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GEORGIA STATE UNIVERSITY. Peter Farina 404-651-4866. Radioactivity & Waste. Structure of the Atom. Nucleus. Neutrons. +. +. +. Protons. Electrons (Electron Clouds). Radioactivity. Definition Any spontaneous change in the state of the nucleus accompanied by the release of energy.

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Peter Farina


Radioactivity & Waste


Structure of the Atom








(Electron Clouds)




Any spontaneous change in the state of the nucleus accompanied by the release of energy.

Major Types

alpha () particle emission (decay)

beta () particle emission (-), positron emission (+) and orbital electron capture (ec)

gamma () decay including internal conversion


Ionizing Radiation



Definition - Any type of radiation possessing enough

energy to eject an electron from an atom,

thus producing an ion.

Major Types of Ionizing Radiation Alpha, Beta, Gamma

Alpha Particle

Large Mass (nuclei) – Helium

Atom with a +2 charge

Beta Particle

Small Mass - Electron

(subatomic particle)

No Mass



Gamma Photon

and X-Rays


 Decay










238U 4He + 234Th

 has a discrete energy that can be measured and related to the parent. The neutron to proton ratio is to low !

4He Nucleus

Ejected from Nucleus


Most of the energy

associated with 


This is radioactive!!


 Decay












3 products share energy – therefore beta has a continuous range of energies

Either too many neutrons or too many protons


Change a neutron into a proton

take away - charge

Electron (negatron)


Change a proton into a neutron

take away + charge



Electron Capture



Change proton into neutron


 Decay




Gamma Photon









  • Emission of a photon from the nucleus
  • Most often occurs after  or  emission when nucleus is left in an excited state
  • Given off with discrete energies
  • Can measure photon energy and possibly identify parent




Radiation Dosimetry Units

Exposure, X:

amount of charge produced anywhere in air by the complete stoppage of all electrons liberated by photons in an incremental volume of air per unit mass of air in that volume.

Standard International (SI) unit: Coulomb/kilogram (C/kg)

Traditional unit: roentgen ( R ) 1 R = 2.58x10-4 C/kg

Exposure definition applies only to photons of energy less than or equal to 3 MeV interacting in air.


Radiation Dosimetry Units

Absorbed dose:


is the energy deposited by any type of ionizing radiation in a volume element of mass.

SI unit: gray (Gy)

Traditional unit: rad 1Gy = 100 rad

Absorbed dose definition applies to all forms of ionizing radiation in any material.


Biological effect of radiation Y at dose X

Biological effect of 250 kVp x-rays at dose X

Both produce the same biological effect.



Relative Biological Effectiveness and Quality Factor

Relative Biological Effectiveness (RBE)

Quality factor (Q)


photon,  1

proton, neutron 10

alpha 20


Relative Biological Effectiveness

Ln (S)

Shoulder of curve indicates

cell repair at low doses

No shoulder - no cell repair



Gamma Photons



Same Biological Effect

Different Dose from 2 types of radiation



Radiation Dosimetry Units

Dose Equivalent

Dose equivalent: allows the description of the biological effect of an absorbed dose of a particular type of radiation or mixed radiations for the Human Body.

Dose Equivalent (DE) in Rem = Dose in Rads x Q

SI unit: sievert (Sv)

traditional unit: rem 1 Sv = 100 rem


For photons: 1 R  1 rad = 1 rem






External Radiation Exposure

Definition: Exposure of the body from radiation originating outside of the body

Level of Hazard and Control Depend Upon:

1. Type of Radiation (Alpha, Beta Gamma)

2. Energy of the Radiation (Low or high energy)

3. Dose Rate (Low or high dose rate)


Reducing External Radiation Exposure

  • Time:
  • reduce time spent in radiation area
  • Distance:
  • stay as far away from the radiation source as possible
  • Shielding:
  • interpose appropriate materials between the source and the body
radioactive waste
Radioactive Waste

We will discuss -

  • Low Level Radioactive Waste
  • High Level Radioactive Waste
  • Mining Tailings
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Radioactive Waste

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)

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Radioactive Waste
  • Low level radioactive waste consists of:
    • Contaminated solids
    • liquids
    • animal carcasses
    • small sealed sources
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Radioactive Waste
  • Low level radioactive liquids are either:
    • Incinerated
    • Deep well injected (not as frequent anymore)
    • Solidified
    • Sewer Disposed (Regulations allow curie levels of some isotopes to be sewer disposed of if dilution is large enough)
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Radioactive Waste
  • Radioactive animal carcasses are either incinerated or buried onsite.
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Radioactive Waste
  • Small sealed sources are “Stabilized” in concrete and buried. Stabilized concrete is concrete that is certified to resist wear for a certain time period.
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Radioactive Waste
  • Low level contaminated solid wastes are buried. GSU has it’s solid waste “Supercompacted” at 30,000 psi to reduce the volume to be buried
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Most low level wastes come from Government and Utilities. These consist of contaminated solids from nuclear reactor usage and weapon construction.Radioactive Waste
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Radioactive Waste
  • Colleges, research and medical applications account for less than 25% of the low level Radioactive wastes created
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Radioactive Waste
  • 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.
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Radioactive Waste
  • 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.
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Radioactive Waste
  • Class C low-level radioactive waste is the most hazardous and must be handled accordingly. It also must be disposed of in a stable form.
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Radioactive Waste
  • There are 3 LLRW Burial sites:
    • Hanford
    • Envirocare
    • Barnwell
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Radioactive Waste
  • Politics of LLRW
    • Compacts
    • On-site burial
    • NIMBY
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Radioactive Waste
  • The compact system was set up by NRC to have all states share in the responsibility of disposal of radioactive waste and to limit waste transport distance. Georgia is in the Southeast compact.
  • Until 1992, all states within the SE compact (excluding Florida) would host a LLRW landfill on a 20-25 year revolving timetable.
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Radioactive Waste
  • Kentucky was the first (Maxie Flats), then South Carolina (Barnwell). In 1995, North Carolina was to open a site but the citizens protested and sued. The State legislature refused.
  • North Carolina was then “kicked out” of the S.E. compact and left with no place to dispose of waste. Other States followed N.C.’s lead and refused
  • This lead to the collapse of the traditional compact system and the
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Radioactive Waste

In the past, many Universities and companies were allowed to bury their radioactive wastes onsite. Some were allowed to deep well inject liquid radioactive waste.

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Radioactive Waste







The true politics of Hazardous Waste

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Radioactive Waste

Did North Carolina, by not opening up a waste site, better protect it’s citizens?

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Radioactive Waste
  • 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.
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Radioactive Waste

Because there is currently no high level radioactive waste disposal facility, HLRW is held On-Site in water pools

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Radioactive Waste

Once these Pools are full, Waste is transferred to casks which are also held on-site

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Radioactive Waste

A HLRW repository is being constructed at Yucca Mountain in Nevada to hold all this waste. NIMBY again is playing a role in the opening

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Radioactive Waste