ML20125D561
| ML20125D561 | |
| Person / Time | |
|---|---|
| Site: | 05000130 |
| Issue date: | 04/28/1966 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20125A538 | List:
|
| References | |
| FOIA-85-54 NUDOCS 8506120402 | |
| Download: ML20125D561 (2) | |
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' SAFETY EVALUATION BY THE RESEARCH AND POWER REACTOR SAFETY BRANCH t
DIVISION OF REACTOR LICENSING IN THE MATTER OF NORTHERN STATES' POWER' COMPANY ,1 f ;
' PATHFINDER ATOMIC POWER' DOCKET NO. 50-130' Q(*
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PROPOSED' CHANGE No,10/ , p Introduction Pursuant to the provisionseof Section 50.59 of the Commission's regulations, the Nsrthern States Power Company, by application dated April 18, 1966 requested ctthorisation of a change to the Technical Specifications of License No. DPR-11 fsr the Pathfinder reactor. This change would (1) allow a decrease in the required sen11tivity of the intermediate range channels No. 5 and No. 6, (2) limit the scram ,
level set point to a maximum of 200 Kw during startup, and (3) restrict the inter- l ,
mediate range chamber currents corresponding to the scram level on the highest ! !
piccammeter range, with the low-out-of-range interlocks bypassed, to a value not less j tharr five times the minimum rated chamber current. This change-is requested because of l '
' difficulties in achieving the minimum sensitivity requirement of 10-9 amps /75 Kw !
curing certain phases of low power operation. l i
Diacuasion l Pcrt of the proposed change requests authorization to operate with intermediate range l !
channels (No, 5'and No. 6) which have sensitivitie ;
Th$ present minimum sensitivity requirement of 10'g ampless/75 than Kw was that presently intended as a reeutred.
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reasonable means of numerically defining the operational range of these channels in tares of directly measurable quantities. Actual operation, however, has shown that ;
th3 sensitivities of the channels are below this value during certain phases of-low power operation.
In support of this request for Change No. 10 the applicant makes reference to Item E ;
" Adequacy of Linear Flux Channel Protectice in the cf Amendment 29, Attachment 1: ,
I t0rmediate Range." Under Item E, the startup accident is analysed with the assumption th:t two rods are being simultanecusly withdrawn because of a single fault within the '
rod selector circuits. This analysis takes no credit for period scram. It further' as:umes, with conservatism, that the operator deliberately changes the ranze switch '
i ptoitions of Channels No. 5 and No. 6 in such a manner as to " keep ahead" of the l cxcursion until scram is initiated by the power-to-steam-flow circuits. In the two l (wsrat) cases studied, scram was initiated at 11.5 Mw and 23 Mw respectively with na cero damage. i i
Ig_the request for this change, the applicant states ". . .the power-to-steam-flow I
- g. %tection (is) related to selected ranges consistent with actual power calibration." t
' ..ius, the proposed sensitivity change, althouah it will af fect the power levels at ! ,
which the intermediate range channels will, by themselves, initiate scram, will not
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8506120402 850214 i PDR FOIA PAYBS-54 PDR (
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cffcet the scram set points of the power-to-steam-flow circuits. Therefore, the analysis s prcsented in Item i remains applicable.
Th3 proposed change would raise the maximum scram level during startup to 200 Kw.
Even though this is higher than the (approximately) 8 Kw now set, it is still well balow the 11.5 and 23 Mw levels which have been shown to be acceptable.
In crder to ensure that a statistically valid signal is availabi low level prtecction channels described herein, a minimum value amperes'should of 5 x 10 gforbethe-required to initiate scram on the highest range with the low-out-of-level
- interlock j
bypassed. Currents of this magnitude, and greater, are known to be satisfactory and ,
cre coimmonly used to feed intermediate range instruments. This limit also requires the cperator to return the channels to this minimum sensitivity if such sensitivity i
.haa,-for calibration purposes at higher power levels, been diminished.
The proposed change retains the intent of the Technical Specifications regarding overlap between the startup and intermediate range channels and the interlocks which enfcree this overlap.
l 'la view of the foregoing, we believe that the Technical Specifications should be ;
l changed as follows: ;
2 a) the following item should be deleted from Table 1:
"(a power level of 75 Kw shall give a current indication not less than 1 x 10-9 asps)." - ,
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j b) in parts (2) and (3) of Items 6.18 a a l
" equal to or greater than 1 x 10should E a(m)ps"nd be deleted and 6.1.8(b) replaced the wordas' ;
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with "two range switch position higher in power than the selected range i
' on which the low level trip interlock of Channels No. 5 and No. 6 is by-
- passed according to 6.1.8(c)."
c) the last sentence of Item 6.1.8(c) should be revised to read "This interlock' on each channel may be bypassed for startup by switching I to a selected'renge~on which the scram level shall not exceed 200 Kw i (except for teste specified in Sections 5.8.2 and 6.1.8(d)): additionally, the scram level on the highest range with such bypass shall correspond to a current not less than 5 x 10-11 amps." l l l We have concluded thatechenge No. 10 does not present significant hasards considerations l
cot described or implicit in the Final Hasards Susunary Report, and that there is t
racconable assursace that the health and safety of the public will not be endansered, i
I Original signed by.
ScgerS.Boyd Roger S. Boyd, Chief .
f Research & Power Reactor Safety Branch 3
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i Division of Reactor Licensing
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