ML19345A380
| ML19345A380 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/06/1967 |
| From: | Boyd R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | |
| Shared Package | |
| ML19345A379 | List: |
| References | |
| NUDOCS 8011210217 | |
| Download: ML19345A380 (2) | |
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i SAFETY EVALUATION BY THE RESEARCH AND POWER REACTOR SAFETY BRANCH DIVISION OF REACTOR LICENSING IN THE MATTER OF YANKEE ATOMIC ELECTRIC COMPANY PROPOSED CHANGE NO. 78 DOCKIT NO. 50.29 In trodt.c tion Pursuant to the provisions of Section 50.59 of the Comission's regulations, Yankee Atomic Electric Company, in Proposed Change No. 78, dated December 30, 1966, requested authorization to change the Technical Specifications attached as Appendix A to License No. DPR-3.
This change would permit the boron con-centration in an isolated primary system loop to be reduced to the main cer,lant concentration if the isolation valve and main coolant pump controls have been secured to preclude inadvertent operation. This change was re-quested to permit more efficient operation when the reactor is operating with an isolated main coolant' loop.
Discussion The Yankee reactor has four main coolant loops that contain a pair of isola-tion valres in each loop. These vcives are provided to isolate a leaking main coolant loop, and thereby enable continued reactor operation at reduced power level. When the. Yankee reactor is operated with an isolated loop, undesired reactivity additions could occur if the relatively cold isolated loop water or isolated loop water at lower boron concentration that the main coolant were inadvertently m5ed with the main coolant. To prevent the addition of cold water, procedural controls and safety interlocks have been designed
- prevent the return to service of an isolated loop unless the water temperature is within specified limits. The addition of water at lower than the main coolant boron concentration is prevented by a Technical Specification require-ment (Section D.2.d.9) that the boron concentration in an isolated loop be maintained at the shutdown concentration (approximately 2400 ppm).
I The operation of the reactor with an isolated loop at high boron concentration results in some operating inconvenience. This results from the small leakage between the main coolant and the isolated loop which requires the continued addition of boron to the isolated loop to maintain its specified concentration, and the removal and disposal of boron which leaks into the main coolant. To permit more efficient reactor operation, Yankee has proposed to operate the isolated loop at boron concentrations as low as the main coolant concentration t
so that the interchange of water will not require any unnecessary boron l
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2 addition or dilution. This mode of operation would only be permitted when the isolation valves and the main coolant pump have been secured by removal of the power source and locking the control switches so that inadvertent operation is precluded. These requirements are sufficent to prevent any undesired reactivity additions by this mechanism. The existing temperature and boron concentration requirements for returning an isolated loop to service would not be affected by this change. Therefore, we believe that the safety of reactor operations would not be adversely affected by this change.
Technical Specifications To implement this change, the following sentence should be adde 6 to Section D.2.d.9 of the Technical Specifications:
"Following isolation of a main coolant loop, when the loop isolation valve and main coolant pump controls have been removed from service and mechanically prevented from operation by lock and key, the boron concentration in the isolated loop may be reduced to that existing in the main coolant system at that time."
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 there is reasonable assurance that the health and safety of the public will not be endangered.
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W Roger S. Boyd,Ihia -
Research & Power Reactor Safety Branch Division of Reactor Licensing Date: JAN 6 1967 7
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