David V. LeMone
Department of Geological Sciences
University of Texas at El Paso
500 West University
El Paso, Texas 79968
(915)747-5275

Lawrence R Jacobi, Jr.
Texas Low-Level Radioactive Waste Disposal Authority
7701 North Lamar, Ste. 300
Austin, Texas, 78752
(512)451-5295

The classification of radioactive waste and what constitutes its lower limit continues to be a national and international problem. American radioactive waste management is now in process of entering an era of decommissioning involving not only the defense-related facilities, but also the commercial operations, most notably nuclear power reactors. Decommissioning and its consequent decontamination actions will generate vast quantities of low-level and very low-level radioactive wastes. The high cost of disposal of all of these wastes in the typical near surface engineered repository (Low-Level A, B, and C) will be prohibitive. Without an adequate dose or risk based lower limit to determine what constitutes radioactive wastes, no rational inventories can be generated. No estimates can be made of the economic feasibility of recycling metals or facilities for reuse, regardless of whether they are within or without governmental or commercial nuclear facilities. It is recommended that the International Atomic Energy Agency concepts of very low level radioactive waste, exclusion, exemption, and clearance be considered for adoption by the national regulatory agencies.

The first two decades of the 21st century will witness the closure and consequent decommissioning of the bulk of the operational commercial nuclear power plants in America. It would seem that now is the proper time to seriously re-examine some of the basic philosophical principles that have been accepted for the classification and disposal of low-level waste (Classes A, B, and C) and, specifically, the volumetrically largest Class A. The potential subdivision of this class into lower levels of radioactive wastes should also be considered.

As of December 31, 1996, some 71 nuclear power reactors with a generating capacity of 17,855 MW(e) of power have been shut down globally (Table I). The United States has 16 reactors (23%) in this group. This loss of power globally is being offset by 36 reactors under construction which will add 27,928 MW(e) to the grid [1]. There are no reactors under construction in America. Decommissioning after shut down of aging and non-economic reactors will have a profound impact on waste management, nationally and globally.

The Class A wastes generated during this forthcoming period are anticipated to far exceed the currently generated operational wastes. The impact on the capacities of the operational commercial and governmental (state and compact) engineered low level repositories will be significant. There is a need for another classification of less hazardous waste below that of Class A that can be disposed of in either specialized, non-engineered, very low level waste repositories or municipal landfills. The adoption of the International Atomic Energy Agency (IAEA) concept of very low level waste (VLLW) would seem to be pragmatically and politically feasible. The acceptance and application of the concepts of exclusion, exemption, and clearance level, in addition to the development of a very low-level radioactive waste category, would likewise seem appropriate.

Exclusion as utilized by the IAEA represents the case where the law does not even consider the radionuclides as waste, as there is no way or necessity to regulate it. An example of this would be naturally occurring radioactivity such as cosmic radiation or the amount of Potassium-40 in the human system. The Nuclear Regulatory Commission (NRC) does not use the term exclusion as a category. It does, however, define a term of similar meaning, that being "background." Background is currently under the process of review and redefinition to include global fallout from nuclear device testing and accidental fuel cycle releases (e.g., Chernobyl) [2].

Exemption, as defined, would be waste that, although not excluded from the law, has sufficiently low radioactivity as to be of no regulatory concern. Exemption is not granted by the NRC for radioactive materials derived from the nuclear fuel cycle, although some consumer products, such as smoke detectors, have been exempted from regulation.

The NRC has attempted to establish a radiation level below which waste would not be considered to be of regulatory concern. This radiation level (BRC, below regulatory concern) was withdrawn in 1993 because of interagency regulatory disagreements and political considerations. The process is once again being handled by the NRC on a case-by-case basis.

The classification of very low-level waste (VLLW), developed by the IAEA, has a clearance level. Above the clearance level, VLLW and other low-level wastes would be sent back for treatment and, on a cost/benefit basis, either recycled or disposed of. Very low-level waste below clearance level would be recycled, reused, or sent to a public landfill. The clearance level in America could be established as either the dividing line between Class A waste and a new very low-level waste class or within the new classification. The continuing problem with this scenario is that it still requires the regulatory establishment to determine another lower level of radioactivity. This radiation level would establish the upper limit of non-radioactive waste.

In order to rationally examine the feasibility of establishing these concepts, a review of the classification of low-level waste is necessary. It also requires consideration of what sort of an impact the adoption of these concepts would have, not only on decommissioning and operational waste streams, but also on economically recoverable materials. The basic IAEA system seems to be applicable. The question of whether the system should conform to standardization or not is debatable.

Low-level waste, as it is utilized nationally, is subdivided on the basis of increasing radioactivity as classes A, B, and C. The problem is that this classification and these subdivisions of low-level waste are unique to our system. Low-level waste, as are the other waste classes (e.g., GTCC, High Level, etc.), is not subject to international agreement. Radioactive wastes are defined and classified by each nation's National Responsible Authority. The IAEA has established a generalized categorization for all radioactive wastes [3]. Unfortunately, the IAEA system has not been universally accepted.

As Saverot points out [4], classification schemes have been adopted on the basis of national needs, resources, and historical development on such parameters as: radionuclide content, origin of waste, radionuclide half-life, hazardous life-time, radiotoxicity, specific activity (in terms of mass and volume), dose rate, etc. In today's world, use of the term low-level invariably leads to confusion. It does not mean the same thing to workers from different nations. Waste subdivisions in France are A, B, and C; in the United Kingdom High, Intermediate, and Low; and in Italy I, II, and III. Japan and America utilize high level and low level waste terminology, but they are not defined within the same limits.

An earlier down-scale microcosm of this problem was evident in the low-level waste subclasses, acceptance criteria, and definitions that were being utilized in Texas, Maine, and Vermont, the members of the proposed Texas Compact [5]. Common low-level radioactive waste categories and their accompanying acronyms are utilized in a non-uniform manner by commercial nuclear power plants in these states. These categories reach a minimum number of 18; these waste terms include such examples as secondary system resins (SSYSRES), fuel pool skimmer filter sludge (FPFILSL), and condensate phase separator filter/demineralizer sludge (CONFDSL). Common non-utility (process metallurgy, manufacturing, industrial and research sources) low-level waste is divisible into two classes: Dry Waste Streams and Process (Wet) Waste Streams. Dry waste streams are split into five general categories and are exemplified by accelerator targets (TARGETS) and compactible trash (COTRASH). categories). Process (wet) waste streams are divisible into four categories which are exemplified by liquid scintillation vials (LIQSC VL) and absorbed liquids (ABSLIQ). The Uniform Low Level Radioactive Waste Manifest should foster some degree of standardization (NRC Form 540-542).

Suggestions of reclassification paralleling IAEA guidelines [6] have failed in the U.S. largely due to problems of historical tradition, national political necessities, volume of necessary data translation, and simple inertia. There would seem to be little hope or incentive for a reversal of this trend at the present time. In the future, as we become more and more an interdependent global society, this trend may be reversed.

Low-level waste and its processing and economics results in a complex set of problems for the generators. In the U.S., the generators, ranked in order of their importance, fall into three primary categories; they are: governmental, commercial power reactors, and a medical, industrial, and research grouping. In the U.S. governmental low-level radioactive waste volume, prior to and after the development of a proactive waste minimization policy, still maintains a ratio of two to one over commercial power reactor low-level radioactive waste. This relationship may be significantly altered as decommissioning of aging reactors becomes more common in the next decade. National commercial reactor waste volumes have been stabilizing. The commercial utilization of reactor and non-reactor isotopes may likewise change the volume and nature of the waste stream.

The character of the low-level waste stream and final waste form changes on its way to a repository as it goes through the processes from generation to treatment and conditioning. An excellent case-in-point is that of the development of waste minimization which has significantly lowered the volume of operational low-level waste in commercial low-level repositories since the volumes peaked in 1980 [7,8]. The cost of waste disposal in commercial repositories in the past has been based on volume. That disposal cost, as a result of operator increased regulatory compliance costs and state surcharges, has seen an increase from less than a dollar per ft³ ($30/m³) in the sixties to $360/ft³ ($12,712/ m³) in 1996. At the present time, waste costs are being calculated on the basis of four factors: density, surface radioactivity, radionuclide content, and volume. Future compact and individual state low-level repositories will likely follow the same pattern of disposal cost charges [9].

Decontamination is defined as the removal or reduction of radioactive contamination utilizing either physical and/or a chemical process(es) [10]. Decommissioning is defined as those actions taken at the end of a nuclear facility's life to retire it from service in a manner that will provide adequate protection for the health and safety of the decommissioning workers and the general public, and for the environment [11]. The ultimate goal of decontamination and decommissioning is the unrestricted release or use of the site (frequently referred to as "Greenfield" status). The currently used term "Brownfield" refers to restricted reutilization of the site. The time frame involved in the return of the facility site to a restricted or unrestricted release is a variable that, dependent on conditions, may range from a few years to several hundred years [10].

Nationally the U.S. Nuclear Regulatory Commission [12] recognizes three decommissioning waste alternatives: DECON, SAFSTOR, and ENTOMB. DECON (dismantlement) was developed for facilities with the capability to fairly rapidly decontaminate the property and return to unrestricted use (e.g., Elk River, Shippingport). SAFSTOR (deferred decontamination) is the condition where a nuclear facility can be safely mothballed and subsequently decontaminated to levels that will permit release to an unrestricted status (e.g., San Onofre-Unit 1 PWR, shutdown in 1992, entering DECON in 2013). ENTOMB is the condition where the radioactive contaminants are encased in a structurally long-lived material. The structure must be appropriately maintained and kept under continued surveillance until the radioactivity decays to a level permitting processing to the level of unrestricted release for the property [13] (e.g., BONUS BWR at Rincon, Puerto Rico, shutdown in June of 1968).

The International Atomic Energy Agency (IAEA) recognizes three generic stages of decommissioning: Stage 1 (Storage with Surveillance); Stage 2 (Restricted Site Release); and Stage 3 (Unrestricted Site Release). The system is based on the timing of deferred decommissioning of the nuclear facility which is tied to cost, worker safety, and public safety [14]. Stage 2 usually ranges from 30 to 40 years, but may be as long as 130 years. IAEA lists six factors influencing the timing. They are: benefit of lower radiation from radioactive decay; social acceptability to delay; cost of maintenance and the surveillance required; involvement of a costly highly trained, specialized staff; waste depository accessibility and acceptance; and requirements for alternative uses for the facility site [14].

Radioactive wastes from a decommissioned reactor are normally low-level (95%) with lesser quantities (approximately 5%) from higher level waste categories [3]. High Level and TRU (transuranic) wastes represent a volumetrically small component of the waste stream, primarily sourced from MOX reprocessing plants and fuel fabrication facilities.

The NRC is interested in developing recycle/reuse regulations for post-operational clean-up of nuclear facilities. They are in process of developing and evaluating a series of risk assessment scenarios by pathway analysis of some 85 radionuclides. Selected scenarios will then be subjected to uncertainty and sensitivity analyses, followed by cost/benefit analysis and subsequent public review [2]. The basic regulatory problems remaining are still in those concerned with the determination of the level of radioactivity and how risk is to be calculated.

Clearance in decommissioning involves both transportable and geographically fixed materials. Meck [2] outlines some of the significant problems existing in the reuse and recycling of transportable materials such as metals. Once the material is cleared it can be taken offsite for commercial use or disposal. Despite regulatory clearance, American scrap metal recycling operations normally will not accept radioactive metals; they, furthermore, scan all incoming metals for the specific prevention of such purchases. This attitude is an outgrowth of earlier costly recovery problems developed in the inadvertent melting and recycling of Cs-137 and Co-60 sources. If uneven national levels of acceptable radiation in recycled metals are adopted, it will undoubtedly have a direct effect on the transboundary shipments of these metals and, subsequently, the future of international metal trade.

Decommissioned, geographically-fixed lands may attain greenfield (released) or brownfield (restricted) status. Brownfield status is, in essence, a variety of the clearance concept in that it is released but either under continued regulator control or in a mode of restricted pathway exposures. Generic solutions for decommissioning are problematic where multiple levels of radioactivity are involved, such as in the recycling of structures which vary in construction, dimensions, internal system radioactivity (pipes, etc.), or indoor radon levels, etc. Generic solutions also do not work well. These may be exemplified by the problems involved in either requiring very low-level waters (e.g., photographic processing and silicon chip manufacture) or manufacture utilization of radioactive feedstocks (e.g., carbon black in the manufacture of pencils). These special problems will require an optimally balanced evaluation among needs, costs, and risks.

The dimensions of the rapidly approaching future decommissioning crisis are enormous. To reiterate, as of December 31, 1996, 442 nuclear power reactor units were in operation around the world with 71 reactors no longer in operation [1]. The IAEA lists 36 units under construction [1]. Commercial reactor units now no longer in operation, which normally have a 30 - 40 year life span, are largely not decommissioned to either "greenfield" (open) or" brownfield" (closed) status. The most disturbing factor, however, is the number of operating units that will be nearing their operational life span in the next two decades. This will be a major factor for consideration here in the U.S. where the majority of the 110 operational units will be nearing or have reached their expected life span. Additionally, the IAEA listed 320 research reactors in operation in 1993 with an additional 200 of these shut down [15]. A significant number of the shut down research reactors are in the process of decommissioning.

Variations in decommissioning planning and operation, waste stream character, and recycling and reuse of power plant reactors are tied to the reactor type. The current operational reactor unit waste inventory would include pressurized light-water reactors (58 %), boiling light-water reactors (22 %), gas cooled reactors (all types) (8 %), heavy-water reactors (all types) (8 %), graphite-moderated light-water reactors (3 %), and liquid metal-cooled fast breeder reactors (1 %). The vast majority (80 %) of the nuclear reactor power units are either light-water pressurized or boiling water types [16].

The low-level waste arising from decommissioned nuclear power reactors is estimated to be 6981 cubic meters (246,499 cubic feet) for a typical 1175 MW(e) pressurized water reactor. Boiling water reactor low-level waste has been estimated as 14,275 cubic meters (504,050 cubic feet) for 1155 MW(e) [13]. These decommissioning estimates also clearly indicate the relatively small volumetric contributions of GTCC wastes to be expected (Table II).

In the next 50 years, the estimated volume of scrap metals that will be generated from decommissioning will be on the order of 12 million metric tons. Nieves and others [12] classify reactor scrap metal into four useful general activity categories: Suspect Radioactive, Surface Contaminated-Removable; Surface Contaminated-Fixed; and Activated. The quantities of the economic scrap metal (copper, iron and steel, and stainless steel) available in a 1,000 MW(e) pressurized and boiling water reactor system can be estimated (Table III).

All reactor metal should initially be considered to be Suspect Radioactive. After initial separation from this designation, Suspect Radioactive metal refers to those components with no surface contamination or activation, typified by systems not associated with reactor fuel or primary coolant systems (e.g., cooling towers, PR steam lines and turbines, etc.). If radioactive contamination is observed, surface decontamination will normally produce a non-radioactive metal.

Surface Contaminated-Removable scrap metal has a significant level of surface contamination that can be removed by decontamination processes to a level permitting unrestricted use. These scrap metals originate in building and systems exposed to primary coolant or fuel during normal operations or during any leaks or spills, observed in such examples as fuel handling machinery, fuel storage pool liner and equipment, etc. Suspect Radioactive and Surface Contaminated-Removable classes of scrap metal are by definition considered to be recyclable [17].

Surface contaminated-Fixed scrap metal, conversely, has significant levels of surface contamination which either penetrates or is bound to the metal. Decontamination techniques are usually not sufficient to lower contamination to an acceptable level for unrestricted use. Examples may be observed in the fuel reprocessing and liquid radwaste systems.

Activated scrap metals have not only significant levels of activation, but also high levels of surface contamination. Examples of this classification would include such components as those associated with the boron poison rods and the reactor pressure vessel. Decontamination is done primarily to reduce worker radiation exposure. These last two categories of the classification are normally considered to be composed of unrecoverable, contaminated metals [17].

Linsley [18, 19] has recently reviewed the history, policies, procedures, and continuing development of the IAEA program on radioactive waste safety standards (RADWASS) and the management of low-level and very low level waste (VLLW). The basis of the program consists of the deliberations and recommendations of expert groups. These groups formulate and develop the basic safety standards, objectives, concepts, and principles. The documents produced by the expert groups are then subjected to a vigorous process of review and re-examination by two overlying, subsequent committees prior to IAEA approval.

Documents produced by this program are divided into a four-level hierarchical series [18]. The highest level (Safety Fundamentals) describe basic safety objectives, concepts, and principles. The second level (Safety Standards) outlines the "mandatory" obligations and requirements necessary to meet the requirements developed in the Safety Fundamentals. The third level (Safety Guides) recommends procedures and gives the necessary guidance to meet the requirements established in the Safety Standards. The basal level of the documents is the Safety Practices which considers practical methods and test cases.

The two fundamental divisions of the international approach to the basic principles of nuclear waste management are the concepts of Intervention and Practices [20]. Intervention (or Restoration) is concerned with restoration of the environment in areas that have been contaminated from past practices (e.g., radium dial painting) and accidents (e.g., Chernobyl), remediation and restoration of abandoned mining and milling operations, and the clean-up of contaminated land areas. The principle of Practices falls into three major units: predisposal, discharge, and disposal. Discharge involves the regulatory control of the release of radionuclides into the environment and is overseen in the IAEA by the Radiation Safety Standards Advisory Committee (RASSAC) rather than RADWASS. Disposal involves the siting, design, construction, and closure of near surface repositories [21], geologic repositories [22], and the U/Th mining and milling of ores. These disposal categories, in turn, have required safety assessments.

The predisposal management of radioactive waste is based on the fundamental IAEA classification scheme [3] and is divided into: Low and Intermediate Level (nuclear fuel cycle facilities), high-level, and the special problems developed in Medical, Industrial and Research wastes. Safety assessments are then examined. A resultant of this effort has been the development of clearance levels for radionuclides in solid materials [23, 24]. The terms exclusion, exemption, and clearance are fundamental to the understanding of the VLLW classification. Exclusion refers to sources that are not controllable. Exemption and clearance are utilized for sources that offer such a low risk to health that regulatory control would be a waste of resources. Exemption wastes are never regulated. Clearance, however, applies to sources released from regulatory control. VLLW broadly covers both exempt and cleared wastes. VLLW activity concentration normally goes up to 104 Bq/g (dependent on the radionuclides) [23].

VLLW arises from regulated practices. Wastes originating from outside regulatory practices are exempt. Activity concentrations in VLLW may range from no enhancement above natural concentrations to concentrations at a level associated with Low-level waste. VLLW commonly develops from nuclear facility operations and decommissioning as well as by-product from medical, industrial and research activities.

Linsley [18] lists six VLLW management options which may be either cleared or controlled. Controlled VLLW includes material reused and/or recycled in the nuclear industry, disposal in engineered facilities, and disposal in special VLLW disposal facilities. VLLW clearance level normally means the division between controlled and cleared VLLW. Waste, after clearance, may be reused and/or recycled outside the nuclear industry, disposed of in public land fills, or incinerators for subsequent disposal of wastes in public landfills. The utilization and application of these six options is usually reflected in the state's national interests and the level of the public's concern.

VLLW can be released for recycle and reuse outside the nuclear industry or for disposal with non-radioactive municipal wastes. VLLW may also be released in restricted situations in which radiation exposure is unlikely to occur. Linsley [18] utilizes the example of recycled steel for bridge construction.

IAEA has recently issued an interim report for comment on clearance levels for radionuclides in solid materials utilizing the application of exemption principles [23]. It summarizes the results of seven studies on 56 radionuclides. These studies include clearance levels for landfill disposal, incineration, recycling (steel, aluminum, copper, and concrete), reuse, and unconditional release. This same volume [23] contains some baseline measurements and ranges for NORM activity concentration in soils, rocks, ore minerals, coal, phosphate fertilizers, construction materials, etc.

In summary the low-level radiation sources and wastes may be excluded, exempted, or placed under regulatory control. Under regulatory control the radiation source can be cleared, be authorized for discharge to the environment, or undergo an authorized disposal route.

The establishment of an American system low-level classification parallel to IAEA's VLLW would be very useful. It would be particularly appropriate to adopt VLLW in order to effectively deal with the increasing quantities of this waste initiating from decommissioning activities. The comparatively high cost of disposing waste in engineered near surface facilities is prohibitive. The design of a simple (i.e., not engineered) VLLW repository is a feasible alternative. The necessity for a VLLW disposal classification equals the critical need in the United States for the development of an intermediate level (specifically for GTCC waste) geological repository.

The potential public relations problem associated with the image of reused and recycled waste outside of the nuclear industry as well as disposal in pubic landfills could bring negative reactions. However, the adoption of VLLW would greatly alleviate current national low-level problems with the adoption of an exemption (or clearance level) class [24].

It is recommended, therefore, that the concepts of low-level classification developed by the IAEA be considered for adoption into the United States system. Their adoption should enable the development of a more reasonable, efficient, cost-effective disposal system, particularly in reference to the very low level radioactive wastes generated in the processes involved in decommissioning. Additionally, the adoption of these concepts will permit a better global exchange of data concerning the challenges involved in the disposal and recycling of low-level wastes.

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