ML19317E147
| ML19317E147 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/29/1974 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19317E146 | List: |
| References | |
| NUDOCS 7912160015 | |
| Download: ML19317E147 (2) | |
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k n.O DUKE POWER COMPANY OCONEE UNIT 2 Report No.:
A0-270/74-9 Report Date:
July 29, 1974 Occurrence Date:
July 18, 1974 Facility:
Oconee Unit 2, Seneca, South Carolita Identification of Occurrence: Failure to provide redundant boric acid sources Conditions Prior to Occurrence:
Reactor at 80 percent full power Description of Occurrence:
Oconee Nuclear Station Technical Specification 3.2.2 requires that at least one source per unit of concentrated boric acid, in addition to the borated water storage tank, be available and operable prior to critical operation.
This can be either the boric acid mix tank (BAMT) or the concentrated boric acid storage tank (CBAST).
On July 18, 1974, the concentrated boric acid storage tank level was noted to have increased, and subsequent sampling showed the concentration was below specification.
The BAMT was not available as a redundant source of boric acid since the vole ? was below that required by the specification.
Reactor shutdown commenced and CBAST bleed and feed to obtain necessary con-centration and volume was initiated.
Upon completion of boric acid transfers cclculated to bring the CBAST into specification, the reactor shutdown was terminated and power level increased.
Following four hours of recirculation, the CBAST was sampled, and the concentration was 8030 ppm. Reactor shutdown recommenced.
On July 19, 1974, the Technical Specifications were satisfied and reactor power level was again increased.
Designation of Apparent Cause of Occurrence:
The concentrated boric acid storage tank was in specification until an in-creasing lovel trend was noted. The cause of the increasing boric acid water level was seat leakage in the demineralized water supply valve 2DW-87.
Analysis of Occurrence:
Technical Specification 3.2.2 requires that the boric acid mix tank contain at least 450 cubic feet of 10,600 ppm boric acid solution, or the concentrated boric acid storage tank contain at least 550 cubic feet of 8,700 ppm boric acid solution, to be considered a redundant source of boric acid. A redundant source of boric acid is required when the inactor is critical to ensure that a single failure will not prevent bo::ation to a cold shutdown condition.
7 912180 o/f
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The result of demineralized water leaking into the concentrated boric acid storage tank was to decrease the concentration of the contents of the tank.
At the time that the level increase was noted and sampled, there were 2,350 cubic feet of 7.257 ppm boric acid solution in the concentrated boric acid storage tank. although the concentration was 17 percent below specifications, t'ie volume was 430 percent above that required.
This quantity of boric acid solution is more than sufficient to permit boration to a cold shutdown cvidition and thus the concentrated boric acid storage tank could have been uscd as a redundant source of boric acid.
It is concluded that the health and safety of the public was not affected.
On Ju3y 19, 1974, a change to the Technical Specifications was approved which allows the equivalent concentrations and volumes to be maintained in the borated acid mix tank and concentrated boric acid storage tanks.
Corrective Action:
Demineralized water valve 2DW-87 was repaired. No further leakage of Jemineralized water into the concentrated boric acid rtorage tank has been noted.
Failure Data:
Grinnell 2" diaphragm valve.
Grinnell, Figure 2471-26-M refers.
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