Transcript Document

Management of disused sealed
radioactive sources
IAEA
International Atomic Energy Agency
Day 9 – Lecture 7
Objective
• To provide some high-level insights into the
hazards associated with sealed sources
• To discuss various methods of judging the
likely magnitude of these hazards based on
The identity of the radionuclide in question
The level of radioactivity
• To consider the implications for predisposal
management
• To consider some disposal options
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Content
• Identification of Problem Sources
• Characterization of disused Sources
• Safe management of
disused sealed sources
• Conditioning and Packaging of Disused
Sources
• Storage of disused sources
• Disposal Considerations
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Introduction
• Disused sealed radiation source
A source permanently sealed in a capsule, or closely bonded and in a
solid form, emitting ionizing radiation and that is no longer in use or
intended to be used
• In use since 1901; until 1940 limited to radium used in
medicine thus resulting in widespread storage of radium
needles
• Today, widely used in medicine, industry, agricultural,
research and consumer products
• Physically small, but contain high concentrations of
radionuclides
• Require heavily shielded containers for safe use, transport and
storage
• Give rise to serious safety problems if not managed properly
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Introduction
• Poor management practices resulted in disused sources
being stored in unsatisfactory conditions or no longer under
regulatory control.
• Deliberate and malicious acts involving disused sources
• Chechens placed a Cs-137 container in Moscow park (1995)
• Lithuanians arrested with Cs-137 in their possession (Vilnius, 2002)
• Accidents involving abandoned, lost or stolen gammaradiation sources
• Cobalt-60 in Juarez, Mexico, 1983
• Cesium-137 in Goiania, Brazil, 1987
• Others include accidents
• Morocco (eight people died)
• Shanxi Province in China (54 injured, 4 died)
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Hazards
• Radioactive sources can present a hazard in
various ways:
External exposure
Ingestion
Inhalation
Dermal absorption
• The type and magnitude of the hazard
depends on the radionuclide and the level of
activity
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Why do we need better management?
• SRS found in virtually all countries – approximately two
million devices containing sources in the US.
• A small percentage are not properly controlled.
• Approximately 375 sources or devices are lost or stolen in
the US each year.
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Reasons for loss of source control
Experience shows that:
• Mobile sources are lost or stolen while in transit.
• Sources are abandoned, either deliberately or
through lack of awareness.
• Sources are stolen, either for the scrap value of
the source or its container
• Political instability and economic hardship.
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Activity ranges of radiation sources
Miscellaneous waste containing DSRS
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Sr-90 radioactive source
recovered in the Rep. of Georgia
Sources used in mobile caesium
irradiators in the former Soviet Union
Miscellaneous waste
containing DSRS
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Categorization of disused sources
• IAEA TECDOC 1344 (Categorization of radioactive sources)
• To provide a simple, logical system for ranking radioactive sources
• Their potential to cause harm to human health
• Group practices in which sources are used into discrete categories
• To provide a fundamental and internationally harmonized basis for riskinformed decision making
• Used as an input to activities relating to the safety and security of
radioactive sources
• Develop or refine (inter)national safety standards
• Develop or refine national regulatory infrastructures to meet the State’s
•
•
requirements
Optimize decisions about priorities for regulation within resource constraints
Optimize security measures for radioactive sources, including potential malicious
use
Emergency planning and response
Develop national strategies for improving control over radioactive sources
•
•
• Each category contains a mixture of radionuclides, half-lives
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Categorization of Radioactive Sources
used in Common Practices
Category
Typical uses
Activity Ratio A/D
1
Radio-thermal generators;
Irradiators; Teletherapy; Gamma
knife
A/D>1000
2
Gamma radiography
Brachytherapy(HDR/MDR)
1000>A/D>10
3
High activity industrial gauges
Well logging
10>A/D>1
4
Brachytherapy (LDR except eye
1>A/D>0.01
Dangerous
sources
plaques & perm implants)
Low activity gauges; Static
eliminators; Bone densitometers
5
Brachytherapy (eye pl. & perm
implants); XRF; ECD
A = source activity;
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0.01>A/D>Exempt/D
D = radionuclide-specific “dangerous” activity
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Categorization of disused sources
• IAEA-TECDOC-1368 (Safety considerations in the disposal of disused
sealed radioactive sources in borehole facilities)
• Categorize sources according to radioactive half-life
• More suitable to define long-term management strategies for disused sealed
radioactive sources
• Make distinction between three categories
• Category 1: Half-life < 100 days
• Category 2: 100 days < Half-life = 30 years
• Category 3: Half-life > 30 years
• Expected required containment period under natural radioactive decay
• Maximum expected activity for each radionuclide in each category
• Radioactive half-life
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Best Options for Disused Sources?
• Return to supplier
• Long term storage (50 y, 100 y, ???)
• Disposal
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Safe management of
disused sealed sources (I)
• Sealed sources are considered to be disused when:
• the practice is decided not to be continue,
• they have decayed to the extent that they
are no longer useful for their original purpose,
• because the appliance in which they are
housed has become outdated, or
• because routine tests have indicated that the
source is leaking.
• Spent or disused sealed sources are not
considered waste in certain States but
the safe management of such sources is achieved by
compliance with the requirements for radioactive waste.
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Safe management of
disused sealed sources (II)
• The most important consideration in the
management of sealed sources, once they are
no longer useful, is the maintenance of
continuity of control.
• The operator and the regulatory body should
make provision to maintain and periodically
review the status of control of such devices
and material.
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Safe management of
disused sealed sources (III)
• Wherever possible, when purchasing sealed sources,
contractual arrangements should allow the return of
sources to the manufacturer or predetermined waste
manager following use.
• Recycling and reuse can involve the following
activities:
 Reuse of sealed sources by the owner or a new owner;
 Recycling of sealed sources by the manufacturer;
 Decontamination and/or reuse of material;
 Recycling and reuse of material that fulfils the conditions
for the removal of regulatory control.
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Safe management of
disused sealed sources (IV)
• Once the disused sealed source is
declared radioactive waste, its
safe management should comply
with the safety requirements for
the management of radioactive
waste
• Safety related details of the
history of disused sealed sources,
considered as waste, should be
included in the inventory.
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Safe management of
disused sealed sources (V)
The following aspects should be considered in respect of
the safe management of spent and disused sealed
sources:
(a) The further authorized use of the disused source by some
other authorized organization;
(b) Return of the source to the supplier;
(c) Temporary storage in its original shielding (for example for
radionuclides with half-lives of less than 100 days);
(d) Conditioning (for example overpacking);
(e) Long term storage (such as in a dedicated storage facility);
(f) Disposal.
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Safe management of
disused sealed sources (VI)
• For spent and disused sealed sources with short halflives, secure storage for decay may be the preferred
option.
• All spent and disused sealed sources should be
conditioned
• Long lived sources are generally conditioned by means
of encapsulation into welded steel capsules to facilitate
future management.
• Conditioning methods should be approved by the
regulatory body.
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Safe management of
disused sealed sources (VII)
• Where the operator does not have the expertise for the
conditioning of spent and disused sealed sources or
adequate storage facilities, arrangements should be
made to transfer the sources to another licensed
organization with proper and adequate facilities.
• Centralized facilities should be established for the safe
long term storage of spent and disused sealed sources
containing 226Ra, 241Am and other long lived
radionuclides.
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Safe management of
disused sealed sources (VIII)
• Sealed sources should not be subjected to
compaction, shredding or incineration;
• Sealed sources should not be removed from their
primary containers,
• Peripheral components of large irradiation equipment
should be removed, monitored and disposed of
appropriately;
• A safety assessment and environmental impact
assessment should be carried out before any
operations are undertaken.
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Safe management of
disused sealed sources (IX)
• For sources (such as spent radium sources) with a
potential for leakage, particular radiological
precautions should also be taken during the handling
and storage.
• Special attention should be paid to monitoring for
surface and airborne contamination. These sources
should be stored in a dedicated area with appropriate
ventilation and equipment.
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Orphan sources
• States should establish and implement appropriate
strategies for these ‘orphan’ sources.
• Strategy should ensure that whenever an orphan
source has been identified, appropriate recovery
measures are taken.
• The State should:
• Identify responsible organizations and
• funding within the State to recover, handle, condition, store
and, if necessary, dispose of the source.
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Accidental generation of radioactive waste
• Loss and misuse of sealed sources can give rise to
accidents and the contamination of working premises
and land.
• This can lead to the unplanned and accidental
generation of radioactive waste.
• Technical and organizational means should be in place,
including the necessary contingency arrangements, for
the processing and storage of any such accidentally
generated radioactive waste.
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Conditioning and packaging
of disused sources
• Conditioning
• Those operations that produce a waste package
suitable for handling, transport, storage and/or disposal
• Conditioning may include the conversion of the waste
to a solid waste form, enclosure of the waste in
containers and, if necessary, providing an overpack
• Packaging
• Preparation of radioactive waste for safe handling,
transport, storage and/or disposal by means of
enclosing it in a suitable container
• Include disused source handling facility in management
strategy
• Source characteristics and national or regional strategy
will determine conditioning strategy
• Conditioning performed for storage must take possible
disposal option into consideration
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Conditioning and Packaging of Disused
Sources
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Storage of Disused Sources
Issues to consider
• Storage conditions are not always satisfactory
• Most sources remain in storage pending availability of
a suitable disposal option
• Adequate final management option for sources
containing short-lived radionuclides
• Centralized storage facility for a country/region
• Various options can be used as storage facilities
– Shipping container
– Corrugated iron shed
– Below surface (basements)
– Boreholes
• Record keeping and radiation protection principles
essential
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Storage of Disused Sources
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Storage of Disused Sources
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Terrorist threat
• New paradigm must be built into your safety case for
operating and disused sources.
• How long will we be concerned about this threat? –
Forever!!
• Concerns many players in the national system of
protection.
• Ultimate responsibility with the Operator.
• Safety and security systems must evolve.
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Disposal of Disused Sources
Issues to consider
• Waste acceptance criteria
– Many sources exceed criteria for near-surface disposal
facilities
– Constitute high, localized conc. (hot spots)
– Unacceptable risk during human intrusion conditions
– Reasonable assurance of compliance with safety
requirements not always adequately demonstrated
– Assumed institutional control not always the answer
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Disposal of Disused Sources
Higher levels of isolation required
– Geological disposal a possibility, but usually not
available
– Lack of long-term waste management infrastructure
– Borehole disposal of disused sealed radioactive
sources
IAEA Safety Guide SSG-1
– Safety considerations in the
disposal of disused sealed
radioactive sources in borehole
facilities
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Disposal of Disused Sources
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Disposal of Disused Sources
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Disposal of Disused Sources
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References
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