05000327/LER-1989-026-01, :on 891107,Limiting Condition for Operation 3.0.3 Entered as Result of More than One Rod Position Indicator (RPI) Per Bank Being Inoperable.Caused by Lack of Preventive Maint.Rpis Adjusted

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:on 891107,Limiting Condition for Operation 3.0.3 Entered as Result of More than One Rod Position Indicator (RPI) Per Bank Being Inoperable.Caused by Lack of Preventive Maint.Rpis Adjusted
ML20005D735
Person / Time
Site: Sequoyah Tennessee Valley Authority icon.png
Issue date: 12/07/1989
From: Bynum J, Hipp G
TENNESSEE VALLEY AUTHORITY
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-026-01, LER-89-26-1, NUDOCS 8912140380
Download: ML20005D735 (7)


LER-1989-026, on 891107,Limiting Condition for Operation 3.0.3 Entered as Result of More than One Rod Position Indicator (RPI) Per Bank Being Inoperable.Caused by Lack of Preventive Maint.Rpis Adjusted
Event date:
Report date:
3271989026R01 - NRC Website

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,1 TENNESSEE VALLEY AUTHORITY-pr a-6N 38A Lookout Place December 7, 1989 7

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U.S. Nuclear Regulatory Commission ATTN:- Document Control Desk Washington, D.C.

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Gentlemen:

ll TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.

50-327 - FACILITY CPERATING LICENSE DPR LICENSEE EVENT REPC"; (LER) 50-327/89026-The enclosed LER provides details-of an event wherein Limiting Condition for Operation 3.0.3 was entered because more than one rod-position indicator per 1

' bank wac-inoperable.- This. event is being reported in-accordance with~

10 CFR 50.73, paragraph a.2.1.B.

Very truly yours, t

TENNESSEE VALLEY #1THORITY-I 4

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. R. Bynum, Vice President Nuclear Power Production Enclostre ec (Enclosure):

Regional Administration U.S. Nuclear Regulacory Commissloc Office of Inspection and Enforcer <.t-Region II-101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 INPO Records Center

. Institute of Nuclear Power Operations 4

1100-Circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennesses 37379 8912140380 891207 PDP ADOCK 05000327 S

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Sequoyah Nuclear Plant,- Unit 1 01Q0 l 0 l 0 l 3l 2 l7,1 loFl0 l6

' " ' ' ' ' ' Entry into LCO 3.0.3 as a result of more than one RPI per b w.k being inoperable because of a lack of preventive maintenance to CRDM cooling system.iampers.

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L On November 7,1989, with Uc!ts 1 and 2 in Mode 1 at 100 and 30 percent power, respectively, Limiting Condition for Operation (LCO) 3.0.3 was entered on Unit 1 as a rssult of more than one rod position indicator (RPI) per bank being inoperable because they were not within the required 12-step tolerunce.

The control rod drive mechanism I

(CRDM) cooling system had been realigned for surveillance testing earlier and had apparently malfunctioned causing the RPIs to become overheated and drif t out of tolerance. Af ter the original CRDM cooling system alignment was restored, the RPIs were edjusted back to within the required 12-step tolerance and the LCO was exited. The root estse of this event is believed to have been a lack of preventive maintenance (PM) on the CRDM cooling system dampers resulting in a malfunction. Because these components are not accessible at power, verification of a malfunction will have to await the next outage. Two contributing causes of this event have also been identified:

(1) equipment

'dsficiencies that interfered with the verification of proper CRDM cooling system b,rformance by operators following the system realignment, and (2) a lack of procedural guidance for the operators on indicators to monitor while realigning the system. As corrective action, the appropriate CRDM cooling system components (such as the dampers) will be placed in a PM syste.;c.

In addition, a more appropriate description for Computer Point T1014A will be determined for its P-250 listing. A section will also be added to the syrtem operating Jrstruction to provide better guidar.ce for the operators when swapping the fang for CRDM enclosure cooling.

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DESCRIPTION OF EVENT

- At 2337 Eastern standard time (EST) on November 7, 1989, with Unit 1 in Mode 1 at 100 percent power, 2.235 pot..tas per square inch gauge (psig), 578 degrees Farenheit (F), and Unit 2 in Mode 1 at 30 percent power, 2,235 psig 559 F, Limiting Condition for Operation (LCO) 3.0.3 was entered on Unit 1 as a result of more than one rod position indicator (RPI) (EIIC Code AA) per bank being inoperable.

Earlier in the same day, the A-A and B-B control rod drive mechanism (CRDM) cooling fans (EIIS Code CD) were in service with suction aligned to the CRDM enclosure.

(See attached simplified sketch.) Preparations were being made to perform Surveillance Instruction (SI) 266.1.2, "18-Month Circuit Breaker Inspection (Westinghouse Type DS 480V) " to test Breaker SQN-1-BCTB-030-0092-B, which supplies power to the B-B CRDM cooler fan. At 2055, the unit operator (UO) swapped from the A-A and B-B CRDM cooling fans to the C-A and D-B fans, aligning their suction to the CRDM enclosure.

At 2121 Computer Point T1014A exceeded its alarm setpoint of 175 F, This computer point prints out in the main control room on the process monitoring computer (P-250) trend typer. At approximately 2200, when the survelliance testing was completed on the B-B CRDM cooling fan, the UO restored the CRDM cooling system to its original configuration, i.e., A-A and B-B CRDM cooling fans in service. After this cooling system realignment, the temperatures indicated by computer point T1014A rapidly returned to normal levels.

At 2337. RPIs for the following control rods were declared inoperable because they indicated more than a 12 step deviation from their respective group demand position indicators:

Control Rod Location Bank Group F-10 Control C 2

K-10 Control C 2

F-14 Control B 2

P-08 Control C 1

K-06 Control C 2

H-08 Control D 2

G-13 Shutdown B 2

The RPIs are temperature sensitive and had drifted out of tolerance. Because LCO 3.1.3.2 contains only an action requirement for a maximum of one RPI per bank inoperable and more than one RPI per bank was inoperable, LCO 3.0.3 was entered ac of 2337. A work request was written at 0030 on November 8, 1989, to adjust the RPIs back to within tolerance.

At 0259 instrument maintenance technicians began adjusting the RPIs with SI-67, " Periodic Calibration of RPI System," utilizing the following general procedure.. working on only one rod bank at a time. Each of the eight rod banks (four control banks and four safety banks) was inserted to 215 steps. When each control bank was inserted LCO 3.1.3.6 (control bank insertion limits) was entered, and when each safsty bank was inserted, LCO 3.1.3.5 (shutdown rod insertion limits) was entered. The l

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Ssquoyah Nttelear Plant, Unit 1 o l5 lo lo l0 l 3l2 l7 8] 9 0l2l6 0 l0 0l3 OF 0l6 TEKf Wmese Apose e seguset ese assuumons/ 44C Fonn JE4's#(IDRPIs were then adjusted, and the rod bank was returned to 228 steps. The average length of time the rod banks were in LCO 3.1.3.5 or 3.1.3.6 was 12 minutes with a maximum duration of 17 minutes.

By 0435 LCO 3.0.3 was exited when all but one bank of RPIs had bacn adjusted back within the allowable 12 step tolerance.

By 0444, the last. bank of RPIs had been adjusted, and all applicable LCOs were exited.

As the RPIs gradually cooled during the remainder of November 8, 1989, their indications ware noted to be drifting in the opposite direction as when they were heating up as.rlier. Starting at approximately 2100 on November 8, 1989, and on into November 9, 1989, the RPI banks were again adjusted to stay within the allowable tolerance.

LCOs 3.1.3.5 and 3.0.3 were entered each time a shutdown bank was inserted for adjustment, and LCO 3.1.3.6 was entered each time a control bank was inserted for adjustment.

CAUSE OF EVENT

Th3 root cause of this event is believed to have been a lack of preventive maintenance (PM) on the CRDM cooling system dampers. Alignment of the CRDM cooling system to the C-A and D-B cooling fans failed to provide adequate cooling to the CRDM enclosure. The auspected reason for the inadequate cooling is a damper malfunction that aligned the cooling fan suction to bypass rather than to the CRDM enclosure.

(See attached simplified sketch.) This reason is suspected because of previous problems with the danpers.

In Septetaber 1988, the cognizant system engineer inspected the CRDM cooling system and identified a number of problems. Work requests were initiated to correct the problems, and the problems were subsequently fixed. However, because the dampers in the system are not covered by a PM program, it is suspected that they.nay have agr.in experienced a malfunction.

Because these components are not accessible at power, varification of a malfunction will have to await the next outage.

Two contributing causes of this event have also been identified. The first is equipment daficiencies that interfered with the verification of proper CRDM cooling system parformance by operators following the swapover to the C-A and D-B cooling fans. The most useful temperature indication available to the operators following swapover would have been the CRDM enclosure exit temperatures measured by TE-30-211E and TE-30-211F, shown on the attached simplified sketch. However, the main control room display for thsse temperatures, the Morgan-1 recorder (TR-56-1), was inoperable at the time of this svant. The temperature indication that was available to the operators in the main control room was the P-250 Computer Point T1014A.

However, this computer point was vaguely labeled as containment air temperature opposite from the refueling gate, which reduced its usefulness to the cperators. The second contributing cause of this event is a lack of guidance for the operators on indicators to monitor while swapping CRDM cooling fans in System Operating Instruction (S0I) 30.3, " Containment Upper and Lower Cooling. Heating and Ventilation". The UO used the CRDM cooling fan suction tamperatures following swapover to verify system performance. These temperatures are measured between the essential raw cooling water coolers and the fan intake and are, therefore, not indicative of CRDM enclosure air temperatures.

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ANALYSIS OF EVENT

This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.1.B. as an oparation prohibited by technical specifications (TSs) because LCO 3.0.3 was entered.

Tha CRDMs are described in Section 4.2.3 of the SQN Updated Final Safety Analysis Report (UFSAR) and the RPIs are described in Section 7.7.1 of the UFSAR.

Compliance with TS requirements for control rods and RPIs ensures that (1) acceptable power distribution limits are maintained; (2) minimum required shutdown margin is maintained; and (3) the potential effects of control rod misalignments are limited. The RPIs are required to be operable to indicate control rod positions, thereby enabling compliance with control rod alignmer.t and insertion limits. LCO 3.1.3.2 contains provisions for continued operation. tith a maximum of one RPI per bank inoperable. When more than one RPI per bank became inoperable, LCO 3.0.3 was entered.

The shift opsrations supervisor discussed the plant condition with the Operations Superintendent cnd the decision was nade to begin a unit shutdown if it appeared that any problem would ba encountered during the calibration of the RPIs.

While still within the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> /6 hour action requirements of LCO 3.0.3, the RPIs were restored to operability and LCO 3.0.3 was exited. The requirements of 13s were thereby complied with and there was no adverse effect on the health and safety of the public or plant personnel.

CORRECTIVE ACTIONS

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As immediate corrective action, the RPIs were adjusted to within the required 12 step tolerance. Work requests have been initiated to investigate and repair as necessary any malfunction of the CRDM cooling system dampers or fans during the next scheduled outage for each unit.

As corrective action to prevent recurrence, the Technical Support group will initiate ections by January 2, 1990, to place the appropriate CRDM cooling system components (such as the dampers) in a PM system.

In addition, by December 15, 1989, the Technical l-Support group will determine a more appropriate description for computer point T1014A l

end initiate actions to revise its P-250 listing. A section will also be added to l-S01-30.3 by February 1,1990, to provide better guidance for the operators when swapping l

tha fans for CRDM enclosure cooling.

ADDITIONAL INFORMATION

Ons previous event has been identified that reported an entry into LCO 3.0.3 as a result j-of more than one RPI per bank being inoperable, as reported in LER 50-327/85009.

This sysnt was caused by an electrical anomaly and was unrelated to the CRDM cooling system.

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The Technical Support group will_ initiate actions by January 2, 1990, to place the appropriate CRDM cooling system components (such as the dampers) in a PM system.

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