ML17317B293
| ML17317B293 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 05/02/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17317B292 | List: |
| References | |
| NUDOCS 7906290092 | |
| Download: ML17317B293 (3) | |
Text
1 UNITEO STATES NUCLEAR'REGULATORYCOMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NOS ~ 28 AND 1
TO FACILITY OPERATING LICENSE NOS.
DPR-58 AND DPR-74 INDIANA AND MICHIGAN ELECTRIC COMPANY INDIANA AHD MICHIGAN POWER COMPANY DONALD C.
COOK NUCLEAR PLANT DOCKET HOS., 50-315 AND 50-316 Introduction By letters dated 'December 20, 1978 and April 4, 1979, the Indiana and Michigan Power Company (one of the licensees) notified the Commission of their intent to remove part-length control rods from Unit 1
and to install anti-rotational devices to prevent the rundown of the part-length control rod drive mechanisms during the April 1979 refueling outage.
By letter dated April 4, 1979 IBMPC also notified the Commission of their intent to install permanent anti-rotational devices in D. C.
Cook Unit 2.
Temporary anti-rotational devices are presently installed in Unit 2..
By letter dated April 23,
- 1979, I8MPC stated the permanent anti-rotational devices would be installed during the first Unit 2 refueling
- outage, expected next fall.
The April 23, 1979 letter also forwarded the fee appropriate for a Class III Operating License Amendment for Unit 1'and a Class I Operating Amendment for Unit 2.
The amendment for Unit 1 would!
= be to authorize the removal of the existing part-length control rods and delete all reference to them from the Technical Specifications appended to Facility Operating License DPR-58.
The amendment for Unit 2 would eliminate all reference to part-length control rods from the Technical Specification appended to Facility Operating License DPR-74.
The part-length rods were not installed when Unit 2, started up because the analysis of their effect on 'plant operation had not been completed at that time.
A The D. C.
Cook Nuclear Plant, Units 1
and 2 (the facilities) are located in Berrien County, Michigan.
Part-Len th Rod Removal Discussion and Evaluation Part-length control
.rods were initially installed in Unit 1 to suppress xenon induced power oscillations in the axial direct, should such oscillations occur.
Part-length control rods were provided for, but not installed in Unit 2.
The Technical Specifications, as now written for both Units require that the part-length rods (PLRs) be withdrawn and excluded from the core at all times during reactor operations.
The PLRs are not needed, used or assumed to be available to achieve required reactor shutdown conditions.
Methods have been developed to all'ow effecti,ve control of xenon oscillations using full-length control rods.
Therefore, the proposed removal from Unit 1 will not cause any change in required reactivity characteristics, or safety margins at full power, low power or shutdown.
Operation of Unit 2 (17 x 17 fuel) without part-length rods was approved to startup that facility.
See SER Supplement No.
7 dated December 1977.
In order to preserve the current dynamic operating characteristics of the reactor (i.e., pressure drops, coolant flow rates, etc.) which could be affected if just removal of the PLRs were to be performed, the licensees propose to install thimble plug assemblies in the spaces previously
.occupied by PLRs in Unit 1.
The thimble plug assembly consists of a flat base pack assembly.
The twenty short rods, called thimble plugs, project into the upper ends of the gui de thimbles to reduce the bypass flow area.
Fuel assemblies without control rods, burnable poiso'n rods, or source rods use identical devices.
Similar short rods are also used on the source assemblies and fuel assembly guide thimbles.
At installation in the core, the thimble plug assemblies interface with both the upper core plate and with the fuel assembly top nozzles by resting on the adapter plate.
The spring pack is compressed by the upper core plate and with the fuel'ssembly top nozzles by resting on the adapter plate.
The spring pack is compressed by the upper core plate when the upper internals assembly
'is lowered into place.
Each thimble plug is permanently attached to the base plate by a nut which is locked to the threaded end of the plug by.
a small lock bar welded to the nut.
All components in the thimble plug assembly, except for the springs, are constructed from type 304 stainless steel.
The springs are wound from an aged hardened nickel base alloy for corrosion resistance and high strength.
These thimble plugs wi 11 effectively limit bypass flow through the rod cluster control guide thimbles in the fuel assemblies from which the PLRs have been removed, just as they currently limit bypass flow in those assemblies which do not contain control rods, source
- rods, or burnable poison rods.
The PLR lead screws will be left in place and a permanent anti-rotation device installed on each PLR lead screw.
The anti-rotational device is constructed of 304 stainless steel.
A temporary device which is presently installed on each PLR lead screw in Unit 2 will be replaced with a permanent one during the first.refueling outage of Unit 2.,
Based on the considerations that the Unit 1
PLRs are not needed for reactor operation, that insertion of the thimble plug assemblies will preserve the current dynamic operating characteristics of the reactor and that the anti-rotational devices will prevent movement of the PLR lead screws, we conclude that these changes are acceptable.
Environmental Consideration We have 'determined that the amendments do not authorize and change in effluent types or total amounts nor an increase in power level and will not result in any significant environmental impact.
Having made this determination, we have further concluded that the amendments involve an action which is'nsigificant from the standpoint of environmental impact
- and, pursuant to 10 CFR 551.5(d)(4), that an environmental impact state-ment or negative declaration and environmental impact appraisal need not be prepared in connection wi-th the issuance of these amendments.
Conclusion We have concluded, based on the considerations discussed above, that:
(1) because the amendments do not involve a significant increase in the probabil'ity or consequences of accidents previously considered and do not involve a significant decrease in a safety margin, the amendments do not in'volve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangere'd by operation in the proposed
- manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of these amendments will not be inimical to the common defense and security or to the health and safety of the public.
Date:
May 2, 1979