ML19326B411
| ML19326B411 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/19/1974 |
| From: | Cavanaugh W, Phillips J, Reuter D ARKANSAS POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML19326B408 | List: |
| References | |
| NUDOCS 8004150775 | |
| Download: ML19326B411 (3) | |
Text
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1.
Abnormal Occurrence Report No.
50-313/74-6
- 2.
- Report Date:
8-19-74 3.
Occurrence Date:
8-11-74 4.
Facility:
Arkansas Nuclear One-Unit 1 5.
Identification of Occurrence: Automatic Reactor Trip (RPS Channels A 4 D) on High Flux reportable under Tech. Spec. 1.8.6.
Note: After re-evaluation and concurrence with Region 2 compliance, an automatic trip is not considered an abnormal occurrence per Tech. Spec. 1.8.6 and 6.
Conditions Prior to Occurrence:
/will not be defined as such in the future.
Steady-State Power Reactor Power 0
Wth Hot Standby Net. Output 0
MWe Cold Shutdown Percent of Full Power 0 Refueling Shutdown Routine Startup Operation V
Routine Shutdown
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Operation Load Changes During Routine Power Operation Other (Specify)
X Zero Power Physics Testing After Initial Criticality.
7.
Description of Occurrence:
i While obtaining the initial conditions for the pseudo-control rod ejection test, the reactor operator was withdrawing CRA 7-4 toward the out limit and compensating for the reactivity addition with CRA Group 5.
During the second withdrawal step of CRA 7-4, the startup rate increased more rapidly than anticipated and the reactor operator attempted to reduce the startup rate by inserting CRA 7-4 which did not respond. As flux continued to increase, the operator selected CRA Group 5 and attempted to halt the power increase; however, the reactor tripped before Group 5 was able to turn the power excursion around. The total amount of positive reactivity added from just critical is estimated to be less than 0.1%
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%4 Abnormal' Occurrence Report No.
50-313/74-6 Sheet 2 8.
Designation of Apparent Cause of Occurrence:
Design Procedure X
Manufacturo Unusual Service Condition Including Installation /
Environmental Construction Component Failure Operator Other (Specify)
Following the reactor trip, it was realized that the control rod "In-Limit Bypass" was required to allow CRA 7-4 to be inserted as the other members of this CRA group were at the In-Limit.
Os 9.
Analysis of Occurrence:
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Due to the fact that the Reactor Protection System high flux bistables were set to trip at less than an indicated 5% of full power (0.5% actual power due to a reduction of the power range amplifier gain trip at approximately 0.25% FP (2.5% indicated), no safety implications are apparent. All equipment functioned properly.
5 The occurrence is considered to be a fault of the Zero Power Physics Test Procedure, as this type of CRA operation is not normal. A caution note should have been included in the test procedure to prepare the operator for such an occurrence.,
- 10. Corrective Action:
Procedure changes were initiated (and implemented the same day) which explicitly caution the operator and test team to be aware of the need to use the in-limit bypass for operation of CRA',s) in the same group are at the in-limit.
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July 5, 1974 NSP-l'O.. Rev. O Page 2 of 3
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p Mc Abnormal Occurrence Report No.
50-313/74-6 Sheet 3
- 11. Pailure Data:
There have been no other occurrences of this type. No equipment mal-function was involved.
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Reviews and Approvals:
Reviewed and Approved by: Plant Safety Committee Yes (
No ( )
O Plant Superintendent Yes %
No ( )
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J July S, 1974 NSP-10, Rev. O Page 3 of 3 l
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