Isolation of waste and its ionizing radiation from the biosphere (i.e. from impacting all living things) for the duration of the waste's hazardous life.*
All human activities engaged in to carry out this principle constitute "active" waste management.** A waste's hazardous life is the period of time during which loss of isolation would result in human health effects (cancer, birth defects, and inheritable genetic mutations) or ecological impacts above the U.S. Supreme Court recognized de minimis risk level of one in a million per lifetime for the maximally exposed individual. The difficulty and cost of waste management is directly related to the waste's activity, hazardous life, volume, and physical-chemical form.
"Active" waste management should include, to the extent that it is possible, waste segregation by half-life or half-life range at the point of generation.
Although important for wastes of all half-lives, this management principle has been most used by the medical community for their largely short-lived wastes. By enabling containers of decayed isotopes to be rotated out (and new waste in) as soon as their hazardous life has ended, storage space requirements are minimized and efficiency is increased, i.e. costs are reduced.
"Active" waste management should prevent the original waste volume from increasing, excepting actions to increase waste form stability (see below).
Volume reduction methods have the potential to increase management efficiency, i.e. reduce management costs. However, any volume reduction methods used (incineration, compaction, etc.) must comply with Principle 1. For example, incineration may produce atmospheric releases that would violate Principle 1.
- In addition to appropriate packaging, waste form stabilization may be necessary to reduce the potential for waste mobilization by the physical conditions which are present in the storage environment. The longer the hazardous life of the waste, the greater the requirement for an equally durable waste stabilization method.
Stabilization methods range from simple absorption of fluids to solidification by mixing the waste with cement, bitumen, etc., to vitrification. Many stabilization methods, in addition to their initial direct cost, increase the volume to be managed and thus decrease management efficiency. For long-lived wastes, however, substantial gains in the duration of waste immobilization (up to and including immobilization for the duration of the hazardous life) can more than offset these increased costs - when the alternative is repeated re-containment and repackaging of an increasing contaminated volume, which result in noncompliance with Principles 1 and 3 (see Principle 7 below). Also, if loss of "active" management is considered likely before the end of the waste's hazardous life, then to the extent that the selected stabilization method contributes to satisfying Principle 1, such up-front stabilization becomes even more important.
Ideally, the stabilization method selected should provide waste immobilization throughout the duration of the waste's hazardous life. The stabilization method selected should be appropriate to the waste's hazardous life. For example, vitrification would probably not be chosen to stabilize cobalt-60 waste (half-life of 5 yrs), but it could be appropriate for americium-241 (a TRU waste with a half-life of 420 yr.). For wastes with long hazardous lives (greater than 10,000 years, perhaps less) even vitrification cannot satisfy this goal.
Facilities for the management of long-lived wastes should be located at site(s):
where existing and foreseeable physical conditions are most favorable for maximizing the longevity of the particular waste form, whether stabilized and packaged or in bulk form (example, soils), and
where, should loss of "active" management or human awareness of the hazard occur, the least cumulative environmental impact to life can be expected to result.
Environmental monitoring should be provided at all waste storage facilities.
The following example based on the West Valley "RTS drum cell" materials illustrates the value of this principle in assessing waste management options:
You are given a waste containing mainly Cs-137 (half-life, 30 yrs) with traces (30 nanocuries/g) of TRU wastes (transuranic wastes consist of man-made isotopes heavier than naturally-occurring uranium) stabilized by mixing with cement and packaged in steel containers. Assume that under dry storage conditions (optimum conditions) such a waste form will maintain its integrity for 300 years. If you're already asking what the original activity of the Cs-137 is, or what the half-lives and activities of the TRU materials are, ignore these for the moment and simply assume the hazardous life of the waste is 300 years. Assume that there are two possible sites for long-term storage. One storage site has been identified where the optimum physical (environmental) storage conditions exist and are projected to prevail throughout the waste's hazardous life (300 yrs). The cost of moving the waste to this site is 10. The other storage site is expected to experience increasingly wet conditions, under which the waste form is expected to deteriorate in 120 years. Periodic re-containment and repackaging of larger contaminated waste volumes during the remainder of the hazardous life is expected to cost 10 (constant units).
- Which site option is better?
- If "active" management were to cease at the wet site after 100 years?
- If recontainment costs were estimated at 5, but "active" management ceased at 100 years?
- If recontainment costs were 20, and "active" management continued throughout the hazardous life?
- What about exposures during remediation?
Now, for each of these scenarios, factor in the TRU content of the waste, 30 millicuries per ton, and ask the same questions. What is the TRU source term? Approximately 200 curies of Am-241 (half-life of 420 years). Is the stabilized waste form "good enough" or, more precisely, long-term cost effective in satisfying Principle 1, considering the TRU source term and the originally proposed DOE/NYSERDA long-term management option: a tumulus (clay-capped landfill)?
Storage facilities should be designed so that the packages of stabilized waste can be retrieved intact in the event that:
the waste form is not expected to maintain its integrity throughout the waste's hazardous life,
the site's storage conditions deteriorate, or
improved waste management technology is developed.
The selection and implementation of available waste management methods, or the development of new methods, which are capable of satisfying Principle 1 should not be governed solely by cost considerations.
Unfortunately, historically, 'too high' cost has been the excuse for not using waste management methods which will satisfy Principle 1. The result is often loss of isolation before the end of the wastes' hazardous lives due to inadequate waste packaging/stabilization and/or poor storage site physical characteristics; or direct environmental discharges whether from exhaust fans, incinerators, or down-the-drain dumping, etc. Such mismanagement is often sold to the public by the radioactive waste generator's PR efforts which overstate, or focus solely on, the benefit to be had from the process which produces the waste (for example, nuclear power's 1950s claim of "electricity too cheap to meter") while understating or ignoring the adverse effects resulting from waste mismanagement.
Cost can and should serve a useful role in the selection of the most cost effective (i.e. efficient) method from among various alternative management methods, all of which satisfy Principle 1. Cost does not always fill this role. For example, although segregation and onsite decay of short-lived isotopes would have been less expensive than paying the escalated disposal costs at the Barnwell, N.C. facility, many medical institutions did not adopt this method until Barnwell temporarily closed.
For relatively short-lived wastes - hazardous lives from 5 to 100 years - waste management methods and physical sites are generally available, although they may be costly, which can provide reasonably high assurance of satisfying Principle 1.
For very long-lived wastes - hazardous lives greater than 10,000 years - application of the best current waste management technologies combined with the best physical storage site characteristics cannot assure satisfaction of Principle 1, irrespective of cost considerations. Such wastes can be divided into two broad categories:
High-activity/low-volume wastes (spent fuel, high level liquid waste, nuclear reactor parts, etc.)and,
Low-activity/high-volume wastes (such as Tonawanda's uranium/radium/thorium-contaminated soils).
High-activity/low-volume wastes should be stabilized as best as is currently possible, e.g. vitrification. Where and how these wastes are then stored should take into consideration:
- the likelihood that at some point before the end of the hazardous life, "active" management will be lost,
- the possibility that new technology may be developed in the future which can be applied to the previously stabilized waste form such that Principle 1 can be more completely, or completely achieved, and
- assuming a loss of "active" management and awareness at some point, the storage site chosen should provide, for the longest period of time foreseeable, those physical conditions which will most prolong the integrity of the stabilized waste form and therefore its isolation from the biosphere. Recognizing that vitrified waste maintains its integrity longer under dry storage conditions, and in view of the possibility expressed in item 2 immediately above, the best temporary management option is probably retrievable storage at a dry surface location, as opposed to a non-retrievable, deep geologic "disposal" option.
Low-activity (lower)/high-volume wastes: DOE has maintained that it would be prohibitively expensive to use the best available stabilization method for these wastes, i.e. vitrification, because of their enormous volume. The Formerly Utilized Sites Remedial Action Program (FUSRAP) [to remediate early weapons production facilities] alone has an estimated 2.6 million cubic yards of contaminated soils and rubble to deal with. Waste management at most of these sites has been extremely poor to almost non-existent, the originally deposited waste being allowed to disperse into the environment contaminating large volumes of soil, water and air. For example, the Tonawanda Site has seen the originally deposited waste volume `grow' over sixtyfold in a mere fifty years. Tonawanda's experience underscores the importance of Principle 3. The tremendous increase in contaminated volume has made long-term management of these wastes (mostly contaminated soils) much more difficult and much more costly, and may have precluded the use of the most effective stabilization method. Since in this case waste form stabilization may not be optimized, it becomes all the more important to select the best physical site for long-term storage of such waste which will be deposited in bulk form.
But what about management of wastes with half-lives falling between these two extremes: wastes with hazardous lives of roughly 100 to 1000 years?
In focusing most of our attention on the very long-lived high-activity/low-volume wastes, there is the danger that we will neglect these materials; that cost constraints, real or perceived will result in the use of inadequate waste stabilization methods and/or non-optimal physical storage site selection, with the result that Principle 1 is not satisfied.
As can be seen from the West Valley example given above, the interplay among waste management principles, waste forms, and storage site physical factors can be complex, particularly when the waste form is poorly segregated, i.e. contains long-lived material mixed with shorter-lived material.
Given the likelihood of future cost constraints, and the questionable nature of future public motivation and will to deal with nuclear waste, it is incumbent upon us to implement the best available waste management now. Such an approach can be expected to markedly decrease the need for, and cost of, future "active" management of these wastes, and to go a long way toward satisfying Principle 1.
* The usual rule of thumb for determining hazardous life - ten times the waste's half-life - can be insufficient to satisfy this risk level depending on the initial concentration or activity (curie amount) of waste. For example, the West Valley SDA (State Disposal Area) contains 47,000 Ci of cesium-137. After ten half-lives, or 300 years, a substantial activity, 47 Ci, will remain - which by then, as a result of ongoing site erosion, could be contaminating Cattaraugus Creek and Lake Erie waters if poor management decisions are made now. Of course, the SDA contains large quantities of other radionuclides, including 120,000 Ci of nickel-63 (half-life, 100 yr.), and 100s of Ci of very long-lived Pu-239 and Pu-240.
** "Active" management as used here should not be confused with "institutional control", a waste management tool defined in current radioactive waste management regulations. Institutional control refers to the provision of site security (fencing, access restriction) and environmental monitoring at a waste management facility for a specified period (not to exceed 100 years in the case of the 10 CFR 61 low level waste repository regulations). It does not imply that Principle 1 will be met throughout this period, whereas "active" management does. Under institutional control, should loss of waste containment occur, corrective measures will not necessarily follow, i.e. public resources and/or motivation may not be available. In retrospect, the management approach taken by DOE and its predecessor agencies at many of their nuclear sites has followed just this pattern (see 8-24-94 ROLE letter to Energy Secretary O'Leary describing the history of the Niagara Falls Storage Site).
[From a February 1995 West Valley Coalition discussion paper by J. Rauch]