Table I Low Level Radioactive Soil and Asphalt Waste
Dr. Shoou-Yuh Chang, PE, and Jeff Knight, EIT
NC A&T
State University
Department of Civil Engineering
Greensboro, NC 27411
Susan R. C. Michaud, and Darrell Daugherty
Lockheed
Martin Energy Systems
Oak Ridge National Laboratory
ABSTRACT
During a nine year span, 1986-1994, the Oak Ridge National Laboratory (ORNL) shipped for disposal, 1,020,000 kg of low level radioactive waste soils and asphalt. A Pollution Prevention Opportunity Assessment (PPOA) was performed on this waste stream to develop improved waste reduction and pollution prevention alternatives to lower the volumes of wastes being generated at the ORNL facility.
It was determined through the PPOA that a total of 670 B-25 boxes had been used for disposal. The average cost of disposal was $9,000 per B-25 box, therefore $6,030,000 was spent on B-25 box handling and disposal. In the nine year period the average weight shipped per B-25 box was 1,424 kg. Theoretically, each B-25 box could be shipped with 3,760 kg of waste materials. Using the average shipment weight it was determined that on average 47% of the B-25 box space was empty. Reasons for the empty space included soil moisture contents, clumping of soils, rocks, and other factors which prohibited complete filling of the B-25 boxes. Realistically, it was determined the B-25 box could be filled to 85% capacity.
Using the techniques of the PPOA several alternatives were developed to enhance the B-25 box disposal program. One option would have the site utilize a designated Quality Control Inspector to monitor waste handling and shipments. Option two would require purchase of a portable vibrator to be used to maximize filling of B-25 boxes. Option three would require the site purchase soil drying apparatus and other equipment to remove moisture from the soils prior to shipment.
Recommendations included Options one and two to maximize the effectiveness of the B-25 box loading and shipment program for radioactive waste soils disposal. After costs for capital outlays and payroll expenses, it was estimated the site could obtain an annual savings of $100,768. Efforts were being incorporated into site procedures which would minimize shipments of B-25 boxes unless they were being filled to capacity or to a capacity that would increase cost savings and thereby reduce disposal costs to the ORNL facility.
INTRODUCTION
Scope
The main objective of the Pollution Prevention Opportunity Assessment (PPOA) at the Oak Ridge National Laboratory Site (ORNL) was to review current waste management practices dealing with low level radioactive soils and asphalts. The areas reviewed included waste generation, handling, packaging, storage, transportation, and disposal of these low level radioactive wastes. The PPOA was to include flow charts, mass balances for wastes, pollution prevention options, economic feasibilities of pollution prevention alternatives, and recommend future pollution prevention activities for the identified radioactive waste streams. The objective was to determine the costs and methods of handling and disposing of low level radioactive wastes and how these current methods could be integrated into future pollution prevention techniques.
Several visits were made to the ORNL site to obtain data on the radioactive soils and asphalts. Additional information was obtained via facsimile transmission from ORNL staff, express mail, telephone conversations, e-mail, or personnel interviews. The following main areas of information were observed or collected to determine current waste management practices:
Regulatory Overview
Solid waste regulation initially was directed under the Resource Recovery Act (RRA) of 1970 and amended by the Resource Conservation and Recovery Act (RCRA) of 1976. Subtitle C governs hazardous wastes and land disposal restrictions for solid wastes. The Pollution Prevention Act of 1990 established federal rules for opportunities to reduce or prevent pollution at the source. Working guidelines for these and other pertinent statutes are contained in the Code of Federal Regulations (CFR). Title 40 of the Code of Federal Regulations contains regulatory guidelines for issues pertaining to the environment. Title 10 of the CFRs contains guidelines for issues pertaining to energy, in particular, 10 CFR 20 contains Standards for Protection from Radiation.
RADIOACTIVE SOIL AND ASPHALT
Organizational Structure
The ORNL Site Waste Management Division is involved with the PPOA for Radioactive Soil and Asphalt including the following personnel; Darrell Daugherty, Susan R. C. Michaud, David Zill, Joe Setaro, Harold Hall, Tom Etheridge, David Wasserman
Current Waste Generation and Disposal Practices
Radioactive waste soils and asphalts are generated primarily through the excavation procedures used during site construction, decommissioning, maintenance, or testing. ORNL procedure ORNL/M-116/R1 regulates the excavation of these radioactive soils and asphalts. Specific Work Plans used by Project Managers at ORNL determine estimates of radioactive soils and asphalts being generated at the various project sites. Because of land ban restrictions, costs, and other environmental factors, these radioactive waste soils and asphalts have been placed into containers for shipment to an aboveground storage facility (SWSA 6). The most commonly used container for radioactive soil and asphalt shipments is a B-25 box.
The B-25 box is designed to contain 2.53 cubic meter of waste materials. As with other solid wastes which are currently regulated, liquid wastes are prohibited from being disposed in a like manner as solid wastes. Approximate dimensions of the B-25 box are 1.36 m X 1.36 m X 2 m. It is a steel container with a hinged top. Twist-tightening clasps on the B-25 box are used for locking the top securely. Pad locks or other locking devices are sometimes added. The B-25 box is painted a standard gray color. The bottom of the B-25 box has raised fork holders to allow for lifting with a forklift. When in use the B-25 box is lined with clear polyethylene sheeting to provide a vapor barrier between the box and the waste material.
Specific work plans at the ORNL reservation determine the estimated quantities of radioactive soils and asphalts to be excavated. These figures are used for the specified allotment of B-25 boxes which are ordered and delivered to the site location. The empty boxes are filled by contractors used for excavation of these radioactive soils and asphalts. Soils are tested by Heath Physics personnel at varying intervals as needed or required to insure the soils being disposed via the B-25 box are actually Category 2 or Category 3 soils (determined by radiation levels). Excavated soils which are placed into B-25 boxes can and sometimes are replaced at the point of generation, being used as backfill soils. Certain restrictions apply to these soils.
Soils typically contain low level radioactive concentrations of Cs-137, Co-60, Sr-90, and other daughter constituents of the decay of U-235 fission products. Radiation level measurements taken by Health Physics personnel indicate soils placed into B-25 boxes exceed 300 dpm/100 cm2 alpha and/or 0.02 mrad/h beta/gamma from readings taken at the surface. Soils with readings less than those stated are allowed to be placed back into the excavation. Soils are primarily clay soils at the ORNL reservation, however some of the soils excavated have portions of fractured native bedrock, namely slates, schists, and granites.
Once soils are collected into B-25 boxes the boxes are sealed and shipped off-site to SWSA 6 for enterement. At SWSA 6, the B-25 boxes are sealed into a concrete monolith using portland cement in a mold. No rebar or other reinforcing materials are used during the sealing process. The encased B-25 boxes are stacked and placed onto a large concrete pad. Once the pad reaches its capacity for storage the area is covered with gravel. The whole area is then covered with topsoils, compacted, and field grasses are planted on top to prevent erosion of soils. The base area of the concrete pad is maintained with a leachate collection and monitoring system for infiltrating precipitation.
Current Radioactive Soil and Asphalt Waste Data
Waste data is compiled from a waste database provided by ORNL. The database includes low level radioactive soil and asphalt data for shipments dating from 1977 to 1994. This PPOA includes waste data for the period 1986 to 1994. The majority (>95%) of the material shipped for disposal was radioactive soil. Only a small portion of the material was asphalt. Changes in environmental laws and regulations have mostly occurred during this period, therefore the database for earlier years did not contain sufficient information to be included in this PPOA. Data included in Table I are totals for the specific year.
Table I Low Level Radioactive Soil and Asphalt Waste
Current Radioactive Soil and Asphalt Disposal Costs
Cost information compiled for this PPOA Report was generated from one figure provided by ORNL staff. All gathered information indicates the approximate overall costs associated with the generation of a waste B-25 box, including excavation costs of the waste soils and asphalts, costs of the box, plastic lining, costs for transportation, costs for sealing with concrete, and costs for placing in the SWSA 6 facility total $9,000 per B-25 box. Based on an overall cost of $9,000/box the following information is obtained:
PROPOSED POLLUTION PREVENTION AND WASTE REDUCTION ALTERNATIVES
Development of Alternatives
Several alternatives were observed for waste reduction and pollution prevention as a part of the PPOA. Other alternatives may have been considered, but were not included in this report as these additional alternatives may not be viable. All alternatives are listed in order of significance.
Option 1
Provide more enhanced quality control for filling, processing, and disposal of radioactive soils and radioactive asphalts. These quality control measures may include one or more of the following steps:
Considerations for Option 1:
Advantages of using Option 1 is that associated costs are not excessive. Cost savings from even slight increases in waste volumes per B-25 box more than offset costs of expenditures for this option. Disadvantages include, more personnel will be involved in the generation of each waste shipment possibly causing delays with paperwork, etc., and procedures will require changing, updating, or development for this option.
Option 2
Purchase a vibrator or shaker to condense materials in B-25 boxes. The vibrator would allow for entrapped air to escape and thereby produce more fillable volume in the B-25 box.
Considerations for Option 2 include:
Advantages would include providing more usable space in the B-25 box and associated cost savings. Disadvantages include the maintenance downtime and health and safety requirements for producing more radioactive material on site.
Option 3
Purchase a soil drying apparatus similar to that used by municipal landfills to dry soils prior to placing in the B-25 box. Excavated soils would be placed onto a conveyor and transported through a soil dryer and then placed into a B-25 box.
Considerations for Option 3 include:
The major advantage of using Option 3 would be that the water content of the waste would be lowered thereby providing a container with a longer integrity (less chance for corrosion). Disadvantages include, the costs of implementation are excessive and problems with insuring the B-25 boxes may still occur.
Other options or alternatives not considered in this PPOA Report include performing aboveground construction and thereby limiting the need for excavations, using larger boxes, soil washing to remove radioactive contamination, and compacting the soils. These options were not chosen for several reasons.
SUMMARY AND CONCLUSIONS
This Pollution Prevention Opportunity Assessment for the ORNL site has resulted in the following summary and conclusions based on the information gained during the assessment phase of this project.
RECOMMENDATIONS
The recommendations provided in this PPOA Report are based on the data collected during the site investigation process, interviews, and documentation reviewed. Other recommendations may be considered should additional information be received. This PPOA uses the recommendations from more than one alternative or option. The options used were Options 1 and 2.
ACKNOWLEDGMENTS
This document is based on research conducted in support of a PPOA of radioactive waste soils and asphalts generated at the ORNL site. This assessment was prepared in response to Department of Energy pollution prevention policies. Mr. Darrell Daugherty served as the PPOA Coordinator at the ORNL site and Ms. Susan R. C. Michaud served as the Waste Management Coordinator from the ORNL site Waste management Division staff. David Zill, Joe Setaro, David Wasserman, and Tom Etheridge of the ORNL site staff also provided assistance in preparation of this document.
Preparation of the report, collection of site data, and development of pollution prevention alternatives was performed by personnel from North Carolina A&T State University, Greensboro, NC. Dr. Shoou-Yuh Chang, P.E. served as the Project Director. Mr. Jeff Knight, EIT, CHMM, graduate assistant to Dr. Chang served as the Project Manager for report preparation and principal writer of this report.
REFERENCES