Radiation Protection in Laboratory work Mats Isaksson, prof. Department of radiation physics, GU mats.isaksson@radfys.gu.se
Fundamental principles (ICRP) Justification Optimisation Application of dose limits
Fundamental principles (ICRP) Justification Any decision that alters the radiation exposure situation should do more good than harm.
Fundamental principles (ICRP) Optimisation The likelihood of incurring exposure, the number of people exposed, and the magnitude of their individual doses should all be kept as low as reasonably achievable, taking into account economic and societal factors. (The ALARA-principle)
Fundamental principles (ICRP) Application of dose limits The total dose to any individual from regulated sources in planned exposure situations other than medical exposure of patients should not exceed the appropriate limits specified by the Commission. N.B. other than medical exposure of patients ICRP-report 103 identifies three exposure situations: planned, emergency and existing
Radiation doses 1 Absorbed dose (unit 1 Gy = 1 J kg -1 ) Used in e.g. radiation therapy to specify the dose to the tumor Different radiation qualities (α, β, γ, n) can cause different degree of harm weighting necessary
Radiation doses 2 Equivalent dose (unit 1 Sv = 1 J kg -1 ) Used to calculate the dose to a tissue or organ Weighting factors for different radiation qualities given by ICRP Can be estimated by measurable quantities e.g.personal dose equivalent
Radiation doses 3 Effective dose (unit 1 Sv = 1 J kg -1 ) Used to calculate the whole body dose that gives the same detriment as the actual partial body dose Enables a comparison of risk from different exposure distributions
Radiation doses 3 Illustration to effective dose
Radiation doses 4 Effective dose (unit 1 Sv = 1 J kg -1 ) Weighting factors for different organs and tissues are given by ICRP Can be estimated by measurable quantities e.g.ambient dose equivalent
The bottom line Effective dose / msv a -1 Medical diagnostics Caesium-137 Naturally occurring radionuclides in food Radon in indoor air K in the body Soil and building materials Never-smoker Smoker (and ex. smoker) Reindeer keepers Frequent air traveller Drinking water problem Cosmic radiation
X-ray and nuclear medicine From Nuklearmedicin by Sten Carlsson and Sven-Eric Svensson (available at http://www.sfnm.se/)
Radiation sources Radioactive sources Unsealed liquid, gas, powder Sealed Technical equipment X-ray machines Accelerators
Ionizing radiation from radioactive elements
X-ray equipment Generation of x-rays X-ray spectrum
Radiation safety in the lab External irradiation Short range radiation, e.g. α, mostly harmless when the source is outside the body β-emitters may cause severe skin damage if they are in contact with naked skin
Radiation safety in the lab Internal irradiation Radioactive substances in non-sealed sources (gas, liquid, powder) cause special concern Can enter the body through ingestion, inhalation, wounds or through the skin
Radiation safety in the lab External irradiation: Factors to be considered Time more time spent in the radiation field gives a larger radiation dose Distance inverse square law (for point source) Shielding shielding material depends on the source (α, β, γ)
Radiation safety in the lab External irradiation: Inverse square law
Radiation safety in the lab External irradiation: Inverse square law
Practical ALARA Practice before working with the real source Education before work Separate office and lab work Wear protective clothing and gloves All labs should be marked with signs Eat, drink etc outside the lab
Radiation safety in the lab External irradiation: Shielding: β- range in mm Electron energy / kev Al Fe Pb Plexi 50 0.02 0.008 0.009 0.04 100 0.07 0.03 0.03 0.1 500 0.8 0.3 0.3 1.5 1 000 2.1 0.8 0.7 3.8 H-3: 19 kev; C-14: 156 kev; S-35: 167 kev; P-32: 1711 kev
Radiation safety in the lab External irradiation: Shielding: γ HVL in mm Photon energy / kev Al Cu Pb 50 14 0.5 0.09 100 16 2 0.12 500 30 10 4.2 1 000 42 14 9 I-125: 35 kev; Tc-99m: 140 kev; I-131: 365 kev; Y-88: 1836 kev
Radiation safety in the lab Internal irradiation: Factors to be considered Activity the larger the activity the larger the radiation dose (for a given radionuclide) Radionuclide amount of energy per disintegration; type of radiation Metabolism element and chemical form determine the residence time in the body and concentration in organs
Radiation safety in the lab Internal irradiation: Effective half-life Radionuclide T 1/2,phys T 1/2,biol T 1/2,eff H-3 12 y 10 d 10 d C-11 20 m 10-40 d 20 m C-14 5 700 y 10-40 d 10-40 d I-125 60 d 140 d 40 d
Radiation safety in the lab Classification of radionuclides Class A: very high radiotoxicity (ex. α- emitters: Pb-210, Pu-238, Cf-252, ) Class B: high radiotoxicity (Na-22, Ca-45, Co- 56, Co-60, Sr-89, In-114m, I-125, I-131, Cs-137, ) Class C: moderate radiotoxicity (C-14, Na-24, P-32, S-35, Ca-47, Cr-51, Fe-55, Fe-59, Co-57, Co- 58, Zn-65, Y-90, I-123, Tl-201 ) Class D: low radiotoxicity (H-3, C-11, Tc- 99m, )
Deterministic effects approximate threshold values >0,1 Gy Effects on embryo and fetus 0,5 Gy Temporary sterility, men 2 Gy Cataract 4 Gy Temporary hair loss 5 Gy Skin erythema 6 Gy Permanent sterlility, men 8 Gy Pneumonia 2-12 Gy Permanent sterility, women
Deterministic effects whole body irradiation Lethal dose (50 % of exposed individuals survive): 3-4 Gy Acute radiation syndrome blood forming organs, gastro-intestinal tract & central nervous system
Stochastic effects no threshold Cancer and hereditary effects Increasing risk with increasing dose Risk factor only applicable on a population level LNT-hypothesis
Laws and regulations Strålskyddslagen SFS 1988:220 Employers obligations Workers obligations Licence demands Waste handling demands Medical examination Young people Strålskyddsförordningen SFS 1988:293
Relevant regulations (SSM) SSMFS 2010:2 Radioactive waste SSMFS 2011:2 Clearance of materials, premises, buildings och grounds SSMFS 2008:25 Radiography SSMFS 2008:51 Protection of workers and the public SSMFS 2008:28 Laboratory work with unsealed radioactive sources
License from SSM for work with ionizing radiation Licensee: Contact person Radiation protection expert (GU) Radiation protection expert (Rad. Phys.) Annhild Larsson License valid to 2016-02-07 University of Gothenburg Annhild Larsson Mats Isaksson
SSMFS 2010:2 Radioactive waste Revised limits Documentation kept for 5 years Yearly report to SSM concerning releases to sewage
SSMFS 2008:51: Dose limits (msv) Worker Student 16-18 a Public Yearly effective dose 50 6 1 Effective dose / consecutive 5- year period Yearly equivalent dose to lens of the eye *) Yearly equivalent dose to skin, hands and feet 100 150 50 15 500 150 50 *) Will probably be revised to 20 msv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 msv
SSMFS 2008:51: Protection of pregnant or breast feeding women Women in fertile ages should be informed of the risks for the fetus Pregnant women have the right to be relocated (if not, the effective dose to the fetus should not exceed 1 msv during the rest of the pregnancy Breast feeding women should not be exposed to a risk of being contaminated in the work
SSMFS 2008:51 Categorization Protected area ( Skyddat område ) Category B worker local rules (could be given verbally) signs with the text skyddat område and type of source Category B (max activity per work activity) Gamma emitting radioniclides: < 100 MBq Beta emitters: < 10 MBq for beta energy > 0,3 MeV < 100 MBq for beta energy 0,1-0,3 MeV No work with open radiography
SSMFS 2008:28 Restrictions on activity in laboratory work N.B. Local restrictions concerning max activity at departments Nuclide Radiotoxicity class Arb I (MBq) Activity/work activity Arb II (MBq) Arb III (MBq) H-3 D 100 1000 10000 P-32 C 10 100 1000 Cr-51 C 10 100 1000 I-125 B 1 10 100 Arb I: Risk of inhalation Arb II: Risk of external and internal exposure; small risk of inhalation
SSMFS 2008:28 Documentation/reporting Data which should be documented, signed and kept available for concerned personnel: Received and stored radioactive substances, and their activities Possession of calibration sources Results from ventilations and contamination monitoring Results from personnel dose monitoring and estimations of internal doses
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