Manohar S. Sohal, Doug W. Akers, and Thomas A. Kerr
Idaho National Engineering and Environmental Laboratory
P. O. Box 1625
Idaho Falls, ID 83415-3815
(208) 526-9412; e-mail: sohalms@inel.gov

This paper summarizes a new national process under development at the Idaho National Engineering and Environmental Laboratory (INEEL) to quantify the behavior of low-level radioactive waste forms. It briefly describes the status of various tasks, including Department of Energy (DOE) approval of the proposed work, several regulatory and environmental related requirements, tests to qualify the waste form, a preliminary schedule, approximate cost, and a protocol that needs to be followed to accomplish the desired objective. It is anticipated that INEEL, Brookhaven National Laboratory (BNL), and possibly other approved test laboratories will perform the majority of the tests. For some tests, special testing services may be used. It should take approximately nine months to provide the final report on the results of tests on a waste form prepared for qualification. It is anticipated that the overall cost of the waste qualifying service is approximately $150,000.

The Nuclear Regulatory Commission's (NRC's) "Technical Position on Waste Form, Revision 1, January 1991,"¹ requires that buried waste forms preserve their structural integrity and be capable of resisting degradation that could cause excessive release of radioactive constituents to the environment. A series of tests has been specified by the NRC in the Technical Position to quantify the behavior of waste forms under simulated burial conditions. Waste generators or waste processing vendors who are responsible for providing these test data, and show that their waste formulations meet regulatory requirements, may receive approval for their waste formulations to be disposed of at licensed waste facilities by the appropriate state regulatory agency.

The INEEL and BNL have longstanding expertise in the testing of a wide range of waste forms under programs sponsored by both the NRC and the DOE. These capabilities are available to qualify new waste formulations that may be used for disposal at a repository site. A brief description of the tests that INEEL and BNL can perform for industry to meet the guidance of the NRC Branch Technical Position is presented in this paper. This paper summarizes the steps that have been taken or being taken to perform the NRC Branch Technical Position Tests, description of the tests, and the labor/cost estimates to complete these tests. It also describes a protocol for the benefit of the users of the testing services.

Several steps need to be taken prior to performing the tests to ensure that INEEL meets the requirements established by DOE to perform the proposed work and also delivers the test results in a cost effective and timely manner to the waste generators. The following steps either have already been taken or are in progress so that all the necessary planning requirements are completed prior to the start of any testing.

The INEEL is a DOE laboratory. Therefore, to perform any work for a customer other than the federal government or federal agencies, the INEEL has to obtain permission from DOE. In August 1996, a work-for-others (WFO) package (#96832) was approved by DOE-Idaho. DOE has agreed in principle to perform this work and has approved an umbrella agreement to proceed with the work. However, this work can also be classified under a category termed "cosponsored" work. In this category, cost of performing the work is borne by both federal and non-federal agencies. A benefit of this classification is that the DOE may waive part or all of the DOE added factor and depreciation cost, amounting to approximately 15% of the total cost. The DOE-Idaho has approved a request for classifying a hypothetical, but very likely work in the "cosponsored" category.

Before starting any tests, INEEL will coordinate the tests to be performed with the regulatory agency(ies) of one or more states. The purpose of this coordination is to optimize the number of tests that the waste generator may be required to perform to meet the state regulations and requirements. This issue is especially pertinent if the waste is slated for disposal in the state being considered for coordination. This coordination may be in the form of contacting the Host State Technical Coordinating Committee and Conference of Radiation Control Program Directors before and after performing the tests.

The INEEL project manager and/or a representative will visit the waste generator site to discuss the tests to be performed and develop a mutually agreed Statement of Work (SOW). Basically, the tests will be the same or similar to those described in this paper. Any deviation from these tests or additional tests will be clearly defined in the SOW. The agreed SOW will form the basis for developing the cost estimate and schedule.

A cost estimate to complete the work will be developed based on the SOW developed. A preliminary generic labor estimate is presented in Table I for INEEL to perform all the tests. The cost estimate will be approximately equal to these labor estimates plus some surcharge by the DOE to perform this service for a non-federal agency and charges to review the test report by the state where the waste is slated for deposition. This estimate will be agreed upon between the waste generator and the INEEL. . The preliminary labor estimate is given in Table I and corresponding cost is approximately $150,000.

A schedule for completing the work described in the SOW will be developed. A preliminary estimate of the schedule is presented in Table II. Based on the availability of personnel at INEEL or BNL, it is expected that the agreed upon schedule will approximate that shown in Table II and will take approximately nine months.

An INEEL representative has examined the proposed work on low-level radioactive waste form qualification testing and has determined that it poses no conflict of interest for Lockheed Martin Idaho Technologies Company. However, there are a number of companies that are barred from conducting any kind of business with Lockheed Martin. Therefore, before discussing any possibility of performing this work, it will be determined whether the waste generator company is on that debarred companies list. It is anticipated and hoped that none of the waste generators will fall in that category.

A general environmental checklist was prepared, and the National Environmental Policy Act (NEPA) documentation was signed. However, for a specific project (for a particular waste generator), it will be determined whether there are any deviations from the signed generic NEPA documentation. If such a deviation is determined, required documentation will be prepared.

For the proposed project, a generic quality assurance plan will be prepared. It has been determined that this plan will be the same or similar to the one prepared by Akers et al.² Whenever the proposed testing is about to begin, a quality assurance plan based on the one presented in Reference 2 will be prepared. It is anticipated that this plan will be adequate for all individual projects.

Before the beginning of testing, a generic test plan will be presented to the INEEL Independent Hazard Review Group (IHRG), who will examine the proposed testing from the point of view of health, safety, and other similar regulations. It is anticipated that one generic type approval will be adequate for all individual projects. However if need arises, a specific review for each individual project will be performed.

The NRC Branch Technical Position on Waste Form summarizes the NRC's regulatory position on waste form qualification. Low-level radioactive wastes are classified as Class A, B, or C, depending on their possible disposal hazard. Class A wastes are considered the least hazardous and Class C the most hazardous. Certain minimum requirements must be met by all wastes identified in 10 CFR 61.56(a).³ They include basic packaging requirements, prohibition against the disposal of pyrophoric, explosive, toxic and infectious materials, and requirements to solidify or absorb liquids.¹ Class B and C wastes have the additional requirement that they have "structural integrity" under expected disposal conditions. This will prevent the slumping or collapse of the disposal system and also prevent accelerated release of radionuclides caused by the disintegration of the waste form that could provide an increased surface area for leaching.

Stability for Class B and C wastes is defined by the following conditions stipulated by the Technical Position:

• The waste should be solid or in a container or structure that provides stability after disposal. (The waste form is expected to last for 300 years if it meets the criteria established in the Branch Technical Position. Thus, the high-integrity containers are required by the NRC to have a design life of at least 300 years.)
• The wastes should not contain free-standing or corrosive liquids. That is, the wastes should contain only trace amounts of liquids. When the wastes are placed in a high-integrity container that provides stability, the free liquid must not exceed 1% by volume of the waste. For solidified wastes, the volume of free liquid must not exceed 0.5% of the waste volume.
• The waste or container should be resistant to degradation caused by radiation.
• The waste or container should be resistant to biodegradation.
• The waste or container should remain stable under the compressive loads in the disposal environment.
• The waste or container should remain stable if exposed to moisture or water after disposal.
• The as-generated waste should be compatible with the solidification medium or container.

To ensure that waste streams are treated to produce uniform waste forms suitable for disposal, generators or waste treatment process vendors are required to process waste streams according to a plant-specific process control procedure (PCP) that documents the treatment process for NRC review.

Listed below are the qualification tests that must be performed to judge whether a waste form meets the stability requirements listed in the Technical Position:

• Compression
• Thermal cycling
• Irradiation
• Biodegradation
• Leach
• Immersion
• Free-standing liquid
• Full-scale waste form.

To minimize costs, simulated, non-radioactive waste samples will be used for the qualification of the waste forms. For leach testing, however, representative radioactive tracers will be used in the specimens, since leaching characteristics can only be accurately tested using radioactive material.

Procedures for these tests are described below.

Acceptance Criteria - Waste forms must have a sufficiently high compressive strength to avoid disintegration from burial stresses and to prevent burial facility slumping. The Technical Position requires a compressive strength of at least 413.7 kPa. However, the NRC recommends that generators achieve "maximum practical compressive strength," rather than just the minimum. For cement-based waste forms, the NRC specifies a minimum acceptable compressive strength of 3,447.4 kPa. This is readily achievable in most cases, since the typical compressive strength of a cementitious waste form is about 34,473.8 kPa.⁴

Testing Methodology - The compression testing procedure is given in ASTM Standard C39.⁵ (In the case of bituminous waste forms, the testing methodology is described in ASTM Standard D1074).⁶ A standard test specimen is a right circular cylinder with a diameter of 50.8 mm and a length of 101.6 mm. Prior to testing, the ends of the cylinder are "capped" with a suitable nonreacting compound that will provide the parallel end surfaces needed for compression testing. A total of five replicate specimens will be tested, and average values of compressive strength and the standard deviation calculated.

Acceptance Criterion - Thermal cycling of waste forms will occur only during storage or transportation. Once the waste form is buried, the surrounding temperature will remain essentially constant. However, the NRC believes that thermal cycling should be used as a means of identifying those waste forms that have superior mechanical characteristics. This is based on the fact that many waste forms contain a variety of constituents that have different thermal expansion rates. Since thermal cycling imposes internal mechanical stresses, it is assumed that any waste form that resists cracking or spalling during this test possesses superior mechanical integrity. To be acceptable, "bare" waste forms (no containers) must undergo 30 thermal cycles between 60EC and -40EC, and a subsequent compression strength test (ASTM C39) must demonstrate that the compressive strength is at least 413.7 kPa. For cementitious waste forms, the strength must be at least 3,447.4 kPa.

Testing Methodology - The thermal cycling procedure will be that given in ASTM B-553,⁷ Section 5.4.1 through 5.4.4. Five replicate specimens will be tested and any spallation or cracking of the waste forms will be documented. The average compressive strength will be determined together with the standard deviation. At least one sample per batch will be checked with a thermocouple to ensure that the temperatures throughout the samples have reached equilibrium before the hold period commences for the two cycling temperatures.

Acceptance Criteria - Gamma radiation is usually present in radioactive wastes. It causes ionization damage that may cause gas generation and, also, strength and ductility changes in waste forms. Waste forms must be gamma-irradiated at ambient temperature to at least 10⁶ gray, or to a higher maximum value if that is expected for a particular waste form. After irradiation, the waste forms are tested for compressive strength. The strength must be at least 413.7 kPa, or at least 3,447.4 kPa for cementitious waste forms.

Testing Methodology - The waste form samples will measure 50.8 mm in diameter by 101.6 mm in length. Four specimens will be irradiated in air to a dose of 10⁶ gray, at a dose rate of about 10⁴ gray/h, at an ambient temperature of 10EC. Slight gamma heating will occur (10B15EC), but it will have little effect on the irradiation damage process. After irradiation, the samples will be compression tested and the average strength and the standard deviation determined. Values will be compared to those for non-irradiated controls.

Acceptance Criteria - Waste forms must be tested for biodegradation (fungal and bacterial) to determine the importance of these types of degradation. The ASTM Standards G21 (fungal)⁸ and G22 (bacterial)⁹ are recommended by the NRC for this purpose. No sign of biodegradation should be observable, and the compressive strength after biodegradation testing should be at least 413.7 kPa, or at least 3,447.4 kPa for cementitious waste forms.

Testing Methodology - In the ASTM G21 test, waste forms measuring 50.8 mm in diameter and 101.6 mm in length are exposed to a mixture of five different types of fungi. Five test specimens are placed in contact with a nutrient-salts agar mixture contained in a sterile dish. A suspension of the fungal inoculant will be sprayed onto the agar and the sample surfaces which will be maintained at 28B30EC, at 85% relative humidity, for 21 days. They will be checked periodically for fungal growth. In the G22 tests, five samples will be placed on the nutrient-salt agar and sprayed with the bacterium pseudomonas aeruginosa. The samples will be maintained at 35B37EC, at 85% relative humidity, for 21 days. Periodically, they will be examined for bacterial growth. After the G21 and G22 tests, the specimens will be tested to determine whether they meet the compressive strength requirements described above.

Acceptance Criteria - Leach testing of waste forms is undertaken to demonstrate that releases offsite due to contact with groundwater are within prescribed limits. The limit is given as a leachability index (L), which is the logarithm of the effective diffusivity of each radionuclide of interest. A waste form has an acceptable leachability if L is greater than six.

Testing Methodology - The ANSI/AND 16.1 standard is the leaching procedure specified in the Branch Technical Position.¹⁰ Three specimens per waste form are to be tested. They will measure 50.8 mm in diameter by 101.6 mm in length. Leaching will be performed for a period of 90 days, except for cementitious samples, which will be leach tested for five days. Deionized water or synthetic seawater is normally used for the leachant, depending on which is shown from preliminary testing to produce the highest leach rate. This will ensure that conservative leachability indices are measured.

Acceptance Criteria - Immersion testing in either deionized water or synthetic seawater will be carried out to determine if a waste form maintains its structural integrity after burial. Short term tests will be initially carried out to determine the most aggressive immersion medium before one or the other is selected for the 90-day immersion tests. Specimens will be cured for 28 days before testing commences.

Testing Methodology - Five specimens per waste form will be tested. During the immersion period, they will be visually inspected for evidence of cracking, spalling, or disintegration. If there are no significant immersion effects, the waste forms will be compression tested, as described above. The waste forms should have a compressive strength of at least 413.7 kPa, except for cementitious waste form, which must have a strength of at least 3,447.4 kPa, but not less than 75% of the preimmersion value. If the average postimmersion compressive strength for cementitious samples is less that 75% of the preimmersion value, additional samples from the same batch will be immersion tested for an extended period of 180 days total to ensure that the long-term strength does not continue to decline with time. For certain types of waste stream (namely resin beads, chelates, filter sludge, and floor drain wastes) additional immersion tests will be carried out because they have been shown to exhibit complex behavior.¹¹ Such specimens will be cured for 180 days in sealed containers. The immersion period will be for seven days, followed by drying in ambient air at a minimum temperature of 20EC for another seven days. After drying, the samples will be visually inspected for cracking or spalling, and then compression tested as described above. The average compressive strength and the standard deviation will be determined.

Acceptance Criteria - Excessive amounts of free standing liquids in contact with waste forms and their containers must be avoided to minimize the release of contaminants and container corrosion. The amount of liquid must not exceed 1% of the waste volume if the waste is placed in a high-integrity container, and less than 0.5% of the waste volume for other containers. The pH of the liquid must be between four and eleven, except for cementitious waste forms, for which the liquid pH must be at least nine.

Testing Methodology - The ANS 55.1 methodology¹² will be used to measure the amount of free-standing liquid. A suitable pH probe will be used to measure the pH of any free liquid.

To ensure that laboratory-scale tests reflect the behavior of full-scale forms, actual prototype waste forms will be prepared. For each type of waste stream, two full-scale waste forms will be prepared by the vendor using procedures and equipment typical of that to be used in the field. Triplicate samples (50.8 mm in diameter by 50.8 mm in length) will be removed from selected locations of each waste form by sectioning or coring. Assuming that the waste forms are of 0.2082 m³-gallon drum size, the samples will be taken from the center and outer regions of the cylindrical forms at locations 1/3 and 2/3 from the bottom of the forms. This will give four testing locations, with three samples per location for each waste form.

The following tests will be performed to check the integrity of the full-scale waste forms:

• Compression tests on the samples after they have been cured for at least 28 days, to determine whether they are similar to those for the laboratory-scale samples
• Ninety-day immersion tests followed by compression testing, to determine that the full-scale waste form gives similar results to the laboratory-scale samples
• Check the samples destructively and compare them to determine whether there is homogeneity within the original full-scale waste form.

Table I briefly outlines the times for the various tests and the associated labor. Once the data have been acquired for a set of tests for a given waste stream, a final report will be prepared. This will take, on average, a period of three weeks to complete. It will include data analysis, preparation of graphics, and a complete description of the testing procedures. All quality assurance will meet the Appendix B of 10 CFR 50¹³ requirements. It will involve documentation, equipment calibration, worker qualification, etc.

The work will be carried out by qualified staff of either INEEL or BNL. Since the hourly support costs for the staff may vary and may be subject to changes, a detailed cost estimate for work performed will be developed at the time of testing.

For irradiation testing at BNL, only two standard waste forms can be accommodated per irradiation cycle, so this will entail two separate irradiations for a given waste batch of four. However, all samples can be accommodated in a single batch at the INEEL.

In all cases, it is noted whether the test will be performed on radioactive or non-radioactive samples as the cost may vary significantly based on this characteristic. Table I lists the tasks to be performed, the expected number of labor hours, and comments on the test. Table II lists the duration of various tasks and when specific tests would be expected to begin and end from a given start date. It is also assumed that existing equipment such as the furnace for thermal cycling and required laboratory equipment is usable and available. In addition, some initial startup costs, such as preliminary tests of the thermal cycling furnace, have not been included as these costs should not be costed to a single customer, but to the Program or to several customers.

If the testing work gets a "cosponsored" work classification by the DOE, the cost can be reduced by a maximum of about 15%. This overall cost reflects a significant emphasis placed on quality assurance, and it will be the first time that the integrated test program is performed in the current regulatory environment. For most tests, including compression, leaching, and full-scale waste form testing, a number of quality assurance standards and samples will be obtained and analyzed to ensure quality data. In addition, emphasis has been placed on a well-defined test plan with appropriate quality assurance requirements. These results will ensure that the data are accurate and will meet NRC requirements.

After completing all the tests, it is anticipated that the INEEL will facilitate review and acceptance of the test reports with: (1) the Host State Technical Coordinating Committee; and (2) the Conference of Radiation Control Program Directors. The states that have disposal facilities are represented on these two groups. The objective of this coordination is that the waste forms meet the regulations for disposal and safe long-term isolation of the waste will contribute to the public health and safety. Review and acceptance of the test reports will directly benefit the states and therefore, is a part of the National Low-Level Waste Management Program under the Low-Level Radioactive Waste Policy Amendments Act of 1985 (Public Law 99-240). Thus, facilitation of the test results with the above two groups will be paid out of the State's Technical Assistance Program. It is hoped that once the test report has been reviewed and accepted by these two groups, states will find it easier to accept the reports. Thus, this testing process will contribute effectively towards continued waste isolation.

The objective of the proposed work is to develop a low-level waste testing process that becomes equally acceptable to various interested organizations, that is, the waste generators, waste processors, and the states that are candidates for accepting redioactive waste for deposition. It should also serve the function of the now defunct NRC process of reviewing the test reports on low-level waste testing.

The INEEL has completed most of the preliminary work needed to initiate a waste testing process. Most of the administrative and procedural matters have been either completed or are in progress. A protocol for the benefit of those willing to use this testing service is provided in Table III. INEEL is in the process of developing similar testing plan for high-integrity containers, which should be ready very soon. Preliminary work to prepare the laboratory setup to start the tests has begun. Comments to improve the testing system are welcome.

Table III. Protocol for Low-Level Waste Form Qualification Testing

This paper was prepared with funding from the National Low-Level Waste Management Program, U.S. Department of Energy, Assistant Secretary for Environment Management, under DOE Idaho Operations Office contract DE-AC07-94ID13223.

1. "Technical Position on Waste Form (Revision 1)," Nuclear Regulatory Commission (January 1991).
2. D. W. AKERS, C. A. DICKE, and D. A. JOHNSON, Subsurface Contaminant Soil/Water Partition (K_d) Assessment Quality Assurance Program Plan, Idaho National Engineering Laboratory Report INEL-96/318 (January 1997).
3. Licensing Requirements for Land Disposal of Radioactive Waste," Code of Federal Regulations 10 CFR Part 61.
4. Workshop on Cement Stabilization of Low-level Radioactive Waste, NUREG/CP-0103, NRC (1989).
5. American Society for Testing and Materials Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens, ASTM C39 (October 1984).
6. American Society for Testing and Materials Standard Test for Compression Strength of Bituminous Mixtures, ASTM D1074 (1980).
7. American Society for Testing and Materials Standard Test for the Thermal Cycling of Electroplated Plastics, ASTM B553 (1979).
8. American Society for Testing and Materials Standard Test for Determining Resistance of Synthetic Polymeric Materials to Fungi, ASTM G21 (1970).
9. American Society for Testing and Materials Standard Test for Determining Resistance of Plastics to Bacteria, ASTM G22 (1976).
10. Measurement of the Leachability of Solidified Low-level Radioactive Wastes by a Short-term Test Procedure, ANSI/ANS Standard 16.1, American National Standards Institute/American Nuclear Society (1988).
11. P. L. PICIULO et al., The Effect of Cure Conditions on the Stability of Cement Waste Forms After Immersion in Water, Brookhaven National Laboratory Report WM-3171-4 (1987).
12. "Solid Radioactive Waste Processing System for Light Water Cooled reactor Plants, Appendix 2," ANSI/ANS Standard 55.1, American National Standards Institute/American Nuclear Society (1979).
13. "Licensing of Production and Utilization Facilities," Code of Federal Regulations 10 CFR Part 50.

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