1. The Internal Radiation Hazard
Ionising Radiation Regulations 1999
Dose Limits and Unsealed Isotopes
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2. Janice Brock University RPO
Brief History :
Roentgen discovers X-rays
Becquerel announces discovery of ‘other’ rays
Thompson deliberately overexposes finger
Generally excepted that frequent/intensive use causes burns
Rollins demonstrates that X-rays can kill guinea pigs
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3. Janice Brock University RPO
British Roentgen Society issues ‘advice’ to X-ray users
Mutscheller proposes ‘permissible exposure limit’of /100 of dose producing skin burn (equivalent to mSv/day)
Roentgen (R) adopted as the unit for measuring dose
Formation of International X-ray and Radium Protection Committee
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4. Janice Brock University RPO
ACXRP recommend tolerance dose of 0.1 R/day ~250 mSv/yr
Wollan appointed first ‘health physicist’ by Manhattan Group
Nobel Prize awarded to Muller for work on the genetic effects
International Committee on Radiological Protection
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5. Uses for ionising radiation Shoe-Fitting Fluoroscope (ca. 1930-1940)
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6. Janice Brock University RPO

7. The Lifestone Cigarette Holder (ca. 1964)
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8. Janice Brock University RPO
                                  
Fuel Saving Device (ca.2005)
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9. Radon Health Mine (Present Day)
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10. Current UK Legislation
International Commission on Radiological Protection (ICRP).
Radioactive Substances Act 1993 (RSA93).
Ionising Radiation Regulations 1999 (IRR99).
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11. Janice Brock University RPO
ICRP - Independent registered UK charity
1. Justification
2. Optimisation (ALARP principle)
3. Dose limitations
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12. Janice Brock University RPO
Radioactive Substances Act 1993 :
Registration : all sources accounted for
Authorisation : radioactive waste minimization
Accountability : cradle to grave
Governing Body : SEPA
Justification : next slide
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13. Janice Brock University RPO
Justification:
Radioactive Substances Act 1993 is a legal requirement for applications to use ionising radiation.
No practice involving the use of ionising radiation shall be allowed unless its introduction produces a net benefit – trivial uses not allowed.
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14. Janice Brock University RPO
When formulating a justification take into account the
following:
Appropriateness of the procedure
Risk versus benefit
Radiological assessment
Safety considerations
Possible environmental impact
Dose limitations – set by UK government
Optimisation – next slide
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15. Janice Brock University RPO
Optimisation:
Radioactive Substances Act 1993
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
Accurate record keeping
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16. Janice Brock University RPO
Ionising Radiation Regulations 1999
Health and safety – all radiation employers must fully comply
Emphasis is on dose limitation – National limits
Comprehensive Approved Code of Practice
Dose Assessment
Governing body – Health and Safety Executive (HSE)
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17. Janice Brock University RPO
Dose Limitation: IRR99
Radiation dose limits for each population group must not be exceeded.
Dose assessments – 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.
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18. Janice Brock University RPO
ICRP 60 (1983) - Dose limit recommendations
Incorporated into IRR 1999
Stochastic effects
Radiation worker > 18 yrs mSv (effective) / yr.
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19. 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
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20. 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 mSv/yr
Lens of eye mSv/yr
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21. 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 bombard
atmosphere producing mu mesons and neutrons resulting in ~ 0.3 mSv/yr
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22. 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
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23. 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,
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24. 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.
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25. Annual Limit on Intake (ALI)
Dose Assessment: IRR99
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.
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26. 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)
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27. Janice Brock University RPO
Dose Assessment:
Committed effective dose per unit intake, expressed in Sv/Bq
More information given than for ALI
e.g. - age of exposed individuals
- status (public or occupational)
- gut transfer factors
- three default lung absorptions -1
E.g. 125I E-8 Sv/Bq (ingestion)
5.3E-9 Sv/Bq (inhalation)
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28. Janice Brock University RPO
Dose Assessment: By measurement
Whole body monitor
Liquid scintillation
Gamma spectroscopy
Portable scintillation counter
Personal dosimeter
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29. 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
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30. 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
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31. 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
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32. Janice Brock University RPO
Use personal protection :
E.g. lab coat, safety glasses/face shield, disposable gloves, disposable apron, appropriate radiation shield.
Additionally :
Personal dosimeter, consider finger badge for some isotopes e.g. P32, contamination monitor.
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33. 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
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34. 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.
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35. 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.
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36. 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.
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37. 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
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38. 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.
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39. Radioactive Waste Label
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40. 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
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41. Contamination Monitoring
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42. 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
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43. 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
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44. 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.
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45. 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.
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