ML19242A097
| ML19242A097 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 06/12/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19242A096 | List: |
| References | |
| SER-790612, NUDOCS 7907310236 | |
| Download: ML19242A097 (4) | |
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I UNITED STATES l
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTIfiG AMENDMEfiT fl0. 66 TO FACILITY OPERATIf;G 1.ICENSE fl0. DPR-57 i
GEORGIA POWER COMPANY i
O3LETHORPE ELECTRIC MEMBERSHIP CORPORATION MUNICIPAL ELECTRIC ASSOCIATION OF GEORGIA CITY OF DALTON, GEORGIA ED',!Ifi 1. HATCH NUCLEAR PLANT, UNIT *io. 1 DOCKET fi0. 50-321
_In troducti on By letter dated May 11, 1979,
) Georgia Power Company (the licensee) has reauested an amendment to the Technical Specifications for Edwin I. Hatch Nuclear Plant, Unit No. 1 (Hatch-1).
The amendment would &llow the count rate en the Source Range Monitor (SRM) channels to drop below 3 counts per second when the entire core is renoved l
or reloaded.
_ Discussion The current Specifications require a minimum count rate of 3 cps for the SRMs during core alterations.
The minimum count rate requirement serves two purposes.
First, it serves as a continuous functional test of the channel.
Second, it assures there are a sufficient number of neutrons in the core so that the SRMs are on-scale and will immediately respond to increases in neutron populction.
These functions are easily satisfied in cores containing exposed fuel, since spontaneous and
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photon-incuced fission in exposed assemblies supply an adequate number of neutrons to obtain 3 cps on the SRMs.
Maintaining 3 ces is no problen during normal refueling due to the presence of exposed fuel.
However, at times when the' entire core
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must be removed from the reactor, the SRM count rate will eventual)"
drop below 3 cps.
The current specifications permit two alternatives 7 9 07 310,c 3c,
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(1) load neutron sources to maintain the count rate, or (2) substitute movable " dunking" chambers for the stationary 5E detectors.
The licensee has noted in his application that both of these alternatives increase the risk of loose objects being dropped into the vessel.
We-note also that both alternatives increase personnel Moreover, experience with dunking chambers indicates problems exposure.
involving both a relatively high failure rate and " pendulum swing" geometric interference.
Therefore, we agree that neutron sources and/or dunking chambers are not desirable if other alternatives exist.
Evaluation Unloading Secuence The proposed Technical Specification would be operative only during spiral unloading and reloading of the core.
In the unloading secuence, fuel cells on the perimeter of the core are unloaded first.
Cells are removed sequentially in a spiral sequence with cells closest to the center of the core removed last.
Control rods may be momentarily with-drawn in cells which are being work 3d on, but all defueled cells will contain inserted control rods.
Until all the fuel is removed, all fueled and nonfueled cells are required to contain control blades by Technical Specification 3.10.B.
As fuel is removed, count rate will drop in the SRM channels.
Since all SRM Cetectors but one are locatcd some distance from the core center, it is doubtful that the old requirement of at least 3 cps in at least 2 channt s could be met.
However, because the proposed spiral unloading does nt; permit imbedded cavities or major peripheral concavities, and because ail control blades will be in place, shutdown margin cannot decrease during defueling.
Under such circumstances, and since Technical Specification 4.10.C will require functional testing of the SRMs prior to beginning core alterations, we find the proposed change is adequate to satisfy both purposes of minimum count rate and is acceptable during cor' unloading.
Loading Secuence The loading sequence differs from the unloading sequence in that two assemblies will first be loaded adjacent to each SRM.
This should increase tne count rate unave 3 cps and thus allc.. Snecification 4.10.C x te m t.
After tnis, :-ir :1 reloading f rc- :ne c.en ter rutuard wil'
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n Such a nodified spiral loading can lead to imbedded unfueled cells in the intermediate arrays.
However, since Specification 3.10.B requires all rods, fueled and unfueled, to have control blades inserted, inadvertent criticality is precluded.
In addition, because all cells start out with control blades in place, inavvertent criticality is unlikely even assuming multiple loading and operator errors.
There are five SRM detectors in the Hatch-l core.
One is located near the center, the other four are approximately half a core radius out.
There is no monitoring problem unless the central (24-29) SRM detector is inoperable.
Assuming this, the first few intermediate arrays at the beginning of the loading sequence will be as much as 3 fuel cells distant from the nearest SRM detector.
This leads to considerable attenuation of neutron flux from the centrai array before it is counted at the detector.
However, because this situation is true for only a limited number of intermediate arrays, an inadvertent criticality in these arrays is extremely improbable as discussed above.
Therefore, in view of the above and of the additional requirement for functional testing of the SRMs prior to beginning core alteration, we find the propored technical specification change to be acceptable for spiral locjing.
Environmental Considerations Ue have deternined that this amendment does not s r -ize a change in ef fluent types or total amounts nor an increase in puer level and will rot result in any significant environnental impact.
Having made this determination, we have further concluoed that this amendment involves an action which is insignificant from the standpoir.t of environmental impact, and pursuant to 10 CFR Section Sl.5(d)(4) that an environmental impact statenent, or negative declaration and environmental impact appraisal need not be prepared in connection with the issuance of this amendment.
Conclusion We have concluded that:
(1) because the amendment does not involve a significant increase in the probability or consequences of accidents previously considered and does not involve a signific' ant decrease in a safety margin, the amendment does not involve a significant hazards ucnsideration, (2) there is reasonable assurance that tha health and safet; cf the public will not be endangered by operation in the proposed and (3) sucn acti ities will be conducted in ccmol'ance with r an r.e r,
the Ec
!ssion's regula*icns and tne issuance of this amendrent will nct be in'.nical to the common defense and security or to t' e health end n
safet' rf the public.
_ ned:
'n e 12, 1079
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. References 1.
Letter, Charles F. Whitmer (Georgia Power Company) to Director of f;uclear Reactor Regulation (ffRC), dated May 11, 1979.
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