The role of the BDC in radioactive waste management, particularly DSRS. How useful is it to human and environmental safety Published work of Dawood et al.

1. The Borehole Disposal Concept-An Option for
Radioactive Waste Disposal
A.M.A. Dawood
(99550237752)
Department of Environmental Engineering
Anadolu University
Eskisehir

2. Order of Presentation:
❏Introduction
❏BDC As a Long-Term Management Solution For DSRS
❏ Safety Requirements For Disposal of DSRS
❏Design of the BDC
❏Operational Requirements of the BDC
❏Closure, Decommissioning and Rehabilitation &
Institutional Controls

3. 1.0 Introduction
● Radioactive sources are
widely used in most IAEA
Member States, in various
industrial, research and
medical applications.
● These sources contain
different radionuclides in
widely varying quantities.

4. 1.0 Introduction
● In some cases, the activity of the source decays to a level
below which it is no longer suitable for its original
purpose or the equipment may have become obsolete,
worn out/damaged, or the source may develop a leak.
● In all these circumstances, the radioactive sources are
referred to as “disused” or “spent”, even though their
activity could still be very high.

5. Intro’
● Disused sealed radioactive sources (DSRS) pose a significant hazard to
human beings and the environment in general if not managed
properly.
● Management of radioactive waste involves tracking, retrieving,
conditioning, characterizing, storing and eventual disposing of the
disused sources.
● This process requires a high level of technical expertise is costly.
● The IAEA through its TC project with NECSA developed a simple and
economically viable option for use by any interested member state;
● This option is termed the Borehole Disposal Concept (BDC).

6. Intro’
● The concept integrates source handling and conditioning on the
surface and emplacement of the sources in an engineered
borehole of narrow diameter (0.26m),
● Borehole depth ranges from 30 to 150 m below surface in a
suitable geological environment.
● Disposal system made up of stainless steel capsule sealed in
another container, also made from stainless steel.

7. Intro’

8. 1.1 Waste management in perspective
From storage to disposal:

9. 1.1.1 Fundamental Principles agreed upon by the international
community for the management of radioactive waste

10. 2.0 BDC as a Long-term Management Solution for DSRS
● Disposal according to IAEA definition, is the emplacement of waste in an
approved, specified facility, without the intention to retrieve the waste.
● This does not necessarily imply that the waste is not retrievable, rather
there is no intention to retrieve the waste.
● The borehole disposal option uses the multiple concepts based on a system
of several passive barriers;
● which consist of the conditioned and packaged waste, repository lining,
back-filling and other engineered barriers within the borehole repository.

11. waste packaged for disposal

12. 2.0 BDC as a Long-term Management Solution for DSRS
● The Borehole Casing stabilizes the
borehole and keeps the repository
dry during the operational period
while acting as additional barrier to
transport of the radionuclides.
● Backfilling materials add additional
barrier between the containers and
aggressive chemicals, prominently
chloride that might initiate
corrosion of the stainless steel
capsule.
★ Schematic illustrations of the two low temperature (left
and centre) and one high temperature (right) concepts
defined by Gibb
★ In high temperature concepts, HLW or SF is disposed of
[very deep disposal]
★ According to Gibb, the HTVDD concept is being less
actively considered internationally than the low
temperature concepts.

13. DSRS
● The sorptivity nature of the backfilling material makes it act as a chemical
buffer to intrinsically limit or reduce the release of radionuclides to the
geosphere;
● It also form a physical and hydrological barrier through which leached
radionuclides must pass before they are released into the immediate
surroundings.
● The underlying common characteristic of the facility is its small physical
size (footprint) at the surface, which reduces the likelihood of human
intrusion.

14. ● The BDC, apart from providing a potentially cost effective and safe disposal
option for countries with limited nuclear infrastructure, it offers the following
benefits:
● Provision of long-term isolation from humans and the environment for small
volumes of high specific activity DSRS in high integrity waste packages;
● Provision of direct and cost effective access to a suitable geological horizon,
using a readily available technology.
● In particular, an appropriate depth of disposal and geological horizon can be
selected in a cost-effective manner;
3.0 Characteristics of the BDC

15. ● It requires limited land area and limited infrastructure;
● It requires short periods of construction, operation and closure;
● It can be developed as and when required to dispose of DSRS as they arise;
● It has a low probability of human intrusion and future disruptive events due to
the small footprint of the borehole and the ability to select a suitable depth;
3.0 Characteristics of the BDC

16. 4.0 Design of the BDC
● Long-term safety of the borehole disposal facility is achieved through
a combination of natural barriers, engineered barriers, operational
procedures and institutional controls.
The design and concept adopted depend on a number of factors:
● The number of sources to be disposed of;
● The type of sources that need to be disposed and their radionuclide
content;
● The period of time over which the sources will arise and the facility
will need to be operational;
● The availability of suitable disposal environments;
● The availability of appropriate drilling and engineering technologies;
and availability of resources.

17. 4.0 Design of the BDC
The BDC design is an ab-initio process implemented from initiation through to
completion. It informs the following activities:
● Suitable site selection: the site should have features which when combined
with the facility and waste package design, provides adequate isolation of
radionuclides from the biosphere for the required periods of time.
● Engineered waste package: refers to the product of conditioning that
includes the waste container and container backfill material prepared in
accordance with requirements for the disposal of DSRS.

18. 4.0 Design of the BDC
● Container durability: the correct selection of container materials is
essential for satisfactory performance of the concept;
● Their resistance to degradation and corrosion in long-term consideration
which is a function of the waste characteristics.
● Other essential factors include; Container dimension, handling of
containers, container shape, container backfill etc.

19. 5.0 Safety Requirements for Disposal of DSRS
● One of the basic requirements of the borehole disposal concept is
the implementation of measures that will afford the protection of
human (workers and general public) and the larger environment as a
function of time.
● Observance of internationally agreed fundamental principles of
radioactive waste management (international principles).
● During the operational phase of the facility, safety can be assured by
conventional operational radiation protection programmes;
guided by relevant international standards (IAEA).

20. 5.0 Safety Requirements for Disposal of DSRS
● Doses to workers and members of the public exposed as a
result of operations at the disposal site shall be as low as
reasonably achievable (ALARA),
Relevant considerations during operation include:
● Separation of drilling and waste emplacement activities,
● Use of remote handling and shielded equipment for waste emplacement,
● Minimization of the potential for accidents and their consequences, and
● Minimization of maintenance requirements in radiation and contamination areas.

21. 5.1 Legal and Organizational Framework
● Besides the development of the
necessary technical and operational
capability, safe management of
radioactive waste is also promoted by the
existence of an appropriate legal
infrastructure.
● The development of a borehole disposal
facility should therefore be carried out in
compliance with any relevant national
and international regulations.

22. 5.1 Legal and Organizational Framework
Particular consideration needs to be given to:
● Compliance with radiation protection criteria for
occupationally exposed workers and members of the public in
normal operation and accidents;
● Compliance with operational limits and conditions, with
specific emphasis on waste acceptance criteria;
● Implementation of corrective actions in case deviations are
detected; and
● Performance of adequate control of the disposal site (e.g.
monitoring).

23. 6.0 Operational Requirements of the BDC
Before the commencement of construction of a repository, a
comprehensive and systematic assessment of its safety throughout its
operating lifetime and the period following closure, must be performed.
● The implementation of the borehole disposal concept in any country
can be divided into several stages, which are embodiment of the
concept and include the following:
● Site selection, site characterisation and data acquisition;
● Operational and long-term (post-closure) safety assessment of the
borehole;

24. 6.0 Operational Requirements of the BDC
●Conditioning of the sources into suitable waste packages;
●Transport of waste packages to disposal facility;
●Preparing the repository;
●Acceptance of waste packages at the repository;
●Emplacement of the waste packages in the repository;
●Closure of the repository; and
●Institutional controls.

25. 7.0 Closure, Decommission and Rehabilitation
& Institutional Controls
● Closure, decommissioning and rehabilitation of the repository will
take place after the receipt of waste ceases and waste emplacement
operations have been completed.
● Engineered barriers, particularly the final cover, are emplaced to
ensure the integrity of the repository and minimize ingress of
infiltrating water to the waste, thereby limiting radionuclide releases,
and also to reduce the likelihood of disturbance by human activities.
● The closure can include the physical marking of the borehole, if
required.

26. 7.0 Closure, Decommission and Rehabilitation
& Institutional Controls
● After repository closure, institutional controls are considered as
an optional activity by the host country.
● The controls can be either active (for example, monitoring and
surveillance) or passive (for example, land use control and
record keeping).
● Controls maintained over a repository after closure are designed
to enhance its safety, in particular, by preventing intrusion into
the disposal units.

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