ML20134F896

Forwards Compliance Evaluation Rept Prepared to Support Amend of Coc GDP-2.Notice of Amend,Forwarded to Ofc of Fr for Publication,Also Encl

ML20134F896
Person / Time
Site:	Portsmouth Gaseous Diffusion Plant
Issue date:	02/05/1997
From:	Yawar Faraz NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	John Miller U.S. ECOLOGY, INC. (FORMERLY NUCLEAR ENGINEERING
Shared Package
ML20134F899	List: ML20134F896 ML20134F913
References
TAC-L32006, NUDOCS 9702100198
Download: ML20134F896 (8)

Text

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February 5,1997 I a l Mr. James H. Miller Vice President, Production U. S. Enrichment Corporation 2 Democracy Center 6903 Rockledge Drive Bethesda, MD 20817

SUBJECT:

CERTIFICATE AMENDMENT REQUEST - PORTSMOUTH GASEOUS DIFFUSION PLANT WITHDRAWAL STATIONS STANDBY OPERATIONAL MODE (TAC NO.

L32006)

Dear Mr. Miller:

Enclosed is a copy of the Compliance Evaluation Report prepared to support the amendment of Certificate of Compliance GDP-2. A copy of the Notice of Amendment, which has been forwarded to the Office of the Federal Register for publication, is also l

enclosed. This notice provides the opportunity for the public to petition for review of the l

decision in accordance with 10 CFR Part 76, Subpart C. Final action on your amendment request will not be taken until after the time allowed for requesting review of the Director's Decision is over. If you have any questions regarding this action, I can be reached at (301) 415-8113.

Sincerely, Original Signed By Yawar H. Faraz, Project Manager Enrichment Section Special Projects Branch Division of Fuel Cycle Safety and Safeguards, NMSS Docket 70-7002 Certificate GDP-2 970210019e 970205 PDR ADOCK 07007002 C PDR

Enclosures:

1. Compliance Evaluation Report

2. Notice of Amendment /

/

OfSTRIBUTION: (Control No. 030SI O l

, Docket 70-7002 f NRC File Center ' PUBLIC KO'Brien Rill CCox, Rill NMSS r/f FCSS t/f WSchwink, FCOB SPB r/f OGC GShear, Rill RPierson G:WENTLTR1.YHF OFC SPB (SPB b SRB, A l NAME Yrarer Mondley b W DATE I M7 l 7$97 /'//)D7 l l /97 / /97 / /97 C = CO /ER E = C)VER & ENCLOSURE I N = WO COPY OFFICIAL RECORD COPY

/pw%% UNITED STATES p* 4 j .j

~t NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20615 4001 January 31, 1997 DOCKET: 70-7002 CERTIFICATE HOLDER: United States Enrichment Corporation Portsmouth Gaseous Diffusion Plant Portsmouth, Ohio

SUBJECT:

COMPLIANCE EVALUATION REPORT: APPLICATION DATED NOVEMBER 8,1996, WITHDRAWAL STATIONS STANDBY OPERATIONAL MODE BACKGROUND On November 8,1996, United States Enrichment Corporation (USEC) submitted a request to revise the Portsmouth Gaseous Diffusion Plant (PORTS) Standby Operational Mode specified in Technical Safety Requirement (TSR) 2.5.1, Withdrawal Station Operational Modes. The amendment changes the TSR Standby Operational Mode definition for the UF, Withdrawal Stations by allowing the compression loop vent path to the cascade to be open. It should be noted that venting of the Withdrawal Station compression loop to the cascade is an authorized operational process at PORTS under the regulatory oversight of the Department of Energy. However, accounting for this procedure was inadvertently left out of the Standby Operational Mode definition by USEC from its proposed TSRs contained in the certification application which has been approved by the NRC.

The subject mode definition as described in the USEC certificate application TSR 2.5.1 states:

"lV Standby Withdrawalloop compressors shutdown or operating on recycle, withdrawal loop UFe supply suction valve open or closed, vent valve (s) closed. The withdrawal loop may still contain stored UF, but station pressure remains below atmospheric."

USEC has proposed to revise the mode definition to state:

"lV Standby Withdrawalloop compressors shutdown or operating on recycle, withdrawal loop UF, supply suction valve open or closed, vent valve (s) establishing a vent path from the compression loop to the cascade are open or closed. The withdrawalloop may still contain stored UF, but station pressure remains below atmospheric."

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2 l l The NRC staff review included two separate information requests (RAl's) from Robert C.

Pierson to James H. Miller dated November 29 and December .31,1996. USEC's  ;

respective responses to these RAl's were from James H. Miller to Carl J. Paperiello dated l December 13,1996 and January 16,1997.  ;

DISCUSSION i l

Three permanently established facilities withdraw uranium in the form of UF, from the l cascade. These are the Tails Withdrawal Facility located in the northeast comer of the X- '

330 Process Building; the Extended Range Product (ERP) Withdrawal Station located in the northeast corner of the X-326 Process Building; and the Low Assay Withdrawal (LAW)

Station located in the west center of the X-333 Process Building. If the need arises, enriched or depleted UF, can be withdrawn at any one facility. For example, the Tails Withdrawal Facility may be used to withdraw enriched uranium (up to 5% assay). Figure 1 shows the UFe flow paths at ERP and LAW while Figure 2 shows the UF, flow paths at the Tails Withdrawal Facility.

UF is withdrawn from the enrichment cascade into cylinders in liquid form at these three locations. To accomplish this, centrifugal withdrawal compresscrs (two in series within each compression loop) compress the gas stream to a pressure (30 to 35 psia) and temperature (high enough to maintain UF,in vapor phase) above the triple point and then condensers cool and condense the UF, vapor. The condenser is vented through a vent ,

return line to the cascade to remove light gases from the top of the condenser and to )

serve as a control mechanism to regulate the condensing pressure. Accumulators are j ptovided to accumulate liquid UF, while cylinder filling is interrupted. Unlike Figure 1 (ERP j and LAW), Figure 2 (Tails) identifies the accumulator as the waste drum which is located )

in the liquid UFe portion between the condenser and the UFe withdrawal manifold. The compressors are located on the second floor of the process building. The accumulators, associated piping, UF, condensers, and valves are located on the mezzanine level between floors. Withdrawal stations (manifolds, cylinder scales and cylinder carts) are located on j the ground floor of the process building. All equipment and piping leading from the cascade to the cylinder are " safe geometry" for the allowed enrichment assays. l Because of the very close assay tolerance required when filling a cylinder and the necessity to maintain accurate inventories of "in-process" UF e, assay monitoring is required for each withdrawal. This is accomplished using a continuous mass-spectrometer. Periodic laboratory analysis is conducted to verify the accuracy of the mass-spectrometer. For the allowed enrichment levels, the withdrawal loop (first stage withdrawal compressor to the withdrawal manifold) is " safe geometry" which means that criticality is not possible even in the presence of a moderator.

Each compression loop at ERP and LAW has a 2-inch line installed from the discharge of the second stage compressor to the vent return header. A 2-inch air-operated valve is installed in this line for the purpose of " manually" or " automatically" relieving high pressure back to the cascade from the loop, when necessary. Only remote " manual" venting is provided for the compression loop at the Tails Withdrawal Facility where the

3 vent line is installed from the discharge of the first stage compressor to the vent return header. While the withdrawal loop is in a condition known as " station recycle," the vent path from the compression loop to the cascade may be opened to evacuate UF, from the compression loop. Under the current TSR Standby Operational mode definition, this compression loop evacuation scheme, which is a DOE authorized activity, would not be allowed, since it requires the vent valve (s) to be closed. Therefore, to continue routine UF withdrawal operations at PORTS, USEC needs to have the Standby Operational Mode definition amended to allow the vent path from the compression loop to the cascade to be open or closed. It should be noted that this amendment does not involve three other vent pathways, i.e., from the condenser, accumulator, and the withdrawal manifold to the vent return header. These pathways will remain closed in the Standby Operational Mode.

Unconfinement of UF.

The proposed change to TSR 2.5.1 permits evacuating UF from the compression loop in the UFe withdrawal station to the cascade, which acts as a low pressure sink, in the Standby Operational Mode. This change will not result in significantly increasing the potential 'or unconfinement of UFe since it only involves venting of UF, from one portion of process piping which confines UFe in the Withdrawal Station to another portion of process piping which confines UF,in the enrichment cascade. In fact, venting the ,

compression loop to the cascade may enhance safety by minimizing the potential for over '

pressurization of the UF, withdrawal loop with subsequent confinement rupture.

Confinement of UF, within the cascade is primarily provided by maintaining the cell high- l side (compressor discharge) gas pressure below 25 psia (TSR 2.2.3.13) and by appropriate quality assurance requirements to process gas piping and equipment (Safety Analysis Report Section 3.8.2.2). Confinement of UF,in the Withdrawal Station compression loop is primarily provided by maintaining UF, pressure below acceptable levels l via the High Pressure Venting (HPV) system and by appropriate quality assurance requirements to process gas piping and equipment (Safety Analysis Report Sections 3.8.1.1.8, 3.8.1.2.8, 3.8.1.3.9, and 3.8.2.2). The HPV, which can be operated in automatic or manual mode at ERP and LAW and only in the manual mode at Tails, relieves to the cascade, any unusual pressure buildup in the Withdrawal Station compression loop.

To avoid enrichment losses, UF,is vented from the Withdrawal Station back to the A-suction of a compressor in the cascade that has UF, of similar enrichment. All A-suction pressures in lines that would receive the vented UFe are subatmospheric. Therefore any confinement failure would likely result in inleakage as opposed to outleakage. In addition, cascade units that would receive vented UF, would likely be comprised of relatively smaller sized equipment containing relatively smaller quantities of UF, since they would be located near the top and at the bottom of the cascade. Therefore, the proposed change will not l result in a significant increase in the potential for UF, releases.

Occupational Radiation Exoosure Neither the cascade nor the withdrawal loops result in significant occupational radiation exposures. Some of the reasons are: (1) the occupancy factor is low, (2) distance from the source is generally high, (3) significant shielding is provided by piping and equipment, (4) depleted and low enriched uranium has low specific activities and are also comparatively low gamma radiation emitters, (5) most of the uranium is in gaseous form

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(low density), and (6) UF,is confined within quality controlled equipment and piping. I Therefore, any transfer of confined UF, from the withdrawal station to the cascade would not measurably modify individual or cumulative occupational radiation exposures.

J Criticality The staff determined that the only credible criticality accident that this TSR change may affect is the one caused by introducing a large quantity of moderator into an unsafe geometry portion of the cascade containing a large quantity of enriched solid uranium deposits. However, the staff has determined that the likelihood of an accidental criticality in the cascade due to wet-air (moderator) inteakage would not be increased significantly for the following reasons:

a. This amendment involves a valve that is internal to several valves even when the pigtail is not attached to the withdrawal manifold. These valves would be in the closed position. Therefore, several misvalving errors would be required to permit significant wet-air inleakage into the cascade through the compression loop vent valve.

b. To maintain the integrity of the UF, pressure boundary, USEC is committed to appropriate quality assurance requirements to process gas piping and equipment (including valves) with diameters of 2 inches or larger.

c. Formation of UO2 F2 in the cascade due to significant inleakage of wet-air would result in compressor vibration and would reduce barrier permeability thus affecting cascade compressor performance which would be observed in the control rooms via motor load indications. Changes in compressor A-suction pressures would also be detected.

d. Introduction of wet-air into the cascade would be detected on the line recorders that continuously indicate nitrogen and oxygen concentrations. l l

Based on the primary reasons provided above, the staff has concluded that the proposed TSR change will not significantly raise the mobability or consequences of a criticality ,

accident. j l

Safeauards and Security The staff has not identified an: safeguards or security related implications from the proposed amendment.

ENVIRONMENTAL REVIEW lssuance of the requested amenament to the Portsmouth Certificate of Compliance (GDP-2), to amend the Withdrawal Stations Standby Operational Mode definition, 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 5". 22(b),

neither an environmental assessment nor an environmental impact statement is requirsd for the proposed action.

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CONCLUSION  !

l l Based on the information provided in this CER, the NRC staff approves and grants this  !

l amendment. Region ill staff have no objection to this proposed action.  !

1 Attachment- I l 1. Figure 1 ERP and LAW UF6 Flow Diagram

2. Figure 2 Tails Withdrawal UF6 Diagram Princioal Contributor (s)

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