ML20204K056
| ML20204K056 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 04/09/1985 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20204K046 | List: |
| References | |
| GL-84-09, GL-84-9, TAC-56045, TAC-56046, TAC-56541, NUDOCS 8504250301 | |
| Download: ML20204K056 (7) | |
Text
i SAFETY EVALUATION REPORT EDWIN I. HATCH NUCLEAR PLANT, UNIT 1 RECOMBINER CAPABILITY REQUIREMENTS OF 10 CFR 50.44(c)(3)(ii) (RESPONSE TO GENERIC LETTER NO. 84-09)
Background
On December 2,1981, the NRC amended 650.44 of its regulations by addition of the provisions in 650.44(c)(3). One of these previsions 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 pennit the required modifications. Those plants for which notices of hearing on appli-cations 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, Hatch, Unit 1 is-affected by the new requirement.
As a result of the new inerting requirements in 550.44(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 l
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 co,ntrol.
Extensive review and independent studies by the NRC staff generally supported the findings of the Mark I Owners Group program.
850'4250301 850409 PDR ADOCK 05000321 P
. 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 con-trol, if certain technical criteria are satisfied. These criteria were pro-vidad in the Generic Letter No. 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:
(1) the Generic Study (Reference 4) is applic'able to the licensce's plant; (2) the plant has Technical Specifications requiring that, when the containment is required to be inerted, the containment atmosphere be less than four percent oxygen; (3) the plant has cnly nitrogen or recycled containment atmosphere for use in all pneumatic control systems within containment; and (4) there are no potential sources of oxygen in containment other than thr re-sulting from radiolysis of the reactor coolant.
Most of the affected Mark I BWR plants have Containment Atmosphere Dilution (CAD) Systens utilizing either nitrogen cr 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 550.44(f) or $50.44(g) must continue to have that system, even though it may be determined with respect to
$50.44(c)(3) that the plant does not rely on that system as the primary means for hydrogen control; thus, a decision on reconbiner capability does not affect the requirenents cf $50.44(f) and s50.44(g) for the " safety grade" purge /
repressurizcticn systen.
8 f.
. Evaluation In a letter dated June 21,1984, (Reference 5), the licensee for Edwin I.
1 Hatch Nuclear Plant, Unit 1, the Georgia Power Company, 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 the Hatch Plant, and, therefore, a recombiner capability is not required. Hatch, Unit 2, was originally licensed on the basis of a non-inerted containment; and, because of the date of its notice of hearing on the application for a construction permit, recombiners were installed during construction. However, the Unit 2 containment was subsequently required to be inerted; also, Unit 2 has a safety grade purge /repressurization system, as does Unit 1.
The licensee states (Ref.
~
5), that they are preparing a submittal to request that the licensing basis for Unit 2, in regard to recombiners be redefined so as to be consistent with the licensing basis for Unit 1.
If this request were filed and were found acceptable by the staff, the recombiners for Unit 2 would be execpt from equiprent cualification requirements. Until receipt and review by the staff of tnis proposed change, Unit 2 nust continue to operate with the safety-grade recombiners being considered as the primary means fcr combustible gas control.
CSB has reviewed -the compliance of Hatch, Unit I with the criteria set by the staff (References 1, 2 and 3). We have found that:
(1) The licensee has participated in the generic study (Reference 4) made by the SWR Owners Group.
The main parateter regarding the applicability cf
(
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- L.
- the study.was. found to be the ratio of the core thermal power to the free
- drywell' volume. The. applicability.of the study to Hatch, Unit 1 was addressed in. Chapter 1.3 of the study.
.We agr'ee that the conclusions of the generic study are applicable to
~
Hatch, Unit '1, provided the following three criteria of Generic Letter l
84-09 are satisfied.-
.(2) Hatch, Unit 1,.-Technical Specification 3.7.A.5 require; 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.
'(3) Hatch, Unit 1, uses recycled containment atmosphere as the primary source, and nitrogen as a back-up source, for all pneumatic systems inside containment. A cross-tie from the drywell pneunatic ' system to the r.cn-interruptible instrument air system is controlled by a removable spool piece, and is used only in the unlikely event that both of the normal pneumatic supply systems fail.
Therefore, we find that Hatch, Unit 1, meets th'e second of the three criteria of Generic letter. 84-09.
(4) The instrument and service air systems at Haten, Unit 1, are disconnected during power operation. The plant does not have breathing air systems, inflatable seals, pressurized penetrations cr l'.SIV-leakage centrol 1
systems which could serve as potential sources of cxygen in the containment.
This was ccnfirmed with the licensee during a telecen, dated March 4, 1985.
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. The licensee has identified.(Ref. 5) three potential sources of oxygen addition into the primary containment:
1)
Use of a cross-tie to the instrument air system in the event that the two normal pneumatic supply systems were to fail; this event can occur only following multiple failures, and therefore, is considered to be
~
- a. low probability event. The CSB finds this potential source to be sufficiently unlikely as to be acceptable.
2)
Failure of H /0 -analyzers using oxygen as a reagent to measure 2 2 hydrogen concentrations could result in a leak of oxygen into
~
containment.
The maximum amount of oxygen available from this source following a single failure is about 420 ft3 This would result, if released into the containment, in an increase of less than 0.2%
oxygen concentration, as confirmed with the licensee during the telecon, dated March 4, 1985. The CSB finds this potential source to be acceptable.
3)
The leakage of secondary containment air into the primary containment represents the third possibly oxygen source. The Hatch Plant's Technical Specifications governing the allowable containment leak rates assure that inleakage rate is small under all circumstances.
The primary containment is nonaally naintained at a positive pressure relative to secondary centainment.
However, if the pressure would 1_
c,
., fall and an inleakage could be. expected, there are means to pressurize the primary containment (Inerting System, N -CAD system) 2 to eliminate this possible source. The CSB finds this to be acceptable.
Conclusions We conclude that the proposed' bases for not furnishing a recombiner capability for Edwin 1. Hatch Nuclear Plant, Unit 1, are acceptable. Hatch, Unit 2, should continue its use of the staff approved recombiner system.
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References:
-(l) Letter from D.'G.'"~
.iut.to All Licensees dated May 8,1984, "Recombiner C,,, ability Requirements of 10 CFR 50.44 (c)(3)(ii)"
(GenericLetter84-09).
'(2)' - Memorandum from R. J. Mattson to D.' G. Eisenhut dated January'24,1984, "0SI Review of Requests-from Mark I/BWR Licensees for Relief from the Hydrogen. Recombiner Capability requirement of 10 CFR Part 50.44."
-(3) :SECY-83-292, " Applicability of Recombiner Capability Requirements of' Revised 10 CFR 50.44 to BWR licensees with Mark I Containments."
(4) " Generation and Mitigation of Combustible Gas' Mixtures in Inerted BWR
-Mark I Containnents," by F. R. Hayes, L. B. Nesbitt and P. P. Stancavage.
.Techr.ical Report HED0-22155/82-NEDC-69/CL SS 1/ June 1982.
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-(5) - Letter from L. T. Gucwa, GPC, to J. F.- Stolz, NRC, dated June 21, 1984,
" Hydrogen Recombiner Capability Requirements of 10 CFR 50.44."
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