ML19347C491
| ML19347C491 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 08/23/1962 |
| From: | Bryan R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19347C490 | List: |
| References | |
| NUDOCS 8011190757 | |
| Download: ML19347C491 (3) | |
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UNITED STATES ATOMIC ENERGY COMMISSION HAZARDS ' NALYSIS BY THE RESEARCH AND POWER REACTOR SAFETY BRANCH A
DIVISION OF LICENSING AND REGU;ATION IN THE MATTER OF YANKEE ATOMIC ELECTRIC COMPANY
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PROPOSED CHANGE NO. 23 DOCKET NO. 50-29 Introduction Pursuant to the provisions of paragraph 3. A. of License No. DPR-3, as amended, Yankee Atomic Electric Company in Proposed Change No. 23, dated May 9,1962, Z.l requested authorization to make certain modifications in their reactor nuclear
...._.l.T WP instrumentation system, n ese modifications consist of the addition of three power range panels, three linear power meters and an auxiliary panel. This m:_.
5 equipment would be used to provide additional initiating signals for reactor scram in the event of high neutron flux levels during power operation. The
- .1 Proposed Change would involve an amendment to Table I of the technical speci-
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fications of Yankee Atomic Electric Company's license and to Section 214 of the license application which is incorporated, in part, into the technical specification by reference.
Discussion Tnere are presently three intermediate and three power range nuclear instru-mentation channels installed in the Yankee reactor. The reactor is protected against high neutron flux levels by a coincident scram circuit which functions when two out of three power range channels exceed a pre-set scram point.
During the control rod movement accompanying power changes, the power range channel readings are not always proportional to the actual power levels present in the reactor. Yankee has indicated that administrative procedures have been instituted to lessen the possibility of such non-proportionality resulting in operation at power levels above the intended scram point.
These procedures require recalibration of the nuclear instrumentation at certain electrical loads before proceeding to higher power levels.
In order to provide additional protection against the possibility of operating the reactor at power levels in excess of the scram point, Yankee has proposed to use the compensated ionization chambers installed in the intermediate range channels to provide additional initiating signals to scram the reactor s:,,
in the event of high flux levels.
This would be accomplished by using signals from the intermediate range channels to feed circuits which are similar to those presently provided for the power range channels.
Six channels would 8'011140.7[f
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i 2-then monitor the neutron flux present in the coa during pcVer operation and would be capable of providing signals to scram the reactor should excessively p
high neutron fluxes exist. Instead of the present coineident arrangement which requires a scram signal on two our of three power range channels, the
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reactor would be scra=med if two out of the six channels exceeded their scram points.
We believe that the modifications in equipment and mode of operation which have been proposed by Yankee should contribute to the safety of operation of the facility. With such changes in effect, it should be less likely that the power level vould rise above the intended scram point without the reactor being shut down auto =atically by the nuclear instrumentation system. We believe, novever, that certain changes should be made in the technical specifications in addition to the changes proposed by Yankee. The number of operable channels required for reactor operation, listed in Table I of the technical specifi-cations under High Neutron Flux Level - Reactor Scram, should be increased from Z" _
2 to h.
In addition, the requirements of Precaution III.5. of Operating 1
Instruction 5040 should be changed to read as follows in order to define the limitations involved in the coincidence requirements more explicitly:
III.5 The following minimum operating instrument requirements must k-be met:
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Four detectors monitoring power which provide automatic f
high level scram protection.
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(1)
In a condition where one upper or one lover power-range channel is inoperative, the reactor can continue to be operated at the existing power level provided no major rod program change is carried out and provided the power range high
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level scram protection is set for single channel operation for the group containing the. failed channel.
(2) In a condition where two power range channels are inoperative, the reactor can continue to be operated at the existing power level provided no major rod program change is carried out and provided the power range high level scram protection is set for single channel operation on both the upper and lover group.
This matter has been discussed with Yankee, and they have indicated their agreement with these additional changes to the technical specifications.
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Conclusion Subject to the above co=:nent regarding Table I of the technical specifications,.
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ve believe that Proposed Change No. 23 does not present significant hazards considerations not described or implicit in the license application as amended to June 23, 1961. We have further concluded that there is reasonable assurance that the health and safety of the public vould not be endangered by operation of the facility as proposed and as modified.
E. G. Case. Chief
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Research & Power Reactor Safety Branch
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Division cf Licensing and Regulat;on
=sE Robert H. Bryan, Chief
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Research & Power Reactor Safety Branch
- - r Division of Licensing and Regulation Mj;(,;-
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Date:
AUG 2 31962
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