ML20211B796
| ML20211B796 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 10/07/1986 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20211B786 | List: |
| References | |
| NUDOCS 8610210120 | |
| Download: ML20211B796 (3) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT N0.102T0 FACILITY OPERATING LICENSE N0. DPR-51 ARKANSAS POWER AND LIGHT COMPANY ARKANSAS NUCLEAR ONE, UNIT N0. 1 D0CKET N0. 50-313 INTRODUCTION By letter dated April 30, 1986, as supplemented July 31,'1986, Arkansas Power and Light Company (AP&L or the licensee) requested amendment to the Technical Specifications (TSs) appended to Facility Operating License No. OPR-51 for Arkansas Nuclear One, Unit No. 1 (ANO-1). The proposed amendment would permit operation with two proposed thermal hydrogen recombiners to be installed in the containment to replace the existing hydrogen purge system and change TSs 3.14 and 4.12.
The recombiners are of a standard design made by Westinghouse. Similar recombiners have been installed.in several other nuclear plants. The licensee has provided justification for the replacement of the hydrogen purge system with the recombiners on the basis that the safety of the plant is improved by providing a high capacity, hydrogen control system which could operate without the need for venting the containment gases to the atmosphere.
EVALUATION 1.
System Modification By letter dated April 30, 1986, the licensee provided information on a new hydrogen control system proposed for installation at ANO-1. The new system would replace the existing hydrogen purge system which, although meeting the applicable regulatory requirements-for hydrogen control, proved to be difficult to maintain. This difficulty was a result of continuous problems with maintenance of the water seals for the purge compressors. This type of compressor is diffic',rit to maintain, and replacing them with a dry seal type compressor would entail high costs. The licensee decided, therefore, to replace the purge compressors with a new, more efficient thermal recombiner system. This system consists of two identical Model B electric hydrogen recombiners made by Westinghouse. The recombiner units are of a standard design approved by the NRC for use in several other nuclear plants. Each unit is capable of handling 100 scfm of' containment gases which is twice the capacity of the existing hydrogen purge system. Hydrogen is recombined with oxygen from air in the recombiner by passing the gases over heated surfaces which supply the energy needed for recombination.
Since this type of recombination does not rely on catalytic effects of the recombiner surfaces,'it cannot be poisoned by impurities which may exist in the containment atmosphere after an accident. The gases in the recombiner flow by natural convection and there are no moving parts. The gases pass through an h0210120861007 p
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- opening in the vertical walls of the unit protected by louvers from spraying water. The heated surfaces are maintained at a temperature between 1150 F and 1400 F.
At this temperature, recombination occurs with 95 percent efficiency for the gases containing less than 3.5 v/o hydrogen.
The containment cooling system has sufficient capacity to remove additional heat generated by the recombiners.
The recombiner units are designed for a lifetime consistent with that of the plant. Performance tests have indicated that they are operable under conditions which are more severe than those postulated to occur following a loss of coolant accident (LOCA). Design, fabrication and erection of the recombiners will be in conformance with Quality Group B and Seismic Category I criteria. Each recombiner will be powered by a separate onsite emergency power bus backed by the diesel generators. The installation of the recombiners will permit periodic inservice inspection and operability testing which will be performed in accordance with the requirements of TS 4.12.
Both recombiner units are to be located inside the containment on the refueling floor (elevation 426 ft.), on the top of the steam generator cavities. This location is recommended by the manufacturer and it assures that the. units will receive uniformly mixed gases from all locations inside the containment.
Mixing will be accomplished by the containment emergency cooling system and/or by the containment spray system. Performance of these systems is not affected by.the installation of the recombiners. Similarly, the existing hydrogen sampling system will remain unchanged. We Save reviewed the design of the recombiners and their installation in the containment of ANO-1 and find that during a design basis accident (LOCA), the system will be capable of maintaining ~
hydrogen concentration in the containment below the flammability limit of 4 v/o.
2.
Technical Specification Change The licensee proposed revised TSs which reflect.the above described system modifications. TS 3.14, " Hydrogen Purge System" will be replaced with "Hydrcgen Pecombiners", and TS 4.12, " Hydrogen Purge System Surveillance" will be replaced with " Hydrogen Recombiners Surveillance". The new specifications are based on the " Standard Technical Specifications for Babcock and Wilcox Pressurized Water Reactors" (NUREG-0103, Rev. 4) as applicable to Westinghouse electric hydrogen recombiners. Proposed TS 3.14 requires two independent recom-biner systems to be operable.
It also specifies the procedure to be followed if one of the recombiners becomes inoperable.
Proposed TS 4.12 specifies the kind and frequency of surveillance operations to be performed on the recombiner system in order to assure its operability. This specification requires that every six months, the operability of the recombiners be verified by performing prescribed tests, and every 18 months, the entire system, including all instrumen-tation and electric circuits, be thoroughly checked.
We have reviewed these proposed TSs and find that they are adequate to assure proper operation of the proposed hydrogen control system based on recombiners.
Based on the considerations discussed above, we conclude that the modification to the ANO-1 hydrogen control system proposed by the licensee meets the require-ments of General Design Criterion (GDC) 41 by providing satisfactory means for post accident hydrogen control in the containment. We further conclude that the
. proposed revised TSs for surveillance and testing of the hydrogen recombiners are consistent with the applicable Standard Technical Specifications and, there-fore, meet the requirements of GDC 42 and GDC 43 for inspection and testing of containment atmosphere cleanup systems. We, therefore, find the proposed replacement of the hydrogen purge system with electric recombiners to be acceptable.
ENVIRONMENTAL CONSIDERATION This 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 previously issued a proposed finding that this amendment involves no significant hazards consideration and there has been no public comment 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.
CONCLUSION We have. 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.
Dated: October 7,1986 Principal Contributor:
K. Parczewski
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