ML20154A120

Discusses Util Evaluation of Proposed Mod to Fines/Debris Vacuum Sys.Evaluation Concluded Mods Bounded by Previous Safety Evaluation & Do Not Present Unreviewed Safety Questions.Proposed Mods Approved

ML20154A120
Person / Time
Site:	Three Mile Island, 07109200
Issue date:	02/21/1986
From:	Travers W Office of Nuclear Reactor Regulation
To:	Standerfer F GENERAL PUBLIC UTILITIES CORP.
Shared Package
ML20154A124	List: ML20154A120 ML20154A135
References
CON-NRC-TMI-86-019, CON-NRC-TMI-86-19 NUDOCS 8603030298
Download: ML20154A120 (2)

Text

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i-DISTRIBUTION:

DN 50-320 s

-NRC PDR l Local PDR l DCS TMI HQ r/f February 21, 1986 TMI Site r/f NRC/THI 86-019 WDTravers MTMasnik RCook CCowgill Docket No 50-320 LChandler IE ACRS:[

Mr. F. R. Standerfer M-town Office Vice President / Director. TMI-2 Service List

{UO. x48h Middletown, PA 17057 l

Dear Mr. Standerfer:

j

Subject:

Fines / Debris Vacuum System Modifications l

l References; . (a) cLetter 4410--86-t-005, F. Standerfer to W. Travers,

.. ' Fines /liebris Vacuum System Modifications, dated January 28, 1986 (b) Letter NRC/THI-85-083, W. Travers to F. Standerfer, Defueling Canister Technical Evaluation Report, dated November 5, 1985 (c) Letter NRC/TMI-85-089, W. Travers to F. Standerfer, Safety Evaluation Report for Early Defueling, dated Novcmber 12, 198G Reference (a) forwarded, for NRC staff review, an evaluation of proposed modification to the Fines / Debris Vacuum System. The proposed mcdifications i

are the result of the need for added flexibility in system operation determined by the experience gained from defueling activities conducted to date. Your evaluation determined that the modifications are bounded by the previous evaluations approved in references (b) and (c).

The proposed modifications include use of a vacuum nozzle that would allow larger debris particles to be vacuumed into the knockout canisters, use of mechanical probes and water jets on the end of the vacuum nozzle to loosen the packed rubble, use of a larger vacuum tool to allow debris removal from the lower head, and vacuuming without the use of a filter on the. discharge of the knockout canister.

The effects of vacuuming larger particles into the knockout canister on the '

criticality analysis and structural analysis' of the canister were reviewed..

!' The structural. analysis approved in reference (b) was independent of the size l

1 of particles loaded into the canister. The criticality analysis was based on ,

fuel pellet size particles. However, independent calculations performed by ,

l the staff in support of the licensee review of the NUPAC-125 8 shipping cask determined that fuel pellet size maximum reactivity in.this case. particles Therefore,provide loading the of optimum sizedebris larger size for

• i would have a negligible affect on canister reactivity and this situation is k.; ___.

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OFFICIAL RECORD COPY NIC FORM 318 (10-80 NRCM O240, ,

__-y l Mr. F.-R. Standerfer February -21, '1986 i .

l bounded by the, analysis in reference (b). =The NRC criticality analysis is i i attached, f

l The mechanical probes and water jets on the vacuum cozzle will use a submersible circulating pump uith a capacity of 25 gpm as the driving force for debris- bed agitation. Since the pump.and. circulating systems will-use RCS '

water and will be completely contained in the internals indexing fixture, it creates no deboration or RCS leakage pathways that have not been previously analyzed.

l Use of a larger vacuum tool -fill permit vacuuming of debris from thd loer l head. The only potential safoty concer6 is impacting of incore irtstrirent tubes with the vacuum nozzle. The _ low impact loads imparted by the vacuum nozzle on the incore instrument tubec arr. unlikely to cause damage. In the unlikely event of damage, the potential consequences of incore instrument tube l failure has been analyzed in the staff's safety evaluation in support of

. Technical Specification Change 46.

l Operation of the vacous 'ystem without a filter on the knockout canister discharge is likely to e ?se a high turbidity and increased radionuclide l concentration in the RCS water. Increased turbidity will require per?Mic shutdown of defueling-operations until visibility improves but wili present no >

adverse safety impact provided prudent judgement is exercised and existbg procedural controls are adhered to. Increased FOS ac' vity levels sty c6ush  :

slight increases in radiation levels on the defu li",, platform, however  :

procedures approved by the NRC staff are currently in place to control the radfological working conditions and will assure no adverse fp;nct on the health and safety of the workers.

He concur with your assessment that the proposed Fines / Debris Vecuum System hodifications are bounded by previously' approved safety evaluation and do not present any unreviewed safety questions. 'We therefore approve the proposed modificattuns contingent upon your submittal of the applicable proce&res subject to Technical Specification 6.8.2.

Sincerely, <

l

/s/ C. Cowgill for-l l William D. Travers Cirector l TlU Cleanup Project Directorate -l l-

Attachment:

As stated cc: T. F. Decraitt R. E. Rogan

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NRC Fm 318 048M NRC" OFFICIAL RECiORD COPY