ML20112D221

Issues 30-day Response After follow-up Testing for NRC Bulletin 96-001, Control Rod Insertion Problems

ML20112D221
Person / Time
Site:	Farley
Issue date:	05/31/1996
From:	Dennis Morey SOUTHERN NUCLEAR OPERATING CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-96-001, IEB-96-1, NUDOCS 9606040139
Download: ML20112D221 (3)

Text

..

, South:rn Nucl:tr Operating Company

" Post Offica Box 1295

.g Birmin0 ham, Alabama 35201 T;lgphona (205) 868-5131 L

Dave Morey Vice President Southern Nudear Operating Company Farley Project the Southern eleCfnc System May 31, 1996  !

Docket Nos.: 50-348 10 CFR 50.54 50-364 U. S. Nuclear Regulatory Commission j ATTN: Document Control Desk l Washington, D. C. 20555-0001 Joseph M. Farley Nuclear Plant 30-Day Response After Follow-up Testing for NRC Bulletin 96-01  ;

" Control Rod Insertion Problems"  !

i Ladies and Gentlemen:

I By letter dated March 8,1996, the NRC issued Bulletin 96-01, " Control Rod Insertion -

I Problems." This bulletin requires licensees to determine the suscep:ibility of the Rod Control System to the phenomena of control rod failure to completely insert. The initial 30-day response was submitted by Southern Nuclear Operating Company (SNC) on April 4,1996.

. In response to the bulletin, SNC committed to measuring and evaluating the control rod drop l times and rod recoil data for all control rods during the first outage on each unit of sufficient duration during calendar year 1996. Within 30 days after completing such measurements, the bulletin requires a report that summarizes the data and documents the results obtained to be submitted. Provided in the Attachment is the 30-day follow-up response for Farley Nuclear l Plant (FNP) Unit 1. Should you have any questions, please advise. i Respectfully submitted, f Allt #

'Ogg Dave Morey Sworn to and subscribed before me this .3/5day of O.<4, 1996

~'

Gj .

W Nota &P lic My Commission Expiras: -l,l999 t

WAS/maf;96-Olsup. doc Attachment 9606040139 960531 e I PDR ADOCK 05000348 G PDR / j cc: Mr. S. D. Ebneter, Region II Administrator L i

Mr. B. L. Siegel, NRR Senior Project Manager

Mr. T. M. Ross, FNP Sr. Resident Inspector

4 -

e V

ATTACHMENT UNIT 1 ROD DROP TESTING Pursuant to the Joseph M. Farley Nuclear Plant response to NRC Bulletin 9 -01, " Control Rod Insertion Problems," control rod testing and evaluation was conducted on Unit I during the May 4-5,1996 planned maintenance shutdown. The test program included verification of timely rod insertion when the reactor trip breakers were opened, rod drop time testing under hot, full RCS flow conditions, examination of the rod drop traces for indications of normal rod recoil, and comparison of the rod drop traces with the beginning-of-cycle rod drop test results. The testing was performed with a maximum rodded assembly burnup ofjust under 36,000 and an average core bumup of 6871.9 MWD /MTU (~ 36% through the current fuel cycle).

On May 4,1996, Unit I was ramped to approximately 5% reactor power and the reactor trip breakers were opened to shut down the reactor. Observation of the shutdown on the DRPI display confirmed that all control and shutdown rods inserted into the core as expected when the trip breakers were opened. There was no evidence of dragging, sticking or other anomatics.

The rod drop time test was conducted with RCS Tavg 2 541 F and all reactor coolant pumps operating.

The test utilized a multiple rod drop test system which permitted testing an entire bank (8 rods) at a time.

All rod drop times were less than the Technical Specification 2.7 second rod drop time limit. The average rod drop time from opening of the trip breakers to dashpot entry (average time Tl) was 1.629 seconds.

The average time from dashpot entry to dashpot bottom (average time T2) was 0.626 second. The slowest falling rod was B06, f3r which the time (TI) to dashpot bottom was 1.862 seconds, and the time from dashpot entry to dashpot bottom (T2) was 0.653 second.

Comparing these results with the times from the beginning-of-cycle rod drop test, the average beginning-of-cycle time to dashpot entry (TI) was 1.636 seconds, and the average beginning-of-cycle time from dashpot entry to dashpot bottom (T2) was 0.609 seconds. The slowest falling rod in the beginning-of-cycle test was also B06, for which the time Tl was 1.848 seconds, and the time T2 was 0.655 seconds.

The following is a detailed listing of the Unit 1, May 4,1996 rod drop test results:

Drop Time (sec)

Rod ID Ti(sec) T2(sec) Total (sec)

F02 1.628 0.636 2.264 B10 1.703 0.615 2.318 K14 1.743 0.636 2.379 P06 1.648 0.612 2.260 K02 1.673 0.638 2.311 B06 1.862 0.653 2.515 F14 1.678 0.603 2.281 P10 1.642 0.616 2.258 F04 1.627 0.639 2.266 D10 1.615 0.670 2.285

, K12 1.578 0.598 2.176 M06 1.642 0.642 2.284 K04 1.665 0.676 2.341 D06 1.587 0.619 2.206 F12 1.622 0.701 2.323 Page 1 of 2

_ _ _ _ _ _ _ _ _ _ _ _ _ __ i

. . . . .- _ . - . - . _ = .- - - . - -- . . .- - .. , - _.

Drop Time (sec) -)

EndIQ Tl(sec) T2(sec) Total (sec)

M10 1.611 0.664 2.275 ,

D04 1.620 0.634 2.254 D12 1.649 0.666 2.315 M12 1.603 0.622 2.225 M04 1.652- 0.633 - 2.285 H06 1.588 0.641 2.229 F08 1.591 0.639 2.230 H10 1.587 0.677 2.264 K08 1.555 0.574 2.129 H02 1606 0.661 2.267 B-8 1.729 0.616 2.345 H14 1.661 0.611 2.272 P08 1.604- 0.665 2.269 F06 1.582 0.603 2.185 F10 1.628 0.639 2.267 K10 1.614 0.651 2.265 K06 1.629 0.612 2.241 G03 1.632 0.596 2.228 C09 1.622 0.601 2.223 i I

J13 1.622 0.584 2.206 l

N07 -1.604 0.567 2.171 J03 1.613 0.572 2.185 i C07 1.656 0.570 2.226 Gi3 1.673 0.600 2.273 N09 1.606 0.572 2.178 E05 1.641 0.626 2.267 El1 1,598 0.658 2.256 L11 1.625 0.722 -2.347 s LOS 1.635 0.673 2.308 G07 1.572 0.621 2.193 i l

G09 1.563 0.573 2.136 J09 1.556 0.599 2.155 J07 1.549 0.566 2.115 Following C .od drop test, the rod drop traces were examined for indications of dragging, especially in the i dashpot r: gion. Dragging would lengthen the time required for a rod to fall and, thus, would increase either I the time to dashpot entry (TI), the time from dashpot entry to dashpot bottom (T2), or possibly both. As the data demonstrate, there are no significant differences between rods in these times. The two slowest falling rods, B06 and K14, were also the slowest during the beginning-of-cycle rod drop test. In the May i 4th test, the total (Tl + T2) drop times for these rods increased only slightly above the times for the beginning-of-cycle test and were still well within the 2.7 second Technical Specification limit for T1.

1 The rod drop traces were also examined for indications of rod recoil (a further indication that the rods are i moving freely in 'he dashpot region). The traces showed strong recoil waveforms, which were quite consistent for an reds, providing a further indication that there was no binding or dragging in the dashpot region.

Page 2 of 2

- - , - , --, ,,n,, . , -