05000346/LER-1981-030-03, /03L-0:on 810512,axial Power Imbalance Limit Exceeded.Caused by Procedural Inadequacy.Procedures ST 5042.02 & EP 1205.16 Have Been Modified

/03L-0:on 810512,axial Power Imbalance Limit Exceeded.Caused by Procedural Inadequacy.Procedures ST 5042.02 & EP 1205.16 Have Been Modified

ML19350E049
Person / Time
Site:	Davis Besse
Issue date:	06/09/1981
From:	David Brown TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19350E041	List: 05000346/LER-1981-030, Forwards LER 81-030/03L-0 05000346/LER-1981-030-03, /03L-0:on 810512,axial Power Imbalance Limit Exceeded.Caused by Procedural Inadequacy.Procedures ST 5042.02 & EP 1205.16 Have Been Modified
References
LER-81-030-03L, LER-81-30-3L, NUDOCS 8106160345
Download: ML19350E049 (3)

LER-1981-030, /03L-0:on 810512,axial Power Imbalance Limit Exceeded.Caused by Procedural Inadequacy.Procedures ST 5042.02 & EP 1205.16 Have Been Modified

Event date:
Report date:
3461981030R03 - NRC Website

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1. J EVENT OESCRIPTION AND PROS ABLE CONSEQUENCES h lo12l l (NP-33-81-33) On 5/12/81 at 1408 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.35744e-4 months <br />, the axial power imbalance limit was exceeded. I Prior to the event, reactor I

g l placing the unit in the action statement of T.S. 3.2.1.

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DVR 81-067 NAME OF PHEPAHLH

TOLEDG EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL-INFORMATION FOR LER NP-33-81-33

.e DATE OF EVENT: May 12, 1981 FACILITY: Davis-lesse Unit l' IDENTIFICATION OF OCCURRENCE:- Axial Power Imbalance Limitt. Exceeded With Reactor Power Greater Than 40%

Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 2031 and Load (Gross NWE) = 680 Description of Occurrence: During the late morning and early afternoon of May'12, 1981, reactor operators were performing ST 5042.02; " Reactor Coolant System (RCS)

Water Inventory Balance" (as required by EP 1202.16, " Reactor Coolant Pump and Motor EmergencyL Procedure") due to a seal failure on Re' actor Coolant Pump (RCP) 2-1 which had occurred ecrlier in the day. Prior to taking RCP 2-1 out of service, reactor power had to be reduced from approximately 100% to 75%. The ensuing xenon transient drove in control rods causing axial power imbalance to go increasingly negative. This effect had to be countered by RCS boration to maintain axial power imbalance within its Technical Specification limits.

In order to perform ST 5042.02 successfully, the RCS has to be maintained as close as possible. to steady state conditions. This entails, among other things, that no additions of boric acid or water to the RCS be made during this test.

At 1402 hours0.0162 days <br />0.389 hours <br />0.00232 weeks <br />5.33461e-4 months <br /> on May-12, 1981, the reactor operators, realizing that axial power im-balance was approaching its Technical Specification limit, stopped ST 5042.02 and injected 30 gallons of boric acid into the RCS. At 1408 hours0.0163 days <br />0.391 hours <br />0.00233 weeks <br />5.35744e-4 months <br /> on May 12, 1981,-the axial power imbalance Technical Specification limit was exceeded. The reactor opera-tors inserted axial power shaping rods (APSRs) 1% (to 24% withdrawn) and, as a result, axial power imbalance was brought back within limits at 1420 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.4031e-4 months <br /> on May 12, 1981.

Exceeding axial power imbalance limits picced the unit in the action statement of Tech-nical Specification 3.2.1 which states that while in Mode 1 and E 40% rated thermal power, with axial power imbalance exceeding the linits specified on figure 3.2-2a of the Technical Specifications, axial power imbalance must be restored to within its Technical Specification limits within 15 minutes or be in hot standby within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.

The total time.that the axial power imbalance Technical Specification limit was ex-ceeded was 12 minutes.

Designation of Apparent Cause of Occurrence: The cause of this occurrence is pro-cedural inadequacy. Procedures EP 1202.16 and ST 5042.02 do not provide proper guidance to the reactor operators during a xenon transient for determining when ST 5042.02 should be performed, how long it should be run, and when, if necessary,

'it should.be't.rminated to avoid exceeding axial power imbalance limits.

EP 1202.16 e

also has conflicting supplementary action steps. Step 1.4.2 suggests running

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ST-5042.02 if idle RCP total seal flow exceeds 2 GPM.

Step 1.4.3 suggests running

'ST 5042.02' unconditionally.

LER #81-030

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTARY INFORMATION FOR LER NP-33-81-33 PAGE 2 p

Analysis'of Occurrence: There was no danger to the health and safety of'the public cr to a?,ation personnel. The reactor operators took corrective action to reverse the trend of the axial power imbalance before the axial power imbalance technical specif* ation limit was exceeded and as a result of this action, restored axial power Ambalance within limits within the time allotted by the technical specifica-tion action statement. No safety limits were exceeded as maximum axial power in-balance was -6.1%.

The technical specification axial power imbalance limit for.

this power history, power level, and RCP combination is -5.8%.

Corrective Action

At 1402 hours0.0162 days <br />0.389 hours <br />0.00232 weeks <br />5.33461e-4 months <br /> on May 12, 1981, the reactor operators, realizing that axial power imbalance was approaching its Technical Specification limits, in-jected 30 gallons of boric acid into the RCS. After the axial power imbalance limits were exceeded, the operators inserted APSRs 1% (to 24% withdrawn). The combination cf boric acid addition and APSR insertion restored axial power imbalance within limits ct 1420 hours0.0164 days <br />0.394 hours <br />0.00235 weeks <br />5.4031e-4 months <br /> on May 12, 1981.

EP 1202.16 has been modified (per modification T-5561) to add guidance for the reac-tor operators when performing ST 5042.02. ST 5042.02 has been modified (per modifica-tion T-5560) to ;ive reactor operators special guidance when performing this test during xenon transient conditions.

Failure Data: There have been no previous similar events.

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