The Activist's Guide to Uranium Mining
(last updated 15 Feb 2011)
3. The regulatory framework required for uranium mining
Introduction to environmental standards for uranium mines and mills
Ways to define standards for contaminants:
- Emission standard at source:
- such as release rate [Bq/s] of radon from the mine, or from the tailings surface, of radionuclides by windblown dust, with effluents and seepage,
can mostly be assured by design, but actual hazards and doses obtained at the point of compliance may differ from the generic calculations on which the standards were based on,
- Concentration standard at point of compliance:
- such as radon concentration in air [Bq/m3]; radionuclide concentrations in dust [Bq/g dust] or [Bq/m3 air], contaminant concentrations in groundwater and surface water [Bq/l], radionuclide concentrations in soil [Bq/g],
requires monitoring, involving uncertainties depending on atmospheric conditions etc.; the actual hazard posed by these contaminant concentrations depends on land usage and behaviour of the residents and may therefore differ from the generic calculations on which the standards were based on,
- Dose standard at point of compliance:
- such as dose from external radiation, or from inhalation of radon and dust,
requires monitoring and modeling; the inhalation pathway involves uncertainties depending on atmospheric conditions; the dose modeling calculations open up endless possibilities for discussions and manipulations; on the other hand, they are the only way to provide an assessment of the actual hazard presented by the contaminants present.
Emission standards are either defined as
While specific release rate standards don't limit the total emission, they do have the advantage of being easier to accomplish by standard designs. Therefore, when establishing a specific release rate standard, the maximum total release from a source must be taken into consideration to limit the concentration or dose at the point of compliance appropriately.
- total emission rates
- for example: Bq/s, as used for radionuclide releases from mine ventilation systems, or as
- specific emission rates
- for example: Bq/l, as used for radionuclide releases in effluents per unit volume, or Bq/(m2·s), as used for radon release rates from tailings deposits per unit area.
Most legislations provide a mix of emission, concentration, and dose standards.
see also Radiation Exposure for Uranium Industry Residents
Types of radiation exposure standards for uranium mine and mill workers
- external radiation exposure
- mostly to gamma radiation, but also some beta radiation, directly measured by portable dose meters carried by the worker on his person,
- inhalation of radon progeny in air, based on
- concentrations directly measured by portable devices carried by the worker on his person, with uptake calculated using standard breathing rates (see also Radon Individual Dose Calculator)
While radon is easier to measure, the radiation dose is mostly caused from the radon progeny; the ratio between radon and radon progeny (expressed by the equilibrium factor) varies, however.
- inhalation of radionuclides in dust, either based on
- calculated or measured contaminant concentrations in air, from which an uptake into the body is calculated using recorded occupancy times and standard breathing rates (see also Uranium Radiation Individual Dose Calculator),
- measured contaminant concentrations in excreta (in particular uranium in urine with uranium mill workers), with uptake calculated using ICRP's biokinetic model for uranium and standard or measured excretion rates (see also Uranium Biokinetics Calculator), or
- measured contaminant concentrations in the body (whole body counting in case of accidental overexposure of uranium mill workers),
With given exposure records, the Uranium Miner Health Risk Calculator can be used to estimate the risk of a particular (former) uranium miner of contracting certain cancers (especially lung cancer), and, in case he has contracted cancer, the probability of this cancer being caused by the radiation exposure.
see also Radiation Exposure for Uranium Industry Workers
Aims of decommissioning
- reduce the health risk for current and future residents to acceptable levels
- reduce environmental hazards to acceptable levels
- spend reasonable efforts to make the measures taken effective in the long-term
Issues for consideration
- What is the acceptable risk level from residual hazards?
- While there exist toxicity thresholds for chemical contaminants, radiological hazards are assumed to have no such threshold; so a decision has to be made about what risk level is acceptable.
The International Commission on Radiological Protection's (ICRP) widely accepted 1 mSv per year radiological dose standard for members of the public, for example, implies a 1 : 286 mortality risk for continuous exposure at this level during a 70-year lifetime. However, risks usually accepted with non-radiological hazards are much lower - in the range of 1 : 10,000 to 1 : 1,000,000 (see also Uranium Toxicity).
- Dose standards for radiological hazards: individual and/or collective dose?
- Individual dose standards limit the health risk for each individual person affected, but the total number of health impacts caused by a site can only be limited by an additional collective dose standard.
- Dose standards for radiological hazards: consideration of hazards from multiple sources
- For areas, where residents may be affected by multiple sources, a decision has to be made, how to deal with the resulting combined risk:
- the project either is allotted the full acceptable risk, independent of the presence of other sources - leading to exceeding the dose limit for multiple sources, or
- the project is allotted a certain fraction of the full acceptable risk, taking into account the currently existing multiple sources - leading to exceeding the dose limit, if additional sources are added in the future, or
- the project is allotted only some fraction of the acceptable risk, independent of the actual number of other sources, to leave room for the addition of future sources.
- Restricted or unrestricted site access after reclamation?
- Matters to be considered include, among others:
- accident hazards from mine openings, pit walls, pit lakes
- radiation hazards from tailings and waste rock deposits
- deterioration of protective covers etc.
- health hazards from intrusion into and misuse of tailings material
- Is there any post-closure use of the site to be permitted, and if so, at what restrictions?
- Post-closure use may damage the disposal cell.
- Point of compliance for contaminant concentration standards and dose standards
- Are these standards to be met...
- on site (in particular for sites with unrestricted access!),
- at the site boundary, or
- only at actually existing residencies (and other existing points of interest)?
- However, land usage may change over longer periods of time
- Occupancy times to be assumed for contaminant concentration standards and dose standards:
- Are these standards to be met...
- for permanent occupancy, or
- some shorter occupancy periods actually encountered at currently existing impact sites?
- However, occupancy behaviour may change over time.
- Type and severity of natural events that the measures taken have to withstand - with and/or without active maintenance (heavy rain, floods, earthquake, burrowing animals, etc.)
- Time period for effectiveness of the measures taken
- The tailings remain radioactive for hundreds of thousands of years, but there are no proven methods available known to stay effective that long. So, what is an acceptable compromise?
- Rationales for groundwater standards for contaminants:
- Return to background
- however, the background is often difficult to determine and subject to fluctuations, and/or a return to background may be impossible to achieve,
- Conform to some general standard
- in some cases, however, the background is already higher than the general standard,
- Conform to some site-specific standard
- this makes the standard an object of negotiation between company and authority - this is not exactly what you call a standard?
- Time allowed for completion of decommissioning after halt of operations
- If no mandatory timeframe is defined, the company each year will present new reasons for not completing - or even not beginning - decommissioning, and the likelihood the site will ever be cleaned up decreases year by year.
see also Bibliography: Cleanup of Radiation Sites
see also Unit Converter