ML20125D567
| ML20125D567 | |
| Person / Time | |
|---|---|
| Site: | 05000130 |
| Issue date: | 04/29/1966 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20125A538 | List:
|
| References | |
| FOIA-85-54 NUDOCS 8506120406 | |
| Download: ML20125D567 (4) | |
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( SAFETY EVALUATION BY THE RESEARCH & F0WER REACTOR SAFETY BRANCH DIVISION OF REACTOR LICENSING NORTHERN STATES F0WER COMPANY FA11tFINDER ATOMIC POWER PLANT DOCKET NO. 50-130 g ,
LOW COUNT RATE STARTUF SPECIFICATION i
}g CHANGE NO. 8 ;
I_ctroduction By application dated March 14, 1966, the Northern States Power Company (NSF)
- requested- a change in the Technical Specifications of License No. DPR-11. The change would allow startup of the Fathfinder reactor with a minimum startup count l' rate of 1/3 counts per second (cys) under certain conditions. We have designated ,
this request Proposed Change No. 8.
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Evaluation
. The Technical Specifications presently require a minimum count rate of 2 eps prior
! to startup. However, due to the extended time required in the approach to operation .
cf the reactor and its nuclear superheater, the antimony-boryllium source will decay l ta the extent that it will not be capable of providing a count rate of 2 eps due to '
j toutrons measured by the out-of-vessel source range detectors. NSF is proposing to
' conduct reactor startup with the count rate as low as 1/3 eps providing special
' procedures, incorporated into the Technical Specifications by this change, are in i t
cffect. NSF reports
' sufficient at 1 x 10" ghat when of percent thefull count rateThus, power. is 1/3even cps, when the source therepower is is a substantial l
. toutron population in the core, the neutron attenuation due to the 32 inches of water i
- in the reflector region results in a low count rate at the detectors. No startup -
- without a source will be performed. ,
NSF reports that the proposed low count rate startup may be necessary at various times throughout the lifs of the plant; specifically, after extended outage and
! citer periods of low power operation. We agree that the proposed startup is (
c:ceptable from a safety standpoint based on our review of the special procedures j l and safety precautions which are discussed below. .
l (1) A source range, key-switch type bypass will permit rod withdrawal with [
! Icss than's 2 eps count rate. Use of a key switch will allow better control by j supervisors than would a jumper. A qualified staff engineer will be present in _
i the control room during the approach to critical. The bypass will also allow I j control rod latching and unlatching which is necessary in the event that in-core !
d:tectors must be used to correlate rod position with core reactivity prior to a l low count rate startup. Other specially supervised tests allowed by the Technical !
( Specifications may also require use of this bypass. We have reviewed the proposed wiring of this bypass circuit and believe it is adequate and that the proposed use i
i cf the bypass is acceptable. ,
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( (2) A low count rate startup will only be performed on a core for which the carrelation of rod position and core reactivity is known. Additionally, rod withdrawal will be in accordance with the specific rod program used to correlate th3 core reactivity.
(3) If any change in the core reactivity or the rod withdrawal program has cccurred since the correlation of rod position versus core reactivity, or if more than four months have elapsed since shutdown, the correlation must be redetermined.
If necessary, in-vessel detectors may be used for this new correlation, which wtli ,
provide a minimum count rate of 2 cys. We believe the restrictions of this paragraph cnd (2) above will assure that the operator has an accurate knowledge of the core rpectivity during all phases of the startup operation. !
(4) Whenever the low count rate approach is being used, the noise level of th3 three source range detectors and associated instrumentation will be demonstrated t3 be less than 1 eps prior to startup. Thus, it will be assured that the detector is providing neutronic information from the core.
(5) The approach to criticality will be done in reactivity insertion increments cpproved by the Operations Committee and Safety Committee. After each increment there will be at least a 2 minute wait before addition of the next increment is initiated. Therefore, if by error the multiplication is increasing at a unre rapid '
rate than predicted, it would be detected before further reactivity has been added y
to the core. The neutron count rate will always be at least 2 cps when the core reactivity reaches a calculated k-ef fective of 0.995. Multiplication versus rod position will be plotted and enough counts will be taken on a scaler at each increment I to obtain 10 percent statistics until the core reactivity is 0.98 when statistics will be required to be better than 3 percent thereafter. Any s1F nificant deviation from the correlated data during startup will require an immediate reactor shutdown until the cause of the discrepancy is determined. We believe these limitations will assure a conservative approach to low count rate reactor startup.
(6) During this type of startup the instrumentation will provide all normal ceram protection including single coincidence short period scram in the startup r:nge and level trip in the intermediate range. Thus, automatic protection is cvailable through the source power range which is capable of terminating any transient condition prior to reactor damage.
Accident Ana' lysis Change No. 5 to the Technical specifications allowed reactivity insertions at rates up to 25 cents per second for both botier only and full core testing. The startup cccident provided in support of this change indicated that with a ramp reactivity codition of 50 cents per second initiated at power levels 1 Mw(t) or lower, there ,
wJs no fuel damage in either the boiler or superheater region of the core. We understand that the maximum rate of addition during low count rate startup would be approximately 12 cents per second. On the basis of previous analysis we believe that even if the operator were to continuously add reactivity at the maximum rate during a low count rate startup, there would be no fuel damage and consequently there 4 s would be no hasard to the public. l k
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Technical hoecifications To implement Change No. 8 the following changes to the Technical Specifications (Appendix A) of License No. DPR-11 should be made:
(1) Add the following to Section 6.1.8(a):
"This interlock may be bypassed manually with the use of a key switch to:
(1) permit control rod latching and unistching as approved by the Operations Committee.
, (2) permit use of low count rate procedure or other supervised tests approved by the Operations Committee and in accordance with these Technical Specifications."
(2) Add the following to Section 7.6.2(d):
"In the event that the source strength is insufficient to produce a count rate of 2 eps due to neutrons on the out-of-vessel detectors in .
the startup channels, approach to criticality may be accomplished provided the count rate is greater then 1/3 cps due to neutrons and the following conditions are adhered to:
(1) Prior approval of all procedures and methods of analysis for the specific startup shall be obtained from the Operations Coenittee and the Safety Commaittee.
(R) A qualified staff engineer shall be present in the control room during startup.
(3) No changes which could significantly affect reeetivity shall have been made to any of the core components or to the core configuration since core reactivity was last correlated with rod position. The specifie rod withdrawal sequence used in the correlation shall be used for this type of startup.
(4) If changes which affect reactivity have been made to the core or any of its components, or the rod withdrawal sequence is changed, or more than 4 months have elapsed since shutdown new correlating data shall be obtained. If in-vessel detectors are used, they shall provide a miniese count rate of 2 cys.
(5) The noise level of the detectors and associated electronics shall be less than 1 cys.
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(6) No reactivity increment shall exceed 1/3 the extrapolated amount to critical. There shall be at least a 2 minute wait before addition of the next increment is initiated. Plots of smaltiplication versus rod position shall be made; and enough counts shall be taken after , ,
each increment on a scaler to provide 10 percent statistics until '
l the core reactivity is 0.98, and to provide 3 percent statistics j thereafter. The count rate shall exceed 2 cps when the core reac- >
tivity is 0.995. Af ter the count rat. sxceeds 2 eps normal startup .
> procedures may be used.- [
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(7) Single coincidence in the startup channel short period scram circuit
. shall be provided. ,
(8) Any significant deviation from the correlated data during startup shall require an inusediate reactor shutdown until the cause of the discrepancy is determined."
Conclusion Based on our review of the information submitted, we have concluded that the low count rate startup procedure specified in Change No. 8 does not present significant hasards considerations not described or implicit in the hasards sunnery ,
rcport, and there is reasonable assurance that the health and safety of the public j will not be endangered. -
I Originalsigned by: ;
Roger S.Boyd l Roger 5. Boyd, Chief i Research & Power Reactor Safety Branch Division of Reactor Licensing ,
, I i
p.e., APR 2 91966 !
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