ML12135A301

NSA-TR-09-14, Rev. 2, Nuclear Criticality Safety Assessment of the Us Ecology Idaho (Usei) Site for the Land Fill Disposal of Decommissioning Waste from the Hematite Site. NSA-TR-09-14. December 2011

ML12135A301
Person / Time
Site:	Humboldt Bay
Issue date:	12/29/2011
From:	Matthews B Nuclear Safety Associates
To:	NRC/FSME
References
NSA-TR-09-14, Rev. 2
Download: ML12135A301 (76)

Text

Attachment 6 Nuclear Criticality Safety Assessment of the US Ecology Idaho (USEI) Site for the Land Fill Disposal of Decommissioning Waste from the Hematite Site, Rev.

2." NSA-TR-09-14. December 2011 (75 pages)

AWS )Ci1NuclearSafety NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Revi 2 Nuclear Criticality Safety Assessment of the US Ecology Idaho (USEI)- Site for the Land Fill Disposal of Decommissioning Waste from the Hematite Site Revision 2 December 2011 12/27/2011 Brian Matthews Date Author Tecncal Reviewer 12/27/2011 Brian Matthews Date Project Manager 001 NuclearSafety AAi

1. I' This document prepared by NuclearSafety Associates, Inc., for Westinghouse Electric Company, under contract.

Harold Eskridge:

HIDP Approval' Date 1

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f NuclearSafety A s soc i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Revision History Rev. #

By Significant Changes 0

R. S. Maurer Original issue Document revised to update the following items:

a Deletion of TBVI; The finalized water treatment system design report (Ref. 10) is referenced in this revision of the NCSA.

Modified DinD Control 01 to recognize that it is normal for some pooling of water to occur within open excavations during remediation operations.

0 Modified DinD Controls 02, 03, and 04 to reflect that radiological survey and/or sampling and analysis may be used to determine 35U content, and B. A. Matthews to relax some of the action limit requirements.

Modified DinD Control 05 and associated DinD D. Mann Safety Feature 01 to reflect that CDs will only be used for containerization of non-NCS Exempt Material.

0 Adjusted the text throughout the document to reflect the abovementioned changes.

• Other minor changes.

• Added a discussion to Section 1.5.1 to address screening of bulky objects and/or metallic items at the excavation area, and captured this new operational flexibility in notes to Administrative CSC 06.

2 B. A. Matthews Document revised to implement minor changes to the wording of controls for clarity.

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"'A tNCSA of the US Ecology Idaho (USEI) Site NuclearSa.e_

NSA-TR-09-14 A ss o c i a t e s Rev. 2 TABLE OF CONTENTS Section Title Pa2e

1.0 INTRODUCTION

9

1.1 DESCRIPTION

OF THE HEMATITE SITE..........................................................................

9 1.2 HEMATITE SITE HISTORY.................................................

10 1.3 HISTORIC OPERATIONS..............................................................................................

10 1.3.1 D ocum ented B urials...............................................................................................

10 1.3.2 Undocumented Burials........................................

14 1.4 C URRENT STATE............................................................................................................. 14 1.5 WASTE MATERIAL FOR BURIAL AT USEI..................................................................

14 1.5.1 Burial waste and contaminated soil.....................................................................

14 1.5.2 Solids Recovered from the Water Treatment System............................................

16 1.6 USEI SITE DESCRIPTION............................................................................................

18 1.7 U SE I SITE H ISTORY........................................................................................................

2 1 1.8 FACILITY DESCRIPTION..............................................................................................

21 1.8.1 G eograp hy.........................................................................................................

.. 21 1.8.2 Landfill C ells........................................................................................................

22 1.8.3 Surface Impoundments..........................................................................................

26 1.9 MANAGING WASTES FOR TREATMENT AND DISPOSAL.............................................. 27 1.9.1 Processing Containerized Waste...........................................................................

27 1.9.2 Processing Bulk Wastes.......................................................................................

28 1.10 SCOPE OF ASSESSMENT..............................................................................................

28 1.11 M ETHODOLOGY.............................................................................................................

28 1.11,1 App roach.........................................................................................................

.. 28 1.11,2 Method of Criticality Control...........................................................................

29 2.0 CRITICALITY SAFETY ASSESSMENT...............................................................

30 2.1 CRITICALITY HAZARD IDENTIFICATION...................................................................... 30 2.1.1 Hazard Identification Method.............................................................................

30 2.1.2 Hazard Identification Results................................................................................

31 2.2 GENERIC SAFETY CASE ASSUMPTIONS......................................................................

34 2.2.1 Fissile Material Assumptions................................................................................

34 2.2.2 Operational Practice and Equipment Assumptions.............................................

34 2.3 NORMAL CONDITIONS............................................................................................... 35 2.4 ABNORMAL CONDITIONS..................

............................... 37 2.4.1 Concentration Limit is Exceeded when Exhumed Burial Waste/

Contaminated Soil is Preparedfor Shipment......................................................

38 2.4.2 Concentration Limit is Exceeded When Solids Recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.,) are Prepared for Shipment........................................................................

45 2.4.3 Wrong Material is Loaded for Shipment to USEI...............................................

50 3

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Oula fe NCSA of the US Ecology Idaho (USEI) Site NuclearSa.__y NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.4. 4 Migration and Localized Concentration of 2 35 U in USEI Landfill Cells, Leachate System, and/or Evaporation pond........................................................

54 3.0

SUMMARY

OF CRITICALITY SAFETY CONTROLS....................................

58 3.1 CRITICALITY SAFETY PARAMETERS..........................................................................

58 3.2 CRITICALITY SAFETY CONTROLS AND DEFENSE-IN-DEPTH CONTROLS.................... 60 3.2.1 Systems, Structures, and Components.................................................................

60 3.2.2 Criticality Safety Controls....................................................................................

60 3.2.3 Defense-in-Depth Controls..................................................................................

65

4.0 CONCLUSION

67

5.0 REFERENCES

68 A PPEND IX A..............................................................................................................................

70 A PPEN D IX B...............................................................................................................................

73 4

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's ft NCSA of the US Ecology Idaho (USEI) Site NucdearSa.et NSA-TR-09-14 A s s o c i a t e s Rev. 2 LIST OF TABLES Table Title Pa~e Table 1-1 Buried Waste Characteristics 12 Table 1-2: Burial Pit Leachate Uranium Data 13 Table 2-1 Criticality Hazards Identified from the What-if Analysis 32 Table 3-1 Criticality Safety Parameters 58 Table A-1 Single Parameter Limits for homogeneous 235U/water mixtures 71 Table A-2 Critical Limits for homogeneous U/water mixtures as a function of U enrichment 72 LIST OF FIGURES Figure Title Page Figure 1-1 Documented Burial Pit Area 11 Figure 1-2 USEI Location Map 19 Figure 1-3 USEI Rail Transfer Facility Interior 20 Figure 1-4 USEI Rail Transfer Facility Exterior 20 Figure 1-5 First Load of Waste in Cell 15 23 Figure 1-6 Cell 15 Liner Installation 24 Figure 1-7 Schematic of Cell 15 Design 25 Figure 1-8 Evaporative Surface Impoundment 27 5

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NuclearSafety A s s o c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Glossary of Acronyms, Abbreviations, and Terms Acronym/Term Definition Foot (12")

Inch (2.54 cm)

ACM Asbestos Containing Material AEC Atomic Energy Commission ALARA As Low As Reasonably Achievable AESOP Work Order Supplement and associated electronic database Bq One radioactive disintegration per second BWCSR Buried Waste and Contaminated Soil Remediation cc Cubic centimeter CFR Code of Federal Regulations Ci Curie (equivalent to 3.7 x 1010 Bq) cm Centimeter cpm Counts per minute CSC Criticality Safety Control Maximum permitted thickness of a layer of buried wastes/contaminated Cut Depth soils that is permitted to be exhumed following implementation of in-situ radiological survey and visual inspection procedures and removal of identified Non-NCS Exempt Material.

DCGL Derived Concentration Guideline Levels D&D Decontamination and Decommissioning DinD Defense-in-Depth Field Container Limited volume container used to package Hot Spots.

Fissile Material Material containing fissile nuclides (e.g., 235U).

FSS Final Status Survey g

Gram GAC Granular Activated Carbon gallon 3.785 L gpm gallons per minute GUNFC Gulf United Nuclear Fuels Corporation HDP Hematite Decommissioning Project HEU Highly Enriched Uranium HPT Health Physics Technician HRGS High Resolution Gamma Spectrometer IX Ion exchange keV Kilo Electron Volt kg Kilogram L

Liter LLW Low Level Waste 9Micro (1.0 x 106) m Meter 6

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NuclearSafety A s so c i ate s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 MAA Material Assay Area - area used to assay Non-NCS Exempt Material in order to determine its 235U mass content.

MARSSIM Multi Agency Radiation Survey and Site Investigation Manual mg Milligram mil One thousandth NCS Nuclear Criticality Safety NCSA Nuclear Criticality Safety Assessment Material containing an insufficient quantity/concentration of fissile nuclides NCS Exempt Material (e.g., 235U) to require NCS controls/oversight An object recovered from an HDP Remediation Area undergoing waste exhumation operations that exhibits certain characteristics. The qualifying characteristics include objects that protrude into material residing beneath the maximum permitted Cut Depth, and/or objects that are inconsistent with the calibration basis of the radiological survey equipment used (e.g.,

Non-Conforming Item metallic items). In the latter case, an exception to this rule concerns objects that were not identified as containing a Hot Spot, have no hidden interior spaces, and clearly do not have any potential for containing Hot Spots. All Non-Conforming Items recovered from HDP Remediation Areas are classified as Non-NCS Exempt Material until proved otherwise by waste evaluation and/or assay.

Non-NCS Exempt Material that has a fissile nuclide concentration greater than the limit Material established for NCS Exempt Material, or materials that comprise un-assayed Intact Containers or Non-Conforming Items recovered during HDP Remediation Area waste exhumation operations. These materials are controlled to ensure their safe handling, packaging, processing, and storage.

p Pico (1.0 x 10-12)

PCE Perchloroethylene Survey Area Clearly delineated area of land subject to in-situ radiological survey, and for which excavation activities are planned.

SNM Special Nuclear Material - material containing fissile nuclides (e.g., 235U)

SSC System, Structure, and Component TCE Trichloroethene U

Uranium UNC United Nuclear Corporation vol. %

Percentage by volume Containers used to hold materials classified as NCS Exempt Material following operations in a WEA and/or MAA.

Waste Holding Area - area used to stage solid wastes generated from site remediation activities that have been categorized as NCS Exempt Material.

WEA Waste Evaluation Area - area used to evaluate Non-NCS Exempt Material for fissile nuclide content.

WTS Water Treatment System 7

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ydI NuclearSafeYa A s s o c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 wt. %

IPercentage by weight yd Yard (36')

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eNCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 Associate s

Rev. 2

1.0 INTRODUCTION

This Nuclear Criticality Safety Assessment (NCSA) is provided to demonstrate that a criticality accident is not credible at the US Ecology Idaho (USEI) site due to the burial of waste received from the Hematite site. The USEI activities include the receipt and burial of waste collected during final decommissioning of the Hematite site whereas the Hematite operations include the exhumation of the waste, limited waste treatment, waste characterization, and shipping preparation.

USEI is currently receiving uranium that is not enriched, whereas the waste shipped from the Hematite plant will involve low and high enriched uranium.

Therefore, the purpose of this NCSA is to demonstrate that the risk of a criticality is not credible based on the process conditions at the Hematite site, very low concentrations of uranium in the waste, and the disposal activities at the USEI Site.

This NCSA is organized as follows:

Section 1 introduces the waste treatment and shipping preparation activities at the Hematite site as well as the waste receipt and disposal activities at the USEI site. An overview of the specific equipment to be used as well as the activities to be performed is also provided.

Section 2 provides the risk assessment of the waste burial operations outlined in Section 1.

" Section 3 summarizes the important facility design features, equipment and procedural requirements identified in the criticality safety assessment provided in Section 2.

• Section 4 details the conclusions of the NCSA for burial of Hematite decommissioning waste at the USEI site.

1.1 Description of the Hematite Site The Westinghouse Hematite site, located near Festus, MO, is a former nuclear fuel cycle facility that is currently undergoing decommissioning.

The Hematite site consists of approximately 228 acres, although operations at the site were confined to the "central tract" area which spans approximately 19 acres. The remaining 209 acres, which is not believed to be radiologically contaminated, is predominantly pasture or woodland.

The central tract area is bounded by State Road P to the north, the northeast site creek to the east, the union-pacific railroad tracks to the south, and the site creek/pond to the west. The central tract area currently includes former process buildings, facility administrative buildings; a documented 10CFR20.304 burial area, two evaporation ponds, a site pond, storm drains, sewage lines with a corresponding drain field, and several locations comprising contaminated limestone fill.

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O N fNCSA of the US Ecology Idaho (USEI) Site uclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 1.2 Hematite Site History Throughout its history, operations at the Hematite facility included the manufacturing of uranium metal and compounds from natural and enriched uranium for use as nuclear fuel.

Specifically, operations included the conversion of uranium hexafluoride (UF6) gas of various 235U enrichments to uranium oxide, uranium carbide, uranium dioxide pellets, and uranium metal. These products were manufactured for use by the federal government and government contractors and by commercial and research reactors approved by the Atomic Energy Commission (AEC). Research and Development was also conducted at the facility, as were uranium scrap recovery processes.

The Hematite facility was used for the manufacture of low-enriched ( i.e., < 5.0 wt.% 235U),

intermediate-enriched (i.e., >5 wt.% and up to 20 wt.% 235U) and high-enriched (i.e., > 20 wt.% 235U) materials during the period 1956 through 1974. In 1974 production of intermediate and high-enriched material was discontinued and all associated materials and equipment were removed from the facility. From 1974 to cessation of manufacturing operations in 2001, the Hematite facility produced nuclear fuel assemblies for commercial nuclear power plants. In 2001, fuel manufacturing operations were terminated and the facility license was amended to reflect a decommissioning scope.

Accountable uranium inventory was removed and Decontamination and Decommissioning (D&D) of equipment and surfaces within the process buildings was undertaken. This effort resulted in the removal of the majority of process piping and equipment from the buildings. At the conclusion of that project phase, the accessible surfaces of the remaining equipment and surfaces of the buildings were sprayed with fixative in preparation for building demolition. More recently, the former process buildings at the Hematite site have undergone demolition, with the majority of the building demolition debris shipped off-site. However, the building slabs remain and will be remediated as part of the pending site-wide remediation operations.

1.3 Historic Operations Historic operations at the Hematite site resulted in the generation of a large volume of process wastes contaminated with uranium of varying enrichment. Records indicate that as early as 1958, facility process wastes were consigned to unlined burial pits situated in the North East comer of the sites central tract.

1.3.1 Documented Burials Based on historic documentation (Ref. 2), 40 unlined pits were excavated northeast of the plant buildings and southwest of "Northeast Site Creek" and were used for the disposal of contaminated materials generated by fuel fabrication processes at Hematite between 1965 and 1970. The documented burial area perimeter is outlined in Figure 1-1. Based on best available information, it is believed that the burial pits are nominally 20' x 40' and 12' deep.

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.NuclearSafety

1. A, A s so c i a t es NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Source: Ref. 2 Figure 1-1 Documented Burial Pit Area Consignment of waste to the burial pits was reported to be in compliance with AEC regulation 10 CFR 20.304 (1964; Ref. 3). Facility operating procedures (Ref. 4) described the size and spacing requirement for the burial pits, in addition to the required thickness of the overlying soil cover (4'), and the quantity of radioactive material that could be buried in each pit. The procedures in place at the time of operation of the burial pits required that buried waste be covered with approximately 4' of soil following completion of pit filling operations. However, it is possible that the soil cover thickness may have been modified over time as the area where the burial pits are located was re-graded on several occasions.

United Nuclear Corporation (UNC) and Gulf United Nuclear Fuels Corporation (GUNFC) maintained detailed logs of burials for the period of July of 1965 through November of 1970.

The Burial Pit log books (Ref. 5) contain approximately 15,000 data entries listing the date of burial, pit number, a description of the particular waste consignment, the uranium mass associated with the subject waste, and miscellaneous logging codes. Some logbook entries also list percent enrichment for the uranium. On-site burial of radioactive material ceased in November 1970.

The information recorded in the Burial Pit log books indicates that the waste consignments comprised a wide variety of waste types. This is further supported by interviews with past employees (Ref. 6). A schedule of the types of waste materials that may be present in the Burial Pits is provided in Table 1-1. The primary waste types expected to be encountered are 11 PRINTED COPIES ARE UNCONTROLLED

TNuclearSafety A s so cia t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 trash, empty bottles, floor tile, rags, drums, bottles, glass wool, lab glassware, acid insolubles, and filters. Buried chemical wastes include hydrochloric acid, hydrofluoric acid, potassium hydroxide, trichloroethene (TCE), perchloroethylene (PCE), alcohols, oils, and waste water.

Table 1-1 Buried Waste Characteristics Process Metals and Metal Wastes High enriched uranium (93-98%)

0 U02 samarium oxide

" Depleted and natural uranium U02 gadolinium Beryllia U0 2 Molybdenum Beryllium plates Uranium dicarbide Uranium-aluminum 0

Cuno filter scrap that included

" Uranium-zirconium.

beryllium oxide

" Thorium U02 a

Niobium pentachloride Chemical Wastes Chlorinated solvents, cleaners and 0

Ammonium bichloride residues (perchloroethylene, Sulfuric acid trichloroethylene) 0 Uranyl sulfate Acids and acid residues 0

Acetone Potassium hydroxide (KOH) insoluables 0

Methyl-alcohol Ammonium nitrate 0

Chlorafine Oxidyne Pickling solution Ethylene glycol 0

Liquid organics Other Wastes Tiles from Red Room floor 0

Contaminated limestone Process equipment waste oils a UO2 THO 2 Paper Towels Oily rags 0

Pentachloride from vaporizer TCE/PCE rags 0

Used Magnorite Used sample bottles 0

NbCI5 vaporizer Cleanout

" Green salt (UF4)

Item 51 Poison equipment Calcium metal 0 Asbestos.and Asbestos Containing Material (ACM)

Source:

Adapted from Ref. 2 The recorded total uranium mass associated with the waste consignments range from 178 g 23U to 802 g235U per burial pit with a maximum amount associated with any single waste consignment (i.e., burial item) of 44 g235U (Ref. 5). The uranium enrichment of waste items consigned to the burial pits ranged from 1.65 wt. % to 97.0 wt. % 235U/U. According to the Burial Pit log books, the five most frequent waste consignments comprised:

" Acid insolubles (2,050 entries);

Glass wool (2,080 entries);

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f v NCSA of the US Ecology Idaho (USEI) Site Nu earýa._

NSA-TR-09-14 A s s o c i a t e s Rev. 2

" Gloves and liners (900 entries);.

" Red Room trash (570 entries); and Lab trash (515 entries).

The waste consignments representing the highest recorded 235U content included:

" Wood filters (4 entries ranging from 22 to 44 g235U);

• Metal shavings (one entry at 41 g235U);

• Leco crucibles (4 entries ranging from 29-31.6 g235U); and

• Reactor tray (one entry at 40.4 g 35U).

Historic consignment of contaminated materials to the burial pits was conducted under a controlled program requiring documentation of each waste consignment. Contaminant controls at the time of disposal (e.g., containerization, bagging, etc.) in conjunction with the documented low surface contamination levels minimize the potential for significant migration of any radiological contaminants by ground water. There were no documented fissile liquid waste consignments (e.g., uranyl nitrate, etc.), possibly due to the inherent risk of contaminating ground water that could migrate offsite.

Quarterly sampling data (see, for example, 235U data excerpted in Appendix B) from wells both within the burial pit area and around the site periphery consistently indicates minimal fissile contaminant presence in the ground water. The quarterly well samples show little to no 235U presence, with results indicating a few pCi/L. The worst-case contamination was noted in some of the leachate for the pits where up to 340 pCi/L 235U (-0.157 mg/L*) was noted (Ref. 10). The following data excerpted from Reference 10 (compiled from water sampling data) provides the basis for the waste water treatment system design.

Table 1-2: Burial Pit Leachate Uranium Data Radioisotope Min.

Max.

Units Uranium 233/234 24 7,900 pCi/L Uranium 235 1

340 pCi/L Uranium 238 24 449 pCi/L Source:

Adapted from Ref. 10

• Conversion of pCi to mg:

Specific activity of 235U = 2.16107x10 6 Ci/g, 3.40x Io-IO ci/L 1-6

= 0.15733 mg/L 2.16107 x 10-6 Ci/g 13 PRINTED COPIES ARE UNCONTROLLED

1 0uFfety NCSA of the US Ecology Idaho (USEI) Site

1. ANuclearSafe NSA-TR-09-14 A s s o c i a t e s Rev. 2 1.3.2 Undocumented Burials It is assumed (Ref. 2) that additional, undocumented, burial pits may exist within the area between the former process buildings and the documented burial pit area.

Based on interviews with former site employees (Ref. 6), it is possible that on-site burials other than burials conducted under 10CFR20.304 (1964; Ref. 3) may have occurred as early as 1958 or 1959. Specifically, three or four burials may have been performed each year prior to 1965 for disposal of general trash and items that were lightly contaminated by then current radiological free release standards (Ref. 8). Based on this information, it is estimated that a total of 20-25 burial pits may exist for which there are no records. Waste consignments to these burial pits (i.e., prior to 1965) were not documented (logged) as they were not considered to contain significant 4uantities of SNM (Ref. 7). No specific information has been found to indicate the explicit nature of the waste consignments associated with these undocumented burials.

1.4 Current State The burial pits are currently in a quiescent state, although the pits may have been subjected to disturbances in the past, including characterization sampling initiatives (Ref. 10). The results of sampling activities indicate a maximum 235U concentration of 53.5 pCi/g, corresponding to a 235U concentration of approximately 2.5 [tg/g(waste matrix). Based on this sample data and the original burial logs, the burial pits are believed to contain only small quantities of 235U (i.e.,

less than I kg235U per burial pit). The findings of more recent (May 2008) extensive site sampling initiatives further support this expectation (refer to Section 1.2.2 of Ref. 19 for further details).

1.5 Waste Material for burial at USEI Waste shipped from the Hematite site may include the following low level sources:

1. Exhumed burial waste from the Hematite burial pits and contaminated soils and backfill material associated with the Hematite burial pits and other remediation areas at the Hematite site; and

2. Solids recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.).

The process for extracting each of these wastes is discussed in the following sub-sections.

1.5.1 Burial waste and contaminated soil Unless exempted by an NCSA, prior to removal of soil/waste from a remediation area of the Hematite site, comprehensive in-situ radiological survey and visual inspection of a clearly defined survey area (i.e., the area to be exhumed) is undertaken to identify Non-NCS Exempt Material.

The in-situ radiological survey will typically use Nal scintillator probes to provide gamma ray measurements of the surface area of interest. The survey technique that may be routinely performed is the Multi Agency Radiation Survey and Site Investigation Manual (MARSSIM) 14 PRINTED COPIES ARE UNCONTROLLED

0 1ety NCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 protocol which involves walking straight parallel lines over an area while moving the detector in a serpentine motion, 2 inches to 4 inches above the surface. Employing the MARSSIM protocol provides a high degree of assurance that all areas will be properly characterized prior to exhumation. Other in-situ radiological survey equipment and survey techniques may be employed provided that they meet procedural requirements.

Other radiological survey equipment may include, but is not limited to, the use of High Resolution Gamma Spectrometers (HRGS). Examples of other survey techniques may include, but is not limited to, the use of motorized equipment.

The objective of the in-situ radiological surveys is to identify Hot Spots. From an NCS perspective, Hot Spots are defined as a distinct in-situ location where detector radiation measurements indicate the presence of an elevated quantity of 235U (whether one object, a group of objects, or a cluster of material) when compared to the quantity of 235U in the surrounding area.

Any item or region of soil/waste with an average fissile nuclide concentration exceeding 0.1 g235U/L is defined as a Hot Spot. The 0.1 g235U/L threshold provides a high degree of assurance that any items with elevated (i.e., non-trivial) levels of 35U contamination would be identified. The in-situ radiological surveys are complemented by visual inspection of the survey area with the aim of identifying:

1) Items that resemble Intact Containers;

2) Non-Conforming Items (i.e., any items with the potential to contain fissile material (e.g., a process filter); bulky objects with linear dimensions exceeding the permitted cut depth; and thick metallic items*.

Hot Spots, Intact Containers and Non-Conforming Itemns are designated as Non-NCS Exempt Materials and must be identified and removed from any HDP Remediation Area undergoing remediation prior to the exhumation of NCS Exempt Materials.

Items that resemble Intact Containers are designated as Non-NCS Exempt Materials because they could potentially contain materials that are inconsistent with the calibration basis of the instruments used for the in-situ radiological surveys, or their dimensions may preclude effective in-situ radiological survey of their content. This is especially important in the event that large containers are encountered (e.g., 55-gallon drums, etc.) because of their large linear dimensions and the possibility that their content could comprise dense and/or high atomic number material (e.g., items or fragments constructed of steel), which could provide more attenuation than accounted for in the in-situ radiological survey equipment calibration basis.

Non-Conforming Items include bulky objects with significant linear dimensions, and metallic items or other dense materials that could provide significant photon attenuation. All Non-Conforming Items are designated as Non-NCS Exempt Materials for the same reasons discussed above for items that resemble Intact Containers.

• The concern with metallic items is that their properties may not be consistent with the calibration basis of the in-situ radiological survey equipment. For example, their high atomic number and/or density could provide more photon attenuation than accounted for in the calibration basis of the in-situ radiological survey equipment.

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pSfety NCSA of the US Ecology Idaho (USEI) Site I~Nuclear aft NSA-TR-09-14 A s s o c i a t e s Rev. 2 Any Non-NCS Exempt Materials identified from the results of the radiological survey and visual inspection are carefully removed, and will not be shipped to USEI unless distributed within low concentration material to reduce the average concentration of the bulk waste materials to no greater than 0.1 g235U/L, or if more detailed characterization later confirms that the Non-NCS Exempt Materials actually qualify as NCS Exempt Material on the basis of low average 235U concentration or low 235U mass content (specifically, a total mass content not exceeding 15 g235U for items packaged in a container with a volume of atleast 5 liters).

A second independent radiological survey/assay measurement will also be performed to provide an additional safety barrier to ensure that the NCS Exempt Materials consigned to the USEl site do not comprise an average concentration greater than 0.1 g235U/L.

Once Non-NCS Exempt Materials have been removed from a surveyed area, the remaining portion(s) of the surveyed area, to a depth not exceeding the maximum permitted cut depth represents material not of interest from a NCS perspective. These NCS Exempt Materials are exhumed and transferred to a suitable material stockpile in a WHA* and will be eventually be shipped to the USEI site.

1.5.2 Solids Recovered from the Water Treatment System During excavation and recovery of contaminated solid wastes from the burial pits a considerable amount of water is expected to intrude into the open excavations, including ground water seepage and rainwater. This water will be evacuated from the excavations to allow recovery of the buried wastes. Water removed during this process will be treated to remove entrained and soluble contaminants prior to release to the site water outfall.

Water will be generated from the following sources:

• Ground water associated with buried waste (leachate);

• Ground water that may seep into the excavation from surrounding soil;

• Precipitation that falls directly into an excavation; and

• Precipitation that falls onto waste and adjacent outside waste-processing areas.

Treatment of the water collected from, in, and around the burial pit excavations involves a number of collection and treatment stages:

• Collection of leachate, ground, and storm water from an excavation or draw-down cavity;

• Settling of course solids in holding tanks;

• Filtration and volatiles adsorption; and

• Filtration and ion exchange polishing.

• An overview of WHA operations is not provided in this NCSA because operations in WIHAs are not subject to NCS controls or oversight.

WHAs are used to stage and accumulate exhumed wastes and impacted soils in preparation for waste consolidation and shipment from the site in large gondola rail cars.

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I Kf0t1 NCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 These treatment processes result in the following solid wastes that must be removed'.

sediments in the tanks, filter bags, filter media, and treatment media. The collection of these waste materials is discussed below.

1.5.2.1 Collection of Sediments from Tanks A drum vacuum will be used to remove wet sediments from the bottom of the WTS Holding tanks. As operationally necessary, the water in a tank to be cleaned will first be emptied using a portable sump pump. The sediments will be radiologically surveyed and/or sampled and analyzed for fissile contamination before removal from the holding tank and at least once a month during tank operations. If the radiological survey and/or sample assay results indicate that the subject solids contain an average concentration exceeding 0.1 g235U/L then the subject solids are designated as non-NCS Exempt Material and must be recovered* directly into Collared Drums (CDs) pre-loaded with absorbent material (e.g., an immobilizing compound) to soak up any residual water associated with the sediments.

Each loaded drum will be lidded,'transferred to a WEA/MAA, and subject to a primary evaluation/assay measurement and a secondary independent evaluation/assay measurement, both of which will be independently verified to determine radiological content. In order to be shipped to the USEI site for burial, the evaluation/assay results must demonstrate that the content of the drum(s) does not comprise greater than 0.1 g235U/L. In the event that the drum content is established to meet NCS Exempt Material criteria at the Hematite site, the materials will be aggregated with other bulk waste streams.

1.5.2.2 Filtration and Treatment Media Change-Outs Periodically, the filtration and treatment media, such as Granular Activated Carbon (GAC) and Ion Exchange (IX) media, will require removal and replacement. The following sub-sections discuss the handling activities for these solid waste materials.

1.5.2.2.1 Filter Bags The polypropylene filter bags (or similar material) will likely require frequent replacement (need for replacement is determined by measurement of the head pressure required to pump water through the filter). Prior to the replacement of a bag filter, its enclosure/vessel pair is radiologically surveyed. If the survey results indicate that the subject bag filter contains an average concentration exceeding 0.1 g235U/L then the bag filter is designated as non-NCS Exempt Material and must be directly loaded into an awaiting CD that is pre-loaded with absorbent material, as necessary, to soak up any residual water associated with the filter media. The loaded CD is then transferred to a WEA/MAA, and subject to a primary evaluation/assay measurement and a secondary independent evaluation/assay measurement, both of which will be independently verified to determine radiological content.

In order to be shipped to USEI for burial, the evaluation/assay results must demonstrate the filter(s) do not contain an average 235U concentration greater than 0.1 g235U/L. In the event that the filter is established to meet NCS Exempt Material criteria at the Hematite site, the filter media will be aggregated

• The sediment recovery process will be achieved by opening the access hatches to the tank and guiding the vacuum suction hose intake to recover the designated non-NCS Exempt Material.

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yNCSA of the US Ecology Idaho (USEI) Site p44fNuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 with other bulk waste streams.

1.5.2.2.2 Treatment Media The treatment beds (GAC and IX) will require periodic changing (need for changing is determined by measurement of the head pressure required to pump water through the respective treatment vessel). Unlike the bag filters, the GAC units will be backwashed to break up the carbon bed and remove entrained solids that are plugging or blinding the carbon bed. Treated effluent water from a tank will be used as backwash water. Water will be pumped from the tank backwards (up) through the GAC vessel being backwashed. The system is designed so that one set of two (2) GAC absorbers can be taken off-line for servicing or backwashing while the system runs at capacity (50 gpm) with only the second set of two (2) GAC units on-line. Backwash water from the GAC vessel being backwashed flows under pressure back to the inlet of storage tank T-3 for removal of suspended solids from the backwash water.

Prior to any replacement of the GAC media, the GAC vessel is valved out of service and the treatment media blown down with a portable air compressor, as necessary, to effectively dry the media. Samples of the media are extracted via the access ports on the media vessel and analyzed for fissile contamination at least once a week during operation to further ensure no significantfissile material concentration accumulates. However, it is noted that radiological survey of the vessels may be performed in lieu of sampling and analysis provided that it is performed with at least the same frequency. In the event that the radiological survey and/or sample assay results indicate that the solids to be removed contain an average concentration exceeding 0.1 g 235U/L, then the subject solids are designated as non-NCS Exempt Material and must be recovered directly into CDs pre-loaded with absorbent material, as necessary, to soak up any residual water associated with the solids. The loaded CDs are then transferred to a WEA/MAA, and subject to a primary evaluation/assay measurement and a secondary independent evaluation/assay measurement, both of which will be independently verified to determine radiological content. In order to be shipped to USEI for burial, the evaluation/assay results must demonstrate the drum(s) do not contain an average 235U concentration greater than 0.1 gU35u/L. In the event that the drum content is established to meet NCS Exempt Material criteria at the Hematite site, the drum content will be aggregated with other bulk waste streams 1.6 USEI Site Description US Ecology Idaho (USEI), Inc., owns and operates a hazardous waste treatment, storage, and disposal facility located approximately 10.5 miles west of Grand View, Idaho. (See Figure 1-2.)

The USEI facility lies far from population centers in an arid climate with low annual rainfall and a high evaporation rate. The 160-acre site in Owyhee County is located on more than 1,000 contiguous acres of land owned by USEI. These factors, in combination with thick sub-surface layers of highly impermeable silts, clays, and sediments, make the site ideally suited for the secure treatment and disposal of hazardous and industrial wastes. USEI manages hazardous waste under a Resource Conservation and Recovery Act (RCRA) Part B Operating Permit (IDD073114654) issued on November 12, 2004 by the State of Idaho.

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Ref. 21 Figure 1-2 USEI Location Map The USEI facility received a state permit to accept an expanded range of low-activity radioactive materials in 2001, and the permit has been amended several times since then. The facility's state RCRA Part B Operating Permit was renewed for a 10-year period in 2004.

USEI is fully permitted to manage RCRA, Toxic Substances Control Act (TSCA), and the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) wastes, and NRC-exempted radioactive waste.

The facility provides waste management services including chemical stabilization of organic and inorganic solids, sludges and liquids, along with landfill disposal, aqueous evaporation treatment, debris treatment, and PCB management and disposal.

USEI offers rail transportation service to the facility from all points in the continental United States (refer to Figures 1-3 and 1-4). Nearly 2,000,000 tons of wastes have been received at the Rail Transfer Facility in the last three years, demonstrating an ability to handle large environmental remediation projects.

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1% NuclearSafety Assoc Aiates NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Source:

Ref. 21 Figure 1-3 USEI Rail Transfer Facility Interior Source:

Ref. 21 Figure 1-4 USEI Rail Transfer Facility Exterior 20 PRINTED COPIES ARE UNCONTROLLED

O Nu fety NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 A s s 0 c i a t e s Rev. 2 1.7 USEI Site History The USEI site was originally constructed as a U.S. Air Force Titan I Missile Complex and eventually decommissioned by the U.S. Air Force in 1965.

In 1973, the State of Idaho permitted Western Containment, Inc. (Wes-Con) to dispose industrial waste at the site. Wes-Con received and disposed industrial and PCB wastes in trenches and in portions of the abandoned Titan Missile silos. In 1980, Wes-Con submitted a Part A notification under the Resource Conservation and Recovery Act (RCRA) for hazardous waste disposal. Envirosafe Services of Idaho, Inc. (ESII) purchased the site in 1981 and was granted RCRA interim status the same year. ESII obtained a RCRA Part B Operating Permit on December 15, 1988, and a TSCA Storage and Disposal Permit on November 29, 1991. The facility was purchased by American Ecology Corporation in January 2001, and renamed US Ecology Idaho, Inc. in May 2001.

The history of construction at the USEI site is summarized below:

a 1984: The first double-lined landfill cell constructed.

1988: Outdoor Stabilization Facility constructed.

1990: Phase I of the second double-lined cell (Cell 14) constructed.

1993: Phase II of Cell 14 completed.

1994: Debris Handling Facility completed.

1998: New Containment Building housing the stabilization units completed.

October 2003: USEI's newest landfill, Cell 15, completed and disposal operations commenced.

2005: Cell 15 Phase II expansion completed.

2007: Cell 15 Phase III expansion completed.

1.8 Facility Description 1.8.1 Geography The USEI facility is located off Highway 78 approximately 10.5 miles west of the town of Grand View, in Owyhee County, Idaho. Grand View has a population of 350. The nearest residence is 1 mile southwest of the site.

The site is situated on a one-mile wide plateau that slopes from south to north. Maximum surface relief on the facility is 90 feet and the mean surface elevation is 2600 feet above sea level. The site is located in a desert environment with an average rainfall of 7.26 inches per year and an average evaporation rate in excess of 42 inches per year.

Castle Creek, the nearest surface water, is an intermittent creek located one-half mile west of the site that lies topographically 150 feet below the facility. The Snake River, the largest surface water source near the site, lies approximately 2Y2 miles north and 350 feet in elevation below the facility. EPA site evaluations indicate little possibility of site flooding due to a number of factors, primarily low rainfall, high evaporation, and location of the 21 PRINTED COPIES ARE UNCONTROLLED

NCSA of the US Ecology Idaho (USEI) Site NuclearSa"e NSA-TR-09-14 A s s o c i a t e s Rev. 2 facility outside the 100-year flood plain.

The facility is located within seismic zone 2 and therefore does not require a seismic standard demonstration under 40 CFR Part 264 Appendix IV.

Currently, USEI has eighteen (18) Piezometers and thirty-nine (39) monitoring wells screened within two aquifers below the site. In accordance with USEI Part B R and TSCA permits, pH, specific conductivity, and a custom list of 28 VOCs are sampled semi-annually.

Sampling for PCB analysis is performed each year. Groundwater sampling is performed in accordance with the requirements of USEI's current operating permit. Analysis is completed by a certified contract laboratory. The results of the semi-annual groundwater sampling and analysis activities are submitted to IDEQ semi-annually, in accordance with the requirements of USEI's RCRA Part B Permit, and to U.S. EPA Region 10 each year, in accordance with the requirements of USEI's TSCA permit.

Runoff due to rain is managed through an engineered drainage collection and containment system. The system directs runoff from the interior of the site into one of three on-site RCRA Surface Impoundments. A run-on diversion system prevents run-on from entering the facility.

Site drainage and run-off controls are designed to contain and control run-off from a 25-year, 24-hour storm (1.75 inches of precipitation). Active waste disposal, storage, and treatment operations are segregated from uncontaminated areas by a series of diversion berms and channels.

The control system consists of drainage swales, engineered grades, drainage conduits, flumes, riprap, and surface impoundments.

A system of interceptor channels collects and conveys run-off from the active waste handling areas to the rain water Surface Impoundments/Collection Ponds. Runoff from clean areas to the active area is prevented by a series of dikes and channels around active units. Run-off may be transferred from Collection Ponds 1, 2, and 3 and routed to the Evaporation Pond for solar evaporation.

Runoff from the active areas of Cells 5, 14 and 15 are collected within the unit and transferred to storage tanks and treated as multi-source leachate. Once the leachate has been treated to below Land Disposal Restrictions (LDRs) leachate is routed to the primary Evaporation Pond (also a RCRA Surface Impoundment) for solar evaporation.

1.8.2 Landfill Cells Two RCRA/TSCA landfills are actively used to dispose of containerized solids, bulk solids, and electrical equipment (i.e., small capacitors, transformer carcasses, etc.).

Construction of Cell 15 was initiated on March 1, 2003 and the cell was in operation by October 2003. Phase I of Cell 15 provided about 1,000,000 cubic yards of cell space. When all phases are complete Cell 15 is designed to contain over 3.6 million cubic yards of material (refer to Figure 1-5). Second phase construction was completed in 2005, and third 22 PRINTED COPIES ARE UNCONTROLLED

X NuclearSafety As so cia t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 phase construction was completed in 2007.

Source:

Ref. 21 Figure 1-5 First Load of Waste in Cell 15 1.8.2.1 Landfill Cell Liner System USEI's landfill liner system for cells 14 and 15 consists of a dual composite liner with a leak detection system overlying the primary liner.

See Figure 1-6 for a schematic depiction. The liner system was constructed from bottom to top as indicated:

• Subgrade: In-situ compacted silty, sandy soil.

" Secondary Soil Liner:

Minimum 36-inches of recompacted clay with a permeability of less than 1 x 10-7 cm/sec.

• Secondary Flexible Membrane Liner: 60 or 80-mil high density polyethylene.

• Leak Detection Zone:

Composite layer consisting of a synthetic drainage net, geotextile fabric, 12-inches of stone, and a secondary geotextile fabric.

" Primary Flexible Membrane Liner: 60 or 80-mil high density polyethylene.

• Primary Leachate Collection Zone:

Composite layer consisting of a synthetic drainage net, geotextile fabric, 12-inches of sand, and a second geotextile fabric.

• Protective Layer: 12-inches of compacted soil.

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NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Source:

Ref. 21 Figure 1-6 Cell 15 Liner Installation 24 PRINTED COPIES ARE UNCONTROLLED

40% NuclearSafety A s s o c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Hazardous Waste Cell 15 Design Source:

Ref. 21 Figure 1-7 Schematic of Cell 15 Design 1.8.2.2 Leachate Collection, Inspection and Treatment The leachate collection system drains and traps moisture and liquids percolating through the landfill. The leachate collection system is protected from clogging by a geotextile filter and protected from physical disturbance by 6-inches of soil. Cells are graded so that liquids drain towards the leachate collection system. The sumps are pumped according to a Leachate Management Schedule outlined in USEI's operating permits.

Leachate levels are checked weekly in the primary leachate systems and daily in the secondary leak detection collection and removal system. Both sumps are checked in the event the facility receives more than

/2 inch of rainfall in a 24-hour period. Leachate is pumped and removed in accordance with action levels established in the Part B Permit.

Records are maintained for each pumping event. Pumping records indicate leachate levels before and after pumping, the volume pumped, and the on-site dispensation of the leachate.

The leachate is managed in accordance with 40 CFR Part 268.7, using a carbon absorption system.

The treated leachate is stored until the required testing is completed.

Upon passing the required parameters, the leachate is disposed in the solar evaporation pond.

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6 IFNCSA of the US Ecology Idaho (USEI) Site Nuclear~aety NSA-TR-09-14 A s s o c i a t e s Rev. 2 1.8.3 Surface Impoundments USEI has three RCRA-permitted surface impoundments for the collection of storm water runoff (Rainwater Collection Ponds 1, 2, and 3). A fourth RCRA-permitted impoundment is primarily used for solar evaporation (Evaporation Pond 1 - refer to Figure 1-8).

USEI's Surface Impoundments are constructed with dual synthetic liner systems and associated leak detection capabilities. The Storm-water pond liner systems are constructed as indicated from bottom to top:

• Subgrade: In-situ compacted silty, sandy soil.

• Secondary Flexible Membrane Liner: 40-mil Medium Density Polyethylene.

Leak Detection Zone: Composite layer consisting of a geotextile fabric, 12 inches of sand, and a collection pipe.

• Primary Flexible Membrane Liner: 60-mil High Density Polyethylene.

• Protective layer: 12 inches of sand, geotextile fabric and 6 inches of stone.

The Evaporation Pond liner system is constructed in a slightly different fashion to place a flexible membrane liner on the surface:

" Subgrade: In-situ compacted silty, sandy soil.

Secondary Flexible Membrane Liner: 40-mil Medium Density Polyethylene.

" Leak Detection Zone: Composite layer consisting of a geotextile fabric, 12 inches of sand, and a collection lipe.

• Primary Soil Liner:

12 inches of compacted clay with permeability of less than 1 x 10-6 cm/sec.

" Primary Flexible Membrane Liner: 80-mil High Density Polyethylene.

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Ref. 21 Figure 1-8 Evaporative Surface Impoundment 1.9 Managing Wastes for Treatment and Disposal The Receiving Department enters all waste management information into the Company's American Ecology Standard Operating Platform (AESOP) system (i.e., weights, reagents, constituents, concentrations, disposal locations, etc.). Depending on the waste in question, wastes received at USEI may be placed in temporary storage, or sent to one of the stabilization units, the debris handling facility, or directly land-filled. In regards to the Hematite waste, approximately 95% of the wastes will be directly land-filled (i.e., no treatment), with the remaining 5% expected to require stabilization for RCRA regulated metals. Upon final waste placement, three-dimensional disposal coordinates are recorded on a Work Order Supplement and associated electronic database (AESOP).

1.9.1 Processing Containerized Waste Waste streams with similar waste codes, characteristics and compatibility are typically consolidated for batch treatment. For example:

F006, 7, 8, 9, 11, 12, 19 waste streams are usually combined.

D004-011 waste streams are usually combined.

Batches are analyzed after treatment to ensure that all treatment standards for all waste codes in the batch have been met.

Containers of debris are also consolidated for treatment; however, there are no concentration-based standards for encapsulation.

Instead, the requirements of 40 CFR Part 268.45 and USEI's permit must be met to ensure that debris was treated for each contaminant subject to treatment.

Containers of waste that do not require further treatment are placed directly into the landfill, based upon compatibility. The coordinates of the containerized wastes are recorded to permit 27 PRINTED COPIES ARE UNCONTROLLED

PWa fM NCSA of the US Ecology Idaho (USEI) Site Nuclear~ai NSA-TR-09-14 A s s o c i a t e s Rev. 2 retrieval in the future, if for any reason this is desired.

1.9.2 Processing Bulk Wastes Bulk wastes requiring treatment may be off-loaded into three different areas; 50-cubic yard stabilization bins at the Stabilization Plant, 100-cubic yard stabilization tanks in the Stabilization Building, or onto the sort floors in the Debris Handling Facility. Alternatively, containerized bulk waste may be stored in one of USEI's RCRA storage areas. Waste off-loaded directly into bins or tanks can be treated immediately.

Wastes that are off-loaded onto the sort floors typically need additional handling prior to treatment.

Downsizing, sorting, crushing and other handing may be required prior to treatment.

Bulk wastes destined for direct landfill are directed to the landfill cell specified on the WPQ summary sheet after inspection and approval for receipt. Waste locations in the landfill are based upon compatibility, and disposal locations are recorded.

1.10 Scope of Assessment This scope of this NCSA is limited to safe handling and disposal of the solid wastes at USEI based on the following low level waste streams being shipped from the Hematite site:

1. Exhumed burial waste from the Hematite burial pits and contaminated soils and backfill materials associated with the Hematite burial pits and other remediation areas at the Hematite site; and

2. Solids recovered from the site Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.).

The safe collection and staging of these wastes is addressed in References 18, and 19.

However, this NCSE credits characterization controls established as one of the numerous factors that provide the basis to demonstrate that a criticality is not credible at USEI for the burial of the Hematite low level waste.

1.11 Methodology 1.11.1 Approach This NCSA uses a risk-informed approach. Risk insights, gained from the findings of the risk assessment, are used to establish aspects of the design and process that are susceptible to faults important to nuclear criticality safety.

The risk informed approach is complemented with an As Low As Reasonably Achievable (ALARA) assessment that is focused on identifying practicable measures that can be reasonably implemented to further reduce the risk of criticality to a level as low as is reasonably achievable. The ALARA assessment also serves to provide an additional degree of confidence that a criticality incident resulting from the activities assessed is not credible.

In summary, the approach used in this NCSA is as follows:

1. Establish the margin of safety between normal (i.e., expected) conditions and foreseen credible abnormal conditions.

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0 NuclearSafety A s s o c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2

2. Determine whether the inherent margin of safety is sufficient to safely accommodate the credible deviations from normal conditions, and if not, identify feature(s) of the process* that are important to ensuring criticality safety under all credible conditions.

3. Establish what additional practicable measures, if any, can reasonably be implemented to ensure that the risks from criticality are as low as is reasonably achievable.

1.11.2 Method of Criticality Control The criticality safety basis for low level waste burial at USEI is provided below and is based on the controls established at the Hematite site.

1.11.2.1 Waste Collection and Characterization Unless exempted by an NCSA, all waste exhumed or otherwise collected will have an initial characterization to ensure that safety it is safely accumulated at the Hematite site and that it meets the concentration limit for safe disposal at USEI. This will involve the use of calibrated instruments performed by trained personnel.

1.11.2.2 Final Characterization for Shipment Unless exempted by an NCSA, all of these waste sources will be verified by second, independent, assay or in-situ measurements to ensure that they do not contain an average 235U concentration greater than 0.1 g235U/L. The combination of the two independent measurements to ensure that the 235U average concentration of the wastes does not exceed 0.1 g235U/L will ensure that they will meet the burial criteria at the USEI site. These verifications along with the low probability to uncover material with high concentrations will ensure that a criticality accident is not credible during receipt and burial at the USEI site.

• In the selection of safety controls, preference is placed on use of engineered controls over procedural controls.

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0 fV NCSA of the US Ecology Idaho (USEI) Site WI ',NuclearSa.ety NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.0 CRITICALITY SAFETY ASSESSMENT The criticality safety assessment is organized as follows:

Section 2.1 describes the hazard identification technique employed in the criticality safety assessment of waste disposal at the USEI site and provides a summary of the hazard identification results.

" Section 2.2 outlines the generic assumptions used in the criticality safety assessment.

• Section 2.3 contains the criticality safety assessment of waste disposal at the USEI site under normal (i.e., expected) conditions.

Section 2.4 contains the criticality safety assessment of waste disposal at the USEI site under abnormal (i.e., unexpected) conditions.

2.1 Criticality Hazard Identification This section outlines the technique used to identify criticality hazards associated with the Hematite waste disposal at USEI site. A summary of the hazards identified is also provided, together with a brief description of their disposition in the NCSA.

2.1.1 Hazard Identification Method The hazard identification technique employed in this criticality safety assessment uses a What-if analysis where the remediation approach and overall objectives are scrutinized and examined against postulated situations, focused on challenging criticality safety. As part of this process, the What-if analysis steps through the eleven (11) criticality safety controlled parameters to determine the extent of their importance to criticality safety.

The eleven (11) criticality safety controlled parameters examined include:

" Geometry

• Interaction

" Mass

• Isotopic/Enrichment

" Moderation

" Density

" Heterogeneity

• Neutron Absorbers

• Reflection Concentration

" Volume The eleven (11) parameters listed above are traditionally considered in criticality safety assessments of processes at operating facilities possessing Special Nuclear Material (SNM).

Typically, the non-processed based nature of decommissioning operations and associated residues limits the ability to control many parameters, resulting in the need to use bounding 30 PRINTED COPIES ARE UNCONTROLLED

5NuclearSafety A s so c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 values for parameters in the NCSA in many instances.

2.1.2 Hazard Identification Results A summary of the criticality hazards identified from the What-if analysis is presented in Table 2-1.

Hazards that result in events with similar consequences and safeguards are grouped in single criticality accident event sequences, analyzed in Section 2.4.

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V~NuclearSafety Associates NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Table 2-1 Criticality Hazards Identified from the What-if Analysis What-if...

Causes Consequences Accident Sequence in NCSA Geometry There are no identified hazards associated with geometry because the safety assessment is based on safe concentration for an infinite system.

Interaction Wrong waste is loaded for

• Procedure non-compliance.

Potential interaction between packages Section 2.4.3 shipment.

that may normally require spacing.

Mass Wrong waste is loaded for Procedure non-compliance.

Potential to exceed a maximum safe shipment.

mass of 235U in a localized area.

Section 2.4.3 There is a reconfiguration of

• Uranium dissolution and Potential to exceed a maximum safe Section 2.4.4 235U solids in a waste cell.

migration due to ground water mass of 235U in a localized area.

and/or water from precipitation.

Potential to exceed a maximum safe mass of 235U in the leachate or evaporation pond(s).

The package/shipment is

• Procedure non-compliance.

Potential to exceed a maximum safe Sections 2.4.1 and 2.4.2 improperly characterized, mass of 23SU in a localized area.

Isotopic/Enrichment

-q0 Z

-4 0rn m~

rn 0a M

CO)

Z0

-I 0

r-r1 There are no identified hazards associated with presence of variable enrichment uranium. This is because the safety assessment is conservatively based on subcritical limits derived for uranium metal at maximum theoretical density, with 100 wt.% 2oU/U enrichment.

Moderation There are no identified hazards associated with moderation of uranium particulates. This is because the safety assessment is conservatively based on subcritical limits derived for uranium-H 20 mixtures at optimum concentration.

Density There are no identified hazards associated with presence of variable density uranium. This is because the safety assessment is conservatively based on subcritical limits derived for uranium metal at maximum theoretical density.

32

0 NuclearSafet' As so c i ate s

NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 What-if...

Causes Consequences Accident Sequence in NCSA Heterogeneity There are no identified hazards associated with heterogeneity of uranium. This is because the safety assessment is conservatively based on subcritical limits derived for homogeneous uranium-H 20 mixtures (with 100 wt.% 235U/U enrichment), for which subcritical limits are smaller than equivalent heterogeneous uranium-H20 mixtures.

Neutron Absorbers There are no identified hazards associated with absence of fixed neutron absorbers. This is because the safety assessment does not credit fixed neutron absorbers.

Reflection There are no identified hazards associated with reflection of uranium. This is because the safety assessment conservatively uses subcritical limits based on full (i.e., 30 cm) thickness close fitting water, concrete, and/or soil reflection conditions, which are considered to bound any credible reflection condition.

Concentration Wrong package(s) are

• Procedure non-compliance.

Potential to exceed a maximum safe shipped.

concentration of 235U in a localized area.

Section 2.4.3 There is a reconfiguration of

- Uranium dissolution and Potential to exceed a maximum safe Section 2.4.4 235U solids in a waste cell.

migration due to ground water concentration of 235U in a localized area.

and/or water from precipitation.

Potential to exceed a maximum safe concentration of 235U in the leachate or evaporation pond(s).

The package/shipment is

• Procedure non-compliance.

Potential to exceed a maximum safe Sections 2.4.1 and 2.4.2 improperly characterized, concentration of 235U in a localized area.

Volume Volume control is not viable due to the large volume of waste to be shipped.

"0 Z

.-I 00 0'a0 C

Z0z 0

.- I I-"

m a

33

'O NCSA of the US Ecology Idaho (USEI) Site Nulear ty NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.2 Generic Safety Case Assumptions The activities considered in this criticality safety assessment relate to the processes as defined in Section 1. This section outlines the generic assumptions on which this criticality safety assessment is based.

2.2.1 Fissile Material Assumptions The pertinent underlying assumptions of the assessment related to the fissile material that may be encountered in these activities are as follows:

" This assessment does not consider fissile nuclides other than 235U. Based on the history of the Hematite site and site documentation (refer to Sections 1.2 and 1.3), there is no expectation that fissile nuclides other than 235U could exist within the Hematite site boundary. In the event that any SNM associated with buried wastes, soils or backfill materials are discovered to contain fissile nuclides other than 235U, a stop work order will be issued.

• Fissile material limits have been derived assuming homogeneous mixtures of 235U with water (1120) and soil.

This approach is conservative with respect to other fissile materials containing uranium, including soils, process wastes, and host rock.

" The fissile material associated with low level waste originating from the Hematite site is predominantly insoluble particulates of uranium as opposed to dissolved, or water-soluble compounds.

" The Hematite waste received at the USEI site will not be treated and will be consigned directly to a waste cell.

2.2.2 Operational Practice and Equipment Assumptions The pertinent underlying assumptions of this NCSA related to operational practice and equipment use are described and documented in Section 1.

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O Wey NCSA of the US Ecology Idaho (USEI) Site X.

NuclearSa.NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.3 Normal Conditions Under normal (i.e., expected) conditions Hematite decommissioning wastes will contain only trace quantities of radionuclides, or at worst, a very low presence of fissile nuclides. This will be verified by comprehensive in-situ radiological surveys prior to waste exhumation, as explained in the following paragraph. Solid wastes generated in the waste water recovery systems will also be characterized at the Hematite site to confirm low concentration of fissile nuclides.

Unless exerfipted by an NCSA, prior to removal of soil/waste from a remediation area of the Hematite site, comprehensive in-situ radiological survey and visual inspection of a clearly defined survey area (i.e., the area to be exhumed) is undertaken to identify Non-NCS Exempt Material.

The in-situ radiological survey will typically use NaT scintillator probes to provide gamma ray measurements of the surface area of interest. The survey technique that may be routinely performed is the Multi Agency Radiation Survey and Site Investigation Manual (MARSSIM) protocol which involves walking straight parallel lines over an area while moving the detector in a serpentine motion, 2 inches to 4 inches above the surface. Employing the MARSSIM protocol provides a high degree of assurance that all areas will be properly characterized prior to exhumation.

The objective of the in-situ radiological surveys is to identify Hot Spots, which are defined as any item or region of soil/waste with an average fissile nuclide concentration exceeding 0.1 g235U/L. The low 0.1 g235U/L threshold provides a high degree of assurance that any items with elevated (i.e., non-trivial) levels of 235U contamination would be identified. The in-situ radiological surveys will be repeated by a second independent measurement to provide an additional safety barrier to ensure that material with an average fissile nuclide concentration exceeding 0.1 g U/L would be detected.

The in-situ radiological surveys are complemented by visual inspection of the survey area by two independent qualified individuals with the aim of identifying objects that are potentially not consistent with the calibration basis. Objects meeting this criterion include:

1) Items that resemble Intact Containers;

2) Non-Conforming Items (i.e., any items with the potential to contain fissile material (e.g., a process filter); bulky objects with linear dimensions exceeding the permitted cut depth; and thick metallic items*.

Refer to Section 1.5.1 for a discussion of these Non-NCS Exempt Materials.

Any Non-NCS Exempt Materials identified from the results of the radiological survey and

• The concern with metallic items is that their properties may not be consistent with the calibration basis of the in-situ radiological survey equipment. For example, their high atomic number and/or density could provide more photon attenuation than accounted for in the calibration basis of the in-situ radiological survey equipment.

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Sfey NCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s sAssociates Rev. 2 visual inspection are carefully removed, and will not be shipped to USEI unless distributed within low concentration material to reduce the average concentration of the bulk waste materials to no greater than 0.1 g235U/L, or if more detailed characterization later confirms that the Non-NCS Exempt Materials actually qualify as NCS Exempt Material on the basis of low average 235U concentration or low 235U mass content (specifically, a total mass content not exceeding 15 g235U for items packaged in a container with a volume of atleast 5 liters). A second independent radiological survey/assay measurement will also be performed to provide an additional safety barrier to ensure that the NCS Exempt Materials consigned to the USEI site do not comprise an average concentration greater than 0.1 g235U/L.

Once Non-NCS Exempt Materials have been removed from a surveyed area, the remaining portion(s) of the surveyed area, to a depth not exceeding the maximum permitted cut depth represents material not of interest from a NCS perspective. These NCS Exempt Materials are exhumed and transferred to a suitable material stockpile in a WJHIA* and will be eventually be shipped to the USEI site.

All Hematite WTS components and wastes (i.e., filters, filter media, sediments) will be radiologically surveyed and/or sampled and assayed to determine radiological content. In the event that the radiological survey and/or sample assay results indicate that the solids to be removed contain an average concentration exceeding 0.1 g235U/L, then the subject solids are designated as non-NCS Exempt Material and must be recovered directly into CDs pre-loaded with absorbent material, as necessary, to soak up any residual water associated with the solids.

Each loaded drum will be lidded, transferred to a.WEA/MAA, and subject to a primary evaluation/assay measurement and a secondary independent evaluation/assay measurement, both of which will be independently verified to determine radiological content. In order to be shipped to the USEI site for burial, the evaluation/assay results must demonstrate that the contents of the drum(s) does not contain greater than 0.1 g 235U/L.

In the event that the drum content is established to meet NCS Exempt Material criteria at the Hematite site, the materials will be aggregated with other bulk NCS Exempt Material waste streams.

• An overview of WHA operations is not provided in this NCSA because operations in WHAs are not subject to NCS controls or oversight.

WHAs are used to stage and accumulate exhumed wastes and impacted soils in preparation for waste consolidation and shipment from the site in large gondola rail cars.

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Nufett NCSA of the US Ecology Idaho (USEI) Site NuA earSa.es NSA-TR-09-14 SA s s o c i a t e s Rev. 2 2.4 Abnormal Conditions Postulated abnormal conditions associated with final waste characterization and burial at the USEI site concern the potential for an increase in uranium mass and/or concentration levels on receipt, or following emplacement within the disposal system.

The following postulated criticality scenarios are discussed and assessed in this section:

• Concentration limit is exceeded when exhumed burial waste/contaminated soil is prepared for shipment;

• Concentration limit is exceeded when solids recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.,) are prepared for shipment;

" Wrong material is loaded for shipment to the USEI site; and

" Migration and localized concentration of 235U in USEI Landfill Cells, Leachate System, and/or Evaporation pond.

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NCSA of the US Ecology Idaho (USEI) Site NuclearSa.ety NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.4.1 Concentration Limit is Exceeded when Exhumed Burial Waste/

Contaminated Soil is Prepared for Shipment 2.4.1.1 Discussion Any waste shipped from the Hematite site to the USEI site must not exceed an average concentration of 0.1 g235U/L. This concentration limit is below the concentration limit for transportation and is substantially below (by a factor of 40) the maximum subcritical infinite sea concentration of 4.0 g235U/L for nominal soil (Appendix A).

This upset scenario involves the waste being improperly characterized for shipment, with the potential to ship waste with an excessively high 235U concentration to be USEI site.

However, the risk assessment that follows demonstrates that the resulting accident sequence is not credible to result in a criticality incident at the USEI site. This assessment is based on the risk presented by excavation operations in the documented burial pit area and is considered to bound other buried waste and contaminated soil areas. Therefore, areas that are subject to reduced NCS controls or are exempt from NCS controls (as justified in a HDP NCSA) are not explicitly discussed in this NCSA.

2.4.1.2 Risk Assessment Based on historic data it is unlikely that the burial pits, individually, could contain an unsafe mass of 235U. According to the documented burial logs (Ref. 5), the recorded total uranium mass associated with the historic waste consignments range from 178 g235U to 802 g 235U per burial pit. Based on best available information, it is believed that the burial pits are nominally 20' x 40' and 12' deep. Using these approximate burial pit dimensions and the highest recorded burial pit inventory of 802 g235U, it is seen that the average concentration of 235U within exhumed burial wastes and contaminated soils would likely not exceed -3.0 mg235U/L, even if no radiological monitoring performed and no segregation of fissile material was undertaken. This very low fissile concentration is more than three orders of magnitude less than the maximum subcritical infinite sea concentration of 4.0 g235U/L for nominal soil (Appendix A).

It is acknowledged that it is possible a burial pit could be excavated that contains burial waste with an elevated concentration of 235U, due to the compaction of process wastes (over time or from the remediation activities), or due to an unusually high incidence of high inventory process waste items in a localized burial area. The burial logs recorded at the time of operation of the burial pits indicate that the vast majority of the 15,000 waste consignments were assigned a nominal 1 g235U inventory, based on the limit of detection capability (Ref. 2). Only a very small number of waste consignments (ten) involved non-trivial 235U loadings. The waste consignments with the highest recorded 235U contents included:

" Wood filters (4 entries ranging from 22 to 44 g235U);

• Metal shavings (one entry at 41 g235U);

" Leco crucibles (4 entries ranging from 29 to 31.6 g235U); and 38 PRINTED COPIES ARE UNCONTROLLED

eNCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2

• Reactor tray (one entry at 40.4 g235U).

The nature of uranium residues associated with typical process wastes is such that it is improbable that the documented burial logs could be grossly in error with respect to fissile loading. Irrespective of the strict documented logging of process waste consignments, which were conducted under procedures in place at the time (Ref. 5), the quantity of 235U associated with the buried wastes would be expected to be low, in criticality safety terms, because:

• Economic and operational incentives would have ensured that the 235u associated with the buried wastes would have been present only as surface contamination. In particular, Highly Enriched Uranium (HEU) had high economic value and there would have been very strong incentives to fully utilize and account for all HEU.

" The dangers of uncontrolled handling of fissile material were fully appreciated during the 1950s, 1960s and 1970s, as by that time several fatalities had been reported.

It is very unlikely that potentially unsafe items would have been deliberately consigned to the burial pits, as operators preparing the waste would have been fully aware of the dangers.

Even if the documented burial logs were grossly in error with regard to fissile loading, the random factors of fissile material distribution, the very high fissile to non-fissile ratio associated with contaminated soil/wastes, and the poor moderating property and reasonable parasitic neutron absorption characteristics of the soil/waste matrix would, in practice, ensure the safety of exhumed buried wastes and contaminated soils.

Unless exempted by an NCSA, prior to removal of soil/waste from a burial area of the Hematite site, comprehensive in-situ radiological survey and visual inspection of the area to be exhumed is undertaken to identify Non-NCS Exempt Materials including Hot Spots, Intact Containers, and Non-Conforming Items. Refer to the discussion in Section 1.5.1 for further details.

Following removal of the identified Non-NCS Exempt Materials the remaining NCS Exempt Materials (up to the maximum permitted cut depth) are exhumed and consigned to the USEI site for disposal. This process ensures that the waste materials consigned to the USEI site for disposal do not comprise an average fissile nuclide concentration exceeding 0.1 g235U/L.

Even if the burial waste/soil exhumed contained a significant uranium concentration, the in-situ radiological survey and visual inspection activities described above would have to fail concurrently before the 0.1 g235U/L average concentration limit could be exceeded for shipment to the USEI site. In addition, the potential to bulk and ultimately ship high 235U concentration wastes to the USEI site is further reduced because the in-situ radiological survey and visual inspection activities are independently performed by two qualified individuals. Based on these considerations, there is no potential for a criticality incident during bulking of wastes at the Hematite site in preparation for shipment, and subsequently, during receipt and burial of the Hematite wastes at the USEI site. This is because this scenario requires independent verifications of the uranium concentration to fail concurrently with the low probability of encountering materials with high uranium 39 PRINTED COPIES ARE UNCONTROLLED

O afetW NCSA of the US Ecology Idaho (USEI) Site uclearaNSA-TR-09-14 A s s o c i a t e s Rev. 2 concentrations.

2.4.1.3 Summary of Risk Assessment Based on the discussion provided above, it is concluded that the following conditions must occur before a criticality accident due to transferring remediation wastes from the Hematite site to the USEI site would be possible:

" Failure of multiple independent simple administrative Criticality Safety Controls (CSCs) related to conducting in-situ radiological surveys and visual inspection to identify Non-NCS Exempt Material would have to occur; and

" The exhumed soil/waste would have to comprise material with a 235U concentration more than three orders of magnitude greater than the worst-case average uranium concentration recorded in the burial logs; and

" The uranium would have to be of a high 235U enrichment; and

• Non fissile and non-hydrogenous elements (e.g., soil) would have to be non-abundant, otherwise these constituents would result in dilution and parasitic neutron absorption.

2.4.1.4 Safety Controls The explicit CSCs relevant to ensuring concentration control for receipt and burial of Hematite wastes at the USEI site are provided below. In addition, a practicable measure for reducing criticality risk is identified and listed as Defense-in-Depth (DinD) control. Its implementation will ensure that the risks from criticality are as low as is reasonably achievable.

Administrative CSC 01: Unless approved by another NCSA, only the following waste with maximum average concentration of 0.1 g235U/L SHALL be allowed for shipment to USE1."

1. Exhumed burial waste from the Hematite burial pits and contaminated soils and backfill materials associated with the Hematite burial pits and other remediation areas of the hematite site

2. Solids recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.).

Administrative CSC 02:

All HDP remediation areas SHALL be radiologically surveyed to identify Hot Spots prior to exhumation of any material, unless exempted by an NCSA. Any identified Hot Spots SHALL be extracted, loaded into a Field Container, and containerized in a CD in accordance with the applicable fissile material exhumation and handling procedures. Following removal, the surveyed area SHALL be re-surveyed to verify the removal of all Hot Spots. Upon confirmation, the remaining portion(s) of the surveyed area may be exhumed to a depth not exceeding the maximum permitted cut-depth, and 40 PRINTED COPIES ARE UNCONTROLLED

la afety NCSA of the US Ecology Idaho (USEI) Site Nule irSa NSA-TR-09-14 A s s o c i a t e s Rev. 2 dispositioned as NCS Exempt Material.

Notes:

1. Hot Spots are defined according to the criteria in NSA-TR-09-15 Adm CSC 04.

2. Sample(s) may be extracted and analyzed for 235U content, and the results used in lieu of in-situ radiological survey results, provided that the samples analyzed are representative of or bound, the entire Hot Spot under investigation.

3. Sample extraction, packaging, transport, and analysis SHALL be performed in accordance with the governing NCSA for these operations.

4. The collar associated with the CD being loaded may be fitted after the drum has been loaded Administrative CSC 03:

In conjunction with in-situ radiological surveys, all HDP remediation areas SHALL be visually inspected prior to exhumation of any material, unless exempted by an NCSA. In the event that any items are identified to potentially comprise Non-NCS Exempt Material (e.g., a process filter is identified), the item(s) SHALL be extracted, placed inside a Field Container, and containerized in a CD, in accordance with the applicable fissile material exhumation and handling procedures.

Notes:

1. Non-NCS Exempt items that possess a volume greater than that of a Field Container may be placed directly into a CD.

2. The collar associated with the CD being loaded may be fitted after the drum has been loaded Administrative CSC 04: Radiological surveys performed in support of CSCs SHALL use only equipment that is approvied and appropriately calibrated to satisfy the NCS Performance Requirement of accounting for potential under-reading due to the effect of credible -variation in uranium distribution, particle size and attenuation of the photon intensity within the surrounding soil/waste medium.

Notes:

1. The NCS Performance Requirement for in-situ radiological surveys dictates that the in-situ radiological screening criteria used for remediation operations is not greater than the detector response imputed for both of the conditions defined below:

a. A uniform distribution of 235U throughout nominal soil up to the maximum permitted cut depth and with a 235U concentration of 0.1 1 235U/L.

b. A compact spherical accumulation of 235 U/nominal soil that 41 PRINTED COPIES ARE UNCONTROLLED

SNfety NCSA. of the US Ecology Idaho (USEI) Site x~,N ucea rSaft NSA-TR-09-14 A s s o c i a t e s Rev. 2 is situated at the base of the maximum permitted cut depth, comprises a total 235U mass content of 350 g235U, and is surrounded by nominal soil.

Administrative CSC 05:

In conjunction with in-situ radiological surveys, all HDP remediation areas SHALL be visually inspected prior to exhumation of any material, unless exempted by an NCSA. In the event that any of the following items are identified, the identified items SHALL be extracted and containerized individually in a CD (i.e., one item per CD) or multiple items per CD consistent with NSA-TR-09-15 Adm CSC 16:

" Items that resemble intact containers;

" Non-Conforming Items (i.e., bulky objects with linear dimensions exceeding the permitted cut depth, and thick metallic items).

Notes:

1. This CSC does not apply to individual Non-Conforming Items when inspected local to the excavation area and determined (using an approved method) to not comprise any significant 235U content. This CSC also does not apply to exhumed Intact Containers that are designated as NCS Exempt Material based on the results of close-proximity radiological surveys of their surfaces (specifically, a fissile nuclide concentration not exceeding 0.1 g2 35 U/L, or a fissile nuclide mass content not exceeding 15 gý35U and occupying a container with a volume of at least 5 liters).

2. The approved inspection methods for determining if an exhumed Non-Conforming Item constitutes Non-NCS Exempt Material are as follows. At least one of these three methods SHALL be applied to determine if an exhumed Non-Conforming Item represents Non-NCS Exempt Material Note that these methods are not required to be applied if the exhumed item is conservatively treated as Non-NCS Exempt Material without any inspection at the excavation area:

a. The item is confirmed to be free of interior spaces (i.e.,

voids) and is determined by radiological surveys of its exterior surfaces to not comprise (as surface contamination) an average fissile nuclide concentration exceeding 0.1 g235U/L.

b. The item satisfies the external surfaces criteria specified in (a) and comprises interior spaces/voids that have been sampled, visually inspected, and/or radiologically surveyed and determined to not comprise material with an average fissile nuclide concentration exceeding 0.1 g235U/L.

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O Nu fety NCSA of the US Ecology Idaho (USEI) Site u earSate NSA-TR-09-14 s s o ci a t e s Rev. 2

c. NCS staff have evaluated the item and determined that it qualifies as NCS Exempt Material based on visual inspections, radiological surveys, or sampling and analysis.

3. The NCS Organization SHALL be contacted for direction in the event that any individual item is too large to fit within a CD.

4. The collar associated with the CD being loaded may be fitted after the "drum has been loaded Administrative CSC 06: Following removal of any identified Non-NCS Exempt Materials from a HDP remediation area, the remaining portion(s) of the radiologically surveyed area may be exhumed and dispositioned as NCS Exempt Material.

However, the material excavation depth SHALL NOT exceed the maximum permitted cut depth established in the radiological survey equipment calibration basis.

Notes:

1. Exceeding the maximum permitted cut depth is an anticipated process upset due to the potential difficulty in performing precise depth excavations.

More than three concurrent instances of failing. to adhere to the maximum permitted cut depth in an excavation area would not present any credible criticality safety concerns, and is credited as an unlikely condition. Consequently, more than three concurrent instances of failing to adhere to the maximum permitted cut depth constitutes a violation of this CSC.

Administrative CSC 07: In the event that a large Intact Container or Non-Conforming Item is identified during visual inspection of a remediation area, removal of material surrounding the item may be necessary in order to facilitate its removal. In this case, the surrounding material SHALL be removed and handled consistent with the fissile material exhumation and handling procedures.

Notes:

1. Intact Containers and Non-Conforming Items may be exhumed by other means (e.g., hoist or crane) provided that the removal method selected minimizes the potential for disturbance of other buried materials compared to other practicable removal methods.

Administrative CSC 08:

Designated Non-NCS Exempt Material SHALL not be consigned to the USEI site for disposal unless evaluated for fissile concentration in a WEA, and/or a MAA and established to actually not contain an average 235 U concentration greater than 0.1 g235 U/L, or distributed within low 2 35 U concentration waste and 43 PRINTED COPIES ARE UNCONTROLLED

NCSA of the US Ecology Idaho (USEI) Site N uclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 demonstrated to not contain an average 235U concentration greater than

0. 1 g235 U/L.

Administrative CSC 09: Administrative CSCs NSA-TR-09-14 CSC 02, 03, 05, 06, 07, and 08 SHALL be followed/observed by a second individual that is independent of the first individual. Equipment used by the second individual in support of these CSCs SHALL be independent of the equipment used by the first individual.

Notes:

1. Independent equipment is defined as equipment that is physically separate. Such equipment may be either diverse (i.e., different manufacturer and/or model) or non-diverse (i.e.,

same manufacturer and model).

2. NSA-TR-09-14 CSC 04 is not required to be independently followed/observed since the set point established in HDP work procedures to comply with CSC 04 is common to both surveys.

DinD Administrative Control 01: HDP remediation areas should be clearly sub-divided/marked with survey area(s) prior to performing radiological surveys by using marking paint, construction flags, and/or stakes, etc. In addition, physical markings or other suitable methods should be used to delineate any identified Hot Spots within each survey area.

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'o eNCSA of the US Ecology Idaho (USEI) Site SNucearSa NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.4.2 Concentration Limit is Exceeded When Solids Recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.,) are Prepared for Shipment 2.4.2.1 Discussion As stated previously, any waste shipped from the Hematite Site to the USEI site must not exceed an average concentration of 0.1 g235U/L. This is significantly below the maximum subcritical infinite sea concentration of 4.0 g235U/L for nominal soil (Appendix A).

This upset scenario involves the Hematite waste being improperly characterized for shipment, with the potential to ship waste with an excessively high ý35U concentration to be USEI site.

However, the risk assessment that follows demonstrates that the resulting accident sequence is not credible to result in a criticality incident at the USEI site.

2.4.2.2 Risk Assessment Waste Water Holding Tanks All sampling to date from wells both within the burial pit area of the Hematite site and around the site periphery consistently indicates minimal fissile contaminant presence in the ground water. The highest concentration observed for samples collected from site wells is only 0.16 mg 235U/L.

This highest recorded concentration is nearly four orders of magnitude less than the maximum subcritical infinite sea concentration of 4.0 g235U/L for nominal soil (Appendix A). Based on this minimal concentration, ground water collection and treatment in the WTS is not expected to accumulate an unsafe concentration of uranium.

It is not expected that large volumes of ground water will be contaminated to a level of 0.16 mg235U/L, however, even if this were to occur, the total mass of 235U associated with a completely filled 20,000 gallon capacity holding tank would be only -12 g. However, it is recognized that any settling of uranium particulates within a holding tank could result in a progressive accumulation of SNM over time.

A drum vacuum will be used to remove wet sediments from the bottom of the WTS Holding tanks. As operationally necessary, the water in a tank to be cleaned will first be emptied using a portable sump pump.

The sediments will be radiologically surveyed and/or sampled and analyzed for fissile contamination before removal from the holding tank and at least once a month during tank operations. If the radiological survey and/or sample assay results indicate that the subject solids contain an average concentration exceeding 0.1 g235UfL then the subject solids are designated as non-NCS Exempt Material and must be recovered* directly into CDs pre-loaded with absorbent material (e.g., an immobilizing compound) to soak up any residual water associated with the sediments. Each loaded drum will be lidded, transferred to a WEA/MAA, and subject to a primary

• The sediment recovery process will be achieved by opening the access hatches to the tank and guiding the vacuum suction hose intake to recover the designated non-NCS Exempt Material.

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NCSA of the US Ecology Idaho (USEI) Site NuclearSafe NSA-TR-09-14 A s s o c i a t e s Rev. 2 evaluation/assay measurement and a secondary independent evaluation/assay measurement, both of which will be independently verified to determine radiological content. In order to be shipped to the USEI site for burial, the evaluation/assay results must demonstrate that the contents of the drum(s) does not contain greater than 0.1 g235U/L. In the event that the drum content is established to meet NCS Exempt Material criteria at the Hematite, the materials will be aggregated with other bulk waste streams.

The combination of these two abovementioned independent measurements will ensure that these sources will meet the criteria for waste acceptance and burial at the USEI site. Based on these considerations, there is no potential for a criticality incident during bulking of solid wastes from the Hematite WTS holding tanks during preparation for shipment, and subsequently, during receipt and burial of these wastes at the USEI site. This is because this scenario requires independent verifications of the uranium concentration to fail concurrently with the low probability of encountering solids with high uranium concentrations in waste water.

Filtration and Ion Exchange Equipment As stated above, all sampling to date from wells both within the burial pit area of the Hematite site and around the site periphery consistently indicates minimal fissile contaminant presence in the ground water. Based on this minimal concentration, ground water collection and treatment in the WTS, including the numerous treatment / filtration equipment, poses little risk of criticality.

In practice, any fissile contaminants entrained in collected water would be accompanied by a far greater quantity of non-fissile, inert particulates, such as soil sediments, etc.

Consequently, any fissile particulates deposited in the WTS treatment / filtration equipment will likely be diluted by a significant quantity of non-fissile material, which generally represent significantly poorer moderators than water*. These material characteristics serve to increase the mass of fissile material required before a criticality accident would be possible.

Recovery and containerization of soiled filters from filtration equipment is achieved by manually accessing the filtration unit, removing the soiled filter and placing the soiled filter in a waste drum. Based on the insufficient fissile material mass within any individual equipment, and the servicing (i.e., recovery of solids) from only one equipment at any one time, it is seen that containerization of solid wastes does not present any criticality risk under normal conditions.

Following loading of a waste drum with solid wastes, the loaded drum is lidded, transferred

• Soil is a significantly poorer moderator than water. For example, the minimum critical mass in a plutonium system moderated by fully water saturated soil (40% soil-in-water) (Fig II.A.6(97)-4 of Ref. 13) is a factor of -2.5 greater than the minimum critical mass for an otherwise equivalent aqueous system (Fig III.A.6-1 of Ref. 13).

Scaling the minimum critical mass of 235U in water (820 g, Table A-i) by the this ratio (2.5), it is estimated that a minimum of -2 kg(235U) would be required for a criticality to be possible by adsorption in soil. Note that the soil composition for the above data is defined in Table III.A.1-6 of Ref. 13.

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Nc fety NCSA of the US Ecology Idaho (USEI) Site s

NuciearSa t NSA-TR-09-14 A s s o c i a t e s Rev. 2 to a WEA/MAA, and subject to a primary evaluation/assay measurement and a secondary evaluation/assay measurement, both of which will be independently verified to determine radiological content. In order to be shipped to the USEI site for burial, the evaluation/assay results must demonstrate that the drum content does not contain greater than 0.1 g235U/L.

In the event that the drum content is established to meet NCS Exempt Material criteria at the Hematite site, the materials will be aggregated with other bulk waste streams.

The treatment beds (GAC and IX) will require periodic changing (need for changing is determined by measurement of the head pressure required to pump water through the respective treatment vessel). Unlike the bag filters, the GAC units will be backwashed to break up the carbon bed and remove entrained solids that are plugging or blinding the carbon bed. Treated effluent water from a tank will be used as backwash water. Water will be pumped from the tank backwards (up) through the GAC vessel being backwashed. The system is designed so that one set of two (2) GAC absorbers can be taken off-line for servicing or backwashing while the system runs at capacity (50 gpm) with only the second set of two (2) GAC units on-line. Backwash water from the GAC vessel being backwashed flows under pressure back to the inlet of storage tank T-3 for removal of suspended solids from the backwash water.

Prior to any replacement of the GAC media, the GAC vessel is valved out of service and the treatment media blown down with a portable air compressor, as necessary, to effectively dry the media. Samples of the media are extracted via the access ports on the media vessel and analyzed for fissile contamination at least once a week during operation to further ensure no significant fissile material concentration accumulates. However, it is noted that radiological survey of the vessels may be performed in lieu of sampling and analysis provided that it is performed with at least the same frequency. In the event that the radiological survey and/or sample assay results indicate that the solids to be removed contain an average concentration exceeding 0.1 g235U/L, then the subject solids are designated as non-NCS Exempt Material and must be recovered directly into CDs pre-loaded with absorbent material, as necessary, to soak up any residual water associated with the solids. The loaded CDs are then lidded, transferred to a WEA/MAA, and subject to a primary evaluation/assay measurement and a secondary independent evaluation/assay measurement, both of which will be independently verified to determine radiological content In order to be shipped to the USEI site for burial, the evaluation/assay results must demonstrate that the drum content does not contain greater than 0.1 g235U/L. In the event that the drum content is established to meet NCS Exempt Material criteria at the Hematite site, the materials will be aggregated with other bulk waste streams.

The combination of the two abovementioned independent measurements will ensure that these sources will meet the criteria for waste acceptance and burial at the USEI site. Based on these considerations, there is no potential for a criticality incident during bulking of Hematite WTS ion exchange media and filter bags during preparation for shipment, and subsequently, during receipt and burial of these wastes at the USEI site. This is because this scenario requires independent verifications of the uranium concentration to fail concurrently with the low probability of colleting any significant uranium concentration 47 PRINTED COPIES ARE UNCONTROLLED

Nu featy NCSA of the US Ecology Idaho (USEI) Site Nuclear NSA-TR-09-14 A s s o c i a t e s Rev. 2 from the waste water.

2.4.2.3 Summary of Risk Assessment Based on the discussion provided above, it is concluded that the following conditions must occur before a criticality accident due to transferring WTS solid wastes from the Hematite site to the USEI site would be possible:

" Failure of multiple independent simple administrative CSCs related to conducting waste evaluation and/or assay measurements would have to occur; and

" The WTS solid wastes would have to comprise material with a 235u concentration more than three orders of magnitude greater than the worst-case average uranium concentration recorded in the burial logs; and

• The uranium would have to be of a high 235U enrichment; and

" Non fissile and non-hydrogenous elements (e.g., soil) would have to be non-abundant, otherwise these constituents would result in dilution and parasitic neutron absorption.

2.4.2.4 Safety Controls The explicit CSCs relevant to ensuring concentration control for receipt and burial of Hematite WTS solid wastes at the USEI site are provided below. In addition, a practicable measure for reducing criticality risk is identified and listed as DinD control.

Its implementation will ensure that the risks from criticality are as low as is reasonably achievable.

Administrative CSC 10: Prior to shipping any WTS solids to the USEI site for burial, the WTS solids (i.e., used filter media, IX beds, solids in the holding tanks, etc.,) identified as Non-NCS Exempt Material through radiological survey and/or sampling and assay SHALL be distributed as necessary and re-evaluated for fissile concentration in a WEA and/or a MAA and established to not contain an average 235U concentration greater than 0.1 g23S U/L.

Administrative CSC 11: Administrative CSC NSA-TR-09-14 CSC 10 SHALL be followed by a second individual that is independent of the first individual. Equipment used by the second individual in support of this CSC SHALL be independent of the equipment used by the first individual, unless approved by an NCSA.

Notes:

1. Independent equipment is defined as equipment that is physically separate. Such equipment may be either diverse (i.e., different manufacturer and/or model) or non-diverse (i.e.,

same manufacturer and model).

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i' fety NCSA of the US Ecology Idaho (USEI) Site NucearSaf NSA-TR-09-14 A s s o c i a t e s Rev. 2 In support of the above Administrative CSCs, radiological survey equipment used for w&aste evaluation operations in a WEA and assay equipment used for material assay operations in a MLAA are designated as Safety Related Equipment, the Safety Functional Requirement being to permit estimation of 235U content when properly calibrated and used in accordance with applicable procedures.

Safety Related Equipment 02:

Radiological survey and assay equipment used in support of waste evaluation operations in a WEA and material assay operations in a M4A (when used in support of a CSC)

SHALL be capable of measuring 235U content when used in conjunction with approved hardware/software (e.g., ISOCS) or an approved calibration basis.

DinD Administrative Control 02: Settled sediments in each of the WTS Holding Tanks should be radiologically surveyed and/or sampled and assayed for 235U content according to the following schedule:

• At least once per month during excavation activities; and

• Prior to clean-out of the sediments from a tank.

In the event a sample assay result indicates a 235U concentration

>0.1 mg/cc (>0.1 g/L) then the NCS organization should be notified.

DinD Administrative Control 03:

The filtration (bag filters) and treatment media (GAC and ion exchange beds) should be radiologically surveyed and/or sampled and assayed for 235U content at least once per week during excavation activities. In the event radiological survey result or sample assay result indicates a 235U mass >350 g 235U further use of the associated media should be discontinued and the NCS organization notified.

DinD Administrative Control 04:

GAC and ion exchange media should be radiologically surveyed and/or sampled and assayed for 235U content prior to clean-out of the media. In the event a sample assay result indicates a 235U concentration >0.1 mg/cc (>0.1 g/L) then the NCS organization should be notified.

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N r

fet NCSA of the US Ecology Idaho (USEI) Site NA ucearSa t NSA-TR-09-14 A s s o cia t e s Rev. 2 2.4.3 Wrong Material is Loaded for Shipment to USEI 2.4.3.1 Discussion As stated previously, any waste shipped from the Hematite Site must not exceed an average concentration of 0.1 g235U/L. This is significantly below the maximum subcritical infinite sea concentration of 4.0 g235U/L for nominal soil (Appendix A).

This upset scenario involves loading the wrong waste for shipment. This upset has the potential to allow the concentration limit to be exceeded by shipping higher concentration non NCS Exempt Materials segregated at the Hematite site to the USEI site. However, the risk assessment that follows demonstrates that the resulting accident sequence is not credible to result in a criticality incident at the USEI site.

2.4.3.2 Risk Assessment As demonstrated in all the previous scenarios for the different sources of wastes, it is considered improbable that the waste streams will contain a 235U average concentration above the 0.1 g235U/L limit for acceptance at the USEI site based on the types of wastes and the low probability of encountering significant concentrations of uranium.

Furthermore, the sampling of wells and soils across the site indicate concentrations well below the USEI concentration limit. In addition to the low likelihood that any wastes with significant concentration will be exhumed, strict controls will be in place to segregate and properly label waste, if waste streams are generated with concentrations above the USEI limits. The controls will be used in up front processes to not only ensure the USEI limits are met, but also to maintain criticality safety at the Hematite site during remediation activities. These strict controls are discussed below.

Based on the results of in-situ monitoring, Hot Spots will be exhumed either into Field Containers as large as 20 liter volume containers (equivalent to a nominal 5-gallon container) and over-packed into collared 55-gallon or larger diameter drums.

The containerized materials will be subsequently transferred to a waste evaluation area for detailed characterization. In the waste evaluation area the waste will be spread to create a thin layer on a 'sorting surface'. Visual inspection and gamma survey (using hand-held gamma detectors) will be used to identify any uranium that is discrete within the waste matrix. Portion(s) of the waste matrix determined to not contain uranium (or to contain acceptably low uranium content) will be extracted and returned to the main waste stream.

The remaining portion(s) of the waste matrix will be packaged into a known geometry container (up to 20 liters in volume) and transferred to an adjacent area for counting using a High Resolution Gamma Spectrometer (HRGS). The HRGS equipment returns a total 235U mass content for the package.

The HRGS mass estimate is assigned to the assayed container, which is labeled with a description of the container content, an item number, date, and 235U mass. The container is then transferred within a collared drum to a secure area for storage or to a repack area (in the event that the drum 235U mass content is relatively small).

In the collared drum repacking area, the drum content (i.e., inner container) is removed 50 PRINTED COPIES ARE UNCONTROLLED

A e

fety NCSA of the US Ecology Idaho (USEI) Site NucearSaf NSA-TR-09-14 A s s o c i a t e s Rev. 2 from the drum and placed into an empty or partially filled standard 55 gallon waste drum (if allowed by packaging limits). The drum inventory log traveler is updated to reflect the new consignment.

The Entry and Repack Zone is the only entrance/exit into or from the secure area. All Non-NCS Exempt Material generated from site operations is brought in collared drums into this Entry and Repack Zone for proper logging of the material. The secure area personnel are given advance notice prior to all transfers to the secure area. The doors of the Entry and Repack Zone are maintained in a locked condition when the secure area is not in operation.

When a collared drum is introduced into the Entry and Repack Zone, personnel first ensure that other Non-NCS Exempt Material is not present in the Entry and Repack Zone. Since the purpose of this Entry and Repack Zone is to consolidate Non-NCS Exempt Material into 55-gallon drums for subsequent storage, the personnel determine an appropriate stored 55-gallon drum to retrieve from the Storage Zone and transfer it to the Entry and Repack Zone. The item from the collared drum is removed and placed into the retrieved 55-gallon drum. The 235U mass tally on the drum is properly updated. The drum is then re-lidded and returned to the Storage Zone. The empty collared drum is verified empty and removed from the secure area. The drum repacking limit is <125 g235U per drum.

All Non-NCS Exempt Material introduced into the Entry and Repack Zone and subsequent consolidations/transfers are logged by the personnel. To ensure that too much Non-NCS Exempt Material does not exist at any given, time within the Entry and Repack Zone, a minimum of two operators with adequate supervision/oversight (such as security cameras) are always present when the secure area doors are unlocked. This ensures that Non-NCS Exempt Material is not brought into the Entry and Repack Zone without the recognition and acceptance of the secure area personnel and supervision. In addition, only a single package of containerized Non-NCS Exempt Material along with an appropriate consolidation drum is approved at a time within the Entry and Repack Zone thereby also preventing too much Non-NCS Exempt Material in this zone at a time.

Operations in a secure storage area that is not also a repack area attract the same generic container logging, entry, segregation and oversight controls.

Even if exhumed burial waste contained a significant uranium concentration, the container labeling and the very prescriptive segregation of the waste that does not meet the USEI limits would have to fail concurrently before any waste could be loaded for shipment to USEI.

Based on these considerations, there is no potential for a criticality incident due to inadvertent transfer of high concentration Hematite segregated wastes to the USEI site.

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NCSA of the US Ecology Idaho (USEI) Site Nuclear afety NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.4.3.3 Summary of Risk Assessment Based on the discussion provided above, it is concluded that the following conditions must occur before a criticality accident due to inadvertently transferring high concentration Hematite segregated wastes to the USEI site would be possible:

" Failure of multiple independent simple administrative CSCs related to segregating and properly labeling Non-NCS Exempt Material, and not allowing shipment of such wastes with concentrations above the USEI limits; and

" The Non-NCS Exempt Material would have to comprise material with a 235u concentration significantly higher than expected based or process history and sampling.

2.4.3.4 Safety Controls The explicit CSCs relevant to ensuring concentration control for receipt and burial of "Hematite WTS solid wastes at the USEI site are provided below.

In addition, CSCs relevant to ensuring segregation of high 235U concentration wastes at the Hematite site are also provided below. These controls ensure that the risks from criticality are as low as is reasonably achievable.

Administrative CSC 01: Unless approved by another NCSA, only the following waste with maximum average concentration of 0.1 g235U/L SHALL be allowed for shipment to USEI."

1. Exhumed burial waste from the Hematite burial pits and contaminated soils and backfill materials associated with the Hematite burial pits and other remediation areas of the hematite site

2.

Solids recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.).

Administrative CSC 12:

The number of qualified personnel present within (or within cognitive surveillance of) a CD repack and storage area during all activities SIHALL be a minimum of three.

Administrative CSC 13: Secure area doors (and zone doors within) each CD repack and storage area SHALL be maintained closed when not in use. The doors SHALL be maintained with two locks in proper working condition. The combination or key of each lock SHALL be different. Supervision SHALL maintain confidentiality from operators of one lock combination or key while operators SHALL maintain confidentiality from supervision of the second lock., Particularly, at no time, will the combination of both locks be known by a single individual.

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1NuclearSafety A s s o cia t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Administrative CSC 14:

Movement/handling of Non-NCS Exempt Materials SHALL be accompanied by at least tvo different persons that are cognizant offissile material handling responsibilities.

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SNul fet NCSA of the US Ecology Idaho (USEI) Site 21#'NuclearSafe NSA-TR-09-14 A s s o c i a t e s Rev. 2 2.4.4 Migration and Localized Concentration of 235U in USEI Landfill Cells, Leachate System, and/or Evaporation pond 2.4.4.1 Discussion The preceding event sequences in this NCSA demonstrate that there is no potential to ship Hematite wastes with an average concentration exceeding 0.1 g235U/L to the USEI site.

This low concentration level is significantly below the maximum subcritical infinite sea concentration of 4.0 g235U/L for nominal soil (Appendix A). This low concentration level is also substantially below a fictitious minimum critical concentration of 1.4 g235U/L for bounding soil consisting of only SiO2 per NUREG/CR-6505 (Ref. 17).

This upset scenario pertains to the 235U migration and reconfiguration into an area of the cell that exceeds the minimum critical concentration.

The risk assessment that follows demonstrates that the resulting accident sequence is not credible to result in a criticality incident.

2.4.4.2 Risk Assessment NUREG/CR-6505 (Ref. 17, pg. 45) demonstrates that nominal soil in a slab configuration requires a lower areal density for a criticality to be possible versus a cylindrical or spherical geometry.

For instance, at a concentration of 0.006 g235U/cm3 (i.e., 6 kg235U/L), the calculated critical areal density is 5.2 kg 235U/m 2 for an infinite slab in a planar configuration whereas the corresponding critical linear density for an infinite cylinder is 7.8 kg 235U/m2.

Therefore, achieving a criticality in a cylindrical geometry requires significant lateral and vertical 235U migration. In addition, NUREG/CR-6505 (Ref. 17, pg.

46) demonstrates the corresponding critical areal density for a spherical geometry is 9.34 kg 235U/m2. Based on the above comparisons, a slab provides the most likely condition for a possible criticality.

Considering that a slab provides the most efficient condition for a criticality, NUREG/CR-6505 (Ref. 17, pg. 96) demonstrates that a slab thickness of 2131 cm.and areal density of 30.2 kg/mi2 is required for a criticality to be possible for corresponding density of 1.4 g235U/L for bounding Si0 2 soil. Therefore, not only does the Hematite waste average concentration of 0.1 g235U/L have to increase by a factor of more than ten, but a significant quantity has to migrate to a layer at least 2131 cm (21.31 m) thick for a criticality to be possible.

For higher 235U concentrations a smaller slab thickness is required, but the concentration factor must also be higher before a criticality could be possible.

For instance, NUREG/CR-6505 (Ref. 17, pg. 99) demonstrates that a slab thickness of 94.57 cm and areal density of 5.4039 kg/mr2 is critical, corresponding to a density of 5.7 g235U/L for the bounding SiO2 soil.

Also, for nominal soil NUREG/CR-6505 (Ref. 17, pg. 94) demonstrates that a slab thickness of 78.86 cm and areal density of 4.732 kg/m 2 is critical, corresponding density of 6.0 g235U/L.

The maximum safe 235U mass of 760 g235U corresponds to a full water-reflected spherical homooeneous mixture of 235U and water -14 L in volume at an optimum concentration of 55 g2ý3 U/L (Ref. 16). It is not reasonable to postulate that such idealized conditions could 54 PRINTED COPIES ARE UNCONTROLLED

et NCSA of the US Ecology Idaho (USEI) Site NuclearSa NSA-TR-09-14 A s s o c i a t e s Rev. 2 be achieved or even approximated in a waste/soil due to the poor moderating characteristics of these soil/waste matefials, relative to full density water, as previously noted. In practice an accumulation representing kilogram quantities of fissile material would be required in a compact volume, and with an efficient geometry and distribution, before a criticality could credibly occur.

Section 10 of NUREG/CR-6505 (Ref. 17, pg. 45) concludes that a concentration factor of greater than ten is not considered credible for migration of 235U' based on the hydrogeochemical modeling and assumptions used for the Envirocare Site. Section 1.4 of NUREG/CR-6505 (Ref. 17, pg. 2) states that no other sites were considered, but the same analysis methods can be used to evaluate other sites. Therefore, the methodology was compared to the conditions at the USEI site and Reference 20 confirms that the methods and results in NUREG/CR-6505 also support that a concentration factor of-greater than ten is also not considered credible for migration of 235U at the USEI site. As stated above, the concentration limit is 0.1 g235U/L for waste shipments from the Hematite site to the USEI site. Based on this low concentration level, a criticality incident is not credible at the USEI site due to migration and concentration of 235U, because it would require a concentration increase by more than a factor of ten and Reference 20 concludes that a concentration increase by more than a factor often is not credible.

The conclusion that a criticality is not credible at the USEI site is further supported by the following supporting information.

Disposal Cell Placement Practices Once in the cell, the concentration of 235U will be reduced by the process of spreading and the inevitable commingling of the Hematite waste with other materials in the cell. This occurs because the Hematite waste will be emplaced concurrently with wastes from other generators. The projected receipts from Hematite are expected to be received over a period of nine months and would comprise approximately five 20-ton truck shipments daily. Since the USEI site receives an average of one hundred 20-ton truck shipments daily, the 235U concentration in the Hematite waste is likely to be reduced by a factor of 20 as a result of the disposal process.

Since the average precipitation at the facility is only 5-7 inches per year, with an evapo-transpiration potential of greater than 42 inches per year, there is very little potential for infiltration once the cell is closed. Since the uranium is an oxide and the cell is an anoxic environment with an approximate pH of 10, it is not readily transportable.

Much of the waste that will be received concurrent to the Hematite waste receipts is treated prior to disposal. The treatment process involves the use of reagents, clay, or other materials that greatly reduce the potential for contaminants to be transported. These treated wastes, which will be commingled with the Hematite waste, will form barriers to moisture infiltration, and also reduce the potential for infiltration to transport any 235U that may leach from the Hematite waste.

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OIerS NCSA of the US Ecology Idaho (USEI) Site Niuclear~afety NSA-TR-09-14 A s s o c i a t e s Rev. 2 For these reasons, no concentration of Hematite waste is anticipated to occur due to existing waste placement practices. Rather, a 20-to-i dilution factor is projected due to waste placement.

Leachate Because USEI's disposal cell meets EPA's Minimum Technical Requirements (MTR), it is constructed of a triple liner system consisting of two synthetic liners and a natural clay liner. Leachate collection systems exist between the two synthetic liners, and above the top synthetic liner. Historic leachate generation data was analyzed to determine whether concentration could occur in the leachate or the leachate sump system.

USEI's disposal cells collect leachate that is generated as a result of precipitation in open cells, dust control water applied to waste in the cells, and condensation of moisture from wastes. Once a cell is closed, the amount of leachate produced decreases with time. The conditions at the USEI facility are such that after five years, leachate is generally no longer being produced in quantities to be pumped. Consequently, consistent with the MTR and design purpose of the cell, the infiltration transport mechanism is nullified for the long-term.

In 2008 USEI generated 300,000 gallons of leachate from its current active disposal cell (Cell 15). The leachate is produced primarily from precipitation and dust control water, and represents the most likely transport mechanism for contaminants in disposed wastes. The leachate is pumped regularly and sampled periodically by USEI, with results reported to the State of Idaho as a condition of the facility's operating permit. Due to the conditions in the disposal cell, the leachate produced meets EPA F039 Non-Wastewater treatment standards for inorganic metals. In other words, such low concentrations of heavy metals are found in USEI's leachate that it does not qualify as a "characteristic" hazardous waste., This is also supported by empirical data documented in annual reports to the State of Idaho and USEPA.

These facts support the view that extremely small quantities of 235U from Hematite waste, if any, would be expected to be transported to the leachate while Cell 15 remains open, and would present no criticality safety concern.

The Hematite waste is expected to be received over a period of nine months. As the waste is received, it will be commingled with other wastes. As the waste is covered, an infiltration and evaporative barrier is formed, limiting the moisture transport mechanism's ability to dissolve and transport available 235U from the Hematite waste.

USEI collects leachate from the sumps in four 16,500 gallon tanks. Periodically, USEI pumps the collected leachate in the tanks through an activated carbon filtration system. The carbon used in the filtration system is a coarse grain grade specifically designed to remove volatile organics and is ineffective for removing metals. Consequently, 235U or other inorganic contaminants do not concentrate in the carbon. Once a year, USEI checks the tanks for sediment and removes any that may have collected.

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fkiy NCSA of the US Ecology Idaho (USEI) Site N uclearSa NSA-TR-09-14 A s s o c i a t e s Rev. 2 Surface Impoundments (Collection and Evaporation Ponds)

Leachate collected in USEI's active landfill sumps is pumped by remote means through an enclosed piping system to large storage tanks where it is commingled with leachate produced by closed, non-radioactive disposal cells. A small dilution factor occurs, but is not used in the calculation below. Conversely, no further concentration occurs in the storage tanks.

Since the leachate produced at USEI's facility meets EPA F039 Non-Wastewater F039 treatment standards for inorganic heavy metals and all other chemicals pertaining to the F039 waste code, it is discharged from the interim storage tanks directly to a RCRA Subtitle K permitted surface impoundment.

All of the liquid being discharged to the surface impoundment is eventually evaporated. If 235U from the Hematite waste were to be discharged to the impoundment, it would be commingled with the sludge already in the impoundment. As of April 2009, the impoundment contains approximately 725 yards of sludge with a density of 90 lbs/ft3 (8.OOE x 108 g). Based on the extremely small quantities of 235U from Hematite waste, if any, that could be expected to be transported to the leachate while Cell 15 remains open, there would be an extremely high non-fissile/fissile material ratio, representing no potential for a criticality incident.

In summary, the waste placement practices, empirical leachate concentration data, and operating practices for USEI's surface impoundment support that the basis that there should be no increase in the 235U concentration to the extent that it would present a credible criticality concern. The conclusions made in References 17 and 20 also demonstrate that a concentration increase by a factor of ten or greater is not credible. Therefore, the conclusion above that a criticality is not considered credible is fully supported based on the 0.1g 235U/L Hematite waste concentration limit, considering a subcritical limit of 1.4 grams 23SU/L for a bounding soil (Si0 2 only) and the maximum subcritical infinite sea concentration of 4.0 g U/L for nominal soil (Appendix A).

2.4.4.3 Summary of Risk Assessment Based on the discussion provided above, it is concluded that it is not credible for this scenario to result in a criticality accident at the USEI site. Consequently no controls are identified to ensure the subcriticality of Hematite wastes at the USEI site. All the controls for this scenario are provided in previous accident sequences to ensure that the USEI site waste acceptance concentration limit of 0.1 g235U/L is not exceeded.

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5NuclearSafety A s so cia t es NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 3.0

SUMMARY

OF CRITICALITY SAFETY CONTROLS 3.1 Criticality Safety Parameters The extent of control of each of the various criticality safety parameters introduced in Section 2.1 is summarized in Table 3-1.

Table 3-1 Criticality Safety Parameters Nuclear Controlled Basis Reference Parameter (Y/N)

The safety assessment of receipt and Geometry N

burial of Hematite wastes at the USEI N/A site does not credit geometry.

The safety assessment of receipt and burial of Hematite wastes at the USEI site credits Interaction N

administrative CSCs to ensure that high Section 2.4.3 concentration wastes that may normally require spacing are not shipped to the USEI site.

The safety assessment of receipt and burial of Section 2.4.1 Hematite wastes at the USEI site credits administrative CSCs to ensure that there is no Section 2.4.3 potential to form a maximum safe mass at the Section 2.4.4 USE1 ite.Section 2.4.4 USEI site.

The safety assessment of receipt and burial of Hematite wastes at the USEI site is Isotopic I conservatively based on subcritical limits derived N/A Enrichment N

for uranium metal with 100 wt.% 235U/U enrichment.

The safety assessment of receipt and burial of Hematite wastes at the USEI site is Moderation N

conservatively based on subcritical limits derived N/A for uranium-H 20 and/or uranium-soil mixtures at optimum concentration.

The safety assessment of receipt and burial of Hematite wastes at the USEI site is Density N

conservatively based on subcritical limits derived N/A for uranium metal at maximum theoretical density.

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NuclearSafety Associates NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Nuclear Controlled Basis Reference Parameter (Y/N)

The safety assessment of receipt and burial of Hematite wastes at the USEI site is conservatively based on subcritical limits derived for homogeneous uranium-H 20 mixtures Heterogeneity N

(with 100 wt.% 235U/U enrichment), for N/A which subcritical limits are smaller than equivalent heterogeneous uranium-H 20 mixtures.

The safety assessment of receipt and burial of Neutron Hematite wastes at the USEI site does not credit N/A Absorbers fixed neutron absorbers.

The safety assessment of receipt and burial of Hematite wastes at the USEI site conservatively uses subcritical limits based on full (i.e., 30 cm)

Reflection N

thickness close fitting water reflection and/or soil N/A conditions, which are considered to bound any credible reflection condition.

The safety assessment of receipt and burial of Section 2.4.1 Hematite wastes at the USEI site credits administrative CSCs to ensure that there is no Section 2.4.3 potential to ship waste with an unanalyzed Section 2.4.4 concentration to the USEI site.

The safety assessment of receipt and burial of Volume N

Hematite wastes at the USEI site does not credit N/A volume control.

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fet NCSA of the US Ecology Idaho (USEI) Site N1 NudcearSa"e NSA-TR-09-I 4 A s s o c i a t e s Rev. 2 3.2 Criticality Safety Controls and Defense-in-Depth Controls This section provides a schedule of Systems, Structures, and Components (SSCs), CSCs and DinD controls that have been established as important to safety in the risk assessment of Hematite waste receipt and disposal at the USEI site.

3.2.1 Systems, Structures, and Components The following SSCs have been recognized as important to ensuring the criticality safety of Hematite waste receipt and disposal at the USEI site. The SSCs are identified as Safety Related Equipment (active function).

Safety Related Equipment 01: Instruments used in support of in-situ radiological surveys (when used in support of a CSC) SHALL be capable of measuring 235U content when used in conjunction with an approved calibration basis.

Safety Related Equipment 02:

Radiological survey and assay equipment used in support of waste evaluation operations in a WEA and material assay operations in a MAA (when used in support of a CSC)

SHALL be capable of measuring 235U content when used in conjunction with approved hardware/software (e.g., ISOCS) or an approved calibration basis.

3.2.2 Criticality Safety Controls The following CSCs have been recognized as important to ensuring the criticality safety of Hematite waste receipt and disposal at the USEI site.

Administrative CSC 01: Unless approved by another NCSA, only the following waste with maximum average concentration of 0.1 g235U/L SHALL be allowed for shipment to USEI:

1.

Exhumed burial waste from the Hematite burial pits and contaminated soils and backfill materials associated with the Hematite burial pits and other remediation areas of the hematite site.

.2.

Solids recovered from the Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.).

Administrative CSC 02:

All HDP remediation areas SHALL be radiologically surveyed to identify Hot Spots prior to exhumation of any material, unless exempted by an NCSA. Any identified Hot Spots SHALL be extracted, loaded into a Field Container, and containerized in a CD

• in accordance with the applicable fissile material exhumation and handling procedures. Following removal, the surveyed area SHALL be re-surveyed to verify the removal of all Hot Spots. Upon confirmation, the remaining portion(s) of the surveyed area may be exhumed to a 60 PRINTED COPIES ARE UNCONTROLLED

I 4., f NCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 depth not exceeding the maximum permitted cut-depth, and dispositioned as NCS Exempt Material.

Notes.

1. Hot Spots are defined according to the criteria in NSA-TR-09-15 Adm CSC 04.

2. Sample(s) may be extracted and analyzed for 235U content, and the results used in lieu of in-situ radiological survey results, provided that the samples analyzed are representative of, or bound, the entire Hot Spot under investigation.

3. Sample extraction, packaging, transport, and analysis SHALL be performed in accordance with the governing NCSA for these operations.

4. The collar associated with the CD being loaded may be fitted after the drum has been loaded.

Administrative CSC 03:

In conjunction with in-situ radiological surveys, all HDP remediation areas SHALL be visually inspected prior to exhumation of any material, unless exempted by an NCSA. In the event that any items are identified to potentially comprise Non-NCS Exempt Material (e.g., a process filter is identified), the item(s) SHALL be extracted, placed inside a Field Container, and containerized in a CD, in accordance with the applicable fissile material exhumation and handling procedures.

Notes:

1. Non-NCS Exempt items that possess a volume greater than that of a Field Container may be placed directly into a CD.

2. The collar associated with the CD being loaded may be fitted after the drum has been loaded.

Administrative CSC 04: Radiological surveys performed in support of CSCs SHALL use only equipment that is approved and appropriately calibrated to satisfy the NCS Performance Requirement of accounting for potential under-reading due to the effect of credible variation in uranium distribution, particle size and attenuation of the photon intensity within the surrounding soil/waste medium.

Notes:

1. The NCS Performance Requirement for in-situ radiological surveys dictates that the in-situ radiological screening criteria used for remediation operations is not greater than the detector response imputed for both of the conditions defined below:

a. A uniform distribution of 235U throughout nominal soil zupto the maximum permitted cut depth and with a U

concentration of 0. 1 g215U/L.

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W6fet1 NCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2

b. A compact spherical accumulation of 235 U/nominal soil that is situated at the base of the maximum permitted cut depth, comprises a total 235 U mass content of 350 g235U, and is surrounded by nominal soil.

Administrative CSC 05:

In conjunction with in-situ radiological surveys, all HDP remediation areas SHALL be visually inspected prior to exhumation of any material, unless exempted by an NCSA. In the event that any of the following items are identified, the identified items SHALL be extracted and containerized individually in a CD (i.e., one item per CD) or multiple items per CD consistent with NSA-TR-09-15 Adm CSC 16:

" Items that resemble intact containers;

" Non-Conforming Items (i.e., bulky objects with linear dimensions exceeding the permitted cut depth, and thick metallic items).

Notes:

1. This CSC does not apply to individual Non-Conforming Items when inspected local to the excavation area and determined (using an approved method) to not comprise any significant 235U content. This CSC also does not apply to exhumed Intact Containers that are designated as NCS Exempt Material based on the results of close-proximity radiological surveys of their surfaces (specifically, a fissile nuclide concentration not exceeding 0.1g U/L, or a fissile nuclide mass content not exceeding 15 g U and occupying a container with a volume of at least 5 liters).

2. The approved inspection methods for determining if an exhumed Non-Conforming Item constitutes Non-NCS Exempt Material are as follows. At least one of these three methods SHALL be applied to determine if an exhumed Non-Conforming Item represents Non-NCS Exempt Material. Note that these methods are not required to be applied if the exhumed item is conservatively treated as Non-NCS Exempt Material without any inspection at the excavation area:

a. The item is confirmed to be free of interior spaces (i.e.,

voids) and is determined by radiological surveys of its exterior surfaces to not comprise (as surface contamination) an average fissile nuclide concentration exceeding 0.1 g235U/L.

b. The item satisfies the external surfaces criteria specified in (a) and comprises interior spaces/voids that have been sampled, visually inspected, and/or radiologically surveyed and determined to not comprise material with an average fissile nuclide concentration exceeding 0.1 62 PRINTED COPIES ARE UNCONTROLLED

NCSA of the US Ecology Idaho (USEI) Site N uclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 g235 U/L.

c. NCS staff have evaluated the item and determined that it qualifies as NCS Exempt Material based on visual inspections, radiological surveys, or sampling and analysis.

3. The NCS Organization SHALL be contacted for direction in the event that any individual item is too large to fit within a CD.

4. The collar associated with the CD being loaded may be fitted after the drum has been loaded.

Administrative CSC 06: Following removal of any identified Non-NCS Exempt Materials from a HDP remediation area, the remaining portion(s) of the radiologically surveyed area may be exhumed and dispositioned as NCS Exempt Material.

However, the material excavation depth SHALL NOT exceed the maximum permitted cut depth established in the radiological survey equipment calibration basis.

Notes:

1. Exceeding the maximum permitted cut depth is an anticipated process upset due to the potential difficulty in peiforming precise depth excavations.

More than three concurrent instances of failing to adhere to the maximum permitted cut depth in an excavation area would not present any credible criticality safety concerns, and is credited as an unlikely condition. Consequently, more than three concurrent instances of failing to adhere to the maximum permitted cut depth constitutes a violation of this CSC.

Administrative CSC 07: In the event that a large Intact Container or Non-Conforming Item is identified during visual inspection of a remediation area, removal of material surrounding the item may be necessary in order to facilitate its removal. In this case, the surrounding material SHALL be removed and handled consistent with the fissile material exhumation and handling procedures.

Notes:

1. Intact Containers and Non-Conforming Items may be exhumed by other means (e.g., hoist or crane) provided that the removal method selected minimizes the potential for disturbance of other buried materials compared to other practicable removal methods.

Administrative CSC 08:

Designated Non-NCS Exempt Material SHALL not be consigned to the USEI site for disposal unless evaluated for fissile concentration in a WEA and/or a MAA and established to actually not contain an average 235U concentration greater than 0.1 63 PRINTED COPIES ARE UNCONTROLLED

O Nu fety NCSA of the US Ecology Idaho (USEI) Site uclear~ai NSA-TR-09-14 A s s o c i a t e s Rev. 2 g 235 U/L, or distributed within low 235U concentration waste and demonstrated to not contain an average 235U concentration greater than 0.1 g235U/L.

Administrative CSC 09: Administrative CSCs NSA-TR-09-14 CSC 02, 03, 05, 06, 07, and 08 SHALL be followed/observed by a second individual that is independent of the first individual. Equipment used by the second individual in support of these CSCs SHALL be independent of the equipment used by the first individual.

Notes:

1. Independent equipment is defined as equipment that is physically separate. Such equipment may be either diverse (i.e., different' manufacturer and/or model) or non-diverse (i.e.,

same manufacturer and model).

2. NSA-TR-09-14 CSC 04 is not required to be independently followed/observed since the set point established in HDP work procedures to comply with CSC 04 is common to both surveys.

Administrative CSC 10: Prior to shipping any WTS solids to the USEI site for burial, the WTS solids (i.e., used filter media, IX beds, solids in the holding tanks, etc.,) identified as Non-NCS Exempt Material through radiological survey and/or sampling and assay SHALL be distributed as necessary and re-evaluated for fissile concentration in a WEA and/or a MAA and established to not contain an average 235U concentration greater than 0.1 g235 U/L.

Administrative CSC 11: Administrative CSC NSA-TR-09-14 CSC 10 SHALL be followed by a second individual that is independent of the first individual. Equipment used by the second individual in support of this CSC SHALL be independent of the equipment used by the first individual, unless approved by an NCSA.

Notes:

1. Independent equipment is defined as equipment that is physically separate. Such equipment may be either diverse (i.e., different manufacturer and/or model) or non-diverse (i.e.,

same manufacturer and model).

Administrative CSC 12:

The number of qualified personnel present within (or within cognitive surveillance oj9 a CD repack and storage area during all activities SHALL be a minimum of three.

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N ftyNCSA of the US Ecology Idaho (USEI) Site NuclearSafety NSA-TR-09-14 A s s o c i a t e s Rev. 2 Administrative CSC 13: Secures area doors (and zine doors within) each CD repack and storage area SHALL be maintained closed when not in use. The doors SHALL be maintained with two locks in proper working condition. The combination or key of each lock SHALL be different. Supervision SHALL maintain confidentiality from operators of one lock combination or key while operators SHALL maintain confidentiality from supervision of the second lock. Particularly, at no time, will the combination of both locks be known by a single individual.

Administrative CSC 14:

Movement/handling of Non-NCS Exempt Materials SHALL be accompanied by at least two different persons that are cognizant offissile material handling responsibilities.

3.2.3 Defense-in-Depth Controls This section lists those controls that either reinforce CSCs, or provide additional protection to ensure that the risk of criticality is as low as is reasonably achievable.

DinD Administrative Control 01: HDP remediation areas should be clearly sub-divided/marked with survey area(s) prior to performing radiological surveys by using marking paint, construction flags, and/or stakes, etc. In addition, physical markings or other suitable methods should be used to delineate any identified Hot Spots within each survey area.

DinD Administrative Control 02: Settled sediments in each of the WTS Holding Tanks should be radiologically surveyed and/or sampled and assayed for 235U content according to the following schedule:

" At least once per month during excavation activities; and

• Prior to clean-out of the sediments from a tank.

In the event a sample assay result indicates a 235U concentration

>0.1 mg/cc (>0.1 g/L) then the NCS organization should be notified.

DinD Administrative Control 03:

The filtration (bag filters) and treatment media (GAC and ion exchange beds) should be radiologically surveyed and/or sampled and assayed for 235U content at least once per week during excavation activities. In the event radiological survey result or sample assay result indicates a 2 35U mass >350 g 3 5 Ufitrther use of the associated media should be discontinued and the NCS organization notified.

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561 NuclearSafety A s so c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 DinD Administrative Control 04:

GAC and ion exchange media should be radiologically surveyed and/or sampled and assayed for 235U content prior to clean-out of the media. In the event a sample assay result indicates a 235U concentration >0.1 mg/cc (>0.1 g/L) then the NCS organization should be notified.

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SFfety NCSA of the US Ecology Idaho (USEI) Site NuclearSaf NSA-TR-09-14 Associates Rev. 2

4.0 CONCLUSION

This criticality safety assessment demonstrates that the disposal of Hematite waste at the USEI site can be safely performed. The assessment has determined that there are very large margins of safety under normal (i.e., expected) conditions and that there is considerable tolerance to abnormal conditions. Under all normal and foreseen abnormal conditions a criticality event is considered either not credible or is precluded by controls in place at the Hemdatite site.

This analysis applies to disposal of Hematite decommissioning wastes at the USEI site. The scope of this assessment is limited to wastes with the following attributes:

1.- Maximum averagefissile nuclide concentration of 0.1 g235U/L;

2. Exhumed burial waste from the, Hematite burial pits and contaminated soils and backfill materials associated with the Hematite burial pits and other remediation areas at the Hematite site; and

3. Solids recovered from the Hematite Water Treatment System (i.e., used filter media, IX beds, solids in the holding tanks, etc.).

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Oj1 NucearSafety NCSA of the US Ecology Idaho (USEI) Site NularaNSA-TR-09-14 0

A s s o c i a t e s Rev. 2

5.0 REFERENCES

1.

NSA-TR-09-08, Rev. 0, NCSA of Sub-Surface Structure Decommissioning at the Hematite Site, D. Vaughn, May 2009.

2.

Historical Site Assessment, Revision 0, DO-08-005.

3.

Code of Federal Regulations, Title 10, Part 20.304, "Disposal by Burial in Soil," 1964.

4.

UNC Internal Memorandum, F. G. Stengel to E. F. Sanders, "Burial of Material,"

May 14, 1965.

5.

Hematite Burial Pit Log Books, Volumes 1 and 2, July 16, 1965, through November 6, 1970.

6.

Westinghouse Electric Corporation LLC, Employee Interview Records, 2000 to 2008.

7.

CE Internal Memorandum, J. Rode to Bill Sharkey, "The Hematite Burial Grounds,"

March 5, 1996.

8.

Selected Soil Areas Survey Plan For Westinghouse Electric Company Hematite, Missouri, C. Wiblin, May 2008.

9.

Buried Waste Characterization Plan for the Hematite Site, NRC Docket 070-0036, June 2006.

10.

Water Treatment System Design Report, Hematite Facility Remedial Action, Westinghouse Electric Company, LCC, Hematite, Missouri, August 2008.

11.

EO-06-004, Revision A, Work Plan for Buried Waste Investigation At the Hematite Site, Westinghouse Electric Company - Hematite Site, October 27, 2006.

12.

American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors, ANS-8. 1, American Nuclear Society.

13.

Atlantic Richfield Hanford Company (1969), Criticality Handbook Volume II, R D Carter, G R Kiel, K R Ridgway.

14.

LA-10860-MS, Critical Dimensions of Systems Containing 235u, 239pu, and 233U, 1986 Revision.

15.

NSA-TR-09-12, Rev. 2, NCSA of Fissile Material Storage at the Hematite Site, B.

Matthews and D. Mann, September 2011.

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Is NCSA of the US Ecology Idaho (USEI) Site X1NuclearSa.#M NSA-TR-09-14 A s s o c i a t e s Rev. 2

16.

.NSA-TR-09-05, Rev. 0, Nuclear Criticality Safety Calculations to Support Criticality Parameter Sensitivity Studies for 235U Contaminated Soil/Wastes, April 2009.

17.

NUREG/CR-6505, Vol. 1, The Potential for Criticality Following Disposal at Low-Level Waste Facilities, June 1997.

18.

NSA-TR-09-13, Rev. 3, NCSA of Water Collection and Treatment Activities at the Hematite Site, B. Matthews and D. Mann, December 2011.

19.

NSA-TR-09-15, Rev. 2, Nuclear Criticality Safety Assessment of Buried Waste Exhumation and Contaminated Soil Remediation at the Hematite Site, B. Matthews, Dec 2011.

20.

SAHEM00194-09-0003, Application of NUJREG-6505V2 to Waste from the Hematite Site, Geological Engineering and Environmental Services Company, February 6, 2009.

21.

Section II US Ecology Idaho Facility Overview.

22.

49 CFR 173.453(c)(1) and (2).

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'NCSA of the US Ecology Idaho (USEI) Site Y. W Nuclear~afety NSA-TR-09-14 A s s o c i ate s

Rev. 2 APPENDIX A Relevant Criticality Data CHARACTERISTICS OF BURIED WASTES AND CONTAMINATED SOILS It is considered that the SNM residues associated with the buried wastes and contaminated structures and soils at the Hematite site is generally a low-riskfissile material because the form and associated matrix conditions are far from optimum for a neutron chain reaction.

The characteristics of the wastes are completely dissimilar to those of an efficient fissile system.

Efficient critical systems comprise:

• Efficient moderating materials;

• Uniform fissile / moderator mixtures;

• Concentrations of several tens of grams fissile per liter;

• Compact arrangements;

• Lack of voidage and diluents;

• Lack of neutron poisons; and

• Efficient reflectors or interaction with otherfissile material.

As each parameter, or combination of parameters, moves away from the optimum the fissile mass required for a criticality increases. As this mass increases the probability that such a high fissile mass could have arisen and remained undetected decreases.

While criticality would be possible under highly non-optimum conditions (e.g., in low density, poisoned systems) the fissile mass needed for criticality (i.e., many kilograms) would far exceed credible quantities.

Single Items The presence of a sufficiently large fissile mass (i.e., _>

a minimum critical mass) in a single accumulation could potentially result in a criticality. The maximum subcritical mass for 235U in water is 760 g (Ref. 12), corresponding to optimum conditions of:

• Spherical homogeneous accumulation of 23SU/ water;

• Full water moderation (i.e., full density water, no poisons, diluents, voidage etc.);

• Optimum concentration of approximately 55 g235U/L (corresponding to a volume of approximately 14 liters);

• Full water reflection; and

• Isotopic content of 100 w/o 235U.

This value has traditionally been used in the assessment of isolated HEU units as a pessimistic but bounding case to generically consider all possible conditions within contaminated wastes.

As discussed above, the nature of SNM residues is such that it is not considered credible that a situation could arise in which all parameters are optimized and the presence of a minimum critical mass would result in a criticality. The reactivity of any system and hence the fissile mass that would be required for criticality is dependent on the combination of a number of parameters, e.g., concentration, moderating properties of the waste matrix, geometry and reflection 70 PRINTED COPIES ARE UNCONTROLLED

NuclearSafety A s socia es NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev.. 2 conditions.

CRITICAL AND SUBCRITICAL LIMITS Table A-1 outlines the subcritical and critical limits for 235U-water systems used in the safety assessment. It is acknowledged that there is potential to exhume or encounter hydro-carbon based liquids that could be more efficient moderators than water. However, due to the nature of the uranium residues and their associated waste matrix, the aqueous limits are considered conservative.

Table A-1 Single Parameter Limits for homogeneous 235U/water mixtures Parameter Critical Maximum Description / Restrictions Limit' Subcritical Limit 2

Any geometrical configuration, even when optimally moderated and fully Mass 820 g235U 760 g235U reflected by water. Applies to all chemical forms (e.g., oxides as powders, metals, etc.).

Unlimited volume of homogeneous Concentration 11.8 g235U/L 11.6 g235U/L solution in any chemical form (e.g.,

nitrate, oxalate, etc.), and in any geometry.

Homogeneous solution in any chemical Volume 6.1 L 5.5 L form (e.g.,.nitrate, oxalate, etc.), at any concentration, fully reflected by water.

Geometry Homogeneous solution in any chemical

(- Cylinder 14.3 cm 13.7 cm form (e.g., nitrate, oxalate, etc.), at any concentration and volume, and fully Diameter) reflected by water.

Homogeneous solution in any chemical Geometry 4.9 cm 4.4 cm form (e.g., nitrate, oxalate, etc.), at any (Slab Thickness) concentration and volume, and fully reflected by water.

Geometry 390 2

372 Homogeneous solution in any chemical Geometry 390 g/ft2 g/ft 2 form (e.g., nitrate, oxalate, etc.), any (Co Slab Areal (0.42 g/cm2)

(0.40 g/cm2) volume (i.e., any slab depth) and fully Concentration) reflected by water.

Source: Ref. 12 and Ref. 13 Notes:

1. Ref. 13, page IIl.B-2

2. Ref. 12, Table 1 Table A-2 outlines the single parameter critical limits for homogeneous U-water systems as a function of the U enrichment.

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1 NuclearSafety A s~s o c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 Table A-2 Critical Limits for homogeneous U/water mixtures as a function of U enrichment U Enrichment Spherical Spherical Critical Critical.

wt.% 23 5U/U Critical Critical

• Cylinder

- Slab Mass Volume Diameter Thickness (g)

(L)

(cm)

(cm) 3#

3200 80.0 38.0 20.0 5#

1950 37.0 28.0 14.0 30.3#

990 11.0 19.0 7.4 100#e 820 6.1 14.3

4.9 Source

Ref. 13 and Ref. 14 Notes:

Ref. 13, page 111.B-2

1. 1. Ref. 14, Figures 14-17 Reference 16 presents the results of a broad and comprehensive set of calculations performed to compare the reactivity of various finite and infinite systems containir~g uranium.

This calculation established a minimum critical infinite sea concentration for a 2 35U/soil mixture of 5.5 g235U/L.

Assuming a maximum safe fissile concentration of 4.0 g235U/L provides a substantial subcritical margin of 0.15 g235U/L. This margin is considered sufficiently large to also address any additional penalty that may be appropriate to account for validation of the materials modeled in the calculations used to establish the limit.

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X NuclearSafety As so c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 APPENDIX B Hematite Site Sampling Data Excerpts License Well Rad Results Sample ID Station ID WS-1 5 WS-15 WS-15 WS-15 WS-15 WS-16 WS-16 WS-16 WS-16 WS-16 WS-15 WS-15 WS-15 WS-15 WS-15 WS-16 WS-16 WS-16 WS-16 WS-16 WS-16 WS-16 WS-15 WS-15 WS-15 WS-15 WS-15 WS-16 WS-16 WS-16 WS-16 WS-16 WS-15 WS-15 WS-15 WS-15 WS-15 WS-16 WS-16 WS-16 WS-16 WS-16 WS-16 WS-16 Screened Horizon Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Sample Date 5/15/2003 3/30/2004 9/29/2004 12/21/2004 1/21/2005 5/15/2003 3/30/2004 9/29/2004 12/21/2004 1/21/2005 5/15/2003 3/30/2004 9/29/2004 12/21/2004 1/21/2005 5/15/2003 3/30/2004 9/29/2004 12/21/2004 1/21/2005 11/2/2007 11/2/2007 Analyte Result Units MDL U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS)

U-235 (AS) 5.0 2.2

-29.2

-17.6 13.8

-58.7

-0.6

-10.8

-12.3

-35.9 0.0 0.0 0.0 0.2

-0.1 1.6 0.3 0.0 0.1 0.0 0.0 0.3 pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/ll pCi/L pCi/L 47.2 20.6 40.3 48.8 68.1 108.0 13.6 57.0 90.0 55.9 0.1 0.0 0.1 0.4 0.2 0.4 0.1 0.2 0.3 0.1 0.5 1.0 73 PRINTED COPIES ARE UNCONTROLLED

M NuclearSafety A s so c i a t e s NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 2nd Quarter 2007 IGMP Rad Results Sample ID GW-WS31-062807 GW-PZ04-062807 GW-WS16-062907 GW-BP20A-062607 GW-BP22A-062507 GW-BP21-062607 GW-NB80-062807 GW-BP17-062807 GW-BP22B-062807 GW-BP20B-062707 GW-WS24-062907 Station ID WS-31 PZ-04 WS-16 BP-20A BP-22A BP-21 NB-80 BP-17 BP-22B BP-20B WS-24 Screened Horizon Jefferson City Jefferson City Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Sample Date 6/28/2007 6/28/2007 6/29/2007 6/26/2007 6/25/2007 6/26/2007 6/28/2007 6/28/2007 6/28/2007 6/27/2007 6/29/2007 Analyte Result Units MDL U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 2.6 pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L 0.1 0.0 0.1 0.1 0.1 0.1 0.0 0.0 0.0 0.1 0.1 3rd Ouarter 2007 IGMP Rad Results Sample ID GW-PZ04-091907 GW-WS31-091907 GW-BP17-092107 GW-BP20A-091807 GW-BP21-092007 GW-BP22A-091807 GW-NB80-092007 GW-WS16-091807 GW-WS24-092107 Station ID PZ-04 WS-31 BP-17 BP-20A BP-21 BP-22A NB-80 WS-16 WS-24 Screened Horizon Jefferson City Jefferson City Overburden Overburden Overburden Overburden Overburden Overburden Overburden Sample Date 9/19/2007 9/19/2007 9/21/2007 9/18/2007 9/20/2007 9/18/2007 9/20/2007 9/18/2007 9/21/2007 Analyte Result Units MDL U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 3.0 pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 74 PRINTED COPIES ARE UNCONTROLLED

w MNuclearSafety As so ci ate s

NCSA of the US Ecology Idaho (USEI) Site NSA-TR-09-14 Rev. 2 4 h Quarter 2007 IGMP Rad Results Sample ID GW-PZ04-120507 GW-WS31-120307 GW-BP17-120307 GW-BP20A-120307 GW-BP21-120307 GW-BP22A-120307 GW-NB80-120507 GW-WS16-120407 Station ID PZ-04 WS-31 BP-17 BP-20A BP-21 BP-22A NB-80 WS-16 Screened Horizon Jefferson City Jefferson City Overburden Overburden Overburden Overburden Overburden Overburden Sample Date 12/5/2007 12/3/2007 12/3/2007 12/3/2007 12/3/2007 12/3/2007 12/5/2007' 12/4/2007 Analyte Result Units U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L MDL 0.0 0.0 0.2 0.2 0.1 0.0 0..1 0.0 1St Ouarter 2008 IGMP Rad Results Sample ID GW-PZ04-030608 GW-WS31-030408 GW-BP17-030308 GW-BP20A-030408 GW-BP20B-030508 GW-BP21-030508 GW-BP22A-030508 GW-BP22B-030608 GW-NB80-030608 GW-WS16-030508 GW-WS24-030408 Station ID PZ-04 WS-31 BP-17 BP-20A BP-20B BP-21 BP-22A BP-22B NB-80 WS-16 WS-24 Screened Horizon Jefferson City Jefferson City Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Overburden Sample Date 3/6/2008 3/4/2008 3/3/2008 3/4/2008 3/5/2008 3/5/2008 3/5/2008 3/6/2008 316/2008 3/5/2008 3/4/2008 Analyte Result Units MDL U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 U-235 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2.2 pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L pCi/L 0.0 0.0 0.1 0.2 0.0 0.0 0.0 0.1 0.0 0.1 0.1 75 PRINTED COPIES ARE UNCONTROLLED