Radiation Protection in Laboratory work

Radiation Protection in Laboratory work

Mats Isaksson, prof.Department of radiation physics, GU

[email protected]

Fundamental principles (ICRP)

Justification

Optimisation

Application of dose limits


Justification“Any decision that alters the radiation exposure

situation should do more good than harm.”


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)


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 (a, b, g, 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”Medical diagnostics

Cosmic radiation

Caesium-137

Naturally occurring radionuclides in food

Radon in indoor air

K in the body

Soil and building materials

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Effective dose / mSv a-1

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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 equipmentX-ray machinesAccelerators

Ionizing radiation from radioactive elements

Generation of x-rays X-ray spectrum

X-ray equipment

Radiation safety in the lab

• External irradiation• Short range radiation, e.g. a, mostly

harmless when the source is outside the body

• b-emitters may cause severe skin damage if they are in contact with naked skin


• 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


• 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 (a, b, g)

Radiation safety in the labExternal irradiation: Inverse square

law

Radiation safety in the labExternal 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 labExternal irradiation: Shielding: b-

range in mmElectron energy / keV Al Fe Pb Plexi50 0.02 0.008 0.009 0.04100 0.07 0.03 0.03 0.1500 0.8 0.3 0.3 1.51 000 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 labExternal irradiation: Shielding: g

HVL in mmPhoton energy / keV Al Cu Pb50 14 0.5 0.09100 16 2 0.12500 30 10 4.21 000 42 14 9

I-125: 35 keV; Tc-99m: 140 keV; I-131: 365 keV; Y-88: 1836 keV


• 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 labInternal irradiation: Effective half-life

Radionuclide T1/2,phys T1/2,biol T1/2,eff

H-3 12 y 10 d 10 dC-11 20 m 10-40 d 20 mC-14 5 700 y 10-40 d 10-40 dI-125 60 d 140 d 40 d


• Classification of radionuclides• Class A: very high radiotoxicity (ex. a-

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: University of GothenburgContact person Annhild LarssonRadiation protection

expert (GU) Annhild LarssonRadiation protection

expert (Rad. Phys.) Mats IsakssonLicense valid to 2016-02-07

SSMFS 2010:2 Radioactive waste

Revised limits

Documentation kept for 5 years

Yearly report to SSM concerning releases to sewage

*) Will probably be revised to 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv

Worker Student 16-18 a PublicYearly effective dose 50 6 1

Effective dose / consecutive 5-year period

100

Yearly equivalent dose to lens of the eye *)

150 50 15

Yearly equivalent dose to skin, hands and feet

500 150 50

SSMFS 2008:51: Dose limits (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

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 2008:51 Categorization

Nuclide Radio-toxicity class

Activity/work activityArb I(MBq)

Arb II(MBq)

Arb III(MBq)

H-3 D 100 1000 10000P-32 C 10 100 1000Cr-51 C 10 100 1000I-125 B 1 10 100

N.B. Local restrictions concerning max activity at departments

SSMFS 2008:28 Restrictions on activity in laboratory work

Arb I: Risk of inhalationArb 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

www.arbetsmiljo.adm.gu.se

www.studentlitteratur.se/#7403-02 (in Swedish)

www.stralsakerhetsmyndigheten.se

Thank you for your patience

Documents

Radiation Protection in Laboratory work