ML19326B411

AO 500813/74-06:on 740811,reactor Protection Sys Channels A&D Tripped on High Flux During Pseudo Control Rod Ejection Test.Caused by Procedural Error.Procedure Changed & Emphasis Placed on in-limit Bypass

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: ML19326B407 ML19326B411
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. l During the second withdrawal step of CRA 7-4, the startup rate increased I 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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800415077I -

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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. c d

July 5, 1974 NSP-l'O.. Rev. O Page 2 of 3

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11. Pailure Data:

There have been no other occurrences of this type. No equipment mal-function was involved. ,

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12. Reviews and Approvals:

Reviewed and Approved by: Plant Safety Committee Yes ( No ( )

O N2 Plant Superintendent

Reference:

Yes % No ( ) ._

T(A) 0 - N8 Date: 7 //

a' Reviewed by:

Licensing Supervisor Date-

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Approved by://7/((8 s 'p Safe'ty Revi Date:

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nagerofNuclearSer(ides Date: 2o ' !'7

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l July S, 1974 NSP-10, Rev. O Page 3 of 3 l

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