05000346/LER-1978-118-03, /3L-0 on 781130:Xe Reactivity Declared to Be Greater than 10% from Equilibrium.Caused by Personnel Failure to Adequately Anticipate the Dynamics of the Xe Transient.Personnel Educated Re Xe Transient Procedures

/3L-0 on 781130:Xe Reactivity Declared to Be Greater than 10% from Equilibrium.Caused by Personnel Failure to Adequately Anticipate the Dynamics of the Xe Transient.Personnel Educated Re Xe Transient Procedures

ML19270E930
Person / Time
Site:	Davis Besse
Issue date:	12/27/1978
From:	Fulmer S TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19270E928	List: 05000346/LER-1978-118, Forwards LER 78-118/03L-0 05000346/LER-1978-118-03, /3L-0 on 781130:Xe Reactivity Declared to Be Greater than 10% from Equilibrium.Caused by Personnel Failure to Adequately Anticipate the Dynamics of the Xe Transient.Personnel Educated Re Xe Transient Procedures ML19270E927
References
LER-78-118-03L, LER-78-118-3L, NUDOCS 7901030154
Download: ML19270E930 (3)

LER-1978-118, /3L-0 on 781130:Xe Reactivity Declared to Be Greater than 10% from Equilibrium.Caused by Personnel Failure to Adequately Anticipate the Dynamics of the Xe Transient.Personnel Educated Re Xe Transient Procedures

Event date:
Report date:
3461978118R03 - NRC Website

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-78-138 DATE OF OCCURRENCE: November 30, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Power level cutoff exceeded with xenon reactivity and control rods not stabilized.

Conditions Prior to Occurrence: The unit was in Mode 1, with Power (SBTI) = 2600, and Load (MWE) = 820.

Description of occurrence: On November 30, 1978, at approximately 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> during an up power maneuver, reactor thermal power was raised to 92% (power level cutoff). The accompanying xenon " burnout" f rom the up power maneuver continued to insert positive reactivity which was compensated for by inserting control rods and boron injection into the Reactor Coolant System. At approximately 0753 hours0.00872 days <br />0.209 hours <br />0.00125 weeks <br />2.865165e-4 months <br /> on November 30, 1978, the control rods reached their allowable insertion limit and thermal power increased to approximately 95%. At approximately 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br /> on November 30, 1978, xenon reacti-vity was declared to be greater than 10% from the equilibrium value for rated ther-mal power. This placed the unit in the Action Statement of Technical Specification 3.1.3.8, which requires thermal power be maintained below the power cutof f until xenon reactivity or control rod reactivity has stabilized.

The continued injection of boron into the Reactor Coolant System permitted reduction of thermal power to less than 92% at approximately 0830 hours0.00961 days <br />0.231 hours <br />0.00137 weeks <br />3.15815e-4 months <br />. This removed the unit from the Action Statement of Technical Specification 3.1.3.8.

Designation of Apparent Cause of Occurrence: The cause of this occurrence is attri-buted to personnel error. The personnel involved failed to adequately anticipate the dynamics of the xenon transient associated with the increase in power. As a result, the relatively slow process of Reactor Coolant System boron injection was not initiated sufficiently in advance to permit proper reactivity control at the desired 92% 1cvel.

Analysis of Occurrence: There was no threat to the health and safety of the public or to unit personnel. The unit was returned to less than 92% thermal power within approximately 15 minutes from the time xenon equilibrium conditions were declared to be in excess of the 10% equilibrium limit. Additionally, chemical analysis indicates no violation of fuel integrity occurred within the core.

i LER #78-118

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I DAVIS-BESSE NUCLEAR P0h'ER STATION UNIT ONE "UPPLEMENTA!. INFOR:fATION FOR LER NP-33-78-138 PAGE 2 i

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Corrective Action

Upon identification of exceeding the 10% equilibrium xenon require-ments boron injection was used to add negative reactivity and control rods were maintained at the insertion limit until thermal power was reduced to within the power 'evel cut-off value.

The importance of maintaining proper plant control, particularly in anticipating tran-sient plant responses, has been discussed with the personnel involved.

Failure Data: There have been no previous incidents involving the power level cutoff being exceeded.

LER #78-118