ML20212E120
| ML20212E120 | |
| Person / Time | |
|---|---|
| Site: | Portsmouth Gaseous Diffusion Plant |
| Issue date: | 10/23/1997 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20212E118 | List: |
| References | |
| NUDOCS 9711030060 | |
| Download: ML20212E120 (6) | |
Text
_ . - _ _ _ _ . _ _ . _ . _ _ _ _ _ . _ _ _ ~ . _ _ . __ _ . _ . - _ _ . _ _ _ _ .
-il ,U
- J
.,L _
.. ** 88:g g*- ,- UNITED STATES
,, y j
NUCLEAR REGULATORY COMMISSION WAsHINoToN. o.C. 20661 @ 001
%, * . . . + / october rf. 1997 DOCKET: 70 7002 CERTIFICATE HOLDER: United States Enrienment Corporation Portsmouth Gaseous Diffusion Plant Portsmouth, Ohio
SUBJECT:
COMPLIANCE EVALUATION REPORT: APPLICATION DATED JUNE 9,1997, AUTOCLAVE CONTAINMENT VALVE TESTING ;
ilACKGROUND On June 9,1997, United States Enrichment Corporation (USEC) submitted a request M revise the Portsmouth Gaseous Diffusion Plant (PORTS) Technical Safety Requirement (ISR) 2.1.3.5, entitled " Autoclave Shell High Pressure Containment Shutdown." The proposed amendment, in accordance with a commitment made in the USEC certificate application, revises TSR 2.1.3.5, to account for the added capability to separately test inner and outer loop autoclave containment valves.
PORTS uses thirteen autoclaves in buildings X 342, X 343 nnd X 344 tn feed, transfer and sample UF6. Tnese autoclaves were designed and constructed in accordance wLa ASME Section Vill and are utilized to confine UF6 and any reaction products in the event of a major UF6 release inside an autoclave. Steam used to heat UF6 cylinders within autoclaves is typically controlled at approximately 5 psig. However, if a large UF6 release occurs inside an autoclave, its internal pressure could rise to as high as 90 psig very rapidly. This is caused by thc transfer of the cylinder pressure fiom the cylinder to the autoclave and by the generation of four moles of hydrogen fluoride gas for one mole of UF6 gas reacting with steara and water in the autoclave. To ensure that the contents of a release are confined inside the autoclave, except for that which is released due to the proper operation of the autoclave pressure relief system (rupture disc rated at near 150 psig and relief valve), each line which penetrates the autoclave boundary is equipped with isolation valve (s). These close automatically to isolate the autoclave in the event of high internal pressure detected by two independent pressure sensors: the actuation pressure being less than or equal to 16 psig. Figures 1 and 2 are schematic diagrams of typical feed, and sample and transfer autoclaves, respectively.
DISCUSSION Each line penetration of the thirteen autoclaves at PORTS, has at least two valves that can serve as isolation valves, and each autoclave has, as part of the autoclave shell high pressure containment shutdown system, two independent high pressure containment actuation channels. As noted in the Description of Noncompliance for issue 3 of the " Plan for Achieving Compliance with NRC Regulations at the Portsmouth Gaseous Diffusion
- Plant" Revision 3 (Compliance Plan) dated July 9,1996, at the tiino of certification, the capability to pressure decay test the autoclave containment valves (i.e., inner and outer loop valves) separately did not exist. According to item 1 of the Plan of Action and
_ Schedule (POA) for issue 3 of the Compliance Plan, USEC was committed to providing this
[Mb
2 capability before July 1,1997, and submitting to the NRC, a revised TSR to reflect the new autoclave containment valvo configuration, in addition, the POA stated that until the capability to separately test the inner and outer loop containment valve is provided, the applicable TSR requirement will be to declare an autoclave inoperable and taken out of service when, in any mode of operation, either containment valve is determined to be inoperable or, in the heating mode, either pressure instrument channel is determined to be inopert ble. According to USEC's certificate amendment request, since this capability has been provided, the Actions conditions of TSR 2.1.3.5 should allow completion of the current operating cycle if only one instrument channel, or one containment isolation valve on one or more autoclave penetrations, is operable. However, if both instrument channels or all containment isolation valves on any one autoclave penetration are inoperable, then TSR 2.1.3.5 requires USEC to shut down the autoclave within one hour, it is noted that the proposed TSR 2.1.3.5 still requires at least two channels and two isolat!on valves on each autoclave penetration to be operable prior to initiating a new operating cycle.
Unconfinement of UF6 The UF6 containment boundaries provided by the cylinder, pigtail and valves inside an autoclave, and steam and UF6 reaction product confinement boundaries provided by the autoclave shell and piping and valves out to and including the second containment valve, are designated as a "O" systems. As such, USEC is required to apply the highest level of quality control (ASME NOA 1) to ensure that the pressure boundaries within these systems are maintained. Taking into consideration the applic,able safety requirements (administrative and installed hardware) for preventing and/or mitigating UF6 releases asso9 cd with autoclaves, and past operetional history at PORTS, the staff concludes that e . . sjor accidental release of UF6 insic an autoclave is highly unlikely. The ,
probatnuty of inoperability of a containmen, valve or an instrument channel during an operating cycle is also low (none have b'an reported since March 3,1997). According to the surveillence requirements of the proposed TSR 2.1.0.5, these containment valves are required to be calibrated semiannually at or below 15 psig, and to be quarterly functionally tested and separately pressure decay tested at 90 p.cig with an acceptable leak rate of 10 psig/ hour or 12 standard cubic feet per minute. Separate pressure decay testing of the containment valves ensures that each operable valve, by itself, will be able to withstand peak pressures generated as a result of a large accidental (elease of UF6 inside the autoclave, it should be noted that requiring an autoclave to prematurely shut down prior to completing an operating cycle could introduce added risk by necessitating additional handling of cylinders containing liquid UF6 for feed, sampling and transfer autoclaves, or by introducing cascade process upsets for feed autoclaves.
Therefore, the staff has concluded that completing the current operating cycle following
.inoperability of one instrument channel or one containment valve on an autoclave penetration will not significantly herease the risk of a UF6 release.
Occuoational Radiation Exposure Allowing completion of the current autoclave operating cycle if one instrument channel, or one containment isolation valve on one or more autoclave penetrations, is inoperable, will
- not measurably increase individual or cumulative occupational radiation exposures. In f act reduced handling of UF6 cylinders would slightly reduce the direct radiation dose received by UF6 cylinder handlers per SWU produced.
. 3 .
.. Criticality _ ;
lhe staff has not determined any credible criticality accident that this TSR change may affect.
Sateauards and Security The staff has not identified any safeguards or security related implications from the proposed amendment.
ENVIRONMENTAL REVIEW lasuance of the requested amendment to the Portsmouth Certificate of Compliance (GDP-2), to amend TSR 2.1.3.5, is subject to the categorical exclusion provided in 10 CFR 51.22(c)(19) and will not have a significant impact on the human environment. Therefore, in accordance with 10 CFR 51.22(b), neither an environmental assessment nor an [
environmental impact statement it required for the proposed action.
CONCLUSION i
Based on the information provided in this CER, the NRC staff recommends approval of this amendment. Region ill staff have no objection to this proposed action.
Attachments:
- 1. Figure 1 Typical Feed Autoclave
- 2. Figure 2 Typical Sample / Transfer Autoclave l Princloal C9ntributor Yawu Faraz Dt3TMtSVTION:
Docket ,4,002 hRC FILI CENTER PUBLIC NMSStM NMSS Dw. Off. rM FCSSgM $PB FM K'oam nul CCos WSchwink, FCOS PHgard Ritt DHafttart Rill
MME ' YFavas ( DHoadey arts) erscat n ,. io , 2 ,,, , n, 11,1 n, g ,,, _ , n, i n, ,,,,
om<1Cin't o,,1CE,.C.Co.,
T 4
. ~ , - e -, m - - -y-. ---- e r
3
. Criticality The staff has not determined any credible criticahty accident that this TSR change may affect.
Safeauards and Security The staff has not identified any safeguards or security related implications from tt e proposed amendment.
ENVIRONMENTAL REVIEW lssuance of the requested amendment to the Portsmouth Certificate Compliance (GDP-2),'.o amend TSR 2.1.3.5,is subject to the categorical exclusion ovided in 10 CFR 51.22(c)(19) and will not have a significant impact on the huma environment. Therefore, in accordance with 10 CFR 51.22(b), neither an environment assessment nor an environmentalimpact statement is required for the propose action.
CONCLUSION Based on the information provided in this CER, the C staff approves and grants this amendment. Region ill staff have no objection to is proposed action.
Attachments:
- 1. Figure 1 Typical Feed Autoclave
- 2. Figure 2 Typical Sample / Transfer Auto ave Princinal Contributor Yawar Faraz DISTRJSUTIOk Docket 70 7002 NetC 74Lt CENTER IBUC NM55 f'f NMSS Dr. Off. t/f FC$$t/f SP8 r/f L'ORemet Rlll CCon Schww*, FCOB PHearut. Rlli DHa::lervl. Rill OFC SPB [ BPS , $PS $P9 m vFaJ74F DW Du-,, Mr ,
__ j DATS /0 / / /37 h /)I 17 i /97 / 19 7 / /97 / /97 / /97 c - cm en - cuven 6 wavne n - no wn " " '
O uNOTCER.YHF OFFICIAL RECORD COPY
o .
e-CONT AINW[Ni (VACUATION (VINT)'
AIR PURCE
_q, 3 t( r (BLDC.)
}, H RUPiutt DISC "w"
5%w%RL1mJIL4 /, ,
(LICf. I I
- _ . . 5' tt WP.
@g_ -
-a CON 1ROL5 - - - - - - - - - - - - -
flull . _ s' s CONDUCIMIT CILLS , )} ({( -_, , ?-) [WtactNCY %
\g Alt closuRt S CYtlNDER l VALYt5
$ProttssloVo$_$yp TF gyp _ .0000 l l
VACUUW Ritstr MhHb (~
/
b-
- H
$ftAW $UPPtY Q j J RtDUNDAN1 4 ,, A LIVit PR00t1 51 ART-UP Q
O [gitWP. VALYt _ gotNsAtt leap 4!gure 1. Typical Feed Aut.oclave
e f
PRt150R(
VACWW RtuCf LDCKING BR[AKIR UNC R'NG UNI Y(NI
/P _
o
=;Nw ifg
/y aa UNC (LLCf. i i
- 9 1[WP.
g@@ --6 CON 1ROL5 -----------s N
!LT . .e
\
ONDUCIMfY Ct(L$ I
_D (WCRC[NCY I ClosuRt S CYUND(R l VALYt1 Ofs M g $--iF- 00000
/l g Il-ttt PURCI R (VAC -4
/ lmp Am sumY gl ~--- --____
- _' .) l
- wik dk - ---- -- - - ------___._J
. \
$f[AW $UPPLY h O RIDUNDANT A ,, # LIV (L PR09($
~
START UP ttWP, VA(y(
O O * '
CON 0(N$Af(
DRAIN TRAP Figure 2. Typical Sample / Transfer Autoclave