of 10 CFR 50.44(c)(3)(ii)."
(4)
Letter from T.
E. Lempges, NM, to D. B. Vassallo, NRC, dated June 29,
- 1984, "Recombiner Capability Requirements of 10 CFR 50.44(c)(3)(ii)."
(5)
Letter from C.
V. Mangan, NM, to D. B. Vassallo, NRC, dated July 31,
- 1984, "Recombiner Capability Requirements of 10 CFR 50.44(c)(3)(ii)."
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