ML20153B345

Insp Rept 70-7001/98-204 on 980831-0903.No Violations Noted. Major Areas Inspected:Ncs Related Open Items,Corrective Actions & Corrective Action Tracking,Criticality Safety & Plant Operations

ML20153B345
Person / Time
Site:	07007001
Issue date:	09/16/1998
From:	Ting P NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
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ML20153B341	List: ML20153B339 ML20153B345
References
70-7001-98-204, NUDOCS 9809230081
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS Docket No: 70-7001 Certificate No: GDP-1 Report No: 70-7001/98-204 l

Certificate Holder: United States Enrichment Corporation

. Location: Paducah Gaseous Diffusion Plant Paducah, Kentucky Dates: August 31 - September 3,1998 Inspectors: Dennis Morey, Inspector, NRC Headquarters Approved By: Philip Ting, Chief, Operations Branch, Division of Fuel Cycle Safety and Safeguards, NMSS Enclosure l

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. 2 I UNITED STATES ENRICIIMENT COfU) ORATION i PADUCAH GASEOUS DIFFUSION PLANT j NRC INSPECTION REPORT

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70-7001/98-204  !

EXECUTIVE

SUMMARY

Areas Inspe_cied i An NRC Headquarters team conducted an announced Nuclear Criticality Safety inspection of the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky, on August 31 to September 3, 1998. The inspection was conducted using NRC Headquarters staff. The inspection focused on a review of NCS related Open Items, corrective actions and corrective action tracking, criticality safety analysis, and plant operations.

l Results

• A non-cited violation (NCV) was identified concerning the use of a Negative Air Machine (NAM) in an area where large containers are excluded by an NCSE.

• Two inspector followup items (IFIs) were opened concerning pending NCS A/NCSE  :

revisions.

• An IFI was opened regarding the adequacy of USEC NCSE bounding assumptions after j the inspector identified a nonconservative assumption in the method used to model oil for .

calculations supporting cascade equipment and processes.

• USEC corrective action and commitment tracking system was determined to be adequate.

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• Initial investigation and processing of a USEC criticality safety event which was repor'.ed under NRC Bulletin 91-01 was observed and was determined to be adequate. l

• Three violations (VIO), one deviation (DEV) (which had been withdrawn), six IFIs, and two unresolved items (URIs) were closed.

• A new USEC validation report intended tojustify calculations involving assays from 2

0 to 9.83wt% "U was determined to be weak. This issue will be resolved in conjunction with a larger NRC effort to clarify validation requirements.

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- 3 REPORT DETAILS 1.0 Plant Operations

a. S_cspe of the Inspection The inspector conducted walkdowns in the C-400 cylinder wash area, the C-360 Sampling building, and the C-310 Withdrawal building.

b. Observali_ons and Findings While conducting a walkdown in building C-310, the inspector observed that containers larger than 5.5 gallons are not allowed north of the cell housings in the upper story of the building. This is a requirement from Nuclear Criticality Safety Evaluation (NCSE) KY/G-255 which is based on the proximity of two NORMETEX pumps in this area. The NORMETEX pumps are used to increase UF6 pressure to 30 psi prior to condensation in building C-310A. Large containers are excluded from the area to prevent their becoming filled with UO 2F 2flakes which would be generated in the event of a leak in the UF6lines.

The insmetor observed that the exclusion area was denoted by a sign which did not clearly identify the exclusion area boundary. The facility operators stated that they interpret the NCSE requirements to mean that the exclusion area is anywhere in the building north of the northernmost cell housings. The inspector determined that the operator interpretation took in the most area and was therefore the most conservative interpretation.

The inspector noted that a Negative Air Machine (NAM) was being used in the exclusion area, between the NORMETEX pumps directly under the high pressure UF6 piping. The NAM was being used in support of the seismic upgrade of the C-310 building in the adjacent C-310A area. The NAM was being used by contractor personnel who were installing structural supports and who had been specifically trained on the use of the NAM. The inspector noted that the NAM was a large container which was open in the exclusion area and requested a determination from the NCS staffif this was in accordance with the NCSE requirements. USEC NCS staff evaluated the location of the NAM and determined that the NCSE requirements for large container exclusion were being violated by the use of the NAM in the exclusion area.

I USEC took immediate actions to correct the situation including shutting down and l covering the NAM, evaluating corrective actions, and removing the NAM from the exclusion area. At the conclusion of the inspection, USEC was evaluating the use of the NAM to support the seismic upgrades with the NAM outside of the exclusion area. This failure constitutes a violation of minor significance and is being treated as a non-cited violation, consistent with Section IV of the NRC Enforcement Policy. Use of the NAM in an area excluded by NCSE is NCV 70-7001/98-204-01.

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c. Conclusions i The inspector identified a violation of a USEC criticality safety requirement to exclude large containers from the area in building C-310 north of the cell housings. Specifically, l USEC was operating an unattended NAM in the area. Immediate effective corrective actions were taken and the inspector determined that safety significance is low due to the low likelihood of a significant quantity of fissile material with sufficient moderator into the NAM.

2.0 Corrective Actions 1

a. Scope of the Inspectinn 1

The inspector reviewed corrective action tracking and closure in conjunction with review of completion of previous open items. The inspector interviewed USEC manager responsible for corrective action tracking and reviewed the assignment of corrective actions, tracking ofcorrective actions in the electronic system, and USEC criteria for completion of corrective actions.

b. Observations and Findings Corrective action assignment and tracking is required under SAR Section 6.9.6. This section requires that corrective actions be assigned and tracked whenever an event or condition requires a written report. The inspector noted that, in many cases, the content of the corrective action packages that were presented in support of open item closure was not directly related to the issue of concern. The inspector pointed specifically to IFI 70-7001/97-208-02 which had a number ofitems in the closure package not related to NCS Self-Assessment. USEC noted that the assigned manager is responsible for the focus of the corrective action activities and the content of the packages. USEC also noted that, for management purposes, ccrrective actions may be added to a commitment that were not directly related to the NRC Open Item.

The inspector observed that management oversight of the corrective action process was focused on Significant Condition Adverse to Quality (SCAQ) related issues, and the quality of corrective action assignment, tracking, and closure for lower tier issues is variable. No safety or regulatory issues were noted in the corrective actions that were reviewed for this report. The inspector determined that issues with safety significance are normally classified as SCAQ and receive adequate management oversight.

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c. Conclusions The inspector determined that the corrective action and commitment tracking is adequate.

All open items reviewed during the inspection were appropriately assigned and tracked.

Open items that USEC represented as closed were determined to be complete.

3.0 Event Reporting and Investigation

a. Scope of the Inspection The inspector reviewed USEC's response to a reportable event that occurred during the l inspection. The inspector accompanied USEC NCS staff during a walkdown of the i affected equipment and observed discussion of the event and preparation of the initial event report by the NCS staff.

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b. Observations and Findmgs l

~ On September 1,1998, USEC discovered that a HEPA filter which had been analyzed L without a pre-filter, actually contained a pre-filter and was being used in an unanalyzed i configuration. The HEPA filter was used in building C-360 to ventilate glove boxes in  ;

l which liquid UF samples were processed. The operators shut down the filter and placed a

! barrier around the equipment as required by procedure. USEC NCS staffinvestigated and l determined that a prefilter was installed and that there was no evidence of fissile material

' in the equipment. An assay of the equipment is required whenever there is a UF release in the hoods and the most recent assay of the equipment had revealed no fissile materialin the filter. USEC determined that safety significance of this event was low due to the absence of fissile material.

The event was reported under NRC Bulletin 91-01 on September 1,1998. The inspector determined that during normal sampling operations, UF6is not expected to be released into the hoods because the samples are enclosed during processing. If any UF6 gets into the hood during processing, it is characterized as a " release" and the HEPA filter is assayed. No fissile material could be seen in the filter which the inspector observed to be in like-new condition.

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USEC determined that an inspection of the equipment performed by a sub-contractor had incorrectly identified which of the building C-360 HEPA filters had a pre-filter. The inspector observed that the inspection documentation had previously indicated that a

prefilter was present but had been lined through. The analysis for this system is contained in NCSE KY/S-222 and does not include analysis for a prefilter. When the system was j preparing for startup, the NCS staffindicated that a prefilter was unanalyzed and the sub-

contractor's inspection report was used as evidence by operators that there was no prefilter in the sample hood HEPA filter.

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c. Conclusions The inspector determined that USEC's immediate corrective actions for the improperly I configured HEPA filter event were in accordance with SAR requirements and with the l low risk significance of the event. '

4.0 NCS Analysis

a. Ecope of the Inspection In conjunction with review of open items, the inspector reviewed USEC NCSEs, interviewed NCS staff concerning the calculations and performed confirmatory or scoping calculations to determine the adequacy of USEC results. .

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b. Observations and Findings NCSE-207, "Five-Gallon Drum Waste Oil Storage at 5.5wt% 2"U at the Paducah Gaseous Diffusion Plant," is being revised to demonstrate that infinite plane layers of

' lumped fissile material separated by layers of oil is the bounding case for arrays of 5-gallon cans of fissile material containing sludge. Completion of the revision of NCSE-207 will be tracked as IFI 70-7001/98-204-02.  !

H The inspector reviewed calculations supporting NCSEs for the Seal Exhaust Pumps.  !

USEC provided electronic copies of the four KENO input files used to model the system and credible upsets. The inspector determined that USEC models bounded the system.

The Seal Exhaust Pump NCSA is being revised to accommodate a higher assay. The NCSA revision will be tracked as IFI 70-7001/98-204-03.

The inspector noted that USEC uses C3 Hi2 as an arbitrary material to model oil in the cascade. This model is based on the molecular formula in the oil Material Safety Data Sheet (MSDS), a standard saturated hydrocarbon C3 Hm.2, and a handwritten note from the oil vendor which describes the oil as having an estimated hydrogen to carbon ration of

.1.94. The inspector performed several confirmatory calculations to determine if the C3Hi2 model was conservative and bounding and determined that if a hydrogen to carbon ration of 2 is used for the filled pump, the multiplication factor will increase by nearly 4%.

USEC reviewed this issue and determined that k,, did indeed increase for this case, possibly due to the way KENO calculates weight fractions for the arbitrary material (i.e.

causing a slight increase in the amount of fissile material modeled). USEC agreed to evaluate whether any cases existed where a limit might be exceeded. The inspector determined that substantial safety remained in all cases in which multiplication increased due to a change in the weight fractions of materials. Evaluation of the oil model will be tracked as IFI 70-7001/98-204-04.

7 The inspector reviewed calculations supporting NCSE.006.001 for the C-400 cylinder

, wash including a review of the KENO input files using the viewer KENO 3D. USEC l provided electronic copies of the most reactive cases of the ten models used to bound the C-400 cylinder wash. The most reactive individual case was determined to be a reflected cylinder heel which was modeled as a hemisphere. The inspector observed that the KENO l

input file for the cylinder heel case contained a hemispherical heel which was not observed !

in the viewer. When the inspector replaced the hemisphere with a cylinder, the new l cylinder could be seen in the viewer. By comparing the input files with KENO PLOT diagrams and performing confirmatory calculations, the inspector determined that USEC results with the hemisphere were adequate. The inspector determined that the viewer, l KENO 3D, would not display a hemisphere. Otherwise, USEC models reflected cases that I bounded the system.

c. Conclus.io_ns The inspector determined that USEC criticality safety analyses use models that bound the system or equipment being evaluated with adequate safety margin. One case of a nonconservative assumption was identified, but safety margin was determined to be adequate.

5.0 y_plidation

a. Scope of the Inspection The inspector reviewed a new USEC validation report, KY/S-221 Rev. 2, which uses new benchmark data tojustify calculations involving assays from 0 to 9.83wt%2 "U. The inspector interviewed the USEC engineer responsiole for the report.

b. Observations and Findings Violation 70-7001/97-208-03 concerned the failure to perform adequate validation of USEC computer codes used for specific criticality safety calculations involving 5.5%

enriched uranium. USEC has revised their validation using new benchmarks that extend the area of applicability to 9.83wt% 2"U. The inspector determined that the issues underlying the violation have been addressed so that the violation may be closed.

Specifically, the violation cited an inadequate extension of the area of applicability by extrapolation of the experimental bias. The new validation covers the area of applicability by reference to benchmarks with enrichments up to 9.83wt%2 "U.

Although the new report eliminates the problem with inadequate extrapolation, the inspector determined that the new report was weak for three reasons:

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1. USEC has not provided suflicient justification for the use of the 2% administrative margin above Swt% assay.

2. USEC incorrectly combined uncertainty with the administrative margin so that the total margin of safety is based only on bias plus administrative margin. PGDP TSR 3.11.4 requires the total margin of safety to include bias, uncertainty, and the administrative margin.

3. USEC has not provided sufficient justification for the selection and use of new benchmarks from 5wt% to 9.83wt%. The report shouldjustify the use of MOX ,

criticals near Swt% and the UO 2 Pi n criticals above Swt% by an appropriate I method such as neutron spectrum analysis.

l PGDP TSR 3.11.3 requires that "A minimum margin of subcriticality of 0.02 in k,g, shall be used to establish the acceptance criteria for criticality calculations." This means that an additional administrative margin of subcriticality must be included in the lin.it for k,g. 2%

has been established previously in certification submittals as adequate for assay up to 5%.

No documentation is available establishing the adequacy of 2% administrative margin for assay above 5%. The validation report should objectively establish the reasonableness of the administrative margin chosen.

PGDP TSR 3.11.4 requires that "The k,g for criticality calculations shall be 5 0.9634 which includes the bias, uncertainty, and the margin of suberiticality." To establish that this requirement has been met, the nu validation report needs to establish an upper limit on k,y which is greater than or equal to 0.9634. The new validation report adds the subcritical margin to the confidence interval [0.9849 - 0.02 on page 28] to claim that the Upper Safety Limit (USL) is 0.9649. A confidence limit, however, only predicts confidence in the sample, not future calculations and, therefore, does not include uncertainty. The lower tolerance limit should have been used [0.9686 - 0.02 on page 27]

to establish the USL for this validation as 0.9486.

All the new benchmarks above Swt% in the new validation report are steel clad UO2 P ins in water. Nothing in the new report establishes that these experiments adequately represent UF6 gas and other configurations in the plant. Although assay is the parameter ofinterest, effects such as spectrum shifting which may influence k,g, must be eliminated.

Some information must be included in the report to convince the reviewer that the chosen benchmarks are reasonable.

A specific error was identified in the statistical calculations on page 27 of the report in Table 4. For the calculation of the Upper Safety Limit (USL) a one-sided tolerance limit factor is required. Using Table T-1lb of NUREG 1475, the value is approximately 2.7 instead of 3.59, as the report indicates. The inspector determined that this does not effect the results.

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9 The inspector determined that the weak validation report has low safety significance because assay at PGDP is presently limited to 2.75wt% The inspector determined that tracking of the validation issues would be performed as part of a broader NRC efTort rather than as an open item in this report.

c. Conclusions The inspector determined that the new USEC validation supporting operations with 2

0 to 10wt% "U is weak and does not justify operations above Swt%. No safety issues were identified regarding the weak validation.

6.0 Open Items i

The inspector reviewed closure packages for Notices of Violation and inspector followup items from previous inspections, conducted walkdowns of associated facilities and systems and interviewed responsible staff to determine the status of corrective actions for the items.

IFl 70-7001/97-201-01 This item concerned implementation of corrective actions for a USEC identified failure to meet double contingency at the cylinder wash facility. The inspector reviewed l NCSE.006.001 for the C-400 cylinder wash, performed confirmatory calculations, interviewed criticality safety staff and system operators, and conducted a walkdown of the system. The inspector observed washing of two cylinders and reviewed the operations against the requirements of NCSA.400.002.01. Operations were observed to be conducted in accordance with NCS A requirements. This item is closed.

VIO 70-7001/97-201-02 This violation concerned storing used HEPA filters in an unanalyzed 3X4 floor array. The inspector reviewed USEC closure package and determined that the NCSE-09, "1000 and 2000 CFM NAM Machines at the Paducah Gaseous Diffusion Plant," had been revised.

The inspector determined that the situation of storing used filters in the 3X4 array is bounded by the revised analysis. This item is closed.

IFI 70-7001/97-201-04 This item concerned the lack of requirements for NCS review of proposed changes to facilities or systems. USEC had committed to develop a procedure containing such requirements. The inspector determined that USEC procedure CP2-EG-EG1046,

" Nuclear Modification Design Development and Implementation Process," has been developed and implemented in response to this IFI. This item is closed.

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!FI 70-7001/97-201-06 l This item concerned inclusion of NCS requirements in the baseline review of the boundary definition manual (BDM). The inspector determined that NCS staff were included in the BDM process. This item is closed.

DEV 70-7001/97-208-01 1

This deviation was withdrawn by letter from Phil Ting dated June 19,1998. This item is closed.

IFI 70-7001/97-208-02 This item concerned the failure to include CM specific requirements in a self-assessment procedure in order to fully implement SAR Section 6.3.5.6. Procedure UEO-1058 has been revised to include CM program assessments. The inspector determined that these requirements, ifimplemented, will result in a self-assessment of the CM program. This item is closed.

VIO 70-7001/97-208-03 This violation concerned the failure to properly validate a USEC computer program for specific criticality safety calculations involving 5.5% enriched uranium. USEC has revised their validation using new benchmarks that extend the area of applicability to 10%. This item is closed.

l URI 70-7001/97-208-04 This item concerned the modeling of 5-gallon drums in NCSE-207. The evaluation assumed that an infinite plane oflumped waste separated by layers of oil was the worst j case situation. Evaluation has demonstrated that removal of the oil layers makes the system more reactive. USEC has demonstrated that the layers of fissile material cannot exist without material in between and that oil is the material that might credibly form the intervening layers. This item is closed.

IFI 70-7001/97-208-05 This item concerned the failure to valve out recirculating cooling water (RCW) when the RCW condensers were empty. USEC has revised NCSA CAS.002.00 to indicate that when a cooler (as opposed to a cell) is shut down, the RCW shall be valved off. This item is closed.

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! URI 70-7001/97-208-11 l This item concerned the failure to comply with an NCSA control for seal exhaust pumps which was later determined to be irrelevant. The control required maintaining oil level less than 4 inches but 'vas not required when assay is less than 2%. The NCSA is being revised. This item is closed.

IFI 70-7001/97-208-12 This item concerned communication of the cylinder yard pre-fire plan to firefighters. The inspector reviewed training which demonstrated that the training had been performed as I crew briefings during February 1998. This item is closed.

VIO 70-7001/98-201-02 This violation concerned the use of procedures with outdated NCSA references. The l correct GEN-04 references have been placed in procedure CP4-CU-CH2103. Procedures CP4-CU-CH2105 and CP4-CU-CH2106 have been placed on hold. Specific NCSA paragraph references were not included in the Inspection report but the inspector observed that the revised procedure contained 5.5 gallon storage and 2 foot spacing requirements to i prevent fissile material accumulation. This item is closed.

7.0 Management Meetings The inspector met with USEC management periodically during the inspection. The ,

inspector presented the inspection scope and findings to members of USEC's staff at the conclusion of the inspection on September 3,1998. USEC acknowledged the findings presented at the meeting.

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. 12 ITEMS OPENED. CLOSED. OR DISCUSSED Items Opened l

NCV 70-7001/98-204-01 Concerns use of a NAM in an area where large open containers are excluded by the NCSE.

l IFI 70-7001/98-204-02 Concerns the completion of the revision of NCSE-207.

IFI 70-7001/98-204-03 Concerns completion of the revision of NCSA.

IFI 70-7001/98-204-04 Concerns evaluation of a nonconservative assumption regarding oil in models of cascade equipment and processes.

Items Closed IFI 70-7001/97-201-01 Concerned implementation of corrective actions for USEC identified failure to meet double contingency at the cylinder wash facility.

VIO 70-7001/97-201-02 Concerned storing used HEPA filters in an unanalyzed 3X4 floor array.

IFI 70-7001/97-201-04 Concerned the lack of requirements for NCS review of proposed changes to facilities or systems.

IFI 70-7001/97-201-06 Concerned inclusion of NCS requirements in the baseline review of the boundary definition manual.

DEV 70-7001/97-208-01 This deviation was withdrawn.

IFI 70n001/97-208-02 Concerned the failure to include CM specific requirements in a self-assessment procedure in order to fully implement S AR Section 6.3.5.6.

VIO 70-7001/97-208-03 Concerned the failure to properly validate a USEC computer program for specific criticality safety calculations involving 5.5%

enriched uranium.

l URI 70-7001/97-208-04 Concerned the modeling of 5-gallon drums in NCSE-207.

i IFI 70-7001/97-208-05 Concerned the failure to valve out RCW when the RCW

condensers were empty.

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URI 70-7001/97-208-11 Concerned the failure to comply with an NCSA control for seal l exhaust pumps.

l IFI 70-7001/97-208-12 Concerned communication of the cylinder yard pre-fire plan to l firefighters.  !

VIO 70-7001/98-201-02 Concerned the use of procedures with outdated NCSA references.

PARTI AL LIST OF PERSONS CONTACTED Lockheed-Martin Utility Services Howard Pulley, General Manager I Ed Paine, Criticality Safety Manager Terry Hofer, Criticality Sdety Keith Ahern, Engineering J.D. Sohl, Operations Steve Penrod, Enrichment V.J. Shanks, Production Support I Russ Starkey, Training Dave Stadler, Regulatory Affairs M.A. Buckner, Operations U.S. Enrichment Corporation Steve Cowne NRC John Jacobson, Resident Inspector l

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14 ACRONYMS USED BDM Boundary Definition Manual CFM Cubic Feet Per Minute DEV Deviation HEPA High Efliciency Particulate Air IFI Inspector Followup Item KENO Name Of A Computer Code KENO 3D Computer Application For Viewing KENO Input Files MOX Mixed Oxide MSDS Material Safety Data Sheet NAM Negative Air Machine NCS Nuclear Criticality Safety NCSA Nuclear Criticality Safety Analysis NCSE Nuclear Criticality Safety Evaluation NCV Non-Cited Violation PGDP Paducah Gaseous Diffusion Plant RCW Recirculating Cooling Water SAR Safety Analysis Report SCAQ Significant Condition Adverse To Quality URI Unresolved item USL Upper Safit, f.imit VIO Violation