ML20132B452

Ro:On 850904,one Reactor Control Blade Failed to Drop on Demand from 64% Removed Position.Probably Caused by Binding in Clutch S-3 Possibly Due to Moisture or Other Effect Reducing Clearance

ML20132B452
Person / Time
Site:	05000083
Issue date:	09/04/1985
From:	Vernetson W FLORIDA, UNIV. OF, GAINESVILLE, FL
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20132B430	List: ML20132B424 ML20132B452
References
NUDOCS 8509260194
Download: ML20132B452 (3)

Text

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i bs t oida'uc= NUCLEAR FACILITIES DIVISION 1#

W.G,VER%ffSON Rt ACTOR htANAGER P )

NUCLEAR REACTOR BUILDING UNIVERSilY OF FLORIDA . .

gal %E$VILLE, FLORIDA 32611 PHONE (904) 392-1429 TELEh $411a September 4, 1985 ATTACHMENT I Nuclear Regulatory Commission Suite 2900 101 Marietta Street, N.W.

Atlanta, GA 30323 Attention: J. Nelson Grace Regional Administrator, Region II Re: University of Florida Training Reactor (UFTR)

Facility License: R-56, Docket No. 50-83 As per telephone call of 4 September 1985, we are reporting the failure of one of the reactor control blades (Safety-3) on the University of Florida Training Reactor to drop on demand from a 64% removed position. This failure (sticking about 31% removed) was discovered by a Reactor Operator as he commenced a pow-er increase from the 1 watt critical position. The operator had accidentally raised the Safety-3 instead of the Regulating Blade for this power increase; in returning it to the normal 640 unit position he felt the response was slug-gish and so he attempted to drop the blade from 640 units withdrawn to check i t. Following clutch current release the blade stopped at the 310 unit posi-tion and was subsequently driven in with the other three blades to shut the reactor down.

Immediate checks involving subsequent removal to various heights show this sticking problem to be intermittant and to conter in the 290-315 unit range but with some apparent sluggishness in the drop from other higher and lower heights. It should be noted that this is essentially a recurrence of the event reported by cur facility in a letter dated January 28, 1985 with subsequent followup in an interim report dated February 9,1985 and closed out in a re-port dated March 26, 1985.

The Executive Committee of the Reactor Safety Review Subcommittee (RSRS) has reviewed the occurrence and concluded that it is a potential abnormal occur-ence as defined in UFTR Technical Specifications, Chapter 1. The RSRS has in-structed NRC notification as por Section 6.6.2. of the .UFTR Tech Specs.

Analysis of the current problem is underway with corrective action to follow based upon inspection results and RSRS recommendations. Based on previous ex-perience with the January 28 event and subsequent corrective maintenance, in-dicatiens are that the sticking problem may be due to a binding in the S-3 clutch possibly due to moisture or other effect reducing clearance. Such bind-ing was icund to be part of the problem in the January 28 event. If this pro- i liminary evaluation' is correct, this binding can be corrected by increasing t the clutch clearance, a check of which has been approved by the RSRS Executive Committee.

g William G. Vernetson Acting Director of Nuclear Facilities September 4, 1985 cc: RSRS Committee E.._,_,,_,_,_ _ II

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NUCLEAR FACILITIES DIVISION , /, % 'e.

MUCLEAR REACTOR BUILDING UNIVERSITY OF RORIDA

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ATTACHMENT II September 4, 1985 MEMORANDUM TO:

FROM:

Reactor Staff 0.

W.G.Vernetson,.1 O

Acting Director of Nuclear Facilities

SUBJECT:

Administrative Shutdown of the UFTR Because of the need to evaluate and fix the sticking safety blade

1. 3, the UFTR is placed on Administrative Shutdown until further notice.

This administrative shutdown precludes all reactor operations in-g volving-operating the reactor except for 1) performing weekly and daily checkouts as far as possible and 2) withdrawal of Safety 3 up to 50 units. Daily checkouts performed for training and non-operational uses of the facility such as for CFCC 'tudents s are also permitted. Withdrawal of Safety-3 more than 50 units is pre-cluded except as specifically authorized in RSRS-approved test and maintenance procedures.

The only other activities allowed during this administrative shutdown are routine. administrative work (updating training re-cords , etc.) , tours of the facilities (no operations) as well as housekeeping and maintenance on the non-nuclear-safety-related equipment in the reactor room provided none of these affect the work in progress or cause unnecessary exposure. Major maintenance is also possible provided approved by proper levels.

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NUCLEAR REACTOR BUILDING GAmeESVtLLE,FLOtt0A 3 Nil UNIVERSITY OF FLORIDA . .

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PHong (ges) 3934429 TELERS4130 m' ATTACHMENT III September 9,1985 MEMORANDUM TO: Reactor Staff FROM: W.G.VernetsonQ

SUBJECT:

Allowable Control Blade Manipulations During the Cur-rent Administrative Shutdown Two points should be noted relative to performance'of weekly ani daily checkouts during the administrative shutdown to correct the problem of the sticking S-3 blade:

First, the RSRS has agreed that the full removal of the S 3 control blade is allowable during the weekly checkouts. To do this will require my authorizing signature. Note that re-moval of S-3 up to 50 units has been allowed with the usual limitations. Obviously this full or. partial removal will only be possible when the blade drive is connected.

Second, care should be exercised whenever the S-3 blade drive is disconnected to assure that _the rupture disk is not broken. Recall that in the dump valve logic whenever the electrical connections to a blade are disconnected, this is like a partially removed blade. Each of the scram checks of one blade actually look like two blades and result in dump of primary coolant to the storage tank. Therefore, a three muute wait is required prior to reset.

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