ML17263A310

Ro:On 930629,malfunction in Rod Control Sys Caused Minor Misalignment Between Control Rods in Group 1 & 2 of Bank D. Cause Under Investigation.Control Rods Will Be Maintained in Manual Control & Bank D Rods Will Be Exercised Daily

ML17263A310
Person / Time
Site:	Ginna
Issue date:	07/02/1993
From:	Widay J ROCHESTER GAS & ELECTRIC CORP.
To:	Linville J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 9307090106
Download: ML17263A310 (12)

Text

ACCELERATE DOCUMENT DISTRIBUTION SYSTEM REGULAT INFORMATION DISTRIBUTIOh+YSTEM (RIDE)

ACCESSIOR NBR:9307090106 DOC.DATE: 93/07/02 NOTARIZED: NO DOCKET FACIL:50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION WIDAYFJ.A. Rochester Gas 6 Electric C'orp.

RECIP.NAME RECIPIENT AFFILIATION LINVILLE,J.C. 'egion 1 (Post 820201) V

SUBJECT:

RO:on 930629,malfunction in rod control sys caused minor misalignment between control rods in Group 1 a 2 of Bank D.

Cause under investigation. Control rods will be maintained in manual control & Bank D rods will be exercised daily.

DISTRIBUTION CODE: IE22D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

. NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72). 05000244 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL' PDl-3 LA 1 1 PD1-3 PD 1 JOHNSON,A 1 1 D INTERNAL: ACNW 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DE/EELB 1 1 NRR/DE/EMEB 1 1 NRR/DORS/OEAB 1 1 NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB 1 1 NRR/DRCH/HOLB 1 1 NRR/DRIL/RPEB 1 1 NRR/DRSS/PRPB 2 2 NRR SPLB 1 1 NRR/DSSA/SRXB 1 1 REG F 02 1 1 RES/DSIR/EIB 1 1 RGN1 FILE Ol 1 1 EXTERNAL: EGGG BRYCEFJ.H 2 2 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYFG.A 1 1 NSIC POOREFW. 1 1 NUDOCS FULL TXT 1 1 D

NOTE TO ALL "RIDS" RECIPIFN'I'S:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 504-2065) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 30 ENCL 30

e U.=-NRC GI DNA Pl 1

ROCHESTER GAS AND ELECTRIC CORPORATION ~ 89 EAST AVENUE. ROCHESTER, N.Y. 146490001 U.S. Nuclear Regulatory Commission July 2, 1993 Region I Attn: James C. Linvllle Chief, Projects Branch No. 3 Division of Reactor Projects

.475 Alfendale Road King of Prussia. PA 19406

Subject:

Rod Control System Malfunction R.E. Ginna Nuclear Power Plant Docket No. 50-244

Dear Mr. Linville:

I As requested, Rochester Gas and Electric is transmitting a description of the activities related to the rod control system malfunction which occurred on 6/29/93. A description of the event and the troubleshooting efforts, an analysis of the impact on safety, and the interim actions to be implemented are Included below.

Event Descrlptfon:

On 6/29/93, a malfunction in the rod control system caused e minor misalignment between the control rods in group 1 and group 2 of bank D. Bank D group 1 was indicating 212 steps on its step counter and 216 steps on the Microprocessor Rod Position Indication system-(MRPI). Bank D group 2 wss indicating 209 steps on its step counter snd 204 on MRPl. This caused a Rod Control Urgent Failure alarm which stopped all automatic and manual rod motion. <Bank D contains 4 rods, 2 in each group. The rods in each group are located symmetrically across the core. Group 1 contains rods C7 and K7, group 2 contains rods G3 and G11.l The troubleshooting efforts are described in Attachment 1.

Efforts to determine the root cause are continuing.

Impact on Safety:

T

• Tech Spec 3.10.4.1 requires the rods to be "operable and positioned within x12 steps of their group step counter demand position". The safety function of the control rods is to shutdown the reactor upon initiation of a reactor trip signal. Control rod movement vis the rod control system is a control function and is not required for the rods to be considered operable. Standard Tech Specs defines operability for a control rod as being tripsble.

Therefore, ss long as the rods are tripable they are operable. Both flux map traces and MRPI indicated that the rods were moving when a demand signal was present. This proves that the 9307090206 930702 PDR ADOCK 05000244

~/ pP S PDR

rods were not "immovable as a result of excessive friction or mechanically untripable" and therefore were operable. Since the alignment specification wss also met, Tech Spec 3.10.4.1 was fully satisfied.

Tech Spec 3.10.1.1 specifies the shutdown margin that must be maintained. Tech Spec 3.10.1.3 specifies that the control rods must be maintained above the Rod Insertion Limits (RIL). The RIL for 100% power is 184 steps on Bank D. The maximum rod insertion was Bank D at 205 steps. Therefore, Tech Spec 3.10.1.3 was satisfied. Since Tavg was on program, and the rods were maintained above the RIL, the shutdown margin requirement was also met.

4 Based on this evaluation, the control rods were operable at all times and all Tech Specs were satisfied, P

The Bank D rods are maintained near the fully withdrawn position in order to maintain axial offset within its target band as required by Tech Specs. Even if uncontrolled rod withdrawal were to occur (ie. urgent failure alarm did not stop rod motion), there would be a very small positive reactivity addition since Bank D rods are in s low worth region. In addition, since the malfunction resulted in movement of a group of rods rather than a single rod. core symmetry would be maintained snd the peaking factors would be less severe. This is consistent with the licensing basis for Ginna as described in UFSAR section 1S.4.2, Uncontrolled RCCA Withdrawal at Power.

Interim Actions:

Until there is reasonable assurance that the cause of the rod control problem has been corrected, the following actions will be taken. The control rods will be maintained in manual control. The Bank 0 rods will be exercised daily to ensure the rod control system is functioning properly. The temperature, in the area of the rod control cabinets, at which ventilation will be increased has been reduced from 92 'F to 85'F in an attempt to mitigate potential temperature related effects. This direction has been provided to Operations through the daily operations plan.

Very uly your Joseph . Widay JPW/001 attachment XC: Mr. Allen R. Johnson (Mail Stop 14D1)

Pro}ect Directorate I-3 Washington, D.C. 20555 U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia. PA 19406 Ginna Senior Resident Inspector

Attachment 1 Rlhji~-'ank D Gioup 1 Rod Control Problem On June 29, 1993 at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> with the plant operating at 97.54 power and normal stoady state condition a Rod Control urgent failure Rod Stop (C30) alarm was received when Control Bank "D" stepped in rasponse to,an Automatic ln domand signal.

Rod Control System indication prior to and after receipt of the Rod Control Urgent Pailure Alarm was as follows:

Bank D Group 1 counter at 211 steps Group 2 counter at 210 steps Bank D Group 1 counter at 212 steps Group 2 counter at 209 steps Urgent Alarm in Logic Cabinet DS1 card light lit on 1BD Slave Cycler printed circuit location A-414 in Logic Cabinet. Light indicates a slave cycler fault.

Bank Overlap counter at 601 steps MBPZ indication for Bank D Group 1 Rods (K7 and C7) was 216 steps. MPRI Indication for Bank D Group 2 Rods (63 and 611) was 204 stops.

I Ambient teeperature in the vicinity of the Rod Control Cabinets was app~Mtely &7 degrees F. at the time the problem occurred.

Setup a Visicorder to monitor Bank D Group 1 >Lift",

"Moveable", and "Stationary" Coil voltages.

Raquestod Operatians reset Rod Control Urgent Failure Alarm.

Requested Operations to step Bank D "IN" one step while monitoring coil valtages with visicorder. Both Groups moved one step in and Visicorder tracos of coil voltages showod praper signal sequencing.

Requested Operatians to step Bank D "IN" a few steps and "OUT" a few steps. This was repeated three times with both groups responding prapexly, Visicarder traces of coil voltages showed proper signal sequencing for both "IN" and "OUT" motion.

Temperature in the vicinity of the Rod Control Cabinets at time of testing was 73 degrees P. Reduction in temperature caused by increased ventilation.

Rod Control Indication at the completian of the above Rod testing was:

Bank D Group 1 Counter at 212 steps Group 2 Counter at 209 steps Bank D P/A converter at 212 steps Per procedure guidance Operations realigned Bank D Group 1 rods with Bank D Group 2 rads at 209 steps, verified P/A converter Bank D indication was at 209 steps, and had ICC position Bank overlap counter at 599 steps.

~ations satisfactorily performed procedure PT-1 (Rod Coatrol System) which verified operability of all control Rode ~

jN On June 30, 1993, analysis of the problem continued. Contact was made with 4estinghouee to inform them of our problem and to also obtain their assistance. hfter several conversations and a lot of research the final consensus was that the supervisory. Logic XX printed circuit was the most probable causa of the problem. The supervisory Logic XI card provides (1) A Buffer Memory Control Circuit which accepts input commands, (2) Feods the Master cycler which generates the "Go", pulsos for rod movement, (3) Feeds the Bank Overlap Circuit for data logging and (4) Outputs to the Slave Cycler which generates current orders for Rod Movement.

Operations performed procedure PT-1 (Rod Control System) procedure to verify operability of all control rods. During the performance of procedure pT-l, z&c personnel obtained recordings of the voltages for Group Counter Coils while stopping the Croup Counters for "XN" and "OUT" movements to ensure that high voltage spikes vore not being fed back into the Logic Cabinet (as was

'experienced at Salem). All voltages vere normal which proved the diodes across the Group Counter coils vere performing their intended function.

RGSE and Westinghouse vere satisfied that Ginna does not have the same problem as Salam; because (1) Salem's problem affected only one Rod cluster where Ginna's affected the whole group, (2) Salem didn't receive an urgont failure alarm, (3) Salem's problem porsisted while Ginna's Problem occurred only once, and (i)

Salem's problem was the Slave Cycler Decoder Card where Ginna'8 problem is upstream in that logic.

On July 1, 1993, the supervisory Logic XI printed Circuit Card was replaced and Operations successfully completed procedure PT-1 (Rod Control System) for proving operability of all control rods.