ML20002C504
| ML20002C504 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/01/1974 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20002C485 | List: |
| References | |
| NUDOCS 8101100382 | |
| Download: ML20002C504 (4) | |
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Consumers Power j
Company DT General Offices: 212 West Mecnegan Avenue. Jackson. Michigan 4 9201
- Area Code 517 788-05S0 April 1, 1974 Mr. John F. O' Leary, Director Re: Docket 50-155 Directorate of Licensing DPR-6 US Atomic Energy Commission Big Rock Point Washington, DC 20545
Dear Mr. O' Leary:
This letter is written to inform you of a n.nor modification that will be performed on one control rod blade at the Big Rock Point Plant during the refueling outage that is presently in progress.
This modification involves removal of the four lover rollers from one control rod blade and is part of an effort to achieve a long-term solution to operating problems that have been experienced in the past.
These prob-lems were involved with the loss of four rollers from a total of three peripheral control rod blades in the Big Rock Point reactor and were previously described in our letters to the Director of Licensing dated April 25,1972 and May 1, 1973 In an attempt to determine a long-term solution to the problems reported in the above-referenced letters, an analysis was undertaken of several possible modifications to the rollers on the lower portions of the peripheral control rod blades. This analysis considered removal of rollers as well as repair to the original design, velding the existing rollers to the control rod blade and installation of a device on the con-trol rod blade that would disturb the flow conditions in the vicinity of the lover rollers.
The analysis concluded that removal of the bottom rollers from a peripheral control rod blade was the most feasible course of action.
The weight of the control rod blade is 113 pounds and the maximum friction force that can be exerted with the rollers removed is calculated to be approximately 95 pounds; thus, a total maximum downward force of 208 pounds exists to retard insertion of the control rod blade into the core.
The total upward hydraulic force that is exerted when inserting the control rod blade is approximately 1800 pounds; thus, s minimum upward force of approxi-mately 1600 pounds exists to move the control rod blade.
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Mr. John F. O'Leiry, Director 2
Dockat 50-155 April 1, 1974 Restorction of the rollers to their original design was rejected because it was likely that if this course of action were taken the problem would recur. The possibility of affixing a device to the control rod blade that would disturb the flow conditions in the vicinity of the rollers (to eliminate roller vibration and subsequent failure) was rejected on the basis of the complexity of the analysis and critical positioning of the de-vice. Rigidly welding the existing rollers to the control rod blade was rejected because the frictional forces would be only slightly reduced (approximately 13 pounds less) when compared to the analysis with the rol-lers removed. Also, velding of the rollers would be costly in terms of plant personnel radiation exposure.
The analysis was reviewed by the NSS vendor (General Electric Company). GE agreed with our recommendation to remove the lower rollers on a peripheral control rod blade. The purpose of the rollers is to reduce friction and prevent galling under heavy side loads. Heavy side loads are not expected to occur in the region below the core. GE recommended that any testing performed following removal of the lower rollers include a con-trol rod drive settling friction test. This test provides a sensitive measurement of the drive line friction and will verify the results of the analysis.
GE assessed the mechanism a failure to be most likely caused by a lateral vibration of the impaired roller (Stellite 3) wearing down the soft pin (Haines 25). The 0.125 inch diameter pin is a wrought alloy with hardness ranging from Rockwell C c-46. They attributed the cause to be flow induced.
Iccal flow turbulances are created in the lower regions of the core (in the vicinity of the lower bottom rollers when the peripheral con-trol rod blades are fully withdrawn) as flow sweeps across the core support plate. The upper ends of the peripheral control rod blades and both ends of the inner 16 control rod blades are in an area that experiences far less flow turbulence. GE also considered that simple spinning of the roller on the pin due to the flow conditions was a possibility. However, this was not considered as likely as a lateral vibration mechanism.
The Big Rock Point's Safety Audit Review Board (SARB) has reviewed the analysis performed including all alternatives and GE recommendations.
SARB recommended that the bottom rollers be removed from one peripheral con-trol rod blade during the present refueling outage and that this blade be operated for one cycle with the rollers removed. SARB further recommended that prior to resuming operation with the lower rollers removed that test-ing (settling friction, scram time and notching) be performed to confirm that there is no significant effect with regard to control rod drive opera-tion. These recommendations are being implemented by the plant staff during the present refueling outage.
Based on the outcome of the testing and operation of the control rod blade with the lower rollers removed for one-cycle, SARB will make further recom=endations with regard to permanent corrective action for the remaining 15 peripheral control rod blades.
If it is deemed desirable to i
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Mr. John F. O' Leary, Dirzctor 3
Dockst 50-155 April 1, 1974 remove the lower rollers from the remaining 15 peripheral control rod blades, a Technicial Specification change will be proposed to appropri-ately modify a descriptive portion of the Technical Specifications.
Based on a review of.the data as summarized above, SARB con-cluded that removal of the lower rollers from one peripheral control rod blade did not require a change to the descriptive portion of the Technical Specifications concerning control rod guidance and did not involve an un-reviewed safety question or increase the probability or the consequences of a previous analyzed accident.
Yours very truly, (Ralph B. Sewell) i i
RBS/pb Ralph B. Sewell.
Nuclear License Adminierator CC: JGKeppler, USAEC 1
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AEC DISTRIBUTICN FOR PART 50 DOCKET MA"""tIAL h
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CONTROL NO: 5927
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FROM:
DATE OF DOC DATE REC'D LTR TWX RPT OTHER Con:umers Power Conpany Jcckton, !!ich. 49201 Mr. R.B. Sewell 6-28-74 7-1-74 X
ORIG CC OTHER SENT AEC PDR XXX TO3 e
SENT LOCAL PDR h
J.F. O' Leary 3 signed CLASS L7; CLASS PROP INFO INPUT NO CYS REC'D DOCKET NO:
XXX XXX 40 50-155 DESCRIPTION:
ENCLOSURES:
Ltr trans the following......
Proposed change to tech specs for the Big Rock Point Plant..........
ACKNOWLEDGED PLANT NAME:
Big Rock Point FOR ACTIC:;/INF02MATICN 7-1-74 JB BUTLER (L)
SCHWENCER (L)
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REGAN (E)
W/ CYS W/ CYS W/7CYS W/ CYS CLARK (L)
STOLZ (L)
DICKER (E)
W/ CYS W/ CYS W/ CYS W/ CYS Paf. (L)
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W/ CYS W/ CYS W/ CYS W/ CYS KNIEL (L)
PURPLE (L)
YOUNGBLOOD (E)
W/ CYS W/ CYS W/ CYS W/ CYS INTERNAL DISTRIBUTION (REGFILE TECH REVIEW DENTON LIC ASST A/T IND VAEC PDR HENDRIE GRIMES
/ DIGGS (L)
BRAITMAN
- 0GC SCHROEDER GAMMILL GEARIN (L)
SALTZMAN
/MUNTZING/ STAFF MACCARY KASTNER COULBOURNE (L)
B. HURT CASE KNIGHT BALLARD KREUTZER (E)
CIAMBUSSO PAWLICKI SPANGLER LEE (L)
PLANS BOYD SHA0 MAIGRET (L)
MCDONALD MOORE (L)(LWR-2)
STELLO ENVIRO REED (E)
CHAPMAN DEYOUNG (L)(LWR-1)
HOUSTON MULLER SERVICE (L)
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NOVAK DICKER SHEPPARD (L)
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ROSS KNIGHTON SLATER (E)
P. COLLINS IPPOLITO YOUNGBLOOD SMITH (L)
D. THOMPSON (2) y REG OPR LONG PROJECT MGR,
TEETS (L)
KLECKER DENISE TEDESCO REGAN WILLIAMS (E)
EISENHUT FILE & REGION (3)
LAINAS WILSON (L)
MORRIS BENAROYA HARLESS STEELE VOLUtER D00D ADIDIkl Al, EXTERNAL DISTRIBUTION I UUR U H l[]l N N lM
- 1 - LOCAL PDR. Charlevoix. Mich.
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- 1 - TIC (ABERNATHY)
(1)(2)(10)-NATIONAL LABS 1-PDR-SAN /LA/NY I -nR00KHAVEN NAT LAS
/1 - NSIC (BUCilANAN) 1-ASLBP(E/W Bldg, Rm 529) l 1 - ASLB 1-W. PENNINGTON, Rm E-201 GT 1-G. ULRIKSON, ORNL 1 - P. R. DAVIS 1-B&M SWINEBROAD, Rm E-201 GT 1-AGMED (RUTH GUSS>LC)
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