IAEAInternational Atomic Energy Agency

Radiation Protection Methods

Sharon PaulkaRegional Training Course RAF 3007-1

Namibia, 17-21 August 2009

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Quick re-cap

• Key areas we have learnt so far• Putting it all together• Using this in Radiation Protection Measures

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Properties of Radiation

• Alpha Particles• Strongly ionising• Weak penetration

• Beta Particles• Lightly ionising• Moderate penetration

• Gamma Rays• Weakly ionising• Strongly penetrating

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What does this tell us

• Alpha Radiation• Strongly ionizing• Potential for lots of damage• Cannot pass through the dead skin cells• Not an issue outside the body• Our body and our clothing form a protective barrier

• BUT – need to keep it outside the body• When inhaled and ingested can be a problem

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Where does Alpha exist

• Need to look at the decay chain

• Need to understand the chemical properties of each element

• Need to understand the process to know where that chemical will be

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Beta Radiation• Short lived Radon Decay Products• Both Alpha and Beta

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Gamma Radiation• Emitted as a result of decay of many isotopes• Each isotope emits a distinct energy gamma• Higher energy gamma’s present the greater risk• The main gamma is from Bi-214 (Radon Decay Product)• Where you have ore or Radon trapped you have gamma

• Uranium itself not a gamma issue• Gamma with decay product Pa-234 (ingrows with Th-234 24 day half life)

• The older the product the more gamma7

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Secular Equilibrium• When all isotopes in the decay chain are the same activity

• Daughter activity increases as parent decreases over time

• Eventually equal• Time taken equal to half life of daughter

• Achieved in 5 - 8 T1/2

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Radon and Radon Decay Products• Radon is a gas with half life

of 3.8 days• In equilibrium with Radium in

24 days• Radon not radiation hazard

• Breathed in and out• Radon decay products

• Short lived• Decay in lungs• Attach to lungs

• If sealed decay products quickly grow into high concentrations

• If ventilated or open air no issues because no time to grow in. 9

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Diurnal Variation of RnD

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0.00

5.00

10.00

15.00

20.00

25.00

18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00 12:00

RnD

Conc

entra

tion

PAEC

(uJm

-3)

Time

Boost Jan 20 IX Jan 22 IX Jan 23 Elut Jan 25 IX Jan 27

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What else is growing in

• Anything with a short half life

• Need to assess the potential impact this will have for each circumstance

• Examples• Pa-234 from Th-234• Po-210

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Chemical Nature• Uranium • Three isotopes, U-238, U-234, U-235• Present in• Ore • Product

• Expect to see it all through the process• Exception is tailings material or barren Lix for ISL

• Anywhere there is dust generation there will be uranium

• Anywhere there is a spill there will be uranium12

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Chemical Nature• Radium• Present in• Ore • Tailings

• Expect to see up to tailings separation• For ISL separated at Elution• Anywhere there is Radium there will be Radon• Chemically similar to Calcium, can co-precipitate out in gypsum

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Polonium-210• Highly radio toxic element• Very high dose conversion factor in BSS• Relatively short half life• Grows in from Pb-210• Low boiling point, volatilises at about 120C• Varies significantly with specific chemistry

• Therefore, anywhere there is a hot process there is the potential for airborne Po-210

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Po-210 example

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• When smelting copper that has uranium present can get Po-210 volatilising

• Ends up in the dust fume• If there is no bleed of the ventilation system Po-210 level quickly build up

• ALSO if old revert is fed back into process the Po-210 has grown back in from Pb-210 and presents its own issues

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Po-210 example

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• At Olympic Dam they have these issues• First discovered by Frank Harris in the early 90’s

• Bleed installed and all Ok• Second discovered only recently• Very difficult to identify• Doses were very high• Feed rate and ventilation fixed the problem

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Po-210 example

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0

2

4

6

8

10

12

14

16

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2003/2004 2004/2005 2005/2006 2006/2007 2007/2008Period

Dose

(mSv

)

Dust Average (mSv) RDP. Average (mSv) Gamma Average (mSv) MAX. Total Dose

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Radiation Protection re-cap

• Identify the Sources• Identify the Pathways• Put in place radiation controls• Monitor• Including calculation of radiation dose

• Report• Review

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Radiation Pathways

• Two general pathways• External exposure

• Exposure from a radioactive source outside the body

• Internal exposure• Exposure from a

radioactive source inside the body

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Exposure to Radiation can only occur when there is a pathway from the source to the person

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Radiation Protection of Workers

• Remove the source

• Remove the person

• Remove the pathway

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Radiation Controls – where to start

• Must understand the process• Identify all the sources & pathways• Use hazard identification & risk assessment processes (part of OHS) to assist

• Ask for plans of mining and process

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Exploration Sources

• Dust• Most types of drilling• Sample handling by drillers, off siders, fieldy’s and geologists

• Splitting of samples• Core cutting• Trenching• Rehabilitation

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Exploration Sources

• Radon Decay Products• ISL drilling – airlifiting• Sample and core storage areas• Inside trenches (early morning temperature inversions)

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Exploration Sources

• Gamma• Drilling samples• Core and sample storage and handling• Portable XRF units• Walls of trenches

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Exploration Sources

• Ingestion• Anywhere radioactive material is handled• From general field mapping and chip sample collection

• Through drilling• Sample and core handling• Trenching• Laboratory analysis

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Exploration Sources

• Transport• At some stage samples will be removed from site

• Potential for public exposure if not preformed properly

• IAEA transport regs• Big question – Does the factor of 10 apply

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The factor of 10• 107. The Regulations do not apply to:

e) natural material and ores containing naturally occurring radionuclides that are either in their natural state, or have been processed only for purposes other than for the extraction of the radionuclides, and that are not intended to be processed for use of these radionuclides, provided that the activity concentration of the material does not exceed 10 times the values specified in para. 401(b), or calculated in accordance with paras 402–406;

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Interpretation of the factor• What does• not intended to be processed for use of these radionuclides

• Mean???

• Need to make a decision on this• Personally I think the intent is to include U exploration

• Risk is low & no different to other NORM28

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Exploration sources• Storage• On site sample storage• More permanent facilities in towns• Need to restrict access to both members of the public and fauna

• Occupational sources• RnD inhalation if sealed• Dust from handling• Ingestion from handling

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EXPLORATION SPECIFICRadiation Protection Controls in Practice

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Exploration specific issues

• Dust during drilling• Water is best, water spray in cyclone• Dust extraction unit• Encourage people to stand upwind of any dust• Use respirators when very dusty

• Dust during trenching• Same as open pit mining water and sealed air-conditioned cabins

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Exploration specific issues

• Dust core cutting• Water should always be used on the cutting wheel

• Respirator back option only• Dust during other sample handling• Sample splitting is very dusty and cannot be done wet

• Issue respirator• Stand upwind if possible

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Exploration specific issues• Gamma• Store all higher grade samples and core in one location within the storage facility• Where possible at the back away from general occupied areas• Sign post area to let people know

• Organise work area so sample storage away from occupied areas

• Have licensed operators only for XRF units and other sources

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Exploration specific issues• Gamma (cont)• Removal of core and samples from the main storage area prior to working with them to minimise the time spent near large amounts of core

• Strongly radioactive core should be covered with metal lids or equivalent shielding

• Do not let geologists store radioactive core or samples in offices or other occupied areas.

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Exploration specific issues• Radon decay products• Stand upwind during ISL airlifting operations• Have storage facilities with open air ventilation• If not possible have procedure for opening then leaving for set time to ventilate

• Discourage the storage of geological samples in office areas

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Exploration Specific Issues• Ingestion• Very similar to mining• Good housekeeping• Clear set of working rules• Good hygiene• Shower and change at end of shift• Wash hands before eating, drinking & smoking

• Wearing of PPE, especially gloves• Use of plastic bags for samples to minimise contaminations spread

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MINING SOURCES

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Mining Sources• Our fist rule was to understand the process• We know our general sources and pathways are• Gamma from ore and product• Dust from ore, tailings and product• Dust from poor housekeeping and spillages not cleaned up

• Radon decay products wherever there is radium• Ingestion of radioactive materials from poor hygiene practices

• Lets look at some specific processes

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Uranium Extraction Processes

• Conventional Mining & Milling• Sulphuric Acid Leach• Pyrolusite (Ranger)• Peroxide or Caros Acid (Nabarlek, Canada)

• Carbonate (Alkali) Leach• Langer Heinrich

• In Situ Leach• Sulphuric Acid & Peroxide (Beverley)• Carbonate & Oxygen (Wyoming)

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In Situ Leach• Not applicable to ALL deposits• Sandstone Hosted Uranium

with appropriate hydrogeology• 18% of World U resource• 7% Australian U resource

• Seen as a more environmentally friendly form of mining

• Low CapEx, quick development

• Generally lower OpEx• Allows access to lower grade

deposits• Low recovery rates• Can be technically challenging

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Typical ISL Process Flow Sheet

Sulphuric Acid

Wellfield

PLS Pond

PLS Sorption De-sorption

Sodium Chloride / Sulphuric Acid

Pregnant Eluant Tank

Peroxide and Caustic Soda

PrecipitationLow Temperature Drying

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ISL Process Sources• Dust from product areas• Dust from poor housekeeping and dry spillages

• RnD from vessels • RnD from Pregnant Liquor Ponds• Ingestion from poor hygiene• Sources from Radiation Gauges• XRF in site laboratory

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ISL Wellfield

Source: SXR Uranium 1 Honeymoon license Application

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ISL Wellfield Sources

• Generally a low dose area• Airlifting of wells can produce radon• Spills in wellhouses can be a dust or ingestion hazard

• Very little contact with ore material, only with sample collection from drilling hence very low gamma doses

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Ranger Process Flow Sheet

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Langer Heinrich Process Flow Sheet

Source: Paladin Langer Heinrich EIS

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Conventional Mining Sources

• Dust• Open pit mining activities• Crushing, screening and conveying of ore material

• Product drying and packaging• Tailings material allowed to dry out or crusting not managed

• Poor housekeeping and spillages not cleaned up

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Conventional Mining Sources

• Radon Decay Products• Main Issue in underground operations• Can increase in open pit during inversions• Present in any areas or tanks that are sealed• Can include crushing buildings• Includes grinding mills• Tailings tend to be a large source term for member of the public doses

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Conventional Mining Sources• Gamma• Larger doses in underground when surrounded by ore

• Any gypsum will have radium scale• High RnD area can have high gamma with Bi-214

• Large CCD vessels or similar with large amounts of ore will have elevated gamma

• Product thickeners and packing bins• Sealed sources and XRF units (some inline)

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Radiation Controls

• Look at all the possible options for control• Use Hierarchy of controls• Assess best option (optimisation - ALARA)

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Hierarchy of Controls• Elimination • Remove the radioactive source

• Substitution • Use an alternative that is not radioactive

• Engineering • Put in place ventilation, shielding or similar

• Administration • standard operating procedures, training, etc.

• Personal Protective Equipment (PPE) • respirators, overalls, gloves

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Best Implemented at Design Phase

• Most effective way to achieve this is to:• Training and awareness of engineering personnel• Radiation risk (Optimisation/ALARA) workshops• Development Design criteria

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Training and Awareness• Specialised radiation safety training for technical personnel• More detail on radiation control (design, management systems)

• Characteristics of radiation of importance (eg; in growth, plate out)

• Senior management• Need a commitment from the very top, inform them of the issues and need for radiation protection

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Optimisation (ALARA) Workshops• Radiation specific risk workshops • Main areas considered;• Set the scene – describe the area• Identification of radiation risks (including specific risks such as bleeds and loops)

• Consideration of process or design changes that might reduce radiation exposure (optimisation)

• Identification of unacceptable radiation related conditions

• Results contribute to Radiation Design Criteria Document

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Design Criteria• Formal documentation used by engineers• Develop radiation design criteria document and guidelines

• Radiation safety designs integrated into the engineering specific design software (CAD)

• Sign off at each design step• Overall aim – to create a space for discussion between engineering and radiation protection personnel

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Administrative Controls• Designation of Areas• Controlled Area• Supervised Area

• Radiation Inductions• Initial for all• Annual re-induction

• Radiation Work Permit System

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Designation of areas• A controlled area is a zone that is clearly marked• Fencing, security, signs, different coloured clothes

• Inside which there is a need to have radiation controls to protect people

• Look at the layout of the process• Draw a line and put it in place• Supervised area generally rest of lease• Outside the supervised area is the public• Need to have item clearance and transport rules outside the supervised area

• Once again need some form or security to protect public57

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Training and Awareness• General radiation safety Induction• Personal presentation to all staff

• Needs to be repeated Annually

• Radiation Workers Handbook and excellent resource

• One of the most important parts of radiation protection program

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Radiation Induction

• Objective• Explain to the worker what uranium• Explain to the worker what radiation is• Expel their fears concerning radiation• Ensure they are aware of all the key risk areas• Go through the general working rules

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What to include• Start with Background Radiation• Explain that it has been around us every day for many

years• Give the alpha, beta gamma explanation and at this point

good to give a physical demo• Tell them the unit of dose and give comparisons and the

dose limit• Let them know the key sources and pathways• Go through the basic rules• Explain about the monitoring program• Answer any questions• Give them a hand out to read

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What not to include• The Atom• Anything that is complicated with maths, physics and chemistry

• Un-necessary information• Keep it short, most time attention spans are short

• Information to raise fear• Need to find the balance between making sure they are cautious but you don’t want them to be fearful of low risk issues

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Annual Re-Induction

• Good opportunity to refresh• Best conducted as part of safety meeting system

• Go through workgroup specific issues• Go through annual doses• Pick a topic that may be an issue and go through the specifics

• Once again needs to be short 15-20 minutes62

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Radiation Work Permit

• Enables specific Controls for high risk jobs• Enables individual dose calculation• Dose will not go to workgroup average

• Job can be properly supervised• PPE can be ensured to be worn• Can be linked to confined space entry and other safety permit systems that are part of the site safety system

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EXTERNAL EXPOSURESRadiation Protection Controls in Practice

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External Exposures• Time and distance• Reduce time spent close to radiation sources

• Avoid posted high radiation areas except when necessary

• Shielding• Can be effective, but needs to be thick

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Design Controls Mine End• Underground• Shotcrete for shielding• Modify mining style or mine design to have ore away from occupied areas

• Construct maintenance workshops and crib rooms on levels with no ore

• Open pit• Would only be an issue in very high grade (shotcrete)

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Shotcrete

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Mining remote from ore body

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Design Controls Process Plant• Layout of large process tanks away from occupied areas

• Process water chemical management to prevent scaling build up

• High grade situations concrete and thick steel shielding

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Administrative Controls• Training of Personnel• Not to take breaks or spend time un-necessarily in high gamma areas

• Sign Posting of Gamma dose rates when over a set action level

• Colour coding of areas

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RADON DECAY PRODUCTSRadiation Protection Controls in Practice

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Design Controls Mine End• Ventilation• Remove radionuclides before inhaled

• Underground• Large ventilation systems with air flow directed so old air not across occupied areas

• Dedicated Vent Officers• Mine Design

• Open Pit - passive72

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Design Controls Process Plant

• Sealed Tanks as required (ISL)• Ventilation of tanks• Layout to have tank vents away from occupied areas

• De-gas pond for acid ISL• Radon modelling• Away from occupied areas• May need some form of ventillation

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Administrative Controls

• Monitoring linked to an alarm system

• Sign posting of areas• Restriction of access

• Training• Confined space entry permit system

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DUSTRadiation Protection Controls in Practice

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Design Controls Mine End• WATER• When wet no dust

• Open Pit• Water trucks on roads and face

• Sealed air-conditioned cabins

• Dust extraction on drill rigs• Underground• Working tend to be very wet

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Design Controls Process Plant• Crushing

• Dust extraction• Water sprays on conveyor

systems• Product Packing

• Sealed rooms• Negative pressure• Dust extraction

• Venturi• Bag house

• Vacuum cleaning system• Automatic Drum Washing

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Administrative Controls

• Hosing up of spillages ASAP

• Housekeeping• Procedures to restrict sweeping

• Respiratory protection

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INGESTIONRadiation Protection Controls in Practice

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Design Controls

• Materials of Contraction• Choose appropriate material

and equipment to prevent breakdown and spillage

• Bunding• Contains spillages to

designated areas• Workplace design

• Minimise need for material contact

• Gate monitoring system

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Administrative Controls• Different colour PPE for high contamination areas

• Shower & Change at end of shift• Provide dirty and clean change rooms

• Provide dedicated work clothes to be left on site

• Boot washes• Vehicle Wash• Wheel wash• Full wash bay 81

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Administrative Controls• Good housekeeping• Regular hosing down of all areas

• Eat and Drink only in crib rooms• Provide hand contamination monitors in crib rooms

• Wash hands before eating drinking smoking• Provide hand washing stations at smoking areas

• Decontaminate equipment leaving the site• Clearance certificate system

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Summary• We need to fully understand and characterise the process and its particular radiation issues• Every site different & every process different

• Get in early where possible with engineering controls

• Need to ensure all workers are trained in the hazards and working rules

• Have good housekeeping and hygiene 83