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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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slide1

GEORGIA STATE UNIVERSITY

Peter Farina

404-651-4866

Radioactivity & Waste

slide2

Structure of the Atom

Nucleus

Neutrons

+

+

+

Protons

Electrons

(Electron Clouds)

slide3

Radioactivity

Definition

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

slide4

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

(Electromagnetic

Radiation)

Gamma Photon

and X-Rays

slide5

 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

+2

Most of the energy

associated with 

(monoenergetic)

This is radioactive!!

slide6

 Decay

+

+

+

+

+

+

+

+

+

+

-

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

Either too many neutrons or too many protons

neutrino

Change a neutron into a proton

take away - charge

Electron (negatron)

anti-neutrino

Change a proton into a neutron

take away + charge

(positron)

slide7

Electron Capture

X-ray

X-ray

Change proton into neutron

slide8

 Decay

+

+

+

Gamma Photon

+

+

+

+

+

+

-

neutrino

  • 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

or

+2

slide9

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.

slide10

Radiation Dosimetry Units

Absorbed dose:

RAD

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.

slide11

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)

radiationQ

photon,  1

proton, neutron 10

alpha 20

slide12

Relative Biological Effectiveness

Ln (S)

Shoulder of curve indicates

cell repair at low doses

No shoulder - no cell repair

Neutrons

Effect

Gamma Photons

Dn

Dg

Same Biological Effect

Different Dose from 2 types of radiation

Dose

slide13

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

millirem

For photons: 1 R  1 rad = 1 rem

slide14

PRECAUTIONS

FOR

AVOIDING UNNECESSARY RADIATION EXPOSURE

slide15

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)

slide16

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
radioactive waste18
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)

radioactive waste19
Radioactive Waste
  • Low level radioactive waste consists of:
    • Contaminated solids
    • liquids
    • animal carcasses
    • small sealed sources
radioactive waste20
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)
radioactive waste21
Radioactive Waste
  • Radioactive animal carcasses are either incinerated or buried onsite.
radioactive waste22
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.
radioactive waste23
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
radioactive waste24
Most low level wastes come from Government and Utilities. These consist of contaminated solids from nuclear reactor usage and weapon construction.Radioactive Waste
radioactive waste25
Radioactive Waste
  • Colleges, research and medical applications account for less than 25% of the low level Radioactive wastes created
radioactive waste26
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.
radioactive waste27
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.
radioactive waste28
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.
radioactive waste30
Radioactive Waste
  • There are 3 LLRW Burial sites:
    • Hanford
    • Envirocare
    • Barnwell
radioactive waste33
Radioactive Waste
  • Politics of LLRW
    • Compacts
    • On-site burial
    • NIMBY
radioactive waste34
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.
radioactive waste35
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
radioactive waste37
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.

radioactive waste38
Radioactive Waste

N.I.M.B.Y.

Not

In

My

Back

Yard

The true politics of Hazardous Waste

radioactive waste39
Radioactive Waste

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

radioactive waste40
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.
radioactive waste41
Radioactive Waste

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

radioactive waste42
Radioactive Waste

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

radioactive waste44
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

radioactive waste45
Radioactive Waste

YOUR THOUGHTS AND DISCUSSION