radiation protection service university of glasgow the internal radiation hazard janice brock...

Radiation Protection ServiceRadiation Protection ServiceUniversity of GlasgowUniversity of Glasgow

The Internal Radiation Hazard

Janice Brock University RPO


Ionising Radiation Regulations 1999

Dose Limits and Unsealed Isotopes




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




1915 - British Roentgen Society issues ‘advice’ to X-ray users

1925 - Mutscheller proposes ‘permissible exposure limit’of 1/100 of dose producing skin burn (equivalent

to 2 mSv/day)

1928 - Roentgen (R) adopted as the unit for measuring dose

1930 - Formation of International X-ray and Radium Protection Committee




1936 - ACXRP recommend tolerance dose of 0.1 R/day ~250 mSv/yr

1942 - Wollan appointed first ‘health physicist’ by Manhattan Group

1946 - Nobel Prize awarded to Muller for work on the genetic effects

1950 - International Committee on Radiological Protection




Shoe-Fitting Fluoroscope (ca. 1930-1940)

Uses for ionising radiation




The Lifestone Cigarette Holder (ca. 1964)




Fuel Saving Device (ca.2005)




Radon Health Mine (Present Day)




International Commission on Radiological Protection (ICRP).

Radioactive Substances Act 1993 (RSA93).

Ionising Radiation Regulations 1999 (IRR99).

Current UK Legislation




ICRP - Independent registered UK charity

1. Justification

2. Optimisation (ALARP principle)

3. Dose limitations




Radioactive Substances Act 1993 :

Registration : all sources accounted for

Authorisation : radioactive waste minimization

Accountability : cradle to grave

Governing Body : SEPA

Justification : next slide




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.




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




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




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)




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.




ICRP 60 (1983) - Dose limit recommendations

Incorporated into IRR 1999

Stochastic effects

Radiation worker > 18 yrs - 20 mSv (effective) / yr.




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




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 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




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




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




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.




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




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)




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)




Dose Assessment: By measurement

• Whole body monitor

• Liquid scintillation

• Gamma spectroscopy

• Portable scintillation counter

• Personal dosimeter




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




Working with Unsealed Isotopes – The Dangers

Internal contamination with radioisotopes can happen through various routes:

1. Inhalation

2. Ingestion

3. Injection

4. Absorption




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




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.




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




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.




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.




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.




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




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.




Radioactive Waste Label




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




Contamination Monitoring




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




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




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.




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.

radiation protection service university of glasgow the internal radiation hazard janice brock...

Documents

ionising radiation slide

slide slide

radiological protection

radium protection committee

present day slide

dose limits

tolerance dose

dose limitations