Radiation Protection Service Radiation Protection Service University of Glasgow University of Glasgow The Internal Radiation Hazard Janice Brock Un iversity RPO The Internal Radiation Hazard Ionising Radiation Regulations 1999 Dose Limits and Unsealed Isotopes
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Radiation Protection Service University of Glasgow The Internal Radiation Hazard Janice Brock University RPO The Internal Radiation Hazard Ionising Radiation.
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Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
The Internal Radiation Hazard
Ionising Radiation Regulations 1999
Dose Limits and Unsealed Isotopes
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Brief History :
1895 - Roentgen discovers X-rays
1896 - Becquerel announces discovery of ‘other’ rays
1896 - Thompson deliberately overexposes finger
1900 - Generally excepted that frequent/intensive use causes burns
1904 - Rollins demonstrates that X-rays can kill guinea pigs
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
1915 - British Roentgen Society issues ‘advice’ to X-ray users
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Members of the Public
Average annual dose of 1 mSv/yr averaging over 5 years
Dose in any one year not exceeding 5 mSv.
UK further restricts that contributions from discharges from nuclear installations must not exceed 0.5 mSv/yr
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Deterministic effects :
No need for separate organ dose limit if 20 mSv/yr adopted
Skin, hands, forearms 500mSv/yr
Feet and ankles 500 mSv/yr
Lens of eye 150 mSv/yr
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Radiation Dose Limits & ICRP 60
Background Radiation :
Gamma - from rock and soil, Glasgow ~ 0.3 mSv/yr
Cosmic - high energy particles from space bombardatmosphere producing mu mesons
and neutrons resulting in ~ 0.3 mSv/yr
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
40K - naturally occurring isotopes of potassium, uranium, thorium and carbon ~ 0.2
mSv/yr
Radon - gaseous decay product of uranium, can contribute an effective maximum annual
dose of ~ 1.2 mSv
Depending on where you live you could receive a background dose of up to 2 mSv/yr
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Dose Assessment:
Absorbed dose DT is measure of dissipated energy/unit mass Unit is the 1Gy 1Gy = Dissipation of 1 Joule/kg
Equivalent dose HT = DT x WR
Measured in Seiverts
1 Gy = 1 Sv for beta and 20 Sv for alpha.
Effective dose E = HT x WT,
Measured in Seiverts
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
The Effects on Health :
Deterministic effect :
An effect which is known to occur above a threshold limit, severity increases with increasing dose.
Stochastic effect :
Effect is not certain to occur but there is a probability of occurrence.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Annual Limit on Intake (ALI)
Intake (of radioisotope) which would give an effective dose equal to the annual dose of a radiation worker when we calculate the accumulated dose over a period of 50 years.
Dose Assessment: IRR99
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
The value of ALI for a particular isotope depends on :
The route of entry
The chemical properties of the isotope
The particle size (especially in the case of inhalation)
The types and energies of the radiation and the physical and biological half-life
Concentration in particular organs, etc
E.g. 125I is given as 2.7 MBq (inhalation) and 1.3 MBq (ingestion)
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Dose Assessment:
Committed effective dose per unit intake, expressed in Sv/Bq
More information given than for ALIe.g. - age of exposed individuals - status (public or occupational)
- gut transfer factors- three default lung absorptions
-1
E.g. 125I - 1.5E-8 Sv/Bq (ingestion) 5.3E-9 Sv/Bq (inhalation)
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Dose Assessment: By measurement
• Whole body monitor
• Liquid scintillation
• Gamma spectroscopy
• Portable scintillation counter
• Personal dosimeter
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
e.g. Thyroid monitoring for 125I intakes
125I accumulates in the Thyroid gland
A type 5.42 probe held at Adams apple ~ 10 cps for 1 kBq intake
1 kBq intake = 1.35 mSv equivalent dose
= 70 Sv effective
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Working with Unsealed Isotopes – The Dangers
Internal contamination with radioisotopes can happen through various routes:
1. Inhalation
2. Ingestion
3. Injection
4. Absorption
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Dangers in the Use of Unsealed Radioactive Materials
Most hazardous activities:
Opening a vial in close proximity - high dose rate
Dispensing from stock solutions – vapour, droplets, aerosols
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
Personal dosimeter, consider finger badge for some isotopes e.g. P32, contamination monitor.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Precautions in the Use of Unsealed Radioactive Materials
Setting up the experiment :
Use the least radiotoxic isotope
Use the minimum activity required
Know the physical and chemical properties of the isotope
Use ‘dummy’ run experiments without radioisotopes
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Working Procedures :
• Laboratory coats must be worn at all times.
• Eating, drinking, smoking or applying cosmetics are prohibited.
• No mouth pipetting.
• Work must not be carried out by a person with an undressed cut or abrasion below the wrist.
• Gloves must be worn.
• Monitor for contamination radiation levels must be carried out routinely.
• Gloves and clothing must be monitored after handling radioactive materials.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Working Procedures Continued :
• Hands must be washed before leaving the laboratory after handling radioactive materials.
• Work should be carried out in lined trays.
• All apparatus used for radioactive materials must be labelled with radioactive warning tape.
• Radioactive waste must be placed in an appropriate container and its radioactivity recorded, along with the relevant date.
• Containers for radioactive materials must not be directly held in the hand if this would cause significant doses to fingers. Particular attention must be paid to this possibility.
• Radionuclides emitting penetrating radiations must be adequately shielded.
• In the laboratory, records must be kept of all stocks and radioactive waste
• Contamination must be cleared up without delay.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Radioactive Waste
Three routes for disposal :
1. Liquid waste, via disposal sink.
2. Solid waste to authorised contractor, via RPS.
3. Gaseous disposal, via authorised fume cupboard.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Radioactive Liquid Waste:
Aqueous waste should be diluted before disposal
Use only marked disposal sinks
Run water through sink to disperse waste (avoid splashes)
Log all activity discharged – very important
SEPA will ask you to justify your disposal figures
Do not exceed your monthly disposal limits expensive!
No organic solvents
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Radioactive Solid Waste :
Segregate the waste into 3H/14C; 32P; others.
Dispose to marked bins only.
Do not put non-radioactive waste into these bins.
Do not put biohazard waste into these bins.
Do not put radioactive waste into ‘normal’ waste bins.
Contents of bins must be labelled.
Units must be in Bq, kBq, MBq etc – legal document.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Radioactive Waste Label
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Precautions in the Use of Unsealed Radioactive Materials
No pipetting by mouth.
No eating, drinking, smoking or applying cosmetics.
Use disposable handkerchiefs.
Wear labcoat (buttoned up).
Wear radiation dosimeter (chest height).
Wear gloves.
Wear plastic apron for high activity solutions
Work in fume cupboard
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Contamination Monitoring
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Decontamination Areas
Decontaminate areas with Decon and work out to in
‘Safe’ level is about 3 Bq/cm2
‘Fixed’ contamination must not exceed 3.5 Svhr-1
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Skin Contamination :Wash (not scrub) skin with soap and running water
Do not use Decon on skin
Do not break the skin
Report all accidents and spillage's immediately to your dept. RPS.
If they are not available contact the University Radiation Protection Service (4471/5878) for advice
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Summary :
The internal hazard is the principal hazard encountered in the use of unsealed radioactive materials.
There is NO shielding from an internal intake.
There is NO distance protection from an internal intake.
Irradiation occurs 24 hours/day.
Emissions will be dissipated in the cells of the body.
Certain isotopes will concentrate in particular organs.
Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow
The Internal Radiation Hazard
Janice Brock University RPO
Optimisation:• Suitable controls are in place to address all significant hazards
• Risks are kept as low as reasonably practicable (ALARP)
• Procedures to continually review risk controls
Dose Limitation:• Radiation dose limits for each population group must not be exceeded.
• When calculating dose limits – do not include exposures received from medical treatments or natural sources.
• Dose records must be kept for each employee.
• Dose monitoring and record keeping provided by an Independent body – e.g. University uses Landaur.