HBL-12-002, Request for 10 CFR 20.2002 Alternate Disposal Approval, and 10 CFR 30.11 and 10 CFR 70.17 Exemption of Waste for Disposal at Us Ecology, Inc
| ML12135A295 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 05/02/2012 |
| From: | Sharp L Pacific Gas & Electric Co |
| To: | Document Control Desk, NRC/FSME |
| References | |
| HBL-12-002 | |
| Download: ML12135A295 (14) | |
Text
Pacific Gas and Electric Company 1000 King Salmon Avenue Humboldt Bay Power Plant Eureka, CA 95503 Loren D. Sharp 707-444-0819 Director andPlantManagerHumboldt Bay Nuclear May 2, 2012 10 CFR 20.2002 10 CFR 30.11 10 CFR 70.17 PG&E Letter HBL-12-002 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-133, License No. DPR-7 Humboldt Bay Power Plant Unit 3 Request for 10 CFR 20.2002 Alternate Disposal Approval, and 10 CFR 30.11 and 10 CFR 70.17 Exemption of Humboldt Bay Power Plant Waste For Disposal at US Ecology, Inc
Dear Commissioners and Staff:
Pacific Gas and Electric Company (PG&E) requests NRC approval of alternate waste disposal at the US Ecology, Inc (USEI) Resource Conservation and Recovery Act (RCRA), Subtitle C hazardous waste disposal facility located near Grand View, Idaho. The waste will consist of approximately 100,000 cubic feet of hazardous waste containing low-activity radioactive debris. The waste material will be from demolition of structures and remediation activities as part of the decommissioning process at the Humboldt Bay Power Plant (HBPP) Unit 3 site.
The radioactive component of the waste will consist of byproduct and Special Nuclear Material (SNM). This portion of the request is made under the alternate disposal provision contained in 10 CFR 20.2002 and the exemption provisions of 10 CFR 30.11 and 10 CFR 70.17. The USEI facility is also permitted by the State of Idaho to accept the hazardous component of the waste (classified as RCRA hazardous for lead content) in accordance with Environmental Protection Agency Code D008.
The Enclosure to this letter provides a conservative radiological assessment of the planned disposal and a description of the waste material. The description includes the physical and chemical properties important to risk evaluation, along with the proposed manner and conditions of waste disposal. Further information about the USEI facility's environmental setting is in Attachment 1 of the Enclosure, in compliance with 10 CFR 20.2002.
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Document Control Desk PG&E Letter HBL-12-002 May 2, 2012 Page 2 The waste material will consist of approximately 100,000 cubic feet (ft3) of soil, concrete, steel, insulation, roofing material, gravel and other metal, wood, and debris; and approximately 50,000 ft 3 (-400,000 gallons) of water associated with decommissioning of the deactivated HBPP Unit 3. The soil and debris waste will be generated from the demolition and dismantlement of HBPP Unit 3 above-grade structures and support components. The water will include low-activity wastewater from HBPP Unit 3 operations that previously was discharged to the environment via the discharge canal. The wastewater will be solidified with clay at USEI and disposed of as a "soil-like" waste. USEI accepts approximately 20 tankers of wastewater for treatment and solidification per week, including a portion that contain low-activity radioactive materials.
Radioactive contaminants, as shown in Table 1 of the Enclosure, have very low concentrations and are well within the Waste Acceptance Criteria (WAC) set forth in USEI's permit issued by the Idaho Department of Environmental Quality (Attachment 5 of the Enclosure). Additionally, Table C.4b of the WAC, "Materials Specifically Exempted by the NRC or NRC Agreement State," specifically allows disposal of byproduct material and SNM with 10 CFR 30.11 and 10 CFR 70.17 exemptions, respectively.
The concentrations of the radionuclides in the waste are expected to be below levels requiring classification as radioactive material for shipment purposes under applicable U.S. Department of Transportation (DOT) regulations (49 CFR 173.401, Subpart I). Verification surveys are performed by USEI on all incoming loads containing radioactive materials to ensure accuracy with shipment paperwork and compliance with its waste acceptance criteria.
NRC Regulatory Issue Summary 2004-08, "Results of the License Termination Rule Analysis," dated May 28, 2004, states that "10 CFR 20.2002 does not establish a specific standard for approving on-site disposal requests. Staffs current practice is to approve on-site disposal based on a criterion of a 'few millirem peryear." PG&E has performed a radiological assessment in consultation with USEI. Based on this assessment, PG&E concludes that potential doses to members of the public, including workers involved in the transportation and placement of the waste, will be less than one millirem Total Effective Dose Equivalent (TEDE) in one calendar year, well within the "few millirem per yeae' criterion established.
A previous HBPP 10 CFR 20.2002 byproduct material alternative disposal request (ref: HBL-10-003, dated April 1, 2010 and supplemented by letter HBL-10-018, dated August 12, 2010), was approved by the NRC in a letter dated November 2, 2010. A second request (ref: HBL-11-006, dated June 7, 2011) was approved by the NRC in a letter dated April 25, 2012. Where appropriate, PG&E answers to the NRC's requests for additional information for HBL-1 1-006 were considered in this submittal.
Document Control Desk PG&E Letter HBL-12-002 May 2, 2012 Page 3 PG&E's alternate disposal request in this submittal is similar to the two previous requests; however, there are two differences, namely the addition of water and SNM debris. It should be noted that on October 27, 2011, NRC approved an alternate disposal request by Westinghouse Electric Co. (WEC) to dispose of low-level radioactive waste from their Hematite facility at the USEI site. The 30,000 cubic yards of WEC Hematite waste consists primarily of soil and debris containing source, byproduct and SNM.
The proposed alternate disposal is in the public interest because it will conserve low-level radioactive waste disposal capacity and also provide a more cost effective decommissioning.
PG&E is requesting your written response to this request within the next three months because of the possibility of HBPP Unit 3 not being able to process liquid radioactive waste onsite and discharge the waste through the discharge canal.
There are no regulatory commitments made in this letter.
If you wish to discuss the information in the enclosure, please contact David Sokolsky at 415-973-5024.
Sincerely, L nD. Shr Directorand Plant ManagerHumboldt Bay Nuclear cc/enc: Elmo E. Collins, Jr., US NRC Region IV John B. Hickman, US NRC Chad Hyslop, US Ecology Idaho James E. Kennedy, US NRC Keith I. McConnell, US NRC Humboldt Distribution Enclosure
Enclosure PG&E Letter HBL-12-002 HUMBOLDT BAY POWER PLANT EVALUATION IN SUPPORT OF ALTERNATE WASTE DISPOSAL PROCEDURES IN ACCORDANCE WITH 10 CFR 20.2002
- 1. INTRODUCTION Pacific Gas and Electric Company (PG&E) requests NRC authorization for alternate disposal of certain low-activity waste containing byproduct and Special Nuclear Material (SNM) from its Humboldt Bay Power Plant (HBPP) Unit 3 Decommissioning Project.
The authority of 10 CFR 20.2002 and the exemptions requested from 10 CFR 30.11 and 10 CFR 70.17 licensing requirements for byproduct material and SNM, respectively, would allow PG&E to transfer these wastes to the US Ecology Idaho, Inc. (USEI) facility for disposal. The USEI disposal facility is a Subtitle C Resource Conservation and Recovery Act (RCRA) hazardous waste disposal facility permitted by the State of Idaho and located near Grand View, Idaho.
Characteristics and operating parameters of the USEI disposal site are summarized in Section 2 of this Enclosure, with detailed information provided in Attachment 1 to this Enclosure. A description of the material to be disposed is included in Section 3. The material description includes physical and chemical properties of the material important to risk evaluation and the proposed conditions of waste disposal. Section 4 provides radiological assessments,, including potential transport dose to the public, as well as USEI worker dose. A Criticality Safety Assessment performed for the USEI site is discussed in Section 5. The conclusion in Section 6 confirms doses will be well below NRC limits. provides MicroShield models and results pertaining to potential external and internal radiological dose hazards to USEI workers and transportation workers. contains a summary of the RESRAD modeling assumptions used to calculate maximum dose projections, as well as copies of the code output files. contains the inadvertent intruder analysis for the construction scenario consistent with the NRC's Request for Additional Information (RAI) on the Westinghouse Hematite project (Docket #070-00036). Attachment 5 contains the Waste Acceptance Criteria (WAC) set forth in USEI's permit issued by the Idaho Department of Environmental Quality. Attachment 6 contains the Criticality Safety Assessment for the USEI site that was performed as part of a prior alternate disposal application for the Westinghouse Hematite site.
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Enclosure PG&E Letter HBL-12-002
- 2. DISPOSAL SITE CHARACTERISTICS The USEI site is located in the Owyhee Desert of southwestern Idaho. It is at the end of Lemley Road, approximately 17 kilometers (10.5 miles) northwest of Grand View, (Owyhee County) Idaho. Grand View has a population of approximately 340. Owyhee County is a ranching and agricultural area of approximately 19,900 square kilometers (7,678 square miles). The county is sparsely populated, with an average population of 0.5 people per square kilometer (1.4 people per square mile per reference 7.1).
This region has an arid climate with an average annual precipitation rate of 7.4 inches.
The USEI site is located on a 1.6 kilometer (1 mile) wide plateau. Maximum surface relief on the facility is 27 meters (90 feet) and the mean surface elevation is 790 meters (2,600 feet) above sea level. The nearest residence is 1.6 kilometers (1 mile) southwest of the site. There are no other land uses in the immediate vicinity of the site.
The NRC has granted USEI several 10 CFR 30.11 byproduct material exemptions and USEI was recently granted a 10 CFR 70.17 SNM exemption for purposes of disposal of various licensee waste streams. Based on the nature of the material, both a 10 CFR 30.11 byproduct material exemption and a 10 CFR 70.17 SNM exemption will be required.
The operational performance characteristics of the USEI site have been reviewed by the NRC and determined to be protective within the NRC's "less than a few millirem (mrem) per yeaf' policy for Alternate Disposal Requests first stated in NRC Regulatory Issue Summary (RIS) 2004-08, "Results of the License Termination Rule Analysis," and reaffirmed in SECY-07-0060, "Basis for Justification and Approval Process for 10 CFR 20.2002 Authorizations and Options for Change."
A detailed description of the USEI facility is provided in Attachment 1 to this Enclosure.
- 3. DESCRIPTION OF THE WASTE The subject waste consists of approximately 100,000 cubic feet (ft3) of soil, concrete, steel, insulation, roofing material, gravel and other metal, wood, debris, and approximately 50,000 ft3 (-400,000 gallons) of water associated with decommissioning of the deactivated HBPP Unit 3. The soil and debris waste will be generated from the demolition and dismantlement of HBPP Unit 3 structures and support components.
Water shipments will include low-activity wastewater from HBPP Unit 3 operations that previously were discharged to the environment via the discharge canal. The wastewater will be solidified with clay at USEI and disposed as a soil-like waste. The liquid solidification process at USEI is routinely used for applicable shipments. All wastes are conservatively assumed to be transported over a minimum of two years.
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Enclosure PG&E Letter HBL-12-002 The waste being considered under this request will include fission products, activation products, and SNM nuclides resulting from HBPP Unit 3 operations. The waste concentrations are expected to be very low as the majority will be surface-contaminated components or installed equipment that PG&E will choose not to decontaminate either during or after dismantlement. Overall, the soil and debris wastes will exhibit an average bulk density of 55 pounds per ft 3 (0.88 grams per cubic centimeter, g/cc),
based on HBPP's waste packaging and shipping experience of similar waste streams.
Water is assumed to have a density of 1.0 g/cc. Radiological characterization of the waste stream was performed through routine sampling and analysis of project waste materials as part of HBPP's 10 CFR 61 characterization program. A summary of the radionuclides and their concentrations are listed in Table 1 below.
A portion of the solid waste may be classified as RCRA hazardous due to the presence of metals (e.g., lead) in accordance with Environmental Protection Agency (EPA) Code D008. The USEI facility is permitted to accept D008 waste, as well as other RCRA metals, for treatment by encapsulation to meet EPA Land Disposal Restriction (LDR) requirements. Some asbestos containing material (ACM) may also be included.
Table 1- Radionuclides Potentially Present in HBPP Wastes Concentration Nuclide (pCilg or pCi/ml)
Ag-108m 1 Am-241 10 C-14 2 Cm-243 2 Cm-244 2 Co-60 5 Cs-137 15 Eu-152 1 Eu-154 1 Fe-55 20 H-3 100 Ni-63 10 Pu-238 4 Pu-239 4 Pu-240 4 Pu-241 150 Sr-90 5 Tc-99 10 U-234 2 U-235 2 U-238 2 Page 3 of 10
Enclosure PG&E Letter HBL-12-002 All shipments will have radioactivity concentrations well within the levels allowed in the site WAC set forth in USEI's permit issued by the Idaho Department of Environmental Quality (provided in Attachment 5). The actual concentrations in the water shipments will be reduced through the solidification process. These concentrations are also below levels requiring the waste to be classified as "radioactive material" for shipment purposes under U.S. Department of Transportation (DOT) regulations.
- 4. RADIOLOGICAL ASSESSMENT As described in the following exposure scenarios, the dose equivalent for the Maximally Exposed Individual (MEI) has been demonstrated to not exceed "a few mrem per year."
The standard of a "few mrem peryear"to a member of the public is set forth in NRC RIS 2004-08. The transportation workers and USEI workers are treated as members of the public because the USEI site, while permitted by the State of Idaho under RCRA to accept certain radioactive materials, is not licensed by the NRC.
External exposure assessments were performed using MicroShield Code, Version 7.02.
Evaluations of potential external and internal dose hazards are discussed in the sections that follow and in Attachment 2. Table 2 of this enclosure is a summary of the total estimated doses for all transporters, as well as USEI workers performing surveying, handling, and disposal tasks on HBPP waste. Table 3 is a summary of the annual dose estimate for each worker group.
4.1. Transport Dose to the Public All materials will be transported by truck to the USEI facility in Grand View, ID. For normal highway transport conditions, the soil and debris will be enclosed in IP-1 intermodal containers (IMC) loaded on chassis trailers, although some IMCs and oversized debris may be shipped on traditional flatbed trailers. Wastewater will be transported in tanker trailers with an approximate capacity of 5000 gallons. All conveyances will be verified to comply with DOT external loose surface contamination limits prior to shipment. Therefore, transport will not pose the potential for internal dose to the drivers or other members of the public.
The distance from HBPP Unit 3 to the USEI disposal facility is approximately 659 miles.
Assuming an average speed of 50 miles per hour, the trip is estimated to take 13.2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. A minimum of eight trucks will be used to transport the entire volume of anticipated waste over the course of the project to achieve maximum logistical efficiency. Shipments are currently scheduled over a two year period to complete the project. Using a minimum of eight trucks, it will take approximately 125 IMC shipments (or 63 shipments per year) and 40 tanker shipments of water per year to complete the project. Each IMC truck driver is expected to make a minimum of 16 round trips between Eureka, CA and Grand View, ID over the course of the project, while each tanker driver is expected to make 10 round trips over the same route (or five trips per year). The soil/debris driver sits approximately 4 meters from the surface of an IMC with approximately 0.2 inches of aluminum shielding between the driver and the waste.
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Enclosure PG&E Letter HBL-12-002 The tanker driver sits approximately 3.3 meters from the surface of the vessel with approximately 0.51 inches of steel shielding between him and the contaminated water.
The tanker shielding includes the tank construction itself as well as outer steel liners.
Because of the very low average concentrations of radionuclides, external doses to the truck drivers are very low. As a result, the dose to other members of the general public can reasonably be concluded to be much less. External dose to a soil/debris truck driver (i.e., total dose) is estimated to be 0.16 mrem or 0.08 mrem/yr while external dose to a tanker truck driver is estimated to be 0.42 mrem or 0.21 mrem/yr.
4.2. USEI Worker Dose Assessment Upon receipt at the facility, the material will be surveyed and screened prior to transporting the waste to the indoor stabilization facility on the USEI site. Five minutes is required to perform a survey of each truck. Based on current practice, a surveyor is assumed to stand at a distance of one meter from the truck or trailer during the survey, with four surveyors sharing the task. The survey crews will survey both the incoming IMCs and tanker trucks upon receipt at USEI, with the surveyor dose rates for the soil/debris trucks used for all workers, including those used for the tanker trucks, as they are higher by approximately 30%. External dose (i.e., total dose) to each surveyor is estimated to be 0.04 mrem, or 0.02 mrem/yr. There will be no additional dose to the HBPP shipment drivers from other'trucks in the vicinity during the surveying, because the external dose rate from other trucks is negligible.
For the purposes of this assessment, it is conservatively assumed that all waste from HBPP Unit 3 will require treatment (for lead) or solidification (for incoming water shipments). In fact, as determined by HBPP through its waste analysis and characterization program, only a small portion of the soil and debris wastes (on the order of 10%) will require treatment. However, 100% of the water shipments will require solidification with clay soils within the USEI indoor stabilization building before burial in the landfill. After surveying, the waste is delivered to the stabilization building by the transport truck driver. The waste to be treated will be placed into a steel-lined concrete tank where it will be mixed with stabilization reagents. Wastes are wetted as they are emptied into the stabilization tank to reduce "dusting." The building is equipped with a negative pressure air handling system so that all air leaving the building is exhausted through High Efficiency Particulate Air (HEPA) filters. The stabilization process requires approximately 45 minutes, during which time the excavator operator, who is in an enclosed cab and wearing a respirator, is approximately 2.8 meters from the waste. Six operators share the stabilization task. External dose to each stabilization operator is estimated to be 0.03 mrem, or 0.016 mrem/yr.
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Enclosure PG&E Letter HBL-12-002 Personnel who work in the stabilization building may also be exposed to airborne activity from "dusting." Significantly, all USEI employees who work with any hazardous materials are required to participate in an Occupational Safety and Health Administration (OSHA) compliant respiratory protection program. Although this proven form of protection is required, conservatively no credit is taken in the internal dose assessment. Stabilization building workers are also the maximally exposed individuals for inhalation dose, primarily because of the assumed exposure time (45 minutes) and the indoor environment. Internal dose to each stabilization operator is estimated to be
.003 mrem, or .0016 mrem/yr. Total dose is estimated to be .06 mrem, or .03 mrem/yr.
After stabilization, the excavator operator removes the treated waste from the stabilization tank and places it into an on-site haul truck for transport to the disposal cell for burial. After delivery to the disposal cell, a bulldozer operator wearing a respirator within an enclosed cab, spreads and compacts the waste. A minimal external dose is calculated for the two bulldozer operators who share the task of spreading and compacting the stabilized waste material once it has been deposited within the disposal cell.
The average time to spread and compact 50 tons of material (which is the capacity of 2.5 IMCs) is 15 minutes. This shorter exposure time results in less potential internal dose from airborne radionuclides than was calculated for an excavator operator.
Personnel working in the disposal cells are also requited to wear air purifying respirators at all times. Again, no credit is taken for this proven form of protection and internal dose is estimated to be the bounding dose calculated for a stabilization operator. The estimated total dose to each disposal cell operator is 0.05 mrem, or 0.025 mrem/yr.
Table 2 - Total Doses to Drivers and USEI Employees for HBPP Project Total Total Total Waste External No. External Internal Project Contact Exposure Internal Trips Dose per Dose per Dose per No. Time Rate1 (m Dose Rate Dist. or Worker Worker Worker Function Persons (hr) rem/hr) (mrem/hr) (M) Reps (mrem) (mrem) (mrem)
IMC Truck Drivers 84 13.2 7.63E-04 0.00E+00 4.0 125 1.57E-01 0.OOE+00 1.57E-01 Tanker Truck Drivers 84 13.2 3.20E-03 0.00E+00 3.3 80 4.21E-01 0.OOE+00 4.21E-01 Survey 2 Crews 4 0.08 8.68E-03 0.OOE+00 1.0 200 3.62E-02 0.00E+00 3.62E-02 Stab. Cell Workers 6 0.75 2.91E-03 2.95E-03 2.8 862.3 3.13E-02 3.18E-02 6.31E-02 Waste Cell Operators 2 0.25 1.79E-03 2.95E-03 2.0 862,3 1.93E-02 3.18E-02 5.11E-02 Notes: 1. All external dose rates calculated using MicroShield Version 7.02.
- 2. The additional volume from the water shipments are incorporated into the survey, stabilization, and landfill tasks.
- 3. It is assumed that the Stabilization and Waste Cell Operations will handle 50 tons of material at a time,
- 4. Assume the same 8 drivers so the doses are additive.
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Enclosure PG&E Letter HBL-12-002 Table 3 - Annual Doses to Drivers and USEI Employees for HBPP Project Annual Annual Total Waste External No. External Internal Annual Contact Exposure Internal Trips Dose per Dose per Dose per No. Time Rate 1 Dose Rate Dist. or Worker Worker Worker Function Persons (hr) (mrem/hr) (mrem/hr) (M) Reps (mrem) (mrem) (mrem)
IMC Truck Drivers 84 13.2 7.63E-04 0.00E+00 4.0 63 7.85E-02 0.00E+00 7.85E-02 Tanker Truck Drivers 84 13.2 3.20E-03 O.00E+00 3.3 40 2.11E-01 0.OOE+00 2.11E-01 Survey Crews 4 0.08 8.68E-03 0.OOE+00 1.0 100 1.81E-02 0.00E+00 1.81E-02 Stab. Cell Workers 6 0.75 2.91E-03 2.95E-03 2.8 432,3 1.57E-02 1.59E-02 3.16E-02 Waste Cell Operators 2 0.25 1.79E-03 2.95E-03 2.0 432,3 9.67E-03 1.59E-02 2.56E-02 Notes: 1. All external dose rates calculated using MicroShield Version 7.02.
- 2. The additional volume from the water shipments are incorporated into the survey, stabilization, and landfill tasks.
- 3. It is assumed that the Stabilization and Waste Cell Operations will handle 50 tons of material at a time.
- 4. Assume the same 8 drivers so the doses are additive.
4.3. Post Closure Dose to the General Public USEI's RCRA permit requires that it demonstrate that no person will receive an annual dose exceeding 15 mrem for 1,000 years after closure of the facility. This standard is more restrictive than the annual 25 mrem total effective dose equivalent (TEDE) stated in 10 CFR 20.1402 for NRC license termination, as well as the limits for near surface disposal of low-level radioactive waste set forth in 10 CFR 61. RESRAD code Version 6.5 was used for modeling the Grand View site for potential long-term post-closure doses. A number of default parameters in the Grand View model have been replaced with site specific parameters consistent with the facility's 2005 permit modification and a report prepared by its consultant (previously submitted to the NRC as part of an RAI response for the exemption request for the Westinghouse Hematite project, Docket
- 070-00036).
Two RESRAD models were run to assess the impact of the HBPP Unit 3 waste on the USEI site. The first model is consistent with USEI's post-closure dose model included in the Part B RCRA permit. This model assumes that all of the HBPP waste is distributed evenly within the contaminated zone (area = 88,221 mi2 , depth = 33.6 m).
The radionuclide concentrations in Table 1 are adjusted to reflect aggregation into the entire landfill volume, resulting in a dilution factor of 5.61 E-04. All other RESRAD code parameters remain the same. The results of the first model show a maximum annual dose of 2.24E-02 mrem at approximately 247 years following closure of the facility. The RESRAD output report for this 'baseline' case is provided in Attachment 3.
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Enclosure PG&E Letter HBL-12-002 The second RESRAD model is a postulated "concentrated burial" scenario, where all of the HBPP waste volume is buried within a much smaller portion of the landfill, resulting in less radioactive waste dilution from volumes of non-radioactive waste received concurrently at USEI. All of the HBPP waste in this submittal is assumed to arrive at USEI in a two month period, rather than two years. This assumption requires adjustment of the area and depth of the contaminated zone parameters in the RESRAD model to an area = 14,704 m 2 and a depth = 4.96 m. These values correspond to the relative portion of the USEI landfill expected to be utilized within a two-month shipping campaign. The 2831 m 3 of waste from HBPP is aggregated into a total landfill volume of 73,080 M 3 , which includes all the waste received from other generators during that time (approximately one-sixth of an average 725,000 tons in a given year, or one sixth of the corresponding annual volume of 438,064 M 3 ), resulting in a dilution factor of 3.87E-02. The results of the concentrated model show a maximum annual dose of 1.59E-01 mrem at approximately 247 years following closure of the facility. The RESRAD output report for the 'concentrated' case is also provided in Attachment 3.
A post-closure inadvertent intruder construction scenario was conducted using the methods found in NUREG-0782, "Draft Environmental Impact Statement on 10 CFR Part 61 Licensing Requirements for Land Disposal of Radioactive Waste," and NUREG/CR-4370, Volume 1, "Update of Part 61 Impacts Analysis Methodology." No credit was taken for dilution of the radionuclide concentrations in these calculations, either in the buried concentrations themselves, as is done in the RESRAD model, or in the NUREG-0782 concentrations. The estimated inadvertent intruder dose rate for the nuclide concentrations in Table 1, without taking credit for dilution, is estimated to be 3.44 mrem/yr, which meets the NRC criterion "few mrem per year" for approval of a low level radioactive waste disposal exemption at an operating site and is well within the 10 CFR 20.1301 dose limit of 100 mrem/yr for individual members of the public from licensed operation.
A copy of the intruder spreadsheet is in Attachment 4.
- 5. CRITICALITY SAFETY A Criticality Safety Assessment for the USEI site was performed as part of a prior alternate disposal application for the Westinghouse Hematite site (see Attachment 6).
The "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, 2011)" verified that wastes containing U-235 may be sent to the USEI site for disposal since very large margins of safety had been incorporated into the normal operating conditions associated with these wastes and the probability for serious abnormal conditions is acceptably small. A maximum fissile concentration of 0.1 gram U-235 per liter of media was developed as an inherently safe concentration of SNM for the exhumed Hematite waste materials. This converts to an equivalent activity concentration of 216 pCi/g U-235 in soil (assuming a soil density of 1 g/cc). The U-235 activity concentration for this submittal (U-235 = 2 pCi/g as shown in Table 1) is at a significantly lower concentration than that previously shown to be inherently safe from a Page 8 of 10
Enclosure PG&E Letter HBL-12-002 criticality perspective. Therefore, it is not necessary to complete a new Criticality Safety Assessment for U-235 waste generated at the HBPP facility.
Mr. Herbert Cember published an inherently safe mass concentration for both U-235 and Pu-239 in reference 7.7, "Introduction to Health Physics, 3rd edition," of 11.94 g per liter (g/L) and 6.9 g/L, respectively, in aqueous solutions. These values are quoted for aqueous solutions, as they are the most favorable geometry for potentially achieving an inadvertent criticality event. They also represent a conservative application with respect to soils and debris waste streams that have far more void space in the shipping containers. The ratio of these values can be used to derive a reasonable estimate of the Table 1 activity concentration of Pu-239 (4 pCi/g) in terms of an equivalent U-235 activity concentration; combining the calculated result of 6.9 pCi/g with the Table 1 activity concentration of U-235, gives 2 pCi/g + 6.9 pCi/g = 8.9 pCi/g equivalent U-235, which is well less than the inherently safe value of 216 pCi/g.
The SNM potentially present in this request for alternate disposal (U-235 + Pu-239) is at significantly lower concentrations than those analyzed to be inherently safe from a criticality perspective for disposal at USEI. Therefore, it is not necessary to implement criticality safety procedures for shipments of HBPP wastes slated for disposal at USEI.
- 6. CONCLUSION PG&E developed this request and related evaluation in consultation with USEI, including health physics personnel responsible for the Grand View disposal facility's waste acceptance and radiological performance assessment programs. This assessment team performed a radiological dose assessment of the material to be shipped and determined that the potential dose to the workers involved in the transportation and placement of the material and to members of the general public after site closure is less than one mrem per year TEDE. This dose is a small fraction of the NRC decommissioning limits for exposure to any member of the public of 25 mrem/yr TEDE, and is well within the "few mrem per year" criterion that the NRC has established in RIS 2004-08.
The total doses to an individual worker for this exemption request and the two previous requests are bounded by the total number of shipments that can realistically be made in one year and the maximum dose for these shipments. For this exemption request, the maximum number of annual shipments that can be made with eight drivers is 400 shipments. Of the these shipments, it is anticipated that there will be a maximum of 60 water shipments and 340 soil/debris shipments in a single year. The highest dose for the water shipments then becomes approximately 0.30 mrem. The maximum dose from the 340 soil/debris shipments is also approximately 0.30 mrem. Therefore, the anticipated maximum dose to the truck drivers would be approximately 0.60 mrem.
Adding more shipments would result in more drivers and therefore more shipments would not increase the dose per driver. Because the estimated doses to other workers involved in the disposal are less than a driver's dose, the doses to the other workers would be less than a few millirem/yr.
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Enclosure PG&E Letter HBL-12-002
- 7. REFERENCES 7.1 American Geotechnics, "Hazardous Waste Facility Siting License Application Cell 16," Project No. 06B-C1202, June 30, 2006, ML100320540, Attachment 7.
7.2 Nuclear Safety Associates, "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.
7.3 US Ecology Idaho, Inc. USEI Site B Permit No. IDD073114654. 2004 7.4 U.S. Environmental Protection Agency, Federal Guidance Report No. 11. "Limiting Values of Radionuclide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Ingestion." EPA-520/1-88-020. US EPA Office of Radiation Programs. September 1988.
7.5 U.S. Nuclear Regulatory Commission, Regulatory Issue Summary 2004-08, "Results of the License Termination Rule Analysis." Office of Material Safety and Safeguards. May 28, 2004 7.6 U.S. Nuclear Regulatory Commission, "Basis and Justification for Approval process for 10CFR20.2002 Authorizations and Options for Change." SECY-07-0060.
Division of Waste Management and Environmental Protection. March 27, 2007.
7.7 Introduction to Health Physics, 3rd edition; Herbert Cember; January, 1996.
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Attachment 1 USEI Site Description Environmental conditions at USEI's site are well-documented in previous submittals to the USNRC, most recently as part of the Westinghouse exemption request for the Hematite, Missouri. project (Docket # 07000036).
In compliance with the requirements of 10 CFR 20.2002, two key documents are attached herein.
" Exhibit A: Hazardous Waste FacilitySiting License Application for Cell 16 (American Geotechnics, dated June 30, 2006); This document describes US Ecology Idaho's environmental setting and was accepted by the Idaho Department of Environmental Quality as part of the 2005 siting process, which resulted In IDEQ approval (December 6, 2006) of USEI's request to expand its landfill operations.