Transcript Document

Radioactive Waste Arising, Waste
Classification, and Safety Requirements
for Waste Disposal
IAEA
International Atomic Energy Agency
Day 9 – Lecture 6
Objectives
• To provide an overview of radioactive waste arising and
classification, waste characteristics and management options.
• To introduce the IAEA waste classification system.
• To discuss about the requirements for the protection of public and
environment and assurance of safety for the waste disposal
facilities during the operational and post-closure period
• To give examples of final disposal choices
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Contents
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Sources of Radioactive Waste
Waste Properties.
Waste Management Approaches
Waste classification
IAEA Waste Classification System
Waste Disposal Options
Requirements for protection of public and
environment and safety of waste disposal facilities
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Introduction
Radioactive waste arises from many
different activities, for example:
• Operation and decommissioning of nuclear
facilities (e.g. nuclear power plants);
• Application of radionuclides in industry,
medicine, and research;
• Cleanup of contaminated sites; and
• Processing of raw materials containing
naturally occurring radionuclides.
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Sources of Radioactive Waste (1)
Nuclear fuel cycle - Power generation
•Operational waste
Ion exchange resins, evaporation and filtering
residues
Metal scrap, thermal insulation material,
protective clothing
 Very low to medium level concentrations of RN
• Spent nuclear fuel
 Large inventory, large number of radionuclides
•Decommissioning waste
 Large amounts
Very low to high concentrations - mainly
activation products
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Sources of Radioactive Waste (2)
Nuclear fuel cycle - Various
• Mining and milling and U ore extraction
–
–
–
Large quantities
Enhanced levels naturally occurring radionuclides
Radium-226, radon-222
• Chemical refining
– small amounts of waste
• Enrichment
– depleted uranium a waste?
• Reprocessing of spent fuel.
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Sources of Radioactive Waste (3)
Industrial applications
• Production of radioactive sources
• Use of radioactive sources
• Sealed sources
Thickness, level and density gauges
Industrial radiography, sterilization facilities
Large number of potentially hazardous
sources
• Unsealed sources
Tracers, monitoring
Mostly short-lived radionuclides
• Co-60, Cs-137, Ir-192, Am-241,…
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Sources of Radioactive Waste (4)
Medical applications
• Diagnosis and treatment
• Large number of administrations and
•
•
•
•
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operations
Short-lived liquid and solid waste
Large activity administrations
High-activity sealed sources
Tc-99m, I-131, P-32, Y-90, Sr-89
Co-60, Ir-192, Cs-137
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Sources of Radioactive Waste (5)
Research and development
•
•
Wide variety of uses
Wide variety of techniques
Other:
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historical sources - radium processing
defense programs – legacy wastes
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Sources of Radioactive Waste (6)
Wastes containing naturally
occurring radioactivity (NORM)
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•
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Phosphate industry
Production of metals
Refractory materials
Energy Production (Oil and
Gas, Coal, Biomass,
Geothermal)
Usually large volumes, Ra-226,
Rn-222
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Waste Management Approaches
Waste and
materials
Pre-treatment
Effluent
discharge
Treatment
Clearance
Conditioning
Recycling
and re-use
Disposal
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Waste Management Approaches
• ‘Delay and Decay’ – hold waste in storage
until sufficient decay has occurred for
desired management approach
• ‘Concentrate and Contain’ – reduce
volume and condition and/or
containerize waste to limit dispersion in
the environment
• ‘Dilute and Disperse’ – discharge waste
in a manner that environmental
conditions reduce concentrations to
acceptable levels
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Waste classification - Purpose
Purpose - for safety, engineering, operational and
regulatory aspects:
•
Devising radioactive waste management strategies,
planning, designing and operating waste management
facilities;
•
Facilitating record keeping and giving a broad indication
of the potential hazards involved in the various types of
waste at the operational level;
•
Communication between interested parties by providing
well understood terminology (e.g., Joint Convention)
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Possible ways to classify
Some of the possible ways to classify waste:
• Classification by origin
Nuclear fuel cycle, isotope production,..
• Classification by physical state
Solid, liquid, gaseous
• Classification by activity concentration
Very Low Level waste (VLLW), Low Level Waste
(LLW), Intermediate Level Waste (ILW), High
level Waste (HLW)
• Classification by half-life
Short-lived waste, long-lived waste
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Need for a classification system?
• Permits appropriate decisions to be made at each
step of lifecycle management of wastes.
• Provides a systematic foundation for waste
segregation programmes.
• Efficient management system for operators
(otherwise decisions are ad hoc or made on case
by case basis).
• Provides essential input for national WM policy &
strategy.
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Summary of IAEA Waste Classification
System (GSG-1)
Objectives
• To set out a general scheme for
classifying radioactive waste that is
based primarily on considerations of
long term safety, and thus, by
implication, disposal of the waste.
• To identify the conceptual boundaries
between different classes of waste and
provides guidance on their definition
on the basis of long term safety
considerations.
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Summary of IAEA System GSG - 1
The IAEA system
(1) Exempt waste
(2) Very short lived waste (VSLW)
(3) Very low level waste (VLLW)
(4) Low level waste (LLW)
(5) Intermediate level waste (ILW)
(6) High level waste (HLW)
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Summary of IAEA System GSG - 1
In the classification scheme, the following options for
management of radioactive waste are considered, with an
increasing degree of containment and isolation in the long
term:
—Exemption or clearance;
—Storage for decay;
—Disposal in engineered surface landfill type facilities;
—Disposal in engineered facilities such as trenches, vaults or shallow
boreholes, at the surface or at depths down to a few tens of metres;
—Disposal in engineered facilities at intermediate depths between a few
tens of metres and several hundred metres (including existing caverns) and
disposal in boreholes of small diameter;
—Disposal in engineered facilities located in deep stable geological
formations at depths of a few hundred metres or more.
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Exempt Waste (EW)
Waste that has been cleared,
exempted or excluded from
regulation as described in Safety
Guide RS-G-1.7 “Application of
the Concepts of Exclusion,
Exemption and Clearance” (2004)
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Very Low Level Waste (VLLW)
Waste containing material that can be slightly
above the exempt region. Disposal facilities for
such waste do not need a high level of containment
and isolation and near surface landfill is generally
suitable. Typical waste would include soil and
rubble with activity low enough not to require
shielding.
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Very Short Lived Waste (VSLW)
Waste that can be stored for decay over a limited
period of up to a few years and subsequently
cleared for uncontrolled disposal or discharge after
a suitable period of storage. This would include
radioactive waste containing short half life
radionuclides typically used for research and
medical purposes.
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Low Level Waste (LLW)
Waste that contains material with radionuclide content above
clearance levels, but with limited amounts of long lived activity. It
requires robust isolation and containing for periods of up to a few
hundred years typically 300. It includes a very broad band of
materials that includes very high activity waste with short half life
that requires shielding and some long lived material at relatively
low activity levels. Such waste would require up to around 300
years of control but would not be hazardous beyond that period
of time. The radionuclides within the waste will decay to activity
levels that are acceptably low from a radiological safety
viewpoint, within a time period during which institutional controls
can be relied upon.
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Intermediate level waste (ILW)
Waste which, because of its high radionuclide
content and the potential mobility of the materials
involved requires a higher level of containment
and isolation than is provided by near surface
disposal. However, needs little or no provision for
heat dissipation during its handling, transportation
and disposal. It may include long lived waste that
will not decay to an acceptable activity level
during the time which institutional controls can be
relied upon.
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High Level Waste (HLW)
Waste with radioactivity levels intense enough to
generate significant quantities of heat by the
radioactive decay process or with large amounts of
long lived activity which need to be considered in
the design of a disposal facility for the waste.
Disposal in deep, stable geological formations is
the preferred option for its disposal. It includes
spent reactor fuel which has been declared as
waste, vitrified waste from the processing of reactor
fuel and any other waste requiring the degree of
containment and isolation provided by geological
disposal.
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IAEA Waste Classification System (2009)
Activity
content
HLW
high level waste
(deep geologic disposal)
ILW
intermediate level waste
(intermediate depth disposal)
Geological
Intermediate
LLW
low level waste
(near surface disposal)
Near surface
VSLW
very short lived
waste
(decay storage)
VLLW
very low level waste
(landfill disposal)
EW
exempt waste
(exemption / clearance)
Landfill
Clearance
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Half-life
Classification as Practiced
•
Many member states still use their own
system, customized to fit local needs.
•
Disposal endpoint is what is most
commonly used to define waste classes.
•
As part of Joint Convention, each
country reports on national system of
waste classification and reports a
national inventory of radioactive waste.
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Waste Disposal Options
Well injection
Surface Disposal
Near-Surface Disposal
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Geological
Surface Discharge
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Selection of Management Options
• Selected options must be consistent with
National policies for waste management;
• Need to consider interdependencies with other
predisposal and final disposal options;
• Adequate characterization of waste is critical.
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Safe Disposal of Radioactive Waste
Objective/Scope of IAEA Publication SSR-5
• The fundamental safety objective is to protect people
and the environment from harmful effects of ionizing
radiation
•
• To achieve this objective this publication sets out
requirements on the site selection and evaluation and
design of a disposal facility, and on its construction,
operation and closure, including organizational and
regulatory requirements
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Disposal
The term ‘disposal’ refers to the emplacement of radioactive
waste into a facility or a location with no intention of
retrieving the waste.
(The term disposal implies that retrieval is not intended; it
does not mean that retrieval is not possible.)
Disposal options are designed to contain the waste by
means of passive engineered and natural features and
isolate it from the accessible biosphere to the extent
necessitated by the associated hazard.
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The specific aims of disposal:
• to contain the waste;
• to isolate the waste from the accessible biosphere and
• to substantially reduce the likelihood of and all possible consequences of inadvertent
human intrusion into the waste;
• to inhibit, reduce and delay the migration of radionuclides at any time from the waste to the
accessible biosphere.
• to ensure that the amounts of radionuclides reaching the accessible biosphere due to any
migration from the disposal facility are such that possible radiological consequences are
acceptably low at all times.
SOURCE
SAFETY
FUNCTIONS
RECEIPIENT
CONTAIN
B
W
OBJECTIVE
I
A
ISOLATE
O
S
S
T
P
INHIBIT,
REDUCE,
DELAY
E
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ACCEPTABLY LOW
IMPACT
H
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Safety Requirements applies to all of the
types of disposal and disposal facilities
•
•
•
•
•
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Specific landfill disposal
Near surface disposal
Disposal of intermediate level waste
Geological disposal
Borehole disposal
Disposal of mining and minerals processing waste
• Safety Guides provide comprehensive guidance on and international best
practices for meeting the requirements in respect of different types of
disposal facility.
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Protection of people and the environment (1)
The IAEA Safety Fundamentals publication Fundamentall
Safety
Principles sets out the fundamental safety objective and
safety principles
that apply for all facilities and activities in radioactive waste
management, including the disposal of radioactive waste.
• The ICRP developed a System of Radiological
Protection that applies to all facilities and activities,
and this system was adopted in the International Basic
Safety Standards.
The ICRP has elaborated the application of the
System of Radiological Protection to the disposal
of solid radioactive waste in its Publications 77 and
81 which it reconfirmed in Publication 103.
• This provides a starting point for the safety
considerations relation to disposal facilities.
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Protection of people and the environment (2)
Radiation protection in the operational period
The radiation safety requirements and the related safety criteria
for the operational period of a disposal facility are the same as
for any nuclear facility or activity involving radioactive material,
and are established in the GSR part 3.
• In radiological protection terms, the disposal facility is
considered to be a source of radiation that is under
regulatory control in a planned exposure situation.
• Expect no significant releases of radioactivity during the
operational period; no doses to public
• The primary goal is to ensure that radiation doses are as
low as reasonably achievable (ALARA) and within the
applicable system of dose limitation.
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Protection of people and the environment (3)
Post Closure Safety Criteria
Safety objective: A reasonable assurance has to be provided that
doses and risks to members of the public in the long term will not exceed
the dose constraints or risk constraints that were used as design criteria.
• The dose limit for members of the public from all planned exposure
situations is an effective dose of 1 mSv in a year, and this or its risk
equivalent are considered criteria not to be exceeded in the future.
• To comply with this dose limit, a disposal facility is designed so that the
estimated dose or risk to the representative person who may be
exposed in the future as a result of natural processes affecting the
disposal facility does not exceed a dose constraint of 0.3 mSv in a year
or a risk constraint of the order of 10-5 per year.
(Risk due to the disposal facility in this context is to be understood as the probability of fatal cancer or serious
hereditary effects.)
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Inadvertent human intrusion in the postclosure period
•
If such intrusion is expected to lead to an annual dose of less than 1 mSv per
year to those living around the site, efforts to reduce the probability of human
intrusion or to limit its consequences are not warranted.
< 1 mSv
Measures not warranted
•
If HI is expected to lead to an annual dose of more than 20 mSv per year to
those living around the site, alternative disposal options are to be
considered, for example disposal of the waste below the surface, or
separation of the radionuclide content giving rise to the higher dose.
> 20 mSv
Alternative disposal
•
If annual doses in the range 1 – 20 mSv are indicated, reasonable efforts are
justified at the facility development stage to reduce the probability of
intrusion or to limit its consequences by optimization of the facility design.
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1 – 20 mSv
Measures considered
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Protection of people and the environment (4)
Environmental and non-radiological concerns
The scope of safety requirements for disposal of radioactive waste
is the protection of the environment against radiological hazards
associated with the radioactive material in the disposal facility.
The assessment of conventional environmental impacts such as
may occur in the construction and operational period for a disposal
facility, e.g. impacts relating to traffic, noise, visual amenity,
disturbance of natural habitats, restrictions on land use and social
and economic factors, as well as non-radiological toxic hazard also
has to be assessed where this is significant.
If non-radioactive materials may affect the release and migration of
radioactive contaminants from the radioactive waste, then such
interactions have to be considered in the SA.
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Safety Requirements for safe disposal of
Radioactive Waste
In order to meet the basic
objective, i.e., to ensure safety
of waste disposal facilities, 26
requirements have been
established in the IAEA
publication SSR-5
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Safety Requirements for safe disposal of
Radioactive Waste
List of 26 requirements (1/2)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
government responsibilities
regulatory body responsibilities
operator responsibilities
importance of safety in the development process
passive safety of the disposal facility
understanding of facility and for confidence in safety
multiple safety functions
Containment of radioactive waste
Isolation of radioactive waste
Surveillance and control of passive safety features
step by step development and evaluation of facilities
Preparation and use of the safety case and safety assessment
scope of the safety case and safety assessment
documentation of the safety case and safety assessment
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Safety Requirements for safe disposal of
Radioactive Waste
List of 26 requirements (2/2)
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
site characterization of disposal facility
design of a disposal facility design
construction of a disposal facility
Operation of a disposal facility
closure of a disposal facility
waste acceptance in a disposal facility
monitoring programmes in a disposal facility
the period after closure and institutional controls
state system of accounting for, and control of, nuclear materia
requirements in respect of nuclear security
management systems
existing disposal facilities
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