Radiation Protection in Laboratory work. Mats Isaksson, prof. Department of radiation physics, GU

Transcription

1 Radiation Protection in Laboratory work Mats Isaksson, prof. Department of radiation physics, GU

2 Fundamental principles (ICRP) Justification Optimisation Application of dose limits

3 Fundamental principles (ICRP) Justification Any decision that alters the radiation exposure situation should do more good than harm.

4 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)

5 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

6 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

7 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

8 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

9 Radiation doses 3 Illustration to effective dose

10 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

11 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

12 X-ray and nuclear medicine From Nuklearmedicin by Sten Carlsson and Sven-Eric Svensson (available at

13 Radiation sources Radioactive sources Unsealed liquid, gas, powder Sealed Technical equipment X-ray machines Accelerators

14 Ionizing radiation from radioactive elements

15 X-ray equipment Generation of x-rays X-ray spectrum

16 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

17 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

18 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)

19 Radiation safety in the lab External irradiation: Inverse square law

20 Radiation safety in the lab External irradiation: Inverse square law

21 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

22 Radiation safety in the lab External irradiation: Shielding: β- range in mm Electron energy / kev Al Fe Pb Plexi H-3: 19 kev; C-14: 156 kev; S-35: 167 kev; P-32: 1711 kev

23 Radiation safety in the lab External irradiation: Shielding: γ HVL in mm Photon energy / kev Al Cu Pb I-125: 35 kev; Tc-99m: 140 kev; I-131: 365 kev; Y-88: 1836 kev

24 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

25 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 m d 20 m C y d d I d 140 d 40 d

26 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, )

27 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

28 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

29 Stochastic effects no threshold Cancer and hereditary effects Increasing risk with increasing dose Risk factor only applicable on a population level LNT-hypothesis

30 Laws and regulations Strålskyddslagen SFS 1988:220 Employers obligations Workers obligations Licence demands Waste handling demands Medical examination Young people Strålskyddsförordningen SFS 1988:293

31 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

32 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 University of Gothenburg Annhild Larsson Mats Isaksson

33 SSMFS 2010:2 Radioactive waste Revised limits Documentation kept for 5 years Yearly report to SSM concerning releases to sewage

34 SSMFS 2008:51: Dose limits (msv) Worker Student a Public Yearly effective dose Effective dose / consecutive 5- year period Yearly equivalent dose to lens of the eye *) Yearly equivalent dose to skin, hands and feet *) Will probably be revised to 20 msv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 msv

35 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

36 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

37 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 P-32 C Cr-51 C I-125 B Arb I: Risk of inhalation Arb II: Risk of external and internal exposure; small risk of inhalation

38 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

39 Thank you for your patience (in Swedish)