ML20002A309
| ML20002A309 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/28/1965 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML20002A308 | List: |
| References | |
| NUDOCS 8011110642 | |
| Download: ML20002A309 (2) | |
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f,AFETY EVALUATION BY THE RESEARCH AND P(NfER REACTOR SAFETY BRANCH DIVISION OF REACTOR LICENSING IN THE MATTER OF YANKEE ATOMIC ELECTRIC COMPANY j
PROPOSED CHANGE NO. 68 I
DOCKET NO. 50-29 i
F Introduction Pursuant to the provisions of Section 50.59 of the Coussission's regulations, Yankee Atomic Electric Company in Proposed Change No. 68, dated October 15, 1965, requested authorization of a change in t he Technical Specifications attached as Appendix A to License No. DPR-3.
This proposed change would authorize the ins tallation of four Secondary Core Supports to limit movement of the reactor core even in the unlikely event the primary core support structure should fail.
Discuss an The Yankee core consists of 76 fuel elements, which weigh about 26 tons, and is contained within the core barrel.
The core barrel is suspended by a flange from the top of the pressure vessel, and primary support for this structure is provided i
by a full penetration weld between the core barrel and the top support flange.
i This weld has adequate strength to support this structure, but is reinforced by i
twelve one-inch thick gusset plates spaced radially around the core barrel. The support welds were recently inspected by dye penetrant and ultrasonic testing i
techniques and found to be in sound cond tion.
i Yankee believes that failure of the primary core support is extremely unlikely, but has proposed to install four Secondary Core Supports to limit the downward motion of the core if a failure should occur.
The secondary support consists of 4
j four stainless steel straps (3/4" x 7 3/4" in cross section) that are firmly attached to the top and bottom of the thermal shield. These straps provide four points of support under the lower core support plate and would limit the downward 3
motion to 5/8 inch. The secondary supports have been designed to preclude vibration, and to absorb the impact of the core structure. The weight of the i
core structure would ultimately be supported by the thermal shield support lugs which are an integral part of the pressure vessel wall. We believe that the-Secondary Core Supports have been adequately designed, and that their instal-lation would provide a desirable additional. safety factor for the Yankee reactor.
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Since the control rods are inserted from the top of the core, downward movement of the core would result in a reactivity addition.
However, the Yankee reactor is operated as a chemical' shim plant with only one group of control rods normally inserted. With this mode of operation, the reactivity addition would be negli-gible if.the core should fall.
The maximum potential reactivity addition (control rods at maximum worth) that could occur for this postulated accident, with the Secondary Core Supports in place, would be during shutdown or low power ' operation.
4 This reactivity addition would be less than 0.005.
Yankee has analyzed this
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2 reactivity addition, and we agree that the resulting transient would not result in any damage to the reactor.
Conclusion We have concluded that the Proposed Change does not present significant hazards considerations not described or implicit in the hazards summary report, and that 4
there is reasonable assurance that the health and safety of the public will not be endangered.
Orghd:r..
Rcter S. Ecy!
Roger S. Boyd, Chief Research & Power Reactor Safety Branch Division of Reactor Licensing Date: OCT 2 81965 1
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