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The views and opinions expressed herein reflect only those of the author. These views or opinions may or may not represent or reflect the views or opinions of any past, current or future employer(s) or colleagues.
Richard O’Brien
Melbourne, Victoria, 2016
3
Why NORM might need control
Very large volumes of material phosphogypsum pile - Florida
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Why NORM might need control
Electricity generation fly ash, bottom ash, volatiles
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Why NORM might need control
Contaminated sites from past practices Coal mining in Silesia – SW Poland
Other contaminants – mine water with high salt concentrations
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Why NORM might need control
Failure of engineered barriers Poor siting
Uranium mine waste repository in Estonia
Documents ICRP Publication 101 – published in 2006
Planned, existing and emergency exposures ICRP Publication 103 – published in 2007 IAEA Safety Glossary – published in 2007
New definition of NORM
RPS-15 – published by ARPANSA in 2008 IAEA TECDOC 1712– published in 2013
“Management of NORM Residues”
GSR Part 3 – published by the IAEA in 2014 DS459 – draft – published by the IAEA in 2014/15
Management Tools
New IAEA waste classification system Planned exposures Existing exposures Graded Approach Assessment Waste minimisation
The new IAEA waste classification system
Very short-lived waste (storage, decay)
Intermediate level waste (intermediate level disposal) Low level waste
(near surface disposal)
High level waste
(deep geological disposal)
Exempt waste (exemption, clearance)
Very low level waste (landfill disposal)
Act
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Half-life
DEFINITION A planned exposure situation is a situation of exposure that arises from the planned operation of a source or from a planned activity that results in an exposure from a source. Since provision for protection and safety can be made before embarking on the activity concerned, the associated exposures and their likelihood of occurrence can be restricted from the outset. The primary means of controlling exposure in planned exposure situations are by good design of facilities, equipment and operating procedures and by training. In planned exposure situations, exposure at some level can be expected to occur. If exposure is not expected to occur with certainty, but could result from an accident or from an event or a sequence of events that may occur but is not certain to occur, this is referred to as ‘potential exposure’.
DOSE LIMIT
1mSv/a for a member of the public
Planned Exposures
DEFINITION An existing exposure is a situation of exposure which already exists when a decision on the need for control needs to be taken. Existing exposure situations include situations of exposure to natural background radiation. They also include situations of exposure due to residual radioactive material that derives from past practices that were not subject to regulatory control or that remains after an emergency exposure situation. REFERENCE LEVEL
1-20 mSv/a for a member of the public
Existing Exposures
• This simply states that the effort put into controlling risk should be commensurate with the level of risk
• This should be axiomatic in any risk management plan
Graded Approach To Risk Management
Original definitions: • NORM - naturally occurring radioactive material • TENORM – technologically enhanced naturally occurring radioactive
material
Since something that is technologically enhanced cannot occur naturally, this led to two ideas: • It makes more sense to consider NORM as material containing
naturally occurring radionuclides • It makes sense to only consider situations (concentrations or
exposures) that are amenable to control
This led to the definition used in the IAEA Safety Glossary: • NORM is any material containing predominantly naturally occurring
radionuclides whose concentrations have been altered from their original values by human action
NORM and TENORM
The latest definition (DS459) introduces several new ideas:
• If, in every process material, the activity concentrations of all radionuclides in the 238U and 232Th decay series are 1 Bq/g or less and the activity concentration of 40K is 10 Bq/g or less, the material is not regarded as NORM, the industrial activity is not regarded as a practice and the requirements for existing exposure situations apply.
• If, in any process material, the activity concentration of any radionuclide in the 238U or 232Th decay series exceeds 1 Bq/g, or if the activity concentration of 40K exceeds 10 Bq/g, that material is regarded as NORM, and the requirements for planned exposure situations apply.
NORM and TENORM
One problem with the use of the terms “planned” and “existing” is that the definitions modify the normally accepted meaning of these words. Another problem with this approach is that a new facility for processing mineral ore could give rise to an existing exposure situation, which is not desirable. These and other difficulties could be overcome by: • using “planned exposure” to describe only proposed operations; • using “existing exposure” to describe only those situations which
exist before a decision on whether to introduce regulatory control is taken, i.e. legacy sites and operational sites which are not under regulatory control;
• Using “controlled exposure” to describe current operations which are licensed.
Issues
Another significant problem with this approach (and the approach adopted in DS459) is shown by the following example: Case 1: Mine waste with an average concentration of 10 Bq/g U-238 in
equilibrium with its progeny and 10 Bq/g Th-232 in equilibrium with its progeny – returned to mine
Case 2: Mine waste with an average concentration of 0.8 Bq/g U-238
in equilibrium with its progeny and 0.8 Bq/g Th-232 in secular equilibrium with its progeny – used as surface landfill – remote site
Case 3: Mine waste with an average concentration of 0.8 Bq/g U-238
in equilibrium with its progeny and 0.8 Bq/g Th-232 in secular equilibrium with its progeny – used as surface landfill – land used for residential purposes
Assessment
Case 2 is an existing exposure, while Case 1 is a planned exposure However, a dose assessment shows that Case 2 gives the higher dose, which is inconsistent with the intent of planned and existing exposures. Cases 2 and 3 are both existing exposures, but the impacts are quite different, because of the different site characteristics Comparing case 3 with natural background, the annual dose to an individual living on this landfill could be of the order of 40 mSv per year.
Assessment
The very long life-times of the radionuclides in NORM (wastes and residues) means that the activity concentrations will not decrease significantly (if at all) over any practical institutional control period that could be applied, following NORM disposal. This is best handled by setting closure requirements that will optimise the probability that the disposal site will remain in compliance with current legislative and regulatory requirements under all reasonably foreseeable circumstances. The simplest way to handle this issue is by carrying out a site-specific impact assessment which allows for a range of possible future uses of the disposal site. This cannot be done relying only on activity concentrations.
Long-term Safety
The example given in the previous slide clearly shows that: 1. It is the exposure scenario(s), not the activity concentration that should
determine how the situation is regulated: • Basing NORM management on activity concentration leads to
contradictory outcomes with respect to planned and existing exposure situations;
• Basing the management of NORM on a tiered assessment process
similar to that described in RPS-15 resolves these situations – it also avoids the possibility of a false negative (classifying a situation as safe when it is not).
2. Regulatory control should be applied to the action, not the material that
is being handled. This is done, for example, with the Transport Code, but should be applied in all situations.
3. Planned and existing exposures are not useful in NORM management.
CONCLUSIONS
Thank you for your attention
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