2. Radioactive Waste
We will discuss –
Radioactivity
Low Level Radioactive Waste
High Level Radioactive Waste
Mining Tailings
3. Radioactivity
Atom is the smallest unit of an element.
It is made up of a nucleus containing proton and
neutron surrounded by electrons.
In the nucleus of an ordinary atom the no. of neutron
is equal to no. of protons. Such a nucleus is known a
stable nucleus.
If the no. of neutron and proton are not equal in a
nucleus then it is called Unstable Nucleus.
Radioactive nuclides continue to decay releasing
radioactive radiations or RADIOACTIVITY.
4. Low Level Radioactive Waste
LLRW are generated when uranium is extracetd and prepared for
nuclear fuel.
They are produced in frequent operations of nuclear power plants
(core water exchange, maintenance and cleanup operation etc).
They are generated from:-
- Research laboratories
- Hospitals
- Diagnostic Centers
- Army Ammunition Plants etc.
Low Level Radioactive waste consists of microcurie, millicurie and
at times curie activity waste.
(A Curie is a unit of nuclear transformations. 1 Curie is 3.7 x1010
transformations per second)
5. Low level radioactive waste consists of:
Contaminated solids
Liquids
Animal carcasses
Small sealed sources
Wash water coming from nuclear powerplant
6. Classification of LLRW
Class A low-level radioactive waste is the least
hazardous, containing mostly short-lived radionuclides that
will be reduced in radioactivity (decay) in a relatively short
time.
It contains only small amounts of radionuclides that take a
relatively short time to decay.
Class A waste will be disposed of in concrete canisters that
will maintain their shape and strength for hundreds of
years.
7. Classification of LLRW (Contd.)
Class B low-level radioactive waste is more hazardous
than Class A waste.
Most of it comes from nuclear reactors. It must be in a
stable form for disposal and will also be disposed of in
concrete canisters.
Stabilization can be accomplished by solidifying liquid
waste, compacting solid waste, or placing the low-level
radioactive waste in a container that will be stable for many
years.
Class B low-level radioactive waste makes up only a small
percent of the waste volume generated; but along with
Class C waste, it contains the largest portion of the total
radioactivity.
8. Classification of LLRW (Contd.)
Class C low-level radioactive waste is the most
hazardous and must be handled accordingly.
It has the highest degree of radioactivity among the
low level radioactive wastes.
It also must be disposed of in a stable form.
11. Treatment of low level waste
Radioactive animal carcasses are either incinerated
or buried onsite.
Low level contaminated solid wastes are buried.
Solid wastes are “Super compacted” at 30,000 psi to
reduce the volume to be buried.
Sewer Disposed (Regulations allow curie levels of
some isotopes to be sewer disposed of if dilution is
large enough).
LLRW are also treated by precipitation, filtration,
ion exchange and thermal evaporation.
12. Disposal of LLRW
For safe disposal LLRW are stored in water tight
R.C.C. containers.
Before placing in containers, the volume is reduced
by techniques like evaporation, and incineration and
compression.
Discharge in open sea bed.
Emphasis is always on recycling and containment in
containers placed in safe deposit vaults.
13. Disposal of LLRW (Contd.)
Small sealed sources are
“Stabilized” in concrete and
buried.
Stabilized concrete is
concrete that is certified to
resist wear for a certain
time period.
14. Discharge of LLRW in to the sea
As the chemical reprocessing is very costly the LLRW
is dumped into the sea.
Provisions of International Commission for
Radiological Protection(ICRP):
- Public must never be exposed to levels above the ICRP recommended
limits.
- Keeping cost in mind, doses should be kept as far below the
mandatory limits as possible.
15. High-Level Radioactive Waste (HLRW)
High-Level Radioactive Waste is the irradiated fuel
from the cores of nuclear reactors, the liquid and sludge
wastes that are left over after irradiated fuel has been
reprocessed (a procedure used to extract uranium and
plutonium), the solid that would result from efforts to
solidify that liquid and sludge from reprocessing.
• The most dangerous radioactive waste.
• Spent fuel comes from nuclear reactors (52,000 tons).
• Liquid and solid waste from plutonium production (91 million gallons).
• About 70 percent of the available storage space is now filled with used
fuel assemblies at Turkey Point.
• It is measured in curies per litre.
16. High Level Radioactive Waste (contd.)
This usually contains plutonium 239 which have
half life period of 24000 years.
It have great difficulties in disposal.
Require careful handling and treatment.
17. Disposal of HLRW
The technology of isotope separation is used.
Plutonium-239 is separated from Uranium- 238.
Before HLRW are solidify they are usually stored in
underground multilayered thick concrete tanks for about
five years.
They are kept in especially designed containers.
They are buried in deep disposal sites.
Favoured sites are bedded salt, basalt or gneiss, where it
is believed that these waste will maintain their integrity.
The only place for long time holding of HLRW in USA is
Yucca mountains in Nevada deserts.
18. Mill Tailing
These wastes are the residues, remaining after the
processing of natural ore to extract uranium &
thorium.
The radioactivity is higher than LLRW and lower
than those of HLRW.
They are often classified as Intermediate level
wastes.
Measured in millicuries per litre.
They are generated in large quantities, and finally
disposed of with LLRW after some treatments.
19. Transuranic Waste
Transuranic waste contains manmade elements
heavier than uranium, such as plutonium, hence
the name “trans” or “beyond” uranium.
Half life of TUW is greater than 20 years.
Transuranic waste primarily consists of clothing,
tools, rags, residues, soil, and debris.
They are categorized as:-
- Contact Handle (CH)
- Remote Handle (RH)
