ML20082L276
| ML20082L276 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 08/26/1991 |
| From: | James Fisicaro ENTERGY OPERATIONS, INC. |
| To: | Martin R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| Shared Package | |
| ML20082L253 | List: |
| References | |
| NUDOCS 9109040046 | |
| Download: ML20082L276 (5) | |
Text
FLG 26 '91 16:39 P.3'5
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August 26, 1991 2CAN089107 Mr. Robert D. Martin Regional Administrator U. S. Nuclear " # latory Commission Region IV 611 Ryan plaza Drive. Suite 1000 Ar11ngton, TX 76011
Subject:
Arkansas Nuclear One - Unit 2 Docket No. 50-368 License No. NPF-6 Request for Temporary Waiver of Compliance
Dear Mr. Martin:
1his letter arovides the written documentation to follow up the Arkansas Nuclear One 'Jnit 2 (ANO-2) verbal request at 2245 hours0.026 days <br />0.624 hours <br />0.00371 weeks <br />8.542225e-4 months <br /> on August 23, 1991 regarding a temporary waiver of compliance from-Technical Specification Limiting Condition for Operation (LCO) 3.1.3.1 Action "g".
This Specification requires that the unit be placed in at least H0f STANDBY within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> if more than one full length or part length CEA is inoserable or misaligned from any other CEA in its group by more than 19 incies. On August 23, 1991 at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br />, while performing-Surveillance Requirement 4.1.3.1.2, which exorcises the CEAs to demonstrate that they are movable, the Group 6 CEAs failed to respond to control room demands.
I&C Technicians were immediately dispatched to determine the.cause of the failure.
The failure was due to a defective relay card in the Control Element Drive Mechanism Control System (CEDMCS).
The card was replaced and the Action Statement was exited at 0118 hours0.00137 days <br />0.0328 hours <br />1.951058e-4 weeks <br />4.4899e-5 months <br /> on August 24, 1991.
The request for the waiver was to allow additional time up-to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to troubleshoot and. correct the problem without subjecting the unit to an unnecessary power reduction or possible shutdown.
The need for additional l
time in a situation like this has been previously recognized by Entergy Operations for ANO-2. A Technical Specification change request which would allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to correct a problem like that experienced on August 23, 1991 1991-was submitted in Entergy Operations letter of April 9,d and approved (2CAN049102). The ANO Plant safety Committee (PSC) reviewe Since the r quested waiver was that request prior to its submittal.
e consistent with the proposed Technical Specification change request, ANO considers this similar request to have been previously reviewed and 9109040046 910027 PDR ADOCK 05000313 P.
Mr. Robert D. Martin August 26, 1991 Page 1 annroved by.the PSC.
The NRC provisionly granted Entergy Operations verbal request for a Temporary Weiver of Compliance at app'oximately 2325 hours0.0269 days <br />0.646 hours <br />0.00384 weeks <br />8.846625e-4 months <br /> on Auw st 23, 1991. A nonprovisienal waiver was granted shortly thereafter.
The attached provides the information required to support the verbal temporary valver of compliance granted on August 23, 1991.
Your cooperation regarding AN0's verbal request is appreciated.
If you have any questions regarding the attached information, please contact my office.
Very truly yours,
.d D e mes J. Fisicaro Director, Licunsing JJF/DEJ/sjf Attachment cc: NRC Resident inspector Arkansas Nuclear One - ANO-1 & 2 Humber 1. Nuclear Plant Road Russellville, AR 72801 Mr. Thomas W. Alexion NRR Project Manager, Region IV/ANC-1 G
U. S. Nuclear Regulatory Commission i
NRR Mail Stop 11-0-23 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852 Ms. Sheri Peterson NRR Project Manager, Region IV/ANO-2 U. S. Nuclear Regulatory Commission NRR Mail Stop 11-0-23 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852
R Xs 26 ' M 16:40-P.5/5 ATTACHMENT ANO-2 TEMPORARY WAIVER OF COMPLIANCE TECHNICAL SPECIFICATION SECTION 3.1:3.2g 9
Description of Conditional Requ_irement for Which Waiver is Required On August 23, 1991 at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br />, Surveillance Requirement 4.1.3.1.2 was being performed.
This surveillance requires each full-length CEA not fully inserted and each part-length CEA which is inserted in the core be demonstrated to be OPERABLE by movement of at least 5 inches in any one direction at least once per 31 days. When attempts were made to move the Group 6 CEAs, in accordance with the surveillance requirement,-they would not respond to control room demands.
I&C Technicians were immediately dispatched to determine the cause of the malfunction.
Troubleshooting by the I&C Technicians included recording electrical current (traces) to the Group 6 Control Element Drive Mechanisms (CEDMs).
From those traces, it was determined that there was no current going to the CEDMs as required to move the CEAs.- The failure was ultimately traced to a defective relay card in the Control Element Drive Mechanism Control System (CEDMCS).
The relay card was replaced, the Group 6 CEAs were exercised and the Action Statement exited at 0118 hours0.00137 days <br />0.0328 hours <br />1.951058e-4 weeks <br />4.4899e-5 months <br /> on August 24, 1991.
Technical Specification Limiting Condition for Operation 3.3.3.1 Action "g" requires that with more t~ nan one full-length or part-length CEA inoperable i
or misaligned from aey other CEA in its group by more than 19 inches
-(indicated position), thht the unit be in 4' least HOT STANDBY within 6 group was-declared inoperable hours. Group 6 contains 5 CEAs.
The enti: 4 at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> on August 23, 1991. Without the temporary waiver of compliance, the unit would have been required to reduce power and' ultimately shut down within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> had the oroblem not been corrected.
It is also very possible that an attempt to perform a controlled unit shutdown with the Group 6 CEAs immovable would have rssulted in a reactor trip.
The Group 6 CEAs are the primary means for controlling Axial shape Index (ASI)
L during power maneuvers.
A controlled shutdown with these rods in:apable of being moved could possibly have lacd to a reactor trip due to ASI imbalance.
Preliminary Evaluatiot, of Safety Significance and Consecuences of Request As described in the AND-2 Safety Analysis Report, the CEAs provide short term reactivity control (long-term reactivity control is accomplished by the-use of soluble poison) and insert a large amount of negative reactivity upon a reactor trip signal from the Plant Protective System (PPS).
The CEAs are also used to control-the power distribution shape of the core.
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AUG 26 '91 16:41 P.6/5 I
i The Control Element Drive Mechanism Control System (CEDMCS) is made up of i
the magnetic jack drive devices (Control Element Drive Mechanisms (CEDMs),
two motor generator sets, reactor trip switchgear, coil power switch (which controls the sequence in which the CEDM coils energize and doenergize), and the CEDMCS operating console.
This console acts as the interface between the operator and the system by directing the control logic for proper sequencing of the CEA coils, which in turn determines the direction of CEA motion, j
An electronic or electrical malfunction in the CEDMCS does not affect the ability of the CEAs to trip if required, but may result in a situation where the CEAs cannot be electrically moved. The CEAs, however, remain trippable and capable of performing their primary safety function of shutting down the reactor upon initiation of a reactor trip signal.
A CEA is considered trippable if the CEA was demonstrated operable during the last performance of Surveillance Requirement 4.1.3.1.2 and met the CEA drop time criteria during testing following the last refueling outage.
A CEA can be assumed to be trippable until CEA traces indicate otherwise.
The Temporary Waiver of Compilance was requested to allow additional time (up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) to troubleshoot and correct the CEDMCS electrical malfunction l
encountered on August 23, 1991.
This additional time was necessary to perform the following:
1)
Allow sufficient time to evaluate the nature of the failure and to develop a systematic work plan, i
2)
Allow suf ficient time to perform troubleshooting activities in a deliberate and systematic manner.
3)
Allow sufficient time to obtain the necessary part and perform repairs.
Basis for No Significant Hazards Consideration Determination In accordance with 10 CFR 50.92(c), Entergy Operations has evaluated whether the proposed Temporary Waiver of Compliance (waiver) involves a significant safety hazards consideration.
Entergy Operations has concluded that the proposed waiver did not involve a significant hazards consideration because the operation of Arkansas Nuclear One, Unit 2 in accordance with the wavier would not:
(1)
Involve a significant increase in the probability or consequences of an accident previously evaluated.
Allowing 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for diagnosis and repair associated with electronic or electrical malfunctions of the CEDMCS is acceptable, since the primary safety function of these CEAs (reactor trip) remains unaffected.
The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowance is considered justifiable in order to provide adequate time to effect repairs without undue exposure to any opera-tional requirement to move the affected CEA group.
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_..-__m FLG'26 '91 16342 P.7/5
[.y is-1 The1 waiver did not alter the requirements of CEA position, insertion L
or alignment limits, ano surveillance requirements so that power and
-peaking distributions used in the safety analysis will remain unaf-F fected.
The waiver did not affect the ability of the CEAs to perform their intended safety function when a safety system setting is reached.
l Therefore, the consequences of accidents related to or dependent upon CEA operation will remain unaffected.
(2) Create-the possibility of a new or different kind of accident from any previously evaluated.
There are no new failure modes or mechanisms associated with the waiver.
The waiver did not involve any modification in the operational-limits or physical design of the involved systems.
The waiver reduced the burden on the control-room staff by allowing sufficient time for system o
repair and prevented the possibility of a reactor trip ihich would have challenged-safety systems.
1 (3)' Involve a significant reduction in the margin of safety The waiver did not affect any Technical Specification margin of safety.
The waiver allowed appropriate actions commensurate with the sign:ficance of the CEDMCS' malfunction, while not subjecting the plant to a transient in response to malfunctions that do not affect l
the capability of'the CEAs to perform their primary safety function.-
l Other Technical Specification limits for reactivity related items, such as shutdown margin and CEA insertion and_ alignment limits remained l
in effect and were complied with to ensure that the safety margins' vere t
maintained.
~ Basis for-No' Environmental Consequences This request for a Temporary Waiver of_ Compliance did not have-a significant affect, impact or change on the quality of the human environment at ANO.
This request, when implemented, does.not _ impact.the ANO-2 Operating License or the Environmental Report.
Therefore, this request did not significantly involve irreversible environmental consequences.-
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