ML20138D487

Rev 2 to NCS Evaluation for Drain Sys in C-710 Facility at Paducah Gaseous Diffusion Plant. Figures 1,2 & 3 Re Fissile Matl Transport, Encl

ML20138D487
Person / Time
Site:	Paducah Gaseous Diffusion Plant
Issue date:	03/30/1997
From:	Hurrell S, Risnie V External (Affiliation Not Assigned)
To:
Shared Package
ML20138D407	List: ML20138D402 ML20138D455 ML20138D480 ML20138D487
References
1493-25, 1493-25-R02, 1493-25-R2, NUDOCS 9705010137
Download: ML20138D487 (67)

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GDP 97-0051 NCSA Number 1493-25 Revision 2 NCS Evaluation for the Drain System in the C-710 Facility at the Paducah Gaseous Diffusion Plant March 1997

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9705010137 970407 PDR ADOCK 0700 0 1

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i l-t NCS EVALUATION FOR THE DRAIN SYSTEM IN THE C-710 FACILITY AT THE PADUCAH GASEOUS DIFFUSION PLANT l

R. J. Winiarski Jr.

Parallax, incorporated NCS Request Number 1648 NCSA Num.ber 1493-25 Rev. 2 i

March 1997 l

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DISCLAIMER j

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This report was prepared as an account of work sponsored by an agency of the United States Govemment. Neither the United States Govemment nor any agency thereof, nor any of their i

employees, makes any warranty, express or implied, or assumes any legal liability or i

responsibility for the accuracy, completeness, or usefulness of any information, apparatus, j

product, or process disclosed, or represents that its use would not infringe privately owned j

rights. Reference herein to any specific commercial product, process, or service by trade i

name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Govemment or any agency thereof. The views and opinions of authors expressed therein do not necessarily state or reflect those of the United States Govemment or any agency thereof.

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I DATE OF ISSUE: March 1997 NCSA NUMBER:1493-25 REQUEST:1648 Rev. 2 NCS EVALUATION FOR THE DRAIN SYSTEM IN THE C-710 FACILITY AT THE PADUCAH GASEOUS DIFFUSION PLANT R. J. Winiarski Parallax, incorporated -

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3-a o-9 7 Chticality Safety Review Date i

t Prepared by LOCKHEED MARTIN UTILITY SERVICES, INC.

Paducah Gaseous Diffusion Plant P.O. Box 1410 i

Paducah, Kentucky 42002-1410 for the l

UNITED STATES ENRICHMENT CORPORATION Under Contract No. USECHQ-93-C-0001 t

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1493 25, Rev 2 Request 1648 Request Rev.

Affected Reason for Revisio,.

Employee Pages initials 1648 1

5,14-18, Incorporate comments received from R.J.W 20,22,25,2 reviewers.

6-27,30, Comments editorialin nature.

32,35,37 1648 2

Appendix C Respond to comments provided by NRC, No S.J.H.

page 36, changes to NCSA.

and Appendix E all pages iv i

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i 1493-25, Rev 2 March 1997 Request 1648 Contents 1.0 I NTRODUCTION.....................................

1 2.0 PROCESS DESCRIPTION 2.1

. Physical Layout........

1-2 2.2 General Operations............................................ 2 2.3 Detailed Analytical Laboratories...........

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3.0 NCS HAZARD IDENTIFICATION 3.1 Description of the Hazard identification Process...................... 10 3.2 Results of the Hazard Identification.............................. 15 4.0 NCS HAZARD EVALUATION 4.1 Nuclear Criticality Parameter Discussion....

................... 15 4.2 NCS Contingency Discussion...............................

16-23 4.3 Conclusions.............................................. 23-24

5.0 CONCLUSION

S AND RECOMMENDATIONS 5,1 Evaluation Summary........................................... 24 5.2 Recommended Conditions of Approval.......................... 24-29 5.3 Limitations and Applicability of this Evaluation........................ 29 5.4 Assum ptions.............................................. 29-30 5.5 Criticality Safety-Related items................................... 30 R E FE R E N C E S......................................................... 31 APP E N D IX A......................................................... 32-34 APP E N DI X B............................................................ 3 5 AP P E N DIX C....................................................... 36-38 APP E N DIX D......................................................... 4 0-41 APP EN DIX E........................................................ 4 2-56 List of Tables Table 3.1: "What-if" Hazard identification....................................

12-14 Table A.1: C-712 Neutralization Pit Sampling Data............................... 32 Table A.2: Additional Sampling Data...................................... 34 Table C.1: Parametric Study of the C-712 Neutralization Pit for Determination of Maximum Allowable Mass........................... 37 Table C.2: Interjection of 13.455 Kg Uranium into the Pit.............

....... 38 Table E.1: Pit Sam pling Data........................................... 48-49

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1493-25, Rev 2 March 1997

' Request 1648 List of Fiaures Figure 1: C-712 Acid Neutralization Pit - Overhead View

.......... 11 Figure 2: C-712 Acid Neutralization Pit - Side View.............................. 11 Figure 3: Parametric Study of the C-712 Neutralization Pit...

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1.0 INTRODUCTION

The purpose of this Nuclear Criticality Safety Evaluation (NCSE) is to provide technical justification for the continued usage of the drain system in the C-710 facility. This analysis will provide the operationallimits and conditions necessary to ensure an adequate margin of safety from criticality for the drain system in C-710, up to the point where it ties into the sanitary sewers, based on current operations as described below. Appropriate recommendations for risk reduction and conditions for approval are derived based on this evaluation.

2.0 PROCESS DESCRIPTION 2.1 Physical Layout The primary missions of the Technical Services Division are to supply quality analytical services to all functions in the plant; provide a broad base of process support activities to support existing equipment and systems; and provide technology for new equipment and system requirements. Analytical services are tailored to plant customer needs and include sample analysis for process control, environmental monitoring, material specification verification, personnel health and safety monitoring, and troubleshooting. A varied capability of personnel expertise and equipment is maintained.

Laboratory and office facilities for Technical Services are housed in the C-710 building with one laboratory in the C-409 building. The C-710 building is a two-story, reinforced concrete, concrete-block structure containing 56,000 square feet of floor space.

The C-710 facility houses many individual laboratories such as the subsampling lab, the radiochemistry lab, and the spectroscopy lab. The top floor houses machinery for fume hood operation and ventilation. Most of the lacoratories which are involved with significant quantities of uranium are housed on the first floor of the building. There are severallaboratories located in the basement, but they deal primarily with samples which typically contain much smaller amounts of uranium, usually in the parts per million (ppm) range. The drain systems for both the basement and the attic tie directly into the sanitary sewer, while the drains from the first floor empty into a collection pit located southwest of the building, the C-712 neutralization pit.

This pit is commonly known as the " acid pit", and its primary function is to neutralize acidic solutions originating from the various laboratories in the building. It is lined with acid brick for this purpose and has a central baffle for diverting incoming flow. Two schematics of this pit have been included as Figures 1 and 2. Several different sized lines are used in the drain system, ranging from 2 inches up to 6 inches in diameter. The main lines used for the first floor drains are 4" Duriron pipes which tie into the 6" acid mains. These mains then lead into the neutralization pit. From the neutralization pit the drain system ties directly into the sanitary sewer, through an overflow system built into the acid pit. The drain openings of concern are the following: 1. Floor drains in the laboratories, 2. Cup drains located in fume hoods, 3. Sink drains in the laboratories, and 4. Various pieces of automatic washing equipment. These pathways are only a concern when they are located in rooms which handle fissile /potentially fissile material, or in the case of the automatic washers, when they are used to clean items which 1

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Request 1648 have fissile /potentially fissile material and/or samples. Thus there are several pathways which are not a concern from a criticality viewpoint. Specific examples of these would be the bathroom outflows, floor drains in the janitors closet, drinking fountain waste, and locker room floor drains. General examples would include rooms used for offices and rooms which do not handle fissile /potentially fissile material and/or samples.

2.2 General Operations As mentioned above, there are several pathways for entry into the drain system. Routine i

operations primarily involve washing items which may be contaminated with uranium bearing material. This would include hand washing equipment in the sinks, washing equipment in a dishwasher (of which there are several throughout the building), or using one of two automatic washing devices in room 21, the subsampling lab. One of the automatic washing devices is

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used to clean UF, sample tubes while the other is used to clean 2S cylinders. One other operation regularly performed in the subsampling laboratory that introduces uranium bearing

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material into the drain system involves clearing out plugged tubes. This operation involves i

filling a sink with water, immersing the plugged tube into the water and clearing the material which is plugging the tube (typically a mixture of UO F and UF.) by inserting a plastic capillary 2 2 tube into the plugged tubes and flushing the plugged tube out with water. The resulting solution, which is collected in the sink, is then discharged directly down the drain system.

Another NCSA' covers the disposal of liquid samples containing uranium throughout C-710.

l Although other pathways are present in the laboratories, introduction of uranium bearing material into the drain system would be through an accident scenario and not routine operations. Most of the fume hoods in the building have working cup drains, and if an accident were to occur while work, which involved uranium bearing material, was being performed in the fume hood any resulting solution or mixture would have a pathway inb tha drain system.

Similarly, if a sample was mishandled near the sink or floor drain, it is conceivable that material could enter the drain system through either of those openings. These and other accident concerns will be discussed in later sections.

2.3 Detailed Analytical Laboratories Laboratory operations which do not use fissile materials may be performed in each laboratory room within C-710. Various instrumentation used includes mass spectrometers, infrared spectrophotometers, atomic absorption, gas chromatography, etc. These laboratories support the chemical, utilities, power, environmental compliance, environmental restoration, waste management, industrial hygiene, and health physics programs. Sample matrices include waters, soils, solids, oils, air filters, smears, bioassay, etc. Room 38 contains HEPA-filtered hoods used for asbestos sample preparation. Laboratories which support the cascade system and/or have NCSA requirements are detailed below.

Concern Areas l

Rooms 2,6,16, & B27 Materials and Chemistry Laboratory l.

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1493-25, Rev 2 March 1997 Request 1648 This area in C-710, rooms 2,6,16, and B-27, is used for testing and technical support activities associated with barrier and cascade chemistry, materials, instrumentation, process systems and equipment, and environmental, safety, and health issues. Fluoride trapping studies, material stability tests, property measurements, thermal analysis, coolant corrosion studies, physical property measurements, exposure tests involving other chemicals such as PCB/ lube oil and trouble-shooting activities are performed this area.

Corrosive gases, HF, F, UF., and CIF are used in both rooms 2 and 6. Fluorine is supplied to 2

3 the area from Room B-2. Small cylinders are used to supply the other corrosive gases, when needed. A cubicle equipped with a HEPA filter in Room 6 is used to house an oven and reactors for corrosive gas and other chemical exposure tests. Tests involving solid uranium fluorides and oxyfluorides and contaminated trapping materials are performed in Rooms 2,6, and 16.

In room 2, on the west wall there is a series of fume hoods which house a flow system that is used for testing chemical trap material. UF,is run through the trap and then through a

" bubbler". The solution is collected and taken over to room 22 for analysis and disposal. In the middle of the room is a bench bay with a sink and several fume hoods, in which uranium bearing materialis handled. On the east wall there are two sinks, but they are not often used.

The sink located in the middle bench bay is used to hand wash equipment (e.g. beakers, flasks, etc.).

On the west wall of room 6 there is a sink which is used to hand wash items. In the rear of the room there is a cubical which houses a system used for testing material for exposure to UF..

This cubical contains an oven, a pump, and two chemical traps. Test material is placed into the oven and tested for exposure to UF, gas. The cubical does contain an emergency ventilation system as well as an auto HF detector. The room also contains a floor drain.

l Rooms 13,15, & 17 These rooms are mainly used in analysis of environmental samples, primarily metals analysis.

Samples are often concentrated by boiling of liquids, leaving a metal rich solution. Specific analyses which are performed in these rooms include arsenic and selenium analysis, tube oil analysis for lifetime expectancy, and inductively coupled plasma analysis. Samples are also analyzed for other metals. No specific actions are performed in the rooms which are likely to j

introduce uranium bearing material into the drain system.

Rooms 7 & 9 Spectrochemical Laboratory This laboratory in C-710, room 9, uses spectrochemical emission methods to conduct specification analyses for metallic impurities in uranium compounds, to identify various alloys, and to perform general qualitative analyses. Room 7 will be performing operations which used to take place in room 22 excluding purity analysis and hydrolysis. Operations which were performed in rooms 22 and 26 were covered under NCSA 1493-05, 3

1493-25, Rev 2 March 1997 Request 1648 Rooms 8 & 12 Chemical Laboratory This laboratory in C-710, rooms 8 and 12, is used for chemicO preparation and wet chemical analysis. This laboratory performs Chemical, Utilities, and Power (CUP), uranium specification, l

Environmental, Safety, and Health (ES&H), and miscellaneous analyses. Room 8 contains one l

perchloric acid hood.

There is a carboy in this room. A FCA for handling seal exhaust oil has also been set up in this room. Equipment is hand washed in the sinks, with the first couple of rinses being disposed of in the carboy. This room handles a much smaller amount of sample material than room 22.

Rooms 21 & 27 Subsampling Laboratory This area in C-710, Rooms 21,21 A, and 27, is used for subsampling uranium compounds (chiefly UF.), sample container preparation, and salvaging excess uranium materials. Uranium process samples are received by the Analytical Laboratory and returned through these rooms, except for certain Isotopic Laboratory samples. UF. samples are received in 2S cylinders (maximum 2,220 grams UF.) or smaller containers.

Several operations in this room involve the introduction of uranium bearing materialinto the drain system on a routine basis. They are listed below:

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Auto tube washing system - System used for cleaning out sample (UF.) tubes. The first cycle (steam) is collected, while the subsequent cycles are discharged directly into the drain system.

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Cylinder wash system - Wash system for cleaning out 2S cylinders. The resulting waste water is discharged directly into the drain system. The cylinder mass difference from before and after the wash is recorded, and differences of up to 13 grams have been found. Some of these differences can be attributed to the end caps, of which there are three types. The end caps do not weigh the same so the mass could be different based on which end caps are on the cylinder before and after being washed. Current procedure allows washing cylinders with a mass difference of up to 30 grams.

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Plugged tube removal-The sink next to the tube washer is routinely used for clearing out tubes which are plugged. The plug is usually a mixture of UO F and UF. The p!ug 2 2 is cleared out in the sink, which has been filled with water to prevent offgassing of any UF, remaining in the tube. The resulting solution in the sink is then discharged directly into the drain system when the plug has been removed.

There are two carboys located in the room, with all rinsate generated from the first couple of rinses when washing equipment being placed in the carboys. After that however, the rinsate is discharged directly into the drain system. There should be little no uranium left on the equipment at that time.

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l UF,is liquefied in the area by heating containers in steam baths. Liquefaction is required for l

subsampling as well as for homogenization of U-tubes. The sampling lab uses 2S cylinders, sampling tubes, MD cylinders, cold traps,20-liter carboys, and solid uranium salvage.

Hazardous substances (UF., F, etc.) are transferred in hoods. This area includes several fume 2

hoods that vent directly to the building roof. Operations are covered under a separate NCSA, l

1493-15.

i Rooms 22 & 26 Water Laboratory This laboratory in C-710, Rooms 22 and 26 is used for chemical preparation and wet chemical analysis. This laboratory performs ES&H, CUP and uranium specification analyses. This laboratory prepares uranium samples for the analysis by the Spectrochemical and Radiochemicallaboratories.

This room contains numerous samples in a variety of containers. Work is performed in fume hoods which have working drains. Items are hand washed in the sink and there is a dishwasher in the room, which may be used by other labs. The dishwasher leads directly into l

the drain system. These rooms do not have any floor drains. Operations in these rooms are j

covered under a separate NCSA, 1493-05. However all uranium analysis operations will be relocated to room 7 except for hydrolysis of UF, and purity analysis, both of which will remain in these rooms.

Rooms 30 & 32 These rooms handle organic samples. One of the operations in this room involves analyzing samples for PCBs.

Rooms 37,37A,378,53 Isotopic Laboratory This laboratory in C-710, rooms 37,37A,37B, and 53, performs isotopic analyses. Rooms 37/378 have ten mass spectrometers which are utilized in performing the isotope measurements. Auxiliary space,37A, is used for office space and record storage. Room 53 has two thermalionization mass spectrometer (TIMS) and a gas source scanning mass spectrometer which are used for measuring uranium, uranium isotopes, and corrosive gases.

Sample and standard quantities of UF are used in making all measurements in rooms 37/37B; however, UF,is in the solid state and the probability of a release is minimal. An exhaust system consists of fume exhaust hoods with HEPA filters that can be positioned over the sample connection points at each mass spectrometer. UF. standards are synthesized in a hood at the south end of Room 37. During part of the mixing operation, UF is in the liquid phase. A breach in the system integrity could result in a maximum release of 1 kg of UF.,

The isotopic Laboratory uses MD cylinders, cold traps, sampling tubes, and UF, standards.

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1493-25. Rev 2 March 1997 Request 1648 Rooms 53A,53,57,57A,59,59A Radiochemical Laboratory This laboratory in C-710, Rooms 53A, 53, 57, 57A, 59, and 59A, is used for chemical preparation of samples for counting or the TIMS analyses. This laboratory performs ES&H, CUP, and UF specification analyses. These laboratories have small quantities of uranium, i

technetium, thorium, and other radioactive elements in the form of sources and standards.

Room 59A is equipped with a HEPA filtration system for low activity radioactive analyses.

One specific operation which is performed in room 53 is the hydrolysis of cold traps in a fume 1

hood sink. The cold trap is placed in a bucket, and that bucket is then placed in the fume hood sink. Water is then run through the cold trap to hydrolyze any UF which may be contained with'in the trap. The maximum amount of uranium that each glass cold trap could contain is 2,192 grams. The resulting solution from running the water into the cold trap is discarded into the carboy which is located next to the fume hood. Approximately nine traps could be hydrolyzed in a day in this room. The NCSA which covers this operation,1493-02, limits the number of glass cold traps in the fume hood sink to 5 at a time.

There is a dishwasher in room 53, against the north wall, but it is not used by analytical service and belongs to another organization. Smallliquid samples are present in the room, from which a small amount is taken from these samples by a hyper dermic needle and placed on a " button" for analysis.

Another operation which is performed in these rooms (specifically room 57) is organic liquid extraction, which the waste water from this operation is discharged directly into the drain system. All samples which are either fissile or potentially fissile will be disposed of in the carboy in room 57.

Rooms 56 & 58 Process infrared (IR) & Gas Chromatograph (GC) Laboratory This laboratory in C-710, Rooms 56 and 58, conducts gas chromatography and infrared spectroscopy analysis of samples. Gas samples from the process buildings are analyzed for organics and halides. Hydrogen (H ) is supplied to Room 56 from a cylinder located on the 2

C-710 back dock. This laboratory contains small quantities of F, CIF, HF, UF., etc. This 2

3 laboratory also performs ES&H analyses. There are two walk in fume hoods, neither of which have a drain. There is one other fume hood in the room, which does have a working drain. The rooms primarily handles samples which are solid. The majority of the liquid samples which are handled in these rooms come from the organic lab room (32). Neither of these rooms has a floor drain. There are sinks in these rooms and equipment is hand washed in them, prior to be washed in a dishwasher. No routine operations are performed in these rooms which are likely to introduce uranium bearing materialinto the drain system. Operations in these rooms are covered under another NCSA, 1493-23.

Not A Concern Areas (Contingent On Maintaining Current Operations)

Rooms 5 & B27 6

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This room primarily handles environmental samples (i.e. ground water samples, urine samples, etc.) which are typically low in uranium (ppm). There is a dishwasher in this room, but its usage i

is restricted to items used in the room. The equipment used in this room is segregated from other labs equipment. There are sinks in these rooms and equipment is hand washed in them, prior to be washed in a dishwasher. No routine operations are performed in these rooms which l.

are likely to introduce uranium bearing material into the drain system.

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Thermal analysis is performed in the roar portion of the room. Samples are small and contained. There are no openings into the drain system in this room. The rest of this room is l

devoted to office space.

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Rooms B2, B6, & B16 Barrier Laboratory 1

i This laboratory in C-710, Rooms B-2, B-6, and B-16, is used for testing, trouble-shooting and l

technical support activities in the areas of barrier and cascade chemistry. The psi test buggy is

- supported in Room B-2, B-6, and B-16.

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Corrosive gases such as UF., F, CIF, and HF, may be used. A 4.9 pound,400 psig F 2

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l cylinder located outside of the C-710 Building on the east wall is used to supply F, to Rooms 2, 6, B-2, B-6, and B-16. Small cylinders are used to supply the other corrosive gases, when i

j needed. A fume hood located in Room B-16 is equipped with a HEPA filtration system.

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These rooms are concemed with barrier technology. There are no set operations being performed in these rooms, they deal more with solving individual problems that occur in various 3

process operations. No operations take place in the sinks, although liquid bearing samples are handled on~ occasion.

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Rooms B2,86, & B16 Environmental Laboratory i

This area in C-710, Rooms B-2, B-6, and B-16, is used for testing and technical support activities associated with environmental, safety, and health issues, chemical and cleaning i

processes, plant utility systems and the RCW water system. Materials containing PCBs, l

' uranium, technetium-99, and other radioactive constituents may be 'used.

Chemical Storage Rooms on the Loading Dock i

i C-710 Room 144 is used for storage of MD and miscellaneous cylinders containing UF, j

standards. C-710 Room 143 is used for storage of uranium salvage materials. Salvage l

materials are mixtures of uranium bearing solutions which are stored in 20-liter carboys or a 30-i gallon drum. C-710 Room 142 is used for storage of organic solvents, acids, small gas j

standards, bulk pump oil, etc.

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i 1493-25, Rev 2 March 1997 Request 1648 There are several sources of uranium bearing liquids stored in Rm 143, notably the carboys.

However the room is controlled access, and contains no openings into the drain system.

Therefore it is not expected that even in an accident scenario any material could be introduced into the drains system.

C-710 Back Dock and Attic The back dock is used as the building's receiving area and as a waste accumulation area. The back dock and attic contain several GSAs, SAAs, FCAs, and PFAAs. There are drains in the dock itself, however these drains discharge out the side of the dock onto the ground and are not tied into the drain system. The attic drain system is tied into the drains from the basement, which lead directly into the sanitary sewer. No operations, involving fissile material, are i

performed in the attic other than storage.

Room 34D This area is at the southwest corner of C-710 and is currently used for storage of surplus laboratory chemicals. A project for removing these chemicals is underway in order that the space may be used for other applications, as yet unspecified. There does not appear to be any sinks in the room, although there may be a floor drain.

Rooms B13-B17 Metallurgy Laboratory This area in C-710, B-13, B-17, B-22, and B-23, is used for materials specifications development, materials testing, metallurgical examination, corrosion studies, and failure

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analysis. Equipment to support these activities is housed in these rooms. Failure analysis may j

be performed on uranium contaminated parts. Contaminated parts are handled in accordance with applicable procedures. Instrumentation testing may be conducted in these rooms during which low concentrations of corrosive gases, such as those associated with the gaseous diffusion process, are used. A self-contained, portable fume hood with a HEPA filtration system is available to this area.

The Valve Test System which provides the necessary capability to conduct extensive qualification testing of candidate replacement process valves is located in Room B-23.

Equipment to support this activity includes large ovens, leak detectors, and a residual gas analyzer system. Facilities are also available for the dismantling and examination of valves and associated components. This system is under construction and is scheduled for operation in FY 1996.

These rooms are used for failure analysis. They generally do not handle contaminated items, but temporary C-zones have been set up and used in the past. No routine operations involving uranium bearing material are performed in the sinks, including washing lab equipment. In the past, some small items (those which could fit into a beaker) had been cleaned in the rooms, but all solution from that operation had been discarded into a carboy.

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1493-25 Rev 2 March 1997 Request 1648 l

Rooms 34,40, & 42 These room handle various environmental or asbestos samples (room 40). All of the samples j

in these rooms which may contain uranium usually are in ppm concentrations, thus they would be labeled as NCS-EXEMPT under the new labeling program.

Rooms 61 & 65 Sample Receiving Laboratory This laboratory in C-710, rooms 61 and 65, receives environmental and waste samples. This

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room is used mainly for storage of incoming samples. There are no operations routinely performed in this room which involve handling of liquid uranium bearing material, other than transportation to and from the room. There are several fume hoods, with working drains, as well as a sink in the room, however they are not used for handling uranium bearing materials.

Room B3 This room is used for storage of used equipment. No operations are performed in this room which involve uranium bearing material.

Room B7 This room is used for performing experiments for various pieces of process equipment, like substitute coolant corrosion studies. The room does contain a " dry box", which was used to handle uranium oxides in the past, although the box hasn't been used for several years. No uranium bearing materials are routinely handled in this room.

Room B11 This area in C-710, Room B-11, is used for the fabrication of test equipment, samples, and special fixturing for existing equipment. Equipment common to machine shops is located in the shop.

Room B61, B65, B22, B23 Instrumentation Laboratory This laboratory in C-710, Rooms B-61, B-65, B-22, and B-23 is used for testing and technical support activities associated with instrumentation for process systems and equipment and environmental, safety, and health issues. Thermal cycling systems are utilized to simulate cascade conditions and numerous pieces of test equipment are maintained to support testing requirements. Test systems are fabricated as needed to facilitate testing of instrumentation and system components, including pressure transmitters, gas and liquid flowmeters, liquid level systems, temperature measurement devices, gas detection equipment, and process analytical instruments.

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1493-25 Rev 2 March 1997 Request 1648 Room B22 The only opening into the drain system is located in the rear of the room, approximately 6 feet off the ground. It is used to discharge cooling water used for testing various machinery. There are no sinks or floor drains in the room.

C-710-A This covered area at the east side of C-710 is used for the storage of gas cylinders and is divided into four compartments separated by concrete walls. The separate compartments are used for segregating fuel gases, UF., acid and oxidizers, and inert gases. Empty cylinders are stored in the compartment with inert gases.

There are various other rooms in the laboratory building. However, these rooms are either used to house occupants (e.g. office rooms, bathrooms, etc.) or are used to house various pieces of equipment to run the labs (i.e. fan room, elevator shaft). They are not a concern for this evaluation.

3.0 NCS HAZARD IDENTIFICATION 4

3.1 Description of the Hazard Identification Process 1

The drainage system in the C-710 facility was analyzed to identify potential deviations from the operational intent. These deviations include equipment failure, personnel error and abnormal process conditions which could possibly lead to a nuclear criticality accident. Using criteria from Guidelines for Hazard Evaluation Procedures, the What-li Checklist ("What-lf") hazard identification technique was selected to analyze the drainage system in the C-710 facility. This i

technique was chosen because of its structured format, straightforward approach, and its utility for identification of both potential hazards and their associated consequences. As the j

technique's name implies, it uses questions which begin with "What If..." and divides them into specific areas related to the consequences of concern. When applying the What-If technique, hazards may be identified that are not specifically criticality safety concerns but are documented in the analysis for completeness and operational risk reduction. These hazards are generally not considered for further investigation. Table 3.1 shows the results of this process.

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1493-25. Rev 2 March 1997 Request 1648 Table 3.1 "What-If" Hazard identification Base What if HazardtConsequence Safeguards Comments 1

an item is washed which contains a large amount of introduction of uranium into the drain e Visualinspection of pieces oflab See Section 4.2.1 uranium ?

system.

equipment which are to be washed e Rensate from wash is collected and disposed ofinto a carboy 2

a sample containing a high concentration of uranium is Introduction of additional uranium into e Require all F/PF samples to be See Section 4.2.2 discharged into the sink ?

the drain system.

disposed ofinto the carboys e Pit is sampled monthly

• No single accident in the lab could introduce enough materiaiinto the pit to exceed the minimum critical mass 3

a sample containing a high concentration of uranium is Same as scenario 2.

See Section 4.2.3 dropped near a floor drain 7 i

4 a carboy is knocked over and spills near a floor drain ?

Introduction of high concentration

• Carboy design not conducive to being See Section 4.2.4 uranium bearing solution.

upset e Floor drains in rooms containing a carboy sealed 5

bucket being used for hydrotysis of cold traps in room 53, introduction of uranium into tr.e drain e Total mass added will not cause the pit See Section 4.2.5 fume hood C-12724, is knocked over and the traps spill system.

to exceed safe mass into the cup drain ?

6 during standards blending performed in room 37, fume introduction of additional uranium into e Maximum amount of material present is See Section 4.2.6 hood C-12783, the material is leaked into the cup drain ?

the drain system.

2220 grams UF., contained within a 2S Operatton is already covered by cylinder NCSE 1493-06.

7 samples containing small amounts of uranium are Accumulation of uranium bearing e Require fissile /potentially fissile samples See Section 4.2.7 routinety poured into the drain system ?

materialin the drain system which to be disposed of in a carboy could exceed minimum critical mass.

8 uranium buildup in the C-712 neutralization pit is greater Potential accumulation of uranium in e Require pit to be sarrpted monthly See Section 4.2.8 than expected 7 the pit above the safe mass.

• Set trigger level for clean-out of pit 12

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1493-25, Rev 2 March 1997 Request 1648 i

' Case What If HazardfConsequence Safeguards Comments 9

the roubne sample provides either wrong data or no data Criticahty is not possible.

• Multiple samples being taken during See Section 4.2.9 (i.e. wrong sample used or samples not taken at all) ?

each sampling period r

a 10 the tube washer in room 21(27) continues to discharge Continuous discharge of uranium e Total mass added will not cause the pit See Section 4.2.10 at waste solution down the drain system ?

beanng materialinto the drain system.

to exceed safe mass 11 the cylinder washer in room 21(27) continues to Continuous discharge of uranium o Total mass added will not cause the pit ~

See Section 4.2.11 discharge all waste solution down the drain system ?

bearing material into the drain system.

to exceed safe mass 13 plugged tubes continue to be cleaned in the sink next to Continuous discharge of uranium o Tubes cleaned have already been See Section 4.2.12 the tube washer in room 21(27) and the resulting solution bearing materialinto the drain system.

through the tube cleaner so no discharged to the drain system ?

adddional mass 13 the efMuent pipe for the C-712 neutralization pit clogs increased buildup of uranium bearing e Historically this has not happened.

See Secten 4.2.13 up?

sludge in bottom of pit.

e No solids large enough to obstruct the pipe would be able to follow the flow path that the fluid must take 14 uraaium bearing material becomes stuck in a drain pipe?

Potential buildup of uranium bearing e Same as above See Section 4.2.14 materialin the pipe.

L 15 uranium bearing waste and/or equipment is placed on Potentialinteradion effects with e The normallevel of the pit is 7 feet See Section 4.2.15 top of the C-712 pit?

materialin the pit.

above the bottom cf the pit, which leaves approximately 3 feet of space between the top of the solution in the pit and the bottom edge of the pit.

e Top of the pit contains two openings for access to the pit, not allowing easy storage of material (i e. drums and/or equipment) above the pit 16 material containing over 5.5 wt% is accidentally disposed introduction of t igher enriched e Restrid handling of higher enriched See Section 4.2.16 of down the drain?

uranium bearing material.

material near drain openings.

17 a fire occurs in the laboratory?

Introduction of several samples into e Total mass added will not cause the pit See Section 4.2.17 the drain system.

to exceed safe mass i

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1493-25 Rev 2 March 1997 Request 1648

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m _, _ ; 72 e*7 18 straight tubes untinue to be cleaned out in the sink ta Continuous decharge of uranium o Total mass added wM not cause the pt See Secbon 4.2.18 mom 217 bearing metenal into the drain system to exceed safe mass a

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1493-25. Rev 2 March 1997 Request 1648 3.2 Results of the NCS Hazard identification Most of the events identified in the What-lf analysis varied widely in scope. Therefore it was l-decided to analyze each concern separately, with bounding cases identified where possible. All of the concerns raised in the What-If analysis are discussed further in Section 4.0 below.

4.0 NCS HAZARD EVALUATION 4.1 Nuclear Criticality Parameter Discussion Mass of fissile material-Controlled through limiting operations which impact the drain system, determining maximum amount of material which could be present during normal operation and demonstrating that two violations are required before a criticality is possible.

Monthly sampling program of the C-712 neutralization pit helps ensures that material does not j

accumulate above the maximum subcritical mass.

l Enrichment - The enrichment of the system is controlled and is allowable up to the plant maximum of 5.5%.

Volume - The volume of the system is controlled for the pit. A parametric study was performed to determine maximum mass allowed in the pit, based on current dimension. If these dimensions changed this study might not be valid. The mass for the 2S cylinder is dependant on the volume of the cylinder, so that will also need to be controlled. In addition, the maximum mass determined for the cold traps was dependant on the volume of the traps.

Geometry - The geometry of the system is controlled, geometry of the system is known and fixed by pipe locations and sizes and the dimensions of the pit. In addition, certain floor drains, those in rooms containing liquid uranium salvage carboys are sealed, preventing solution from entering the drain system. Both the tube washer and the cylinder washer in room 21 have a fixed number of positions for washing either tubes or cylinders. This fixes the number of items that may be washed at one time. Also, the maximum mass determined for the cold traps was dependant on the geometry of the traps.

Density - The density of the solution is not controlled, system likely to be dilute due to high flow rate through the pit.

I Moderation - Moderation is not controlled, system likely to be over moderated and dilute due to high flow rate through the pit.

Interaction - Interaction is not controlled, however the pipe layouts are known for the facility.

Reflection - Reflection is not controlled, however full reflection is used in referenced documents.

Neutron absorption - Neutron absorption is not controlled.

15 i

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es 1493-25. Rev 2 March 1997 Request 1648 4.2 NCS Contingency Discussion 4.2.1 What if an item is washed which contains a large amount of uranium?

A requirement will be put in place requiring all pieces of laboratory equipment which are to be washed to be visually inspected. Any item which is seen to be contaminated with uranium bearing material shall be hand washed, with the rinsate from the wash being collected and disposed of into a carboy. All solutions from the first floor drain system are eventually discharged into the C-712 neutralization pit. The concentration of i

uranium in this pit is routinely determined through periodic sampling. This sampling has been increased to a more regular testing schedule from the previously bi-annual sampling. Based on numerous discussions with laboratory personnel and several tours of the lab rooms, it was decided that this concern was bounded by case 5 below in the event that an item is washed which contains a large deposit of uranium bearing material, as no single item in the laboratory will contain a greater amount of uranium than the amount which could accumulate in a metal cold trap.

4.2.2 What if a sample containing a high concentration of uranium is discharged into the sink?

After several tours and discussions with most of the laboratory personnel, it was determined that the levels of uranium in samples which are handled are low enough that no single act of accidental discharge of a sample which would exceed the minimum critical mass of UO F (22.3 kg of uranium)'. Through numerous discussion with lab 2 2 personnel (as detailed in the specific laboratory description in Section 2.3), it was decided that the amount of uranium contained in any single sample can be considered to be bounded by the mass of material which could be contained in a metal cold trap (Case 5). Thus this scenario is considered to be bounded by the arguments presented for cases 5 and 7.

4.2.3 What if a sample containing a high concentration of uranium is dropped near a floor drain?

This scenario is identical to the scenario of a sample containing a high concentration of uranium being discharged into the sink, with only the route of entry being different. As all drain systems in a given room drain into the same place, either the neutralization pit or the sanitary sewer, this case is considered to be bounded by the scenario of entry into the sink.

4.2.4 What if a carboy is knocked over and spills near a floor drain?

I Use of the carboy and associated accidents were analyzed in another NCSE, 1493 02.'

j However, the effects of spilling a full carboy near a drain opening were not loo *Ked at.

The cart used for storage and transportation of the carboys is unlikely to be tipped over 16 i

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i' 1493-25, Rev 2 March 1997 1

Request 1648 l

accidentally. As nearly all sinks are either higher than or even with the cart, only a floor

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drain would provide a likely opening in the event of the cart being tipped over and the carboy spilt. A solution for this scenario would be to seal the floor drains in the rooms

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which contain a carboy. The rooms which contain both a carboy and a ficor drain are t

1 the following: Room 53 (TIMS) Lab which has 4 floor drains, room 12(8) which has 3 l

floor drains, and room 21(27) which has 1 floor drain. Thus a total of 8 floor drains would have to be sealed. Double contingency is provided through the unlikeliness of the carboy spilling and in having the floor drains sealed, so that in the event of the carboy l

being spilled no solution could enter the drain system.

l l

4.2.5 What if the bucket being used for hydrolysis of cold traps in room 53 is knocked over and the contents from the cold traps spill into the cup drain?

l Hydrolysis of cold traps is covered under another NCSE, 1493-02'. However the accident scenario of spilling the solution into the drain was not investigated. Based on 4

calculations performed in 1493-02, a single cold trap (metal) could contain a maximum j

of 3.81 kg of uranium, while a glass cold trap could contain up to 2.691 kg of uranium.

j The NCSA associated with the operation limited the number of glass cold traps in the hood sink in room 53 to five. Metal cold traps are hydrolyzed in a fume hood in room i

21, however this fume hood does not contain an opening to the drairi system, and the floor drain in this room will be sealed, per case 4. Even if all five of tne glass cold traps In room 53 were full of uranium and accidentally spilled into the sink so that the contents were introduced into the drain system at once, this would only add 13.455 kg of uranium to the pit. This amount is approximately 60% of the minimum subcritical mass for UO F 2 2 at 5.5 wt% enrichment, so the acute introduction of uranium into the pit would not cause

]

a criticality, based on the results of several SCALE cases (see Table C.2).8 After the material enters the pit, it will begin to disperse as it follows the flow path down and under the baffle. The amount of uranium at that point, even if added to the normal amount of 253.71 kg uranium (see case 7) would be well below the maximum subcritical mass of 426.8 kg (Appendix C). Thus a second accident would have to occur before a criticality would be possible.

4.M ' What if during standards blending performed in room 37, the material is leaked into the cup drain?

This operation is covered by a separate NCSE, 1493-03.' in addition, the materialis always contained, either in cylinders, the transfer line, or in a sample tube. According to the hazard identification study performed for 1493-03, the amount of material involved i

with the preparation of a single standard is between 1 and 1.5 kilograms. The exception to this is the MD cylinder, which does contain more than a safe mass for 5.5 wt%

uranium. However, this cylinder is maintained below atmospheric pressure and in-leakage to the cylinder would be detected by the dual samples taken for verification of assay. Another operation performed in the hood is the of filling straight tubes from a 2S cylinder. If the 2S cylinder was completely emptied then it could potentially introduce up to 2220 grams of UF into the drain system. This case is bounded by case 5 as the

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1493-25, Rev 2 March 1997 Request 1648 amount of material involved is below that which could be contained in a metal cold trap.

i 4.2.7 What if samples containing small amounts of uranium are routinely poured into the drain system?

Current operations performed in the various laboratories throughout the C-710 facility are precluded from discarding fissile /potentially fissile samples into the drain system, however this is not written down (i.e. in a procedure) and is more an understood way of i

performing operations. Another NCSE,1493-02, covers the handling and disposal of

)

liquid samples which contain uranium, in order to ensure that fissile material is not routinely poured down the drain, it will be required that all fissile or potentially fissilo samples be disposed of into a carboy. In addition, consider that on average, a sample a l

day is accidentally disposed of down the drain system (1.5 a day if only regular work days are considered), for a total of 30 samples a month. Assuming that each sample contained uranium equivalent to a metal cold trap (3.81 kg), this would introduce 114.3 kg uranium into the pit over the entire month, it should be noted that there would be serious questions raised, were this amount of uranium being poured into the drains.

Combined with the normal operations performed in room 21 (covered in cases 10-12 &

18), the total amount of uranium introduced into the pit would still only be 157.76 kg.

The parametric study of the pit (contained in Appendix C) showed that the pit could contain up to 426.8 kg of uranium (uniformly distributed) at any concentration, and still be suberitical. Even if the pit were at the maximum allowable concentration (0.34 g22sU/L), the total amount of uranium in the pit would be 253.71 kg, which is significantly below the maximum allowable amount. Thus the monthly sLmpling of the C-712 neutralization pit will ensure that the average levels of uranium concentration in the pit are below the maximum allowable concentration, ensuring double contingency for accidental disposal of fissile /potentially fissile samples into the drain system.

4.2.8 What if uranium buildup in the C-712 neutralization pit is greater then expected?

- Based on current sampling data, the concentration of uranium in the pit is extremely low, an average concentration of 1.00258 g uranium per cubic centimeter, based on the initial sampling results (see Appendix A). In order to ensure that the total amount of uranium in the pit is kept low enough that no single accident can exceed the maximum subcritical mass, a conservative safety factor will be applied. A normal safety factor which is applied to mass is 0.45, which allows double batching of that mass to be accounted for. The safety factor which will be applied to the mass allowed in the pit will be half of this normal value, or 0.225. This results in a total allowable mass of 96.03 kg, or an average concentration of 0.34 grams assU per liter. This concentration could therefore be doubled, and still be well below the maximum subcritical mass, as i

determined through the parametric study (see Appendix C). If this value is exceeded on any of the samples then the entire pit will have to be drained and cleaned out. The 18

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f 1493-25. Rev 2 March 1997 Request 1648 waste generated from this activity shall be collected in appropriate waste drums, depending on the highest concentration detected in the pit. However, based on current sample data, the concentration of uranium in the pit would have to increase by two orders of magnitude before presenting a problem.

4.2.9 What if the routine sample provides either wrong data or no data (i.e. the wrong sample used or samples not taken at all)?

4 I

The sampling plan which is being used (see Appendix D) requires that multiple samples be taken from the pit on a routine basis. Therefore, multiple failures would be required to generate a set of false data for the pit. However, this does not address the accident of no samples being taken. The maximum concentration allowable in the pit is set at O.34 grams 23sU per liter, or 96.03 kg total uranium. According to the arguments given for case 7, the maximum amount of uranium which could be added to the pit over a month's time is (114.3 kg + 39.99 kg + 2.44 kg + 1.0234 kg) = 157.76 kg. If this amount were doubled to 315.51 kg uranium (representing a failure to sample one month and catch the mass present), and assuming that the highest allowable amount of uranium I

was present in the pit the preceding month (96.03 kg), the total mass of uranium would 4

j be 411.46 kg. This is below the maximum suberitical mass of 426.8 kg, determined through a parametric study of the pit (see Appendix C). Thus during normal operation, l

with the maximum allowable concentration already present in the pit, accidentally 1

skipping the required monthly sampling of the pit would not result in the accumulation of an unsafe mass of uranium in the pit. It will be required that the pit be sampled on a monthly schedule, in order to show double contingency in the event that the pit is not sampled at it's regularly scheduled time.

4.2.10 What if the tube washer in room 21(27) continues to discharge all waste solution down the drain system?

The tube wash system (i.e. the Cadillac) can wash up to 25 of the new U shaped tubes, once the new manifold is in place. Currently the tube washer is limited to washing 23 tubes, based on obstructed valves. Each tube could contain a maximum of 55 grams 5

UF., per procedure. If a tube contained greater than this mass after being filled, then material would have been withdrawn prior to usage to get the tube at or below 55 grams. If it is assumed that every tube was completely filled with UF when placed on

)

the tube washer, then the total mass of UF which could be introduced into the drain system would be 1,375 grams, or 930 grams of uranium (determined through the percentage of uranium in UF., based on weight fractions), per use of the tube washer.

In order to ensure that the mass of uranium introduced into the drain will not cause the pit to accumulate an unsafe mass, a limit on the number tubes that can be cleaned per week will be required. Limiting the number of tubes cleaned to 250 per week will ensure that the maximum amount of uranium which could be introduced into the drain from i

operation of the tube washer would be (250 tubes per week x 4.3 weeks per 19

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1493-25, Rev 2 March 1997 Request 1648 month)(37.2 grams uranium) = 39.99 kg of uranium. This amount, when added to the i

maximum amount of uranium in the pit from normal operations, would not introduce enough material into the pit to exceed the maximum suberitical mass, as determined from a parametric study performed for the pit (see Appendix C). Therefore, usage of the tube wash system will be restricted to ten times per week. Double contingency for this accident is met in that it has been demonstrated (see case 9) that doubling all normal operations which impact the drain system would result in a safe mass of uranium for the pit.

i 4.2.11 What if the cylinder washer in room 21(27) continues to discharge all waste solution down the drain system?

The cylinder wash used in room 21(27) of the laboratory has the ability to wash up to 12 cylinders at a time. Per current laboratory procedure' each cylinder is weighed prior to being placed into the washer. If a cylinder is found to be more than 30 grams above its empty weight it is retumed to the subsampling manifold and evacuated further (i.e. of UF.). Thus the total mass of UF, which could be present in the washer waste solution would be (12 cylinders)(30 grams UF.) = 360 grams, or 244 grams uranium (determined through weight fractions), per use of the cylinder wash. In order to ensure that the mass of uranium introduced into the drain will not cause the pit to accumulate an unsafe mass, a limit on the number cylinders which can be cleaned per month will be required.

Limiting the number of cylinders cleaned to 120 per month will ensure that the maximum amount of uranium which could be introduced into the drain from operation of the cylinder washer would be (120 cylinders per month)(20.33 grams uranium) = 2.44 kg of uranium. It has already been demonstrated (see case 9) that doubling all normal operations which impact the drain system would result in a safe mass of uranium for the pit. Even if one of the cylinders was completely filled with UF,(maximum of 2220 grams)7 and placed in the washer, the total mass of UF, which would be present in the waste solution would be (2220 grams) + (11 cylinders)(30 grams) = 2,550 grams of UF.,

or 1730 grams uranium. This amount, when added to the maximum amount of uranium in the pit from normal operations, would not introduce enough material into the pit to exceed the maximum subcritical mass, as determined from a parametric study performed for the pit (see Appendix C).

4.2.12 What if plugged tubes continue to be cleaned in the sink next to the tube washer in room 21(27) and the resulting solution discharged to the drain system?

As discussed earlier, the tube wash system can wash a up to 25 of the new U shaped tubes. As only tubes which have already been on the automatic tube wash system will be cleared in this sink, the total mass as calculated for case 10 would remain constant.

If the tube was cleared of a plug in the sink then that material would not have been removed from the tube when it was washed. Thus only the rout of entry for the material will change, with the overall total remaining constant. This case is thus considered to be bounded by case 10.

20

1493-25, Rev 2 March 1997 Request 1648 4.2.13 What if the effluent pipe for the C-712 neutralization pit clogs up?

The effluent pipe for the neutralization pit is approximately 7 feet above the bottom of the pit. All material reaching the pit will have passed through either 4 or 6 inch drain lines. In addition, most openings to the drain system have a 2 inch diameter, as the outlet pipe has a diameter of 6 inches, there should not be a problem with the pipe clogging, as any material which would have become stuck in that diameter pipe would never have reached the pit in the first place. The physical layout of the neutralization pit ensures that unless the inlet pipe becomes heavily backed up, all material in the pit is forced to settle to the bottom of the pit and then rise up to the outlet pipe entrance. It is extremely unlikely that any object large enough to clog the 6 inch diameter pipe would be able to transverse this route. However, if a large volume of waste solution was suddenly discharged (i.e. the condenser bank), it is conceivable that floating " jetsam" could travel over the baffle wall and possibly clog the effluent pipe. In that event, the pit would eventually fill up with waste solution from the labs. Once the solution had risen approximately 6 inches it will begin to flow back up the inlet pipe. This does not present a problem for criticality safety, as the concentration limit was derived msuming that the pit was completely full, and all of the piping associated with the dM.,,wem in C-710 is below the safe diameter. Another aspect of this is a concem f,.,vng term accumulation of materialinto the pit. The routine sampling which has been initiated has revealed that there is a semi-permanent layer of sludge in the bottom of the pit. In the -

event that the pit clogs up, it is likely more uranium is going to settle out into the sludge.

However, it has been shown that material could accumulate in the pit for two months

. with out exceeding the maximum subcritical mass (Appendix C). It is not credible that the pit could be clogged up for that long without it's condition being noticed, as the average daily flow through rate is approximately 2300 ga! Ions, or over half the total volume of the pit (see Appendix B). Thus the condition that the pit is clogged would be noticed long before two months had passed, and so this scenario does not have the potential for introducing enough uranium into the pit to exceed the maximum subcritical mass of 426.8 kg.

I 4.2.14 What if uranium bearing material becomes stuck in a drain pipe?

]

All pipes used in the C-710 facility have internal diameters which are below the maximum safe diameter for an infinite cylinder, which is 8.75 inches per KY/S-230s, in addition, most of the solution which enters the drain system is sanitary water, used in rinsing off used laboratory equipment. The only operations which actively willintroduce material into the drain system will be those located in room 21 or routine accidental disposal of samples down the drain, as discussed above. The washers (i.e. cylinder and tube) run for over an hour and introduce large quantities of water along with the uranium bearing material from the items being cleaned, either tubes or cylinders. If a pipe did become clogged, the waste solution in that pipe would eventually back up to the source (i.e. a sink). There is no criticality concern from the material in the pipe, as it is a safe diameter for 5.5 wt% enrichment.

21

1493-25, Rev 2 March 1997 Request 1648 4.2.15 What if uranium bearing waste and/or equipment is placed on top of the C-712 pit?

The normal depth of the solution contained in the pit is approximately 7 feet above the bottom of the pit, which leaves approximately 3 feet of space between the solution and the bottom edge of the top of the pit. In addition, the solution inside the pit is likely to be i

dilute, with any concentrated material settling to the bottom of the pit. Normal-operations do not involve staging of fissile bearing material or equipment above the pit.

i 4.2.16 What if material containing over 5.5 wt% is accidentally disposed of down the drain? -

The only sources of material with an enrichment over 5.5 wt% will be either standards and/or calibration sources and smears from contaminated items from other sites. The enrichment of material will be restricted when the potential exists to impact the drain system. Normal, everyday operations for the majority of the laboratory will not involve material which is over this limit. The other argument will be that the parametric study that was performed determined a safe level of 2"U allowable in the pit, assuming normal distribution of the material throughout the pit. This. concentration level corresponds to a maximum mass of 2"U of 23.474 kilograms in the pit. No single standard or smear of higher enrichment will cause the pit to exceed this mass, even if the pit was already at its highest concentration (resulting in 5.28165 kg "U). Combined with the fact that 2

while dropping a solution filled object into a sink is not considered "unlikely", it still will not happen often, especially when dealing with objects containing over 5.5 wt% (due to the scarcity of these items).

4.2.17 What if a fire occurs in the laboratory?

1 if a fire were to occur in a laboratory, then the potential could exist that several sample containers could melt or shatter, releasing their contents near an opening to the drain system. However, the total amount of fissile material which would be involved in such an accident, in a position to enter the drain system can be considered to be bounded by scenario number 5. This scenario involves the acute interjection of up to 13.455 kilograrns of uranium into the drain. An extremely large number of samples, all containing high concentrations of uranium solution would need to be involved in a fire for this value to be exceeded.

4.2.18 What if straight tubes continue to be cleaned out in the sink in room 21?

The tube wash rack, located in the sink in Room 21(27) can wash up to 8 of the 3/8" straight tubes. Each tube could contain a maximum of 22 grams UF., per procedure'. If a tube contained greater than this mass after being filled, then material would have been 22 i

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1493 25, Rev 2 March 1997 l

RequeM 1648

.with' rawn prior to usage to get the tube at or below 22 grams. If it is assumed that d

every tube was completely filled with UF, when placed on the tube washing rack, then i

the total mass of UF. which could be introduced into the' drain system would be 176 grams, or 119 grams of uranium (determined through the percentage of uranium in UF.,

l based on weight fractions), per use of the straight tube washing rack. In order to ensure i

l that the mass of uranium introduced into the drain will not cause the pit to accumulate an unsafe mass, a limit on the number of straight tubes can be cleaned a ' week will be l

required. Limiting the number of tubes to 16 per week will ensure that the maximum amount of uranium which could be introduced into the drain from operation of the tube washer would be (16 tubes per week x 4.3 weeks per month)(14.875 grams uranium)' =

1.0234 kg of uranium. Thic amount, when added to the maximum amount of uranium in the pit frcm normal operations, would not introduce enough material into the pit to i

exceed tha maximum subcritical mass, as determined from a parametric study performed for the pit (sae Appendix C). Therefore, usag'e of the straight tube wash system will be restricted to twice per week. Double contingency for this accident is met in that it has been demonstrated (see case 9) that doubling all normal operations which impact the drain system would result in a safe mass of uranium for the pit. It should be noted that this operation is not performed in a fume hood, nor are the tubes fastened to the washing rack and if this amount of UF was actually inside these tubes significant quantities of HF gas and heat would be released by the reaction of UF and water.

4.3 Conclusions The pit is designed to precipitate material out of solution, generating regions of concentrated material. This observation is born out by the samples which have been taken out of the pit.

l The pit flow through rate is substantial, however, replacing approximately half of the waste solution in the pit, assuming that it was full during normal, daily operations. Approximately half of the fluid introduced into the pit is sanitary water, originating from several series of condenser i

banks containing cooling water." The maximum amount of uranium which could be introduced into the pit during routine operations is 157.76 kilograms per month. According to the parametric study performed for the pit (Appendix C), up to 426.8 kg of uranium could be present in the pit at any concentration, and the pit will remain subcritical. It will be required that the pit be sampled on a monthly basis, to ensure that in the event the sampling is not performed when scheduled the pit will not accumulate enough uranium to exceed the maximum subcritical amount of 426.8 kg (case 9). The worst case accident scenario of mass being added to the pit is where the contents from hydrolyzing five glass cold traps are spilled (case 5) resulting in the acute addition of up to 13.455 kg uranium to the pit. This would result in a total mass of 267.165 kg uranium in the pit, assuming that the concentration was already at maximum and normal operations had occurred for the past month. Double contingency for the pit is ensured in that two separate accidents, both resulting in the addition of uranium to the pit are required before the maximum subcritical mass of uranium could be exceeded. It should be noted however, that the monthly sampling which has been initiated has demonstrated that the concentration in the pit is fairly average throughout, with a higher concentration in the bottom most layer. This observation supports the theory that the heavy flow rate through the pit tends 23 E

, ~.

,,.m.#..

1493-25. Rev 2 March 1997 Request 1648 to carry material out of the pit in a regular manner, and that the total mass of uranium expected is well below the maximum values used throughout this evaluation.

Another issue however, is the lack of CAAS coverage for the C-712 neutralization pit in the event of a criticality, since double contingency does not imply that criticality is impossible. An analysis performed by Safety Solutions looked at the probability of criticality, given the conditions set forth in the associated NCSA, and found it to be incredible, thus obviating the need for CAAS coverage. His analysis has been includea as Appendix E.

5.0 CONCLUSION

S AND RECOMMENDATIONS

- 5.1 Evaluation Summary Formal criticality analysis techniques have been applied in the NCS evaluation for the drain system in the C-710 laboratory facility. Specific scenarios of concem were identified in the What-If analysis which could lead to an accidental criticality. The likelihood of achieving conditions which could lead to a criticality were not quantified by this study, however, and risk reduction measures must be taken wherever possible.

5.2 Recommended Conditions of Approval General Ooeratina Reauirements 1.

Enrichment shall be limited to 5.5 wt% when the potential exists for introduction of material into the drain system.

Basis: The mass limit used for calculation of the maximum allowable concentration is based on an enrichment of 5.5 wt%. This limit on enrichment will ensure that the concentration limit remains valid.

2.

The floor drains in the following rooms shall be sealed with epoxy : Room 53 (4 drains),

Room 12(8) (3 drains), and Room 21(27) which has one floor drain.

Basis: In order to ensure that no solution will enter the drain system in the event of a carboy spilling, all floor drains in rooms that contain a carboy shall be sealed. Thus even if a carboy is knocked over and spills, the solution will not enter the drain system.

3.

An annual visualinspection of the integrity of the floor drain seals shall be performed and documented. Any deficiencies shall be noted and repairs shall be implemented immediately.

Basis: The seals on the floor drains in the above mentioned rooms need to be inspected in order to ensure that the floor drains in the above mentioned rooms are sealed, the seals shall be periodically inspected 24

1493-25, Rev 2 March 1997 l

Request 1648 4.

If the concentration in the C-712 neutralization pit exceeds 0.34 grams "50 per liter, I

i then all use of the drains, excluding sanitary lines, in C-710 shall be discontinued and

}

NCS department contacted prior to resuming use of the drains in C-710.

i Basis: A concentration of 0.34 grams "5U per liter represents the maximum subcritical mass for UO F,in the pit, per the parametric study and given the interior dimensions of 2

the C-712 pit. If the pit were uniformly at this concentration, there could be a maximum.

of 96.03 kg uranium in the pit. This level could be doubled to 192.06 kg uranium and j

the total mass in the pit would still be below the maximum subcritical mass limit i

. (Appendix C).

j.

5.

All laboratory equipment shall be visually inspected prior to washing. Any item which contains visible uranium contamination shall be washed so that the rinsate can be collected and disposed of into NCS approved containers (e.g. a carboy). If an item l

contains hidden cavities which may contain uranium bearing material, then that item shall also be washed so that the rinsate from the wash can be collected and disposed of j

f j

into NCS approved containers. The cylinders and tubes being washed in the automatic washers (including the washing of plugged tubes in the sink next to the tube washer) in room 21 shall be excluded from this requirement.

2-t Basis: This requirement will help prevent the introduction of small quantities of uranium -

i bearing materialinto the drain system. By visually inspecting the piece of equipment before washing it, deposits of material which would normally be washed directly into the -

drain will now be collected and disposed ofinto a carboy. The exception to this requirement will be three process in room 21 of the laborato y, as they have already been separately discussed in this evaluation.

6.

No fissile and/or potentially fissile samples shall be disposed of down the drain.

3 i

Basis: Any sample which is labeled either fissile or potentially fissile shall be disposed of l

Into a carboy or other NCS approved collection device, and not poured down the drain.

- Restricting the disposal of fissile /potentially fissile samples from the drain will ensure that the samples which contain uranium and are a concem from a criticality safety view will be disposed of properly and not introduced into the drain system.

7.

The number of tubes which may be cleaned in the tube wash system (i.e. the Cadillac),

located in Room 21 of the C-710 laboratory facility shall be limited to a maximum of 250 tubes per week.

Basis: The number of tubes that are cleaned in the tube washer needs to be limited in order to ensure that the maximum critical mass is not exceeded in the pit. This operation routinely has the potential to introduce quantities of uranium into the drain system, and thus needs to be limited so that potential accumulation of uranium in the pit will be detected by the monthly sampling.

25 i

i 4

,m m.

m,

---n 1493-25, Rev 2 March 1997 i

l Request 1648 8.

The number of_ cylinders which may be cleaned in the cylinder wash system, located in Room 21 of the C-710 laboratory facility shall be limited to a maximum of 120 cylinders per month.

l l

Basis: The number of cylinders that are cleaned in the cylinder washer needs to be l

l limited in order to ensure that the maximum critical mass is not exceeded in the pit. This l

operation routinely has the potential to introduce quantities of uranium into the drain system, and thus needs to be limited so that potentit.1 accumulation of uranium in the pit will be detected by the monthly sampling.

i 9.

The number of straight tubes which may be cleaned in the straight tube wash rack, located in a sink in Room 21 of the C-710 laboratory facility shall be limited to a t

maximum of 16 tubes per week.

Basis: The number of straight tubes that are cleaned in the straight tube washing rack needs to be limited in order to ensure that the maximum critical mass is not exceeded in i

the pit. This operation routinely has the potential to introduce quantities of uranium into i

the drain system, and thus needs to be limited so that potential accumulation of uranium in the pit will be detected by the monthly sampling.

10.

The carboys used for liquid uranium salvage shall be restricted from entering rooms which have a floor drain (s), unless those floor drains have been sealed (e.g. Rooms 21(27),8(12), and 53).

Basis: The carboys are currently restricted to certain rooms, per NCSA 1493-02. Of those rooms,3 rooms had open floor drains which needed to be sealed (see control #2),

in order to ensure that the carboy is not taken to a room where the potential exists for an accessible entry into the drain system, carboys shall be restricted to those roonis which do not have a floor drain or have had any floor drain (s) sealed.

C-712 Neutralization Pit Samolina Reauirements 1.

The C-712 neutralization pit shall be sampled on a monthly basis. The samples shall be taken as follows:

1 sample taken from each corner of the pit, at the bottom of the pit 1 sample taken from the center of the pit, at the bottom of the pit 2 samples on each side of the baffle, at a height of 1 foot above the I

bottom of the pit 1 sample on each side of the baffle, at a height of 4 feet above the bottom of the pit Total Samples Required 11 Basis: In order to ensure that uranium does not accumulate in the C-712 neutralization pit, it shall be required to be sampled on a regular basis. Monthly sampling is necessary to ensure that the pit remains below subcritical mass limits, even in the event that the pit l

26 i

1 1493-25, Rev 2 March 1997 Request 1648 is not sampled at its regularly scheduled time. The locations of the samples taken are specified to ensure that a representative series of samples from the pit are used.

2.

The samples taken from the C-712 pit shall be analyzed as follows:

a The samples taken from the bottom of the pit shall be stored and allowed to settle for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. After that time, the free flowing water above the settled material shall be decanted, and the remaining sludge shall be analyzed by-gamma emission and the results reported in grams 235U per liter for the sludge.

b The remaining samples shall be also analyzed by gamma emission and the results reported in grams 23sU per liter for the total sample.

Basis: The samples which are taken from the pit shall be' analyzed in such a manner that representative results are obtained from them. That is why the analytical methods which are to be used for the samples is required.

Posting Requirements Signs as worded below shall be posted in appropriate locations throughout the C-710 facility.

The wording shall be placed on approved Nuclear Criticality Safety Requirements sign (s) per CP2-SH-NS1031. The sign (s) shall be positively fastened in a manner which will withstand day-to-day operations.

NUCLEAR CRITICALITY SAFETY REQUIREMENTS OPERATIONS WHICH IMPACT THE DRAIN SYSTEM 1.

Enrichment shall be limited to 5.5 wt% when the potential exists for introduction of materialinto the drain system.

2.

All laboratory equipment shall be visually inspected for uranium contamination prior to washing.

3.

No fissile and/or potentially fissile samples shall be disposed of down the drain.

1493-25 Signs as worded below shall be posted in appropriate locations in Rooms 21 & 27 in the C-710 facility. The wording shall be placed on approved Nuclear Criticality Safety Requirements sign (s) per CP2-SH-NS1031. The sign (s) shall be positively fastened in a manner which will withstand day-to-day operations.

NUCLEAR CRITICALITY

.)

1, 27 l]

1i1 f'

e

. =. ---.

7 l

l l

1493-25, Rev 2 March 1997 Request 1648 SAFETY REQUIREMENTS OPERATIONS WHICH IMPACT THE DRAIN SYSTEM 1.

Enrichment shall be limited to 5.5 wt% when the potential exists for introduction of materialinto the drain system.

2.

All laboratory equipment shall be visually inspected for uranium contamination prior to washing.

3.

No fissile and/or potentially fissile samples shall be disposed of down the drain.

4.

The number of tubes which may be cleaned in the tube wash system (i.e. the Cadillac) shall be limited to a maximum of 250 tubes per week.

5.

The number of cylinders which may be cleaned in the cylinder wash system shall be limited to a maximum of 120 cylinders per month.

6.

The number of straight tubes which may be cleaned in the straight tube wash rack shall be limited to a maximum of 16 tubes per week.

7.

An annual visualinspection of the integrity of the floor drain seal shall be performed and documented. Any deficiencies shall be noted and repairs shall be implemented immediately.

1493-25 Signs as worded below shall be posted in appropriate locations in Rooms 8(12) and 53 in the C-710 facility. The wording shall be placed on approved Nuclear Criticality Safety Requirements sign (s) per CP2-SH-NS1031. The sign (s) shall be positively fastened in a manner which will withstand day-to-day operations.

NUCLEAR CRITICALITY SAFETY REQUIREMENTS i

OPERATIONS WHICH IMPACT THE DRA!N SYSTEM 1.

Enrichment shall be limited to 5.5 wt% when the potential exists for introduction of materialinto the drain system.

l 2.

An annual visual inspection of the integrity of the floor drain seal (s) shall be performed and documented. Any deficiencies shall be noted and repairs shall be implemented immediately.

28 j

a

(

( ~ _. - -. -. - -.

.~.-.-.

1493-25, Rev 2 March 1997 i

Request 1648 2

3.

All laboratory equipment shall be visually inspected for uranium contamination prior to washing.

2 4.

No fissile and/or potentially fissile samples shall be disposed of down the drain.

4 i

1493-25 a

Signs as worded below shall be posted in an appropriate location on the carboys used for liquid j

uranium salvage in the C-710 facility. The wording shall be placed on approved Nuclear Criticality Safety Requirements sign (s) per CP2-SH-NS1031. The sign (s) shall be positively fastened in a manner which will withstand day-to-day operations.

NUCLEAR CRITICALITY i

SAFETY REQUIREMENTS i

l TRANSPORTATION OF THIS CARBOY 1.

The carboys used for liquid uranium salvage shall be restricted from entering rooms i

which have a floor drain (s), unless those floor drains have been sealed (e.g. Rooms 21(27),8(12), and 53).

1493-25 i

5.3 Limitations and Applicability of this Evaluation I

This analysis evaluated the drain system in the C-710 laboratory facility. The analysis in this l

evaluation is applicable only to the operation as described and performed under the guidelines f

and restrictions given in the controls to be issued in Nuclear Criticality Safety Approval 1493-25.

The limits given in this document and associated NCSA are not applicable to any other operation or equipment, however these controls do impact other operations including use of the carboys (1493-02). In addition, modifications to either equipment or operations which are regulated by requirements in the Conditions of Approval must be approved by Nuclear Criticality i

Safety. Changes to this evaluation will be made as required to analyze the effects of changes,

. and a revised approval will be issued if deemed necessary.

l 5.4 Assumptions Used in this Evaluation 1.

There is no significant neutronic interaction between different pipes in the drain system.

l i

2.

The average daily flow rate through the pit is approximately 2300 gallons, i

3.

For long term accumulation in the pit, the material settles out evenly throughout the pit.

i i

2 29 3

4

1493-25. Rev 2 March 1997 Request 1648 4.

The total mass of uranium which is accidentally disposed of into the drain system through one accident scenario can be bounded by 114.3 kilograms.

5.5 Criticality Safety-Related items 1.

The C-712 neutralization pit has the following dimensions: 120 inches high,77 inches deep, and 102.5 inches in width. These were the dimensions used to calculate the capacity of the pit in order to determine maximum allowable concentration.

2.

Engineering seals are required for the floor drains that preclude the introduction of liquids into the drains in the following rooms: 4 floor drains in room 53, 3 floor drains in room 12(8), and 1 floor drain in room 21(27).

3.

The largest diameter p; ping used in the C-710 laboratory drain system, up to the point of entry into the sanitary sewer is 6 inches.

4.

The bottom of the effluent pipe for the C-712 neutralization pipe is approximately 7 feet from the bottom of the pit.

)

5.

The maximum number of sample tubes which can be placed on the automatic tube washer in room 21 is 25.

4 l

l 30

)

{

i I

!i

e 1493-25, Rev 2 March 1997 Request 1648 REFERENCES 1.

Elliot, K. and J.C. Dean, Nuclear Criticality Safety Evaluation of the Liquid Uranium Salvage Operations in the C 710 Laboratory Facility, NCSA 1493-02, PGDP, Paducah, KY, November,1993.

2.

Guidelines forHazard Evaluation Procedures, Center for Chemica; Process Safety, A1CHE, New York,1992.

3.

Baltimore, D., SubcriticalDinensions for Water-Reflected UO,F, and Water Systems at 5.5 Weight Percent Enrichment, KY/S-222, PGDP, Paducah, KY, October,1993.

4.

King, S. P., Nuclear Criticality Safety Evaluation of the UF, Standard Storage and Handling in the C-710 Building at the Paducah Gaseous Diffusion Plant, 1493-03, PGDP, Paducah, KY, April,1995.

5.

Spiceland, M. T., Gaseous UF, Subsampling and Transfer, CP4-TS-AS7104, PGDP, Paducah, KY, May 11,1995.

6.

Bagwell, W.

R., Cleaning 2S Sample Cylinders, CP4-TS-AS102, PGDP, Paducah, Kentucky, March 3,1995.

7.

King, S.P., Nuclear Criticality Safety Evaluation of the UF, Subsampling Laboratory in the C-710 Building at the Paducah Gaseous Diffusion Plant, 1493-15, PGDP, Paducah, KY, August,1993.

8.

Hoffman, G.W., Infinite Cylinder Safe Diameterfor 5.5% Assay, KY/230, PGDP, Paducah, KY, May,1994.

9.

Spiceland, M. T., Gaseous UF, Subsampling and Transfer, CP4-TS-AS7104, PGDP, Paducah, KY, May 11,1995.

10.

Fitzgerald, J.M., C-712 Neutralization Pit - Flow Rate Characterization, KYlL-1778, PGDP, Paducah, KY, November 12,1991.

11.

C.V. Parks, et al, SCALE: A Modular Code System for Performing Standardized Computer Analysis for Ucensing Evaluation, NUREG/CR-0200, Rev.4, (ORNL/NUREG/CSD-2), April, 1992.

12.

Software Configuration Control Program for the Nuclear Criticality Safety Code System (SCALE), PGDP, P-ESH-184, September 9,1993.

13.

J.T. Bracey, et al., Validation of the Paducah Gaseous Diffusion Plant Nuclear Criticality Safety Code System for 16 and 27 Group Cross Sections YYlS-221, September,1993.

31

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_. ~...

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_. -.. ~

1 I

1493-25, Rev 2 March 1997

{

Request 1648 APPENDIX A j

Table A.1 C-712 Neutralization Pit Sampling Data l

Date Sample

. Uranium Assay Number Concentration (wt% 23sU) 1 j

(ug/mL) 03/25/92 WC-2 0.171 0.812 10/05/92 WC-248 282.22^

0.8 i

j 04/12/93 WC-869

< 1.0177 NA 07/26/93 WC-2212

< 1.0177 1.267 i

j 09/20/94 WC4-738

< 1.0177 NA 12/08/94 WC4-1041 2.1031 0.97

^ This sample is most likely from the bottom of the pit, whereas the others are from the.

j top.

4 f.

During the preparation of revision 2 to this document, additional sampling data was gathered. This data is provided in Appendix E.

4 C-712 Neutralization Pit Data l

The C-712 neutralization pit has the following dimensions:

{

- Depth 10'(7' usable) i Height 8' 6.5" Width 6' 5" i

Total Internal Volume H, x W. x D, = 4,097.33 gallons (15,520.2 Liters)

{

So based on the maximum safe mass of UO F of 426800 grams, and using a safety factor of 2 2 I

O.225 (half of 0.45), the maximum concentration of uranium in the pit is as follows:

i l

4 3

e 4

32 4

s 4

1493-25, Rev 2 Mad 1997 Request 1648 1

l (426.8 kgs Uranium) EO

= 6.1875 peu (15.52or) e

= (6.1875 emu)(0.055 wt%)

t

=0.34031 grams u2" t

l l

l i

e 33 jI I

e J

1493-25, Rev 2 March 1997 i

Request 1648 APPENDlX A (continued)

The following table contains a listing of the data collected during the initial, baseline sampling of the C-712 neutralization pit. The average concentration found was 1.00258 PPM, with an average enrichment of 0.6326 wt% 23sU. The maximum concentration was 1.42 PPM and the highest enrichment detected was 0.737 wt%.

Table A.2 Additional Sampling Data Sample Number Depth Side 225U Concentration Result TIMS-U TIMS-U235 1

WC5-694D 6 FT WEST 1.38 PPM 0.528 wt%

WC5-694 6 FT WEST 1.42 PPM 0.529 wt%

WC5-695 6 FT WEST 1.38 PPM' O.527 wt%

WC5-696 6 FT EAST 1.09 PPM 0.697 wt%

i WC5-697 6 FT EAST 1.14 PPM 0.703 wt%

WC5-698 4 FT WEST 1.18 PPM 0.534 wt%

4 WC5-699 4 FT WEST 1.16 PPM 0.536 wt%

WC5-700 4 FT EAST 1.06 PPM 0.665 wt%

WC5-701 4 FT EAST 1.06 r >M 0.678 wt%

r l

WC5-702 2 FT WEST i.01 PPM 0.604 wt%

WC5-703 2 FT WEST 1.03 PPM 0.586 wt%

WC5-704 2 FT EAST 1.05 PPM 0.640 wt%

WC5-705 2 FT EAST 1.06 PPM 0.659 wt%

WC5-706 1.5 FT WEST 1.08 PPM 0.606 wt%

l WC5-707 1.5 FT WEST 1.06 PPM 0.606 wt%

WC5-708 1.5 FT EAST 1.05 PPM 0.647 wt%

WC5-709 1.5 FT EAST 1.12 PPM 0.646 wt%

WC5-710 1 FT WEST 0.96 PPM 0.626 wt%

WC5-711 1 FT WEST 1.11 PPM 0.614 wt%

I WC5-712 1 FT EAST 0.96 PPM 0.663 wt%

WC5-713 1FT EAST 0.99 PPM 0.660 wt%

WC5-714D 6 IN WEST 1.04 PPM 0.633 wt%

WC5-714 6 IN WEST 1.06 PPM 0.635 wt%

WC5-715 6 IN WEST 1.05 PPM 0.627 wt%

WC5-716 6 IN EAST 1.02 PPM 0.652 wt%

WC5-717 6 IN EAST 1.04 PPM 0.656 wt%

WC5-718 BOTTOM NWEST 0.45 PPM 0.714 wt%

WC5-719 BOTTOM NEAST 0.58 PPM 0.703 wt%

WC5-720 BOTTOM SWEST 0.13 PPM 0.737 wt%

WC5-721 BOTTOM SEAST 1.17 PPM 0.704 wt%

WC5-722 BOTTOM CENTER 0.19 PPM 0.709 wt%

i i

34

l r

l l

1493-25, Rev 2 March 1997.

Request 1648 APPENDIX B

' According to an internal memo from J. M. Fitzgerald', during normal conditions the pit is approximately 70% full, with the bottom of the outlet pipe approximately 7 feet above the bottom of the pit. The inlet pipe is roughly 4 inches above the outlet pipe and once the level of the solution in the pit rises 4 inches, the incoming liquid begins to back up into the inlet pipe.

This pipe consists mainly of 6 inch diarneter conduit, laid at a slight grade to provide drainage into the pit. The pipe drops roughly 2 feet in height over its approximately 215 foot length. It was determined that the average daily discharge rate from the pit was approximately 2900 i

gallons, with a large part (up to half) of the discharge flow rate being sanitary water, which is used as cooling water in several laboratory systems.' However, this number may be not be conservative, as it was obtained by applying normal working condition over half of the day, instead of a normal 8 hour9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> work day. Applying the normal working day (day-shift weekdays in l

his report) average gallons per hour rate to only 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> of the day [(8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />)(195 gph)) = 1,560 gallons while applying the off shift average to the remaining 16 hour1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> gives [(16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />)(47)] =

{

752 gallons. Summing these two up the daily average flow through rate for the pit is 2,312 gallons, which still represents a significant portion of the total capacity ofihe pit. 'The weekend flow rate is lower, an average of 38 gallons per hour or only 912 gallons per day, however the '

activities in the laboratory facility is also greatly curtailed.

It can be argued therefore, that the majority of the contents in the pit would be cleared out daily.

In order to generate a database on the average concentration of uranium throughout the pit, the pit was sampled weekly for the first month.' Based on the sampling data already collected, along with the detailed descriptions of lab activities, the sampling frequency was re-evaluated '

and reduced to monthly sampling,' which is necessary to ensure double contingency in the event that the pit is not sampled when required.

4 4

35

1493-25 Rev 2 March 1997 Request 1648 APPENDIX C The pit flow through rate is substantial replacing half of the waste solution in the pit (assuming that it was full) during normal daily operations. Approximately half of the fluid introduced into the pit is sanitary water, originating from several series of condenser banks containing cooling

. water. The sampling program has demonstrated that the concentration in the pit is fairly uniform throughout, with a slightly higher concentration in the botic most layer. These observations support the theory that the heavy flow rate through the pit tends to carry material out of the pit in a regular manner and that material settles out evenly throughout the pit. Based on the dimensions listed in Appendix A for the C-712 neutralization pit, a parametric study was performed to determine the maximum subcritical mass allowed in the pit at any concentration.

Cases were constructed using the SCALE code, varying the concentration of uranium as a function of height, maintaining the overall mass of uranium constant at approximately 426 kgs.

l The pit was modeled with water replacing the uranium solution a's solution height decreased and all sides of the pit modeled as 12 inches concrete. No credit was taken for the central baffle or the fact that during normal operations the liquid level in the pit will not exceed 8 feet in height (outflow pipe is approximately 7.5 above the pit floor). Thus the actual volume available in the pit is much less than accounted for in the model, resulting in a conservative concentration limit.

The calculations were performed using the KENOV.a module in the Standardized Computer Analyses for Licensing Evaluation (SCALE), Version 4.2, to calculate the neutron multiplication factor, K,." The SCALE package is located in the validated version of Nuclear Criticality Safety Code Software (NCSCS) at the Paducah Gaseous Diffusion Plant (PGDP). NCSCS is loaded on a VAX 8800, node PADVX4, and has a configuration control plan.i2 ENDF/B-IV 27 energy group cross sections were used in the evaluation. The experimental data used in the validation describes the area of applicability of the computer code." The area.of applicability covers this analysis, and the validation is applicable for low-enriched 2"U systems, such as the one modeled in this evaluation. A minimum k,, was established such that any KENOV.a calculated k,, that is equal to or greater must be considered critical. The k,n includes a bias m

established by correlating the results of critical benchmark experiments and a margin of suberiticality.

A maximum subcritical mass of 426.8 kilograms uranium was determined based on the case

}

results listed in Table C.1 below. Utilizing a safety factor of 0.225, the corresponding safe concentration of 2"U allowed in the pit is 0.34 grams per liter. The lower than normal safety factor was chosen in order to provide double contingency, in the event that the pit is just at the allowable concentration limit and is not sampled as required. It corresponds to half of the normal 0.45 safety factor which is routinely used.

36 i

a

}

~

l 1493 25. Rev 2 March 1997 Request 1648 l.

{

Table C.1 Parametric Study of the C-712 Neutralization Pit for Determination of Maximum Allowable Mass p

Height Height Concentration K,

Sigma K,+20 1

(ft)

(cm)

(gU/L)

(a) 10 304.8 27.50 0.20821 0.00047 0.20915 i

9 274.32 30.56 0.22920 0.00042 0.23004

)

[

8 243.84 34.38 0.25534 0.00051 0.25636 l

}

7 213.36 39.29 0.28103 0.00057 0.28217-l 6

182.88 45.83 0.32064 0.00070 0.32204 f

5 152.4 55.00 0.37046 0.00078 0.37202 4

121.92 68.75 0.43803 0.00099 0.44001 3

91.44 91.67 0.53349 0.00111 0.53571 l

2 60.96 137.50 0.67312 0.00161 0.67634 i

1 30.48 275.00 0.88252 0.00255 0.88762 11" 27.94 300.00 0.89714 0.00228 0.90170 l

10" 25.4 330.00 0.90968 0.00285 0.91538 e.

9" 22.86 366.67 0.92393 0.00330 0.93053 j

8" 20.32 412.50 0.93094 0.00301 0.93696 i

7" 17.78 471.43 0.93498 0.00295 0.94088 i

6" 15.24 550.00 0.93310 0.00325 0.93960 j

5" 12.7 660.00 0.91962 0.00359 0.92680 I

Based on the dimensions listed in Appendix A for the C-712 neutralization pit, a study was i

performed to ensure the criticality safety of the pit in the event that up to 13.455 kg uranium i

were acutely added (see What-If #5. Cases were constructed using the SCALE code, varying l

the concentration of uranium as a function of sphere radius, maintaining the concentration of uranium in the pit constant. The pit was modeled using the same geometry as before, with all p

sides of the pit modeled as 12 inches concrete.

1 The calculations were performed using the KENOV.a module in the Standardized Computer Analyses for Licensing Evaluation (SCALE), Version 4.2, to calculate the neutron multiplication i

factor, K,." The SCALE package is located in the validated version of Nuclear Criticality l.

Safety Code Software (NCSCS) at the Paducah Gaseous Diffusion Plant (PGDP). NCSCS is j

loaded on a VAX 8800, node PADVX4, and has a configuration control plan." ENDF/B-IV 27

{

energy group cross sections were used in the evaluation. The experimental data used in the i

validation describes the area of applicability of the computer code." The area of applicability covers this analysis, and the validation is applicable for low-enricaed rasU systems, such as the one modeled in this evaluation. A minimum k,was established such that any KENOV.a l

calculated k, that is equal to or greater must be considered entical. The k. includes a bias n

37

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m 1493-25, Rev 2 March 1997 Request 1648 established by correlating the results of critical benchmark experiments and a margin of suberiticality.

Based on these results (see Table C.2 below), it was decided that the acute interjection of 13.455 kg uranium into the pit, even when at maximum allowable concentration would not cause the pit to become critical. Thus another accident would need to occur before a criticality was possible.

Table C.2 Acute Interjection of 13.455 Kg Uranium into the Pit Radius (cm)

Concentration Keff Sigma (c)

Keff + 2 o (gU/L) 13.18932.

1400 0.80289 0.00410 0.81109 12.88946 1500 0.77563 0.00422 0.78407 12.61515 1600 0.76908 0.00415 0.77738 38

I 149 25, Rev 2 Mard 1997 Request 1648 Figure 3 Parametric Study of the C-712 Neutralization Pit 1

0.95 Maximum Allowable Value 0.9 --

0.8 0.7 --

0.6 e

m

+

3 x

3 0.5 --

3 5

0.4 0.3 N'

c.:

O.1 0

10 100 1000 Height (cm) 39 l

I I

me "

1493-25, Rev 2 March 1997 Request 1648 APPENDIX D Sampling Plan for the C-712 Neutralization Pit Initial Baseline Sampling i

+

This sampling plan was performed once, in the initial start-up of the routine sampling program. It is intended to provide an estimate of the concentrations expected in the various areas of the pit, and to provide guidance for future sampling needs.

i Bottom Samoles 5 Required - One sample in each comer of the pit and one in the' center.

Total Samples Required 5

Bottom Laver Samoles 2 Samples on each side of the baffle at the following heights above the bottom of the pit:

6 inches,12 inches, and 18 inches.

Total Samples Required 12 Intermediate Laver Samoles 2 Samples on each side of the baffle at the following heigiits above the bottom of the pit:

2 feet,4 feet, and 6 feet (this should be just below the top of the liquid in the pit).

Total Samples Required 12 Overall total number of samples for initial sampling plan 29 Weekiy Sampling Plan (Projected for first month only)

This plan should help determine the required frequency of the permanent sampling plan.

It will extend the number of histories available and allow a more detailed picture of the conditions which can be routinely expected in the pit.

Bottom Samoles 5 Required - One sample in each comer of the pit and one in the center.

Total Samples Required 5

Intermediate Laver Samoles 40 4

l

^

l 1493-25, Rev 2 March 1997 Request 1648 2 Samples on each side of the baffle at 1 foot above the bottom of the pit, Weekly Sampling Plan (continued) l and 1 sample at 4 feet above the bottom:

Total Samples Required 6

Overall total number of samples for weekly sampling plan 11 Based on the results of this sampling program (both the initial as well as the weekly), a permanent sampling program has been established. This program will require that eleven samples be withdrawn from the pit. The period between sampling will be monthly, as this is the maximum period in which double contingency can be met for activities in the laboratory as described above.

Routine Monthly Sampling Plan Bottom Samoles 3 Required - One sample in each comer of the pit and one in the center.

Total Samples Required 5

Intermediate Laver Samoles 2 Samples on each side of the baffle at 1 foot above the bottom of the pit, and 1 sample on each side of the baffle at 4 feet above the bottom:

j Total Samples Required 6

Overall total number of samples for monthly sampling plan 11 Analysis Reauired The bottom samples shall be analyzed by two different methods. First, the entire sample shall be analyzed by a gamma spectroscopter. Following that, the sample will be allowed to settle.

Once the sample has settled for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, the free liquid above the slurry will be decanted off and the resulting solution analyzed for 22sU. The intermediate layer samples will simply require a gamma spectroscopy analysis for 22sU.

l T

41 l

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1493-25, Rev 2 March 1997 Request 1648 t

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APPENDIX E i

i i

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t 4

j FREQUENCY OF A CRITICALITY ACCIDENT I

IN THE C-712 NEUTRALIZATION PIT i

Prepared by i

Safety Solutions l

Stephen Hurrell 11645 S. Monticello Dr.

t Knoxville, TN 37922 i

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1493-25. Rev 2 March 1997 Request 1648 FREQUENCY OF A CRITICALITY ACCIDENT IN TIIE C-712 NEUTRALIZATION PIT The C-712 Neutralization Pit, located underground near the southwest corner of Building C-710, receives liquid waste effluent from the process drains and sinks inside the building. The sinks and drains that flow to the neutralization pit are located in individual laboratories on the first floor of the building.

The primary function of the neutralization pit is to neutralize acidic solutions originating in the various laboratories inside the building. Neutralization is accomplished through the dilution provided by the other waste streams in the building. Since the laboratories discard small quantities of uranium during normal operations, the potential for the accumulation of the discarded uranium into a critical configuration was semi-quantitatively evaluated.

As discussed in Appendix A, the neutralization pit is 8.54 ft long x 6.41 ft wide x 10 ft deep.

The pit is provided with a vertical barrier in the center of the pit slightly elevated above the bottom. The pit discharge pipe to the sanitary sewer is on the opposite side of the barrier from the C-710 inlet pipe which forces the effluent to the bottom of the pit before it flows up and out the discharge line. This l

design increases the turbulence and therefore reduces the tendency of the uranium to settle near the l

bottom of the pit. The sampling data documented in Appendix A of NCSA 1493-25 indicates that the l

uranium discharged to the drain system does not appreciably settle to the bottom of the neutralization pit.

l l

In order to preclude a criticality in the neutralization pit, control measures documented in NCSA 1493-25 Sect. 5.2 will be applied. In addition to the control measures applied specifically to the pit, all of the fissile material operations performed in Building C-710 have separate NCSAs with criticality controls that provide defense-in-depth. This analysis postulates failure to follow the recommended conditions of approval. The frequency of forming a critical configuration in the neutralization pit assuming failure to follow the recommended conditions of approval is conservatively estimated using the event tree shown in Fig.1. The initiating event and event tree events are discussed in more detail in later sections of this report.

Recommended conditions of approval from NCSA 1493-25 pertinent to this analysis are listed below:

the enrichment of uranium handled in the laboratories with drains to the neutralization pit is limited to 5.5 wt % 2"U when the potential exists for introduction of material into the drain l

system. (NCSA GEN-32 controls the handling of samples that exceed 5.5 wt % 2"U to l

43 t

MAxNUM AttOWARE MORE TIMN 30 LETAL MORE THAN -50 MORE TIMN 120 PIT CONCENTRATCN COLD TRAPS PER TUDES PER wi t K ARE CREOERS PER

y o

REACHED MONTH OtSCt%RGED WAStLD.

MotCH AhT WASHED.

': y e

TO DRAF4

{g m*l t i?

PITCONC SAh!PLE TUDEWASif CYLWASII SEQ #

END FREQUENCY "5,

0.1/ YEAR SE-03 5E-03 SE-02 a

1 CC 1.25E-07/ YEA R 2

NC 3

NC 4

NC 5

NC G

NC 7

NC 8

NC t

CC - CR!TCAL COtFCURATION NC - to CRITCAL COtECURATION

. CONS 0ERS PROBABLITY TFMT SUFTCEt# NUPEER OF CONTARERS ARE AVALAELE FOR LilSt%t0LFC TO OCCUR I

FIG.1 PITCRIT EVENT TREE Ih

________m__

_._-.___--._-_.__m______-_m.___________________m_____.__.-_a._a____u__

_2__._.__

. - - - _. _ - _ _ _ _ _ _N

4 1493-25, Rev 2 March 1997 Request 1648 minimize the potential for introduction of higher assay material into the drain. NCSA 1493-l 25 considered the inadvertent introduction of higher assay material into the drain.)

l the floor drains in rooms where carboys ase used to store fissile and potentially fissile samples will be sealed with epoxy and inspected annually to preclude the inadvertent introduction of uranium contaminated lab waste through the floor drains the neutralization pit will be sampled on a monthly basis and operations will be suspended if the concentration exceeds 0.34 grams "U per liter 2

the tube wash system located in Room 21 of C-710 shall not wash more than 250 tubes per l

week the cylinder wash system in Room 21 of C-710 shall not wash more than 120 cylinders per j

month Operations in C-710 are analytical rather than production oriented. As a result only small quantities of uranium are normally handled in the individual C-710 laboratories. NCSA controls require the collection of fissile and potentially fissile samples in a carboy that is geometrically favorable. Items to be washed are visually inspected prior to washing such that the rinsate from heavily contaminated items can be collected in a geometrically safe carboy. These normal operating procedures preclude the discharge of significant quantities of uranium to the neutralization pit.

Floor drains, in rooms where carboys are used, will be sealed with epoxy and the seals inspected annually. Therefore, the frequency of a criticality in the neutralization pit due to erroneous discharges to these floor drains is not considered credible. The only room with an open floor drain that could be expected to receive fissile or potentially fissile waste solutions is Room 6. Room 6 is used for exposure testing of materials to be used in the cascade. It is not designated as a fissile material area and any UF.

or UO F used in the room is depleted in the "U isotope. Further analysis of accident scenarios 2

22 involving the inadvenent release of uranium contaminated waste to the floor drains is not warranted.

Since the maximum product enrichment of the plant is limited to 5.5 wt% under HAUP, only standards and limited quantities of special material from offsite will exceed this enrichment in the C-710 laboratories. These operations are controlled by a separate operation-specific NCSA in which any discharges to the drain system would be severely restricted. As a result further analysis of events that result in the discharge of uranium that exceeds 5.5 wt % 2"U is not warranted.

45

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l 1493-25, Rev 2 March 1997 Request 1648 l

l PITCRIT EVENT TREE The PITCRIT Event Tree, shown in Fig.1, models accident scenarios that could cause uranium in excess of the maximum allowable mass (426.8 kgU) to accumulate in the C-712 Neutralization Pit.

The initiating event and event tree events are described in subsequent sections of this analysis. It should l

be noted that since some of the errors discussed below involve the same individuals, the event tree l

modeled dependencies between the event tree events.

l PITCONC Initiating Event The PITCONC initiating event postulates failures in the nuclear criticality safety control system that would permit the uranium concentration in the pit to exceed the control value of 0.34 grams 2"U/ liter. As discussed in Sect. 4.2 of NCSA 1493-25, single or even multiple failures of the controls in place would not result in the pit concentration exceeding this value. This maximum permissible concentration was based on the following conservative assumptions:

the assay of the pit is 5.5 wt % 2"U,

+

the pit contains its maximum volume of 15,520 liters, and

+

the permissible uranium loading of the pit is 96.03 kg of uranium.

+

The conservative nature of these assumptions is addressed below.

The assays of uranium handled in the C-710 laboratories are representative of operations conducted across the PGDP site. While some of the samples handled at the lab in the future will be at the Higher Assay Upgrading Project (HAUP) maximum enrichment of 5.5 wt% "SU, approximately one-third of the samples will be from the tails, feed, and lower enrichment portions of the cascade where the enrichment is between 0.25 and 1.0 wt % 2"U. These enrichments can not cause a critical configuration l

without significant outside manipulation of the system that are intended to cause a criticality. While l

these lower enrichments provide a marginal contribution to the "U inventory, their higher "U content l

2 2

tends to reduce the reactivity of the neutralization pit. At a PGDP maximum plant product enrichment of l

2.0 wt % 2"U, the assay ofinitial samples taken from the neutralization pit averaged 0.6326 weight l

percent "U or approximately 30% of the maximum enrichment. Extrapolating these results to HAUP 2

operations at a maximum product assay of 5.0 wt % 2"U results in an average pit assay of 1.58 wt %

2"U, significantly less than the 5.5 wt % assumed for the maximum pit concentration calculation in Appendix A.

'Ihe pit is assumed to contain 15,520 liters, based on the given dimensions, so as to make the l

maximum permissible concentration as low as possible. However, the neutralization outlet pipe to the 1

sanitary sewer is 7 ft above the bottom of the pit restricting the usable pit volume to approximately l

l 10,864 liters. Therefore, the greatest uranium loading of the pit assuming an assay of 5.5 wt % and a l

l i

46 l

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1493-25. Rev 2 March 1997 Request 1648 maximum permissible concentration of 0.34 g "U/ liter is.67.16 kg U, which is well below the 2

permissible uranium loading of 96.03 kg U that was calculated assuming the maximum pit volume of l

15,520 liters it should be noted that this maximum permissible concentration is 200 times the average l

fissile concentration,1.7E-03 g "U/ liter, based on seven months of sampling data at the maximum 2 wt l

2

% 2"U operations. Following the transition to 5 wt % 2"U operations, the number and uranium mass of l

the samples is expected to remain approximately constant; only the "U mass of the samples is expected l

2 to increase. This increase is expected to be a factor of 2.5 (i.e., ratio of 5 wt % 2"U to 2 wt % 2"U).

l Based on 5.0 wt % 2"U operations, the average fissile concentration of the pit might be expected to be l

4.2SE-03 g "U/ liter (i.e.,2.5 times 1.7E-03g "U/l). Under these operating conditions, the maximum l

2 2

permissible concentration is 80 times the expected average concentration at 5.0 wt % operations.

l The permissible uranium loading of 96.03 kg U is based on the maximum allowable mass of 426.8 kg U determined in Appendix C. This maximum allowable mass was determined by a parametric study of the reactivity of the neutralization pit. The maximum allowable mass was multiplied by a safety factor of 0.225 to obtain the permissible loading of 96.03 kg U. This safety factor is one half the 0.45 safety factor normally used to calculate the maximum safe mass for nuclear criticality safety purposes.

This more conservative safety factor enhances the criticality safety controls implemented for the neutralization pit operation.

The neutralization pit is approximately 70% full during normal operations. The average flow rate through the pit is approximately 2300 gallons per day. Based on available information, the water inventory of the pit changes completely every two to three days. Therefore, it is not considered credible for large deposits of uranium to accumulate and settle to the bottom under such dynamic conditions of flow. Various labs within C-710 routinely discharge waste solutions that dilute the uranium l

concentration of the pit. These sources of uranium-free solution are for the most part independent l

operations. As a result it is unlikely that a common cause event would eliminate the dilution of the pit by l

uranium-free solution discharges. However, the analysis presented in this evaluation conservatively l

assumed no dilution (uncontaminated discharges) of the pit uranium inventory during a month in which l

operational errors result in the discharge oflarge quantities of uranium.

l Seven months of sampling data for the neutralization pit at 2.0 wt % operations shown in Table l

E-1, indicates a maximum fissile concentration in the pit of 7.6E-03 g "U/l Assuming an assay of 5.5 l

2 wt % following the implementation of HAUP, this fissile concentration is expected to reach 1.9 E-02 g l

2"U/1(i.e.,2.5 times 7.6E-03 g "U/l) corresponding to a pit inventory of 3.75 kg U for the 10,864 liter l

2 usable volume. In order to reach the maximum allowable fissile concentration of 0.34 g "U/l, l

2 approximately 63.41 kg U at a maximum 5.5 wt % 2"U must be added to the 3.75 kg U already in the pit.

l The frequency of such a large quantity of uranium of any enrichment being added to the pit over a short l

period is estimated to be 0.10/ year based on the routme inventory of sample material present in C-710.

l 47

TABLE E-1 PIT SAMPLING DATA

)

1493-25. Rev 2 March 1997 Request 1648 i

Sample Number Result Maximum All Samples EC6-131 9.2E-05 9.2E 05 EC6-132 2.8E-05 2.8E-05 EC6-133 0.0E+00 0.0E+00 l

EC6-134 4.6E-05 4.6E-05 l

l EC6-135 3.5E-05 3.5E-05 I

l EC6-136 0.0E+00 0.0E+00 l

EC6-137 2.0E-03 2.0E-03 EC6-138 4.7E-03 4.7E-03 EC6-139 4.4E-03 4.4E-03 EC6-140 3.0E-04 3.0E-04 EC6-141 4.5E-03 4.5E-03 l

Average -

1.5E-03 4.7E-03 0.0E+00 EC6-147 0.0E+00 1.0E-05 l

EC6-148 -

1.0E-05 1.0E-04 EC6-149 1.0E-04 4.0E-05 EC6-150 4.0E-05 3.8E-05 EC6-151 3.8E 3.3E-04 EC6-152 3.3E-04 1.7E-03 EC6-153 1.7E-03 3.5E-03 EC6-154 3.5E-03 4.6E-03 i

EC6-155 4.6E-03 4.1 E-03 EC6-156 4.1 E-03 1.0E-04 EC6-157 1.0E-04 4.6E-05 Average 1.3E-03 4.6E 03 2.9E-05 j

EC6-177 4.6E-05 5.5E-05 EC6-178 2.9E-05 4.6E-05 EC6-179 5.5E-05 0.0E+00 EC6-180 4.6E-05 5.9E-05

-EC6-181 0.0E+00 3.4E-03 EC6-182 5.9E-05 4.4E-03 EC6-183 3.4E-03 4.3E-03 EC6-184 4.4E-03 2.9E-03 EC6-185 4.3E-03 4.1 E-03 EC6-18G 2.9E-03 2.7E-05 EC6-187 4.1E-03 4.0E-05 Average 1.5E 03 4.6E-03 3.6E-05 1

EC7-1 2.7E-05 3.5E-05 EC7-2 4.0E-05 2.5E-05 i

EC7-3 3.6E-05 3.5E-05 I

EC7-4 3.5E-05 4.7E-03 J

EC7-5 2.5E-05 7.4E-03 EC7-6 3.5E-05 4.5E-03 48

TABLE E-1 PIT SAMPLING DATA EC7-7 4.7E-03 3.5E-03 u93-25. m 2 March 1997 EC7-8 nequest 164s 7.4E-03 6.4E-03 EC7-9 4.5E-03 0.0E+00 EC7-10 3.5E-03 1.7E-05 EC7-11 6.4E-03 2.2E-05 Average 2.4E-03 7.4E-03 0.0E+00 EC7-48 0.0E+00 4.4E-03 EC7-49 1.7E-05 7.6E-03 EC7-52 2.2E-05 4.5E-03 EC7-53 0.0E+00 2.9E-03 EC7-54 4.4E-03 5.9E-03 EC7-55 7.6E-03 4.3E-03 EC7-56 4.5E-03 5.4E-03 EC7-57 2.9E-03 3.0E-04 EC7-58 5.9E-03 7.0E-03 Average 2.8E-03 7.6E-03 3.0E-05 0.0E+00 EC6-76 4.3E-03 0.0E+00 EC6-77 5.4E-03 0.0E+00 EC6-78 3.0E-04 1.0E-05 EC6-79 7.0E-03 0.0E+00 EC6-80 3.0E-05 2.0E-05 EC6-81 0.0E+00 3.0E-05 ECB-82 0.0E+00 4.0E-05 EC6-83 0.0E+00 3.0E-05 EC6-84 1.0E-05 3.0E-05 EC6-85 0.0E+00 2.0E-05

)

Average 1.7E-03 7.0E-03 5.0E-04 5.5E-03 EC6-98 2.0E-05 3.3E-03 EC6-99 3.0E-05 3.0E-04 I

EC6-100 4.0E-05 2.0E-04

EC6-101 3.0E-05 1.7E-03 Average of all samples EC6-102 3.0E-05 EC6-103 2.0E-05 7.6E-03 Max imum of all samples EC6-104 5.0E-04 EC6-105 5.5E-03 EC6-106 3.3E-03 EC6-107 3.0E-04 EC6-108 2.0E-04 Average 9.1E-04 5.5E-03 i

49 I

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1493-25. Rev 2 March 1997 Request 1648 The probability that the uranium added to the pit is all 5.5 wt % 2"U is conservatively estimated l

l to be 1.0. This is extremely conservative since approximately 33% of the samples processed in C-710 l

are less than 1.0 wt % 2"U. Although the probability of disposing of lower enrichments is greater than l

that cited for 5.5 wt % 2"U, the mass of uranium disposed of would have to be increased in order to l

j exceed the maximum allowable fissile concentration of 0.34 g "U/1. Therefore, the frequency of the pit l

2 fissile concentration equaling or exceeding 0.34 g "U/l (more than 17 times the expected maximum l

2 concentration at 5.0 wt % operations) is conservatively estimated to be 0.1/ year. Mishandling of l

laboratory samples that would cause the Ussile concentration to exceed 0.34 g "U/l is the PITCONC l

2 initiating event and is estimated to occur with a frequency of 0.1/ year.

l In order to determine if a single act of accidental discharge is a criticality concern, the number l

and size of the largest containers routinely handled was evaluated. Since the C-710 laboratories are analytical in nature, only sma!! sample-size (55 g U) quantities are commonly handled. Although the largest uranium-bearing containers routinely handled is a metal cold trap with a maximum volumetric inventory of 3.81 kg uranium, Room 37 where metal cold traps are processed does not contain an j

opening to the neutralization pit. In fact the material accumulated in metal cold traps is refed to the j

enrichment cascade in Building C-360. It should also be noted that the metal cold traps are routinely l

]

emptied after three months of service such that they contair. no more than 1 kg U. Glass cold traps are l

j the second largest " sample" containers by volume with a maximum inventory of 2.69 kg uranium. These l

traps are removed from the mass spectrometer and hydrolyzed at the end of each day. As a result of the l

daily hydrolyzation, the nominal inventory of the glass cold traps is closer to 10 grams uranium. Room l

53, where the glass cold traps are handled, contains a sink that empties to the neutralization pit. During l

normal operations, the glass cold traps are hydrolyzed by adding water to the cold trap while it is in a l

bucket. The solution of uranium that results from the hydrolyzation process is discarded to a carboy l

located in the room. The number of glass cold traps present in the hood is limited by an NCSA to 5 or l

less resulting in a maximum hood inventory of 13.45 kg uranium conservatively assuming the volumetric l

capacity of the cold trap is filled with uranium, in order to exceed the minimum critical mass of 22.3 kg l

uranium, nine glass cold traps (four more than authorized) would have to be present in Room 53. The frequency that the room limit of 5 would be exceeded by 4 traps is extremely low. The probability that l

the glass cold traps would contain 2.69 kg U is unlikely considering that during normal service these l

traps are hydrolyzed once a day so that they contain less than 10 grams. The probability that the l

inventory of the glass cold traps would be erroneously discarded diiectly to the drain is unlikely based on l

operator training. The subsequent accumulation of the contents of these cold traps into a critical l

configuration is not considered credible. Therefore, a single accidental event that would result in the l

discharge of more than a minimum critical mass of uranium is not considered credible.

l 50

e 1493-25, Rev 2 March 1997 Request 1648 Based on the preceding discussion and the fact that the pit is sampled on a monthly basis, it is extremely unlikely that the fissile concentration of the pit would ever exceed the maximum permissible j

concentration of 0.34 g SU/ liter. However, for the purposes of this analysis it is conservatively assumed that the concentration would equal or slightly exceed the maximum concentration i time in 10 years.

l The frequency of exceeding the maximum permissible concentration, the PITCONC initiating event, is conservatively assumed to be 0.1/ year.

l

)

SAMPLE Event Tree Event The SAMPLE event models violation of the established procedures and criticality safety controls that specify fissile and potentially fissile samples shall not be disposed of down the drain. In this model the samples are erroneously drained to the neutralization pit via a cup sink. In Sect. 4.2.7 of NCSA l

1493-25, it is assumed that for an entire month a sample per day is erroneously discharged to the pit from Room 53. Each sample is conservatively assumed to contain 3.81 kg U, the inventory of a metal cold trap. To demonstrate the conservative nature of this assumption, routine samples have an inventory of 55 g U. As previously discussed, the metal cold traps are refed to the cascade at C-360. The error considered in this event tree event involves failure to follow operating procedures by hydrolyzing the uranium in a metal cold trap and releasing the uranium solution directly to the drain system. In order to l

erroneously hydrolyze a metal cold trap, the operator must remove the metal cold trap valving which is l

not an activity encountered during the routine hydrolyzation of glass cold traps. This error repeated l

every day for 30 days would result in a total discharge of 114.3 kgs of U to the neutralization pit.

The metal cold traps are used to accumulate uranium from operation of the mass spectrometers.

l The metal cold traps are changed when the inventory of the trap contains 1,000 grams of uranium. Only l

1 of the mass spectrometers is currently designed to accept metal cold traps. If this instrument were used l

on a daily basis, it would be changed approximately once every 3 months. Future plans call for the use l

of 11 total metal cold traps that would also require changing on a 3 month cycle. The probability that l

one cold trap per day would be available for mishandling such that its inventory could be discharged to l

the neutralization pit is conservatively estimated to be 0.1.

l The basic human error probability for the first commission of this error based on Reference 1 is 5 E-02/ demand. The probability that the operator would discharge a second metal cold trap to the pit in a month from this operation given that the first cold trap was erroneously discharged to the pit is (5E-02)2 provided that the two events are independent. Similarly, the probability of an erroneous discharge of the third cold trap given discharge of the first two cold traps is (5E-02)' provided the events are independent.

Accordingly, the probability of the thirtieth error given the first twenty-nine errors is (SE-02)' provided independence of the events. However, the events are not necessarily independent. The fact that the postulated error is repeated day after day may be a result of a common cause failure (e.g., inadequate 51 u -

I b

t 149L25. Rev 2 March 1997 Request 1648 training). Although the supervisor has repeated opportunities to discover the errors throughout the month, the probability of the errors going undiscovered for a period of a month given the potential for l

dependence between events is conservatively assumed to be 1.0 (i.e., no error identification by the l

supervisor). Accordingly, the probability that this many metal cold traps are available for release and l

that more than 114.3 kgs U are discharged to the neutralization pit by this mishandling activity is 5 E-

03. It should be noted that two metal cold traps per day at their maximum inventory could be 2

erroneously discharged to the pit with the maximum permissible concentration of 0.34 g "U present in the pit without exceeding the maximum safe mass of 426.8 kg U.

TUBEWASH Event Tree Event The TUBEWASH event models the probability that more than the NCSA limit of tubes require l

washing such that subsequent operator errors result in an excessive discharge of uranium to the l

neutralization pit. The controls described in Sect. 5.2 of NCSA 1493-25 limit the operation of the tube l

wash system in Room 21 to 10 times per week with a maximum of 25 tubes per wash cycle. This system is routinely operated at approximately 60 % of this capacity or 150 tubes per week. Assuming each tube washed contains the volumetric maximum of 55 grams of UF. (37.2 g U), the quantity of uranium l

permitted to be discharged to the neutralization pit each month is 37.2 kg U. This is a conservative l

estimate since most tubes are smaller holding less material and the operator collects the rinsate from the l

most contaminated initial wash operation and places it in the geometrically safe carboy. The l

TUBEWASH event models the probability that this many tubes are present in the tube wash facility such 4

that human errors result in the operation of the tube wash system more than 10 times per week.

Since the operation is currently run at 60 % of the NCSA limit, the probability that there would I

be more than the NCSA limit of tubes to be washed was estimated to be 0.10. The basic human error l

probability of operating the tube wash system 11 times one week in violation of the NCS controls is 5 E-l 02 based on Reference 1. Although the supervisor has repeated opportunities to discover the error l

throughout the month, the probability of the error going undiscovered for a period of a month is l

conservatively assumed to be 1.0 in this analysis (i.e., no error identification by the supervisor).

l Accordingly, the probability that more than the NCSA limit of tubes would be available to be washed such that more than 37.2 kgs U could be discharged to the neutralization pit is 5 E-03. Under accident conditions, the tube wash system in Room 21 could be incorrectly operated 20 times per week and two metal cold traps per day in Room 53 could be erroneously discharged into the pit at its maximum permissible concentration of 0.34 g "U/ liter without exceeding the maximum safe loading of 426.8 kg 2

U.

52

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1493 25, Rev 2 March 1997 j

Request 1648 i

It should be noted that the tube wash system in Room 21 is routinely operated by different l

]

personnel than those that complete the cold trap hydrolyzation activity in Room 53. Therefore, no l

{

dependence between these operations is assumed in the model.

l 1

1 i

CYLWASH Event Tree Event i

i j

The CYLWASH event tree event models the probability that more than the NCSA limit of l

l cylinders require washing such that subsequent operator errors result in an excessive discharge of l

uranium to the neutralization pit. The controls described in Sect. 5.2 of NCSA 1493-25 limit the l

l operation of the cylinder wash system in Room 21 to a maximum of 120 cylinders washed per month l

f' The cylinder wash system is currently operated as cylinders are receiv' d and this throughput corresponds l

e l

to 80% of the NCSA limit. A significant deviation that would result in more cylinders requiring washing l

}

than the NCSA limit permits is not anticipated. The probability that the number of cylinders that require l

l washing exceeds the NCSA limit such that the mishandling described below can occur was l

t 4

conservatively estimated to be 0.10 based on an 80% operating capacity. Assuming all the cylinders l

l washed contain the maximum of 30 grams of UF. (20.3 g U) per Reference 2, the quantity of uranium in the waste discharged to the neutralization pit each month is 2.44 kg U. Although the maximum inventory of a cylinder to be washed is limited to 20.3 g uranium, it is unlikely but possible that a l

violation of the NCSA could occur such that a filled cylinder could be inadvertently placed in th'e cylinder washer. In the extremely unlikely event that one filled cylinder per cylinder wash cycle were l

placed in the washer, the monthly discharge to the neutralization pit would be 24.3 kg uranium. The

[

CYLWASH event models human errors that result in the operation of the cylinder wash system 10 times

{

per month'with eleven cylinders at their maximum inventory for washing and the twelfth cylinder filled with uranium (i.e.,2.2 kg uranium).

The basic human error probability of operating the cylinder wash system in violation of the NCS l

controls is 5 E-02 based on Reference 1. However, the cylinder wash system is operated by the same l

q group ofindividuals that operate the tube wash system. Therefore, the dependence between the two l

1 eperations must be addressed in the model. It is conservatively assumed that if an operator fails to l

t operate the tube wash system correctly, that operator will have an increased probability of operating the l

1 3

cylinder wash system incorrectly. This is a conservative assumption since the operator is trained for l

f[

each piece of equipment and there is a separate NCSA posting control for each piece of equipment. The l

posting provides the operator a daily reminder of the correct operation of that equipment. The basic l

l human error probability of 5 E-02/ demand was increased to 5 E-01/ demand to account for the l

4 dependence between the two operations. The fact that the error must be repeated in order to exceed the l

4 maximum safe loading and that supervision fails to detect this error is considered extremely unlikely.

)

Although the supervisor has repeated opportunities to discover the error, the probability of the error f

53 e

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, o e j

1493-25, Rev 2 March 1997 j

Request 1648 going undiscovered 10 times in a month is conservatively assumed to be 1.0 in this analysis (i.e, no error l

l identification by the supervisor), Accordingly, the probability that more than the NCSA limit of l

cylinders are available to be washed such that more than 24.1 kgs U could be discharged to the neutralization pit is 5 E-02. In order to accumulate masses approaching the maximum allowable mass (426.8 kg U), the cylinder wash syrtem must be incorrectly operated 10 times in a month with its maximum inver. tory exceeded by the inventory of one filled cylinder (24.3 kg U), the tube wash system accidently operated more than 20 times per week (74.4 kg U), and more than two metal cold traps per day er sneously discharged to the pit (228.6 kg U) at the maximum permissible pit concentration of 0.34 l

~

. liter (96.03 kg U).

It should be noted that the dependence between the tube wash and cylinder wash systems has l

j

' been addressed by the event tree model.

l l

RESULTS Only one of the postulated accident scenarios shown in the PITCRIT Event Tree is -

conservatively assumed to result in a critical configuration. This scenario involves a neutralization pit that equals orjust exceeds the maximum allowable pit concentration of 0.34 grams "U per liter. In 2

order for the pit to exceed the maximum allowable concentration, the following errors must all occur within the same month:

the contents of more than 30 metal cold traps which are normally refed to the cascade are l

a erroneously discharged to the drain (114.3 kg U),

the tube wash system is erroneously used to wash more than 250 tubes per week without l

=

collecting the rinsate from the irsitial wash during one week in the month (37.2 kg U), and l

the cylinder wash system is erroneously used to wash more than 120 cylinders per month with one filled cylinder per each wash cycle (24.3 kg U).

The frequency of this accident scenario, shown in Fig.1, is estimated to be 1.25E-07/ year, Since l

. this accident scenario involves the accumulation of only 271.83 kg U in the pit, more than 154 kg U in l

additional discharges from other lab areas would have to occur near the same time to result in a critical l

configuration. The probability of such an occurrence is also unlikely which further reduces the l

calculated frequency of this event. Since the determination of the maximum allowable mass considered l

uniform distributions of uranium in relatively thin layers in the bottom of the pit with water reflection, l

cvents that would cause uniform layering in a horizontal plane are considered in the model. It should be l

noted that this evaluation did not consider the normal dilution and turnover of pit contents every two l

i days. The conservative approach taken in this evaluation assumed the pit to be filled with solution at its l

maximum permissible concentration of uranium. The postulated uranium contaminated discharges to the l

pit during the month were not considered to be diluted by the building uranium-free discharges. The net j

54

'l

~

l

. a o*

]

1493-25, Rev 2 March 1997 Request 1648 effect of this approach is to add uranium to the pit without adding any water. Since more total uranium l

is assumed to be present with this approach, it bounds the case in which low water levels at the l

maximum poemissible concentration are subjected to the same postulated discharges. As a result, this l

conservative approach bounds unusually low water levels in the pit that might be caused by such events l

as drain system maintenance activities that would prevent uranium solution discharge dilution. It dso l

took no credit for the supervisor discovering operator errors or the potential for the pit sampling analysis l

to identify a pit fissile concentration that exceeds 0.34 g "U/l. Based on this information and event tree l

2

. analysis, a critical configuration due to the accumulation of uranium in the C-712 Neutralization Pit is not considered a credible event.

)

55 t

l l

>1

_.. =..

[q';2j Re 2 Much 1997 u

REFERENCES 1.

Burns, R. S. And Turner, J.H., Method Used to Estimate Screening-Level Total Failure Probabilityfor Human Error Events, K/GDP/SAR-42, Martin Marietta Energy Systems, Inc., Oak Ridge, TN, July 1994, 2.

Spiceland, M.T., Gaseous UF, Subsampling and Transfer, CP4-TS-AS7104, Lockheed Martin Utility Services, Inc., Paducah, KY, May 11,1995.

l l

,.l 56 i

e

to GDP 97-0051 l

NCSA-PLANT 043.A00 Figures 1,2, and 3 1

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