ML20217H637

Responds to Rl Woolley Ltr Re Paducah Gaseous Diffusion Plant,Compliance Plan Issue 3,action 9,ASME Code Interpretation & Assessment Results.Addl Info Required to Support Final Disposition of Issue

ML20217H637
Person / Time
Site:	07007001
Issue date:	10/10/1997
From:	Pierson R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Toelle S UNITED STATES ENRICHMENT CORP. (USEC)
References
TAC-L32012, NUDOCS 9710160183
Download: ML20217H637 (2)

Text

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10 7/0l

p. %q$\ UNITED STATES s

g ') NUCLEAR REGULATORY COMMISSION wAsHINGf oN, D.c. Im6H001

%, /g October 10, 1997 Mr. Steve Toelle Nuclear Regulatory Assurance and Policy Manager United States Enrichment Corporation 2 Democracy Center 6903 Rockledge Drive Bethesda, MD 20817

)

SUBJECT:

PADUCAH GASEOUS DIFFUSION PLANT, COMPLIANCE PLAN ISSUE 3

' AC'!ON 9, ASME CODE INTERPRETATION AND ASSESSMENT RESULTS (TAC NO. L32012) l

Dear Mr. Toelle:

The purpose of this letter is to resond to Robert L. Woolley's letter to me dated December 31, 1996, on the above subject. NWC staff has reviewed your cubmittal and is requesting additional information to support a final disposition of this issue.

The purpose of requiring an ASME code pressure vessel for the storage and transfer of UF. is io ensure that the risk is extremely small that a vessel fWlure would result in the release of UF.

to the environment, By using only an ASME code vessel, with appropriate pressure relief, inadvertent over pressurization should not result and catastrophic failure of the vessel should be avoided. In the worst case, over pressurization would result only in a limited release of UF.

gas through a pressure relief valve.

ASME Section Vill, Division 1, UG-125 requires that all pressure vessels shall be provided with protective devices to prevent over pressurization. The pressure relieving device is required to prevent the pressure from rising more than 10% or 3 psi, whichever is greater, above the maximum working pressure of the vessel. In the case of the UF. cylinder, your submittal states that the working pressure is 200 psig. Therefore, pressure relief would be required to prevent pressure greater than 220 psig. ASME Code paragraph UG 125(g) states that protective devices need not be installed directly on a pressure vessel when the source of the pressure is extemal to the vessel and is under such positive control that the pressure in the vessel cannot exceed the maximum allowable working pressure (200 psig). The note to this paragraph clarifies that pressure reducing valves are not sufficiently positive in action to prevent excess pressures from being developed.

Your letter and the accompanying attachments states that the pressure vesselis contained completely within the autoclave during heating, and that in the worst case, pressure will not exceed 207 psig. Therefore, it is clear that the source of pressure is external to the cylinder, and that controls on the autoclave will prevent pressures from exceeding 220 psig. However, your submittal does not make it clear whether the device (s) that prevents steam pressure I)b t

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0 Mr. S. Toelle, USEC 2 psig from entering the autoclave is an automatic, non reciosing device (UG 126 and 127), then pressure relief valves on individual cylinders would not be required.

I would appreciate your response to this letter, including a timetable for further actions, within 90 days of the date of the letter. If you have questions with regard to this response, please feel free to contact me on 301415 7192.

Sincerely.

l Original Signed By

, Robert C. Pierson, '.! ef i

Special Projects Branch Division of Fuel Cycle Safety and Safeguards, NMSS Docket 70 7001 Certificate GDP 1 l

DISTRIBUTION: (Control No: 050S)

Docket 70-7001 ;NRC File Center ' PUBLIC NMSS r/f FCSS r/f SPB r/f Rlli KO'Brien, Rlli PHiland Rlli OFC SPB # .SPB (_ PS , [ S Ad NAME CRaddak boadley_ [M/rtin Rk erson DATE f fW97 'l N97 ///@97 h /P/97 / /97 C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY G:\ctr\uf6 cyl.wpd