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Basic Radiation Protection

Basic Radiation Protection. Radioactivity. Nuclide – a particular atomic nucleus with a specific number of protons (p) and neutrons (n). For example 31 P 32 P 33 P Approximately 1700 known nuclides. About 1400 are unstable – RADIONUCLIDES .

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Basic Radiation Protection

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  1. Basic Radiation Protection

  2. Radioactivity Nuclide – a particular atomic nucleus with a specific number of protons (p) and neutrons (n). For example31P32P 33P Approximately 1700 known nuclides. About 1400 are unstable – RADIONUCLIDES. Radionuclides - imbalanced numbers of p and n. - emit particles/energy to improve stability

  3. Radioactivity Gamma photon Radionuclide Excess energy Disintegration Stable daughter Excited daughter Charged particle

  4. Sources SEALED – a radioactive source containing radioactive material where the structure is designed to prevent, under normal use, any dispersion of radioactive substances e.g. Am/Be sealed in stainless steel capsule UNSEALED - dispersible Solids – powders Liquids – aqueous or organic Gases – e.g. Xe-133 MACHINES – e.g. x-ray and neutron generators

  5. Main Emissions Helium nuclei (2p + 2n) + 2 positive charge 4 mass units Alpha (a) High speed electrons • 1 negative charge • 0.0005 mass unit Beta (b) Electromagnetic photons No charge No mass Gamma (g)

  6. energy gained by an electron passing through an electrical potential of 1 volt 1 eV = Energy Energy of emissions ÞELECTRONVOLTS (eV) 1 eV is a very small energy = 1.6 x 10-19 joules. Normally emission energies are in keV or MeV range.

  7. Ranges Particle Energy (MeV) Range Tissue Air Alpha 3 - 7 < 1mm few cm Beta H3 0.018 0.05mm 4mm C14 0.156 0.3mm 2cm P32 1.70 8mm 600cm Gamma 0.1 – 0.6 V. Large V.Large

  8. Activity (A) Rate of disintegrations in a large group of nuclei. A(t) µ N(t) which means EXPONENTIAL DECAY. SI unit is BECQUEREL(Bq) 1 Bq = one disintegration per second. Another commonly used but old unit is CURIE (Ci) 1 Ci = 3.7 x 1010 Bq or 1 mCi = 37 MBq

  9. Ao A(t) = Ao exp (- lt) ½Ao T½ = 0.693 / l Half-Life where l is the radioactive decay constant

  10. Radionuclide Half-Life H3 12.3 years C14 5760 years P32 14.3 days S35 87.2 days Cs137 30.2 years Eu152 13.5 years I131 8.04 days Typical Half-Lives

  11. Bremsstrahlung • “Braking Radiation” • X-rays produced when b particles are • slowed down very rapidly as they come • very close to an atomic nucleus. • shielding materials (e.g. Perspex) have • relatively low atomic numbers in order to • slow them down more gradually.

  12. Absorbed Dose (D) • Energy imparted to matter in small volume • Mass of the small volume • 1 Gray (Gy) = 1 Joule of energy absorbed • in 1 kg of matter i.e. 1 J / kg • Gy is a HUGE dose of radiation. • (Old units : 1 gray = 100 rads)

  13. Equivalent Dose - H Absorbed Dose x Radiation Weighting (Grays) Factor (WR) Sieverts (Sv) which are still J / kg WR = 1 for photons and betas of any energy. (Old units : 1 Sv = 100 rem) H =

  14. Effective Dose (E) Accounts for uneven irradiation of the body. Represents overall risk from a whole body exposure. E = wTx HT where HT = Equivalent dose to tissue / organ “T” wT = Tissue weighting factor Tissue weighting factors represent risks of detrimental radiation effects to different organs or tissue S T

  15. Tissue Weighting Factors • Gonads 0.08 Breast 0.12 • Red bone marrow 0.12 Liver 0.04 • Colon 0.12 Oesophogus 0.04 • Lung 0.12 Thyroid 0.04 • Stomach 0.12 Skin 0.01 • Bladder 0.04 Bone surfaces 0.01 • Brain 0.01 Salivary glands 0.01 • Remainder 0.12 • includes: Adrenals Upper large intestine • Small intestine Muscle • Kidney Spleen • Pancreas Uterus • Thymus å WT = 1

  16. Internal Radiation Amount of radionuclide in body Dose rate in organ lEFF = lR + lB exp(-lRt) exp(-lBt) exp(-lEFFt) exp(-lEFFt) Time Time (post ingestion)

  17. Equivalent dose summed over a 50 year period. HT(50) = Committed Equivalent Dose AlsoCommitted Effective Dose

  18. Annual Limit of Intake (ALI) The amount of radionuclide (in Bq) which when taken into the body will result in : Committed Effective Dose = Dose Limit (20mSv) Radionuclide ALI (MBq) Inhalation Ingestion Sodium-22 10 7 Iodine-131 1 0.8 Also depends on chemical compound.

  19. Principles of Radiation Protection • Justification – Benefits > Risks • Optimisation - ALARP • Dose Limitation

  20. Practical Protection Measures External Radiation Distance: inverse square law. : always use remote handling (if poss). Shielding: placed between worker & source. : attenuates the radiation. : lead for g, perspex for energetic b. Time : be as quick as safely possible.

  21. To use tongs or not to use tongs? 30cm 10mins @ 1mSv/min Þ 10 mSv 1cm 1min @ 900mSv/min Þ 900 mSv

  22. Personal Monitoring • Normally TLD badges. • Worn as instructed in local rules. • Do not try to remove TLDs from holder. • Damaged holders replaced immediately. • NOT left in radiation areas, left on radiators, washed etc. • Returned for reading promptly. • Special monitors for wrists, eyes etc. NOT whole body one.

  23. Practical Protection Measures Internal Radiation Use all appropriate protective clothing e.g. lab coats, gloves, glasses. No mouth work. Only handle sources in designated areas. Know the whereabouts and how to use the decontamination kit.

  24. Do NOT eat drink or smoke in an area where unsealed radioactive substances are handled. “What the? …… This is lemonade! Where’s my preparation of tritiated thymidine?”

  25. DO NOT WEAR LAB COATS IN THIS ROOM

  26. Legislation The Environmental Permitting Regulations 2016 (EPR2016) + 2018 Amendment The Ionising Radiations Regulations 2017 (IRR17)

  27. EPR2016 Protection of General Public and Environment. PERMITS: to keep & use sealed radioactive sources. Subject to national security SEALED : to keep and use unsealed radioactive substances and accumulate/dispose of waste OPEN : Policed by The Environment Agency (EA)

  28. Record Keeping • Date received, radionuclide, activity • Location stored • Details of removal for use, date, activity • Activity present in stock at end of month • Dates of disposal • Total activity disposed of and by which route each month • Total activity of waste accumulated at end of each month

  29. Where does all the waste go ? SOLID : Very Low Level Waste (VLLW) Þ skip by user. Low Level Waste (LLW) from bins in labs collected and taken for incineration (or landfill burial) Sealed sources – specialist contractor LIQUID : Aqueous – down the drain Organic – collected and sent for incineration

  30. Waste Disposal IS VERY EXPENSIVE: When buying new sources – think about disposal costs and work this into the grant application

  31. Orphans Radioactive sources or materials or waste that does not have an ‘owner’ Creates a lot of work for RPO RPO has to pay for its legal disposal PLEASE NO ORPHANS X

  32. When an Inspector Calls !! • Poor accounting of sources and waste • Lost sources • Unauthorised disposal of waste • Over-accumulation of waste • Failure to keep suitable and sufficient records • Failure to use best practicable means (BPM)

  33. Offences Variety of offences & penalties Penalties can be applied to anyone within the University - not just the COO or Department Head Non-compliance with Permit conditions/schedules - up to £20,000 fine and/or up to 6 months in prison Failure to keep records - a fine and/or up to 3 months imprisonment

  34. IRR17 • Protection of the Worker. • Policed by The Health & Safety Executive (HSE). • Risk Assessments (8) • Annual Dose Limits (12) • Area Classification and Monitoring (17, 20) • Local Rules (18) • Accounting for, Keeping and Moving • Radioactive Substances (29+30)

  35. Risk Assessment Must be made prior to commencing any new work involving ionising radiation. Identify hazards Who could be harmed Evaluate risks Significant hazard but is it a risk? Record findings Review / revise

  36. Occupational (mSv) Public (mSv) Effective Dose 20 1 Eye Lens Skin Extremities 20 500 500 15 50 - Annual Dose Limits (ICRP103) Stochastic Deterministic

  37. Area Classification and Monitoring Controlled : > 3/10th of any dose limit. : significant risk of spreading contamination. Supervised : reviewed as to controlled status. : > 1/10th of any dose limit. : effective dose > 1mSv per year. Monitoring for Contaminationmust be done regularly (at least weeklyµnature of work).

  38. Local Rules • Names of appointed persons • Duties and responsibilities • Classification of areas • Systems of work • - record keeping • - ordering • - experimental procedures • Personnel monitoring procedures • Dose investigation level – 2mSv • Contingency plans – loss, theft, spillage Read, Understand and Sign (RP6 form)

  39. Accounting for, Keeping and Moving Radioactive Substances House-keeping and records for quantity & location Stored substances kept in suitable receptacle & store Suitable & labelled package whilst being moved

  40. Each source must have an ‘owner’ Sources markedpermanently with unique ID number, trefoil and key data Due to the physical size often not possible Label the container – can lead to loss when users put the wrong sources back in the wrong pot Record Keeping IRR17 Regulation 29 and EPR2016 Permit conditions Inventory list of all sources – RPS should maintain a central record of all sources Source usage record for each source – date logged out, to where and why, by whom, date logged back in to store Monthly checks on locations with a record of the check Records of disposals Regulatory Control

  41. Radionuclide (*) Source ID number (*) Activity (*) and supplier's reference date (*) Date received onto the premises If in equipment – what type, model, serial number Current location Current leak test certificate (*) Current source ‘owner’ Date and manner of disposal of the source Keep these for at least two years (IRR17) but will also need these ones (*) at disposal time Records

  42. Records of Leak Test source (identification number) date carried out who did the test method of test instrument used (serial number) numerical result pass or fail action if failed Leak Testing

  43. Removal of sources from pieces of equipment Care with LSC sources – very small and can be difficult to extract (without an angle-grinder!!) Will need a suitable store for source once out Remove all the labels from the equipment before scrapping ! Disposal options Perhaps Exempted or VLLW via decay Solid incineration – if in Permit conditions Supplier might take back Sale or gifting to bona-fide organisations Specialist disposal ACB, Gamma Services, Babcock etc. Disposal

  44. Source Security • Sources must be held securely • Locked in a secure/shielded store when not in use • ONE physical barrier OK for most materials • BUT some higher activity sources need at least TWO physical barriers + alarms + PIR + CCTV etc. • High Activity Sealed Sources – HASS • Comply with guidelines from NaCTSO • Inspections by Counter-Terrorism Officers

  45. Transport of Radioactive Materials (Carriage of Dangerous Goods Regulations) Consignor – prepares and/or sends Carrier – physically transports Consignee – receives If going to be Consignor or Carrier – must contact The Radiation Protection Office to discuss arrangements e.g. Type of package, vehicle placards Must not be in private car – insurance invalidated Even as Consignee – written procedure for receipt

  46. The Radiation Protection Office (RPO) Professor Pete Cole (Room 406 794 3467) Radiation Protection Adviser / Radioactive Waste Adviser Miss Louise Nicholson (Room 406 795 7305) Radiation Protection Adviser / Radioactive Waste Adviser Mr John Ryan (Room 407 794 3466) Radiation Protection Technician Mr Paul Davies (Room 407 794 3465) Radiation Protection Technician rad.pro@liv.ac.uk

  47. Work of the RPO (includes!!) • Advice to University staff on complying with regs. • Departmental audits to ensure safe practice. • Liaison with EA, HSE, NRPB, SRP and AURPO. • Disposal of radioactive waste. • Monitoring staff doses. • Dealing with incidents and issues. • Communicating with the media.

  48. The RPO Website www.liv.ac.uk/radiation Details of RPO and how to contact us. Basic information on radiation hazards. Documents - Generic Local Rules. - Online Radiation Worker Registration - Waste Collection Request Forms. - Risk Assessment Forms.

  49. Radioactive Substances Whoops! Basic Radiation Protection and Legislation Overview Thanks for Listening

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