Presentation - Medarbetarportalen

Report
Radiation Protection in
Laboratory work
Mats Isaksson, prof.
Department of radiation physics, GU
[email protected]
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
(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”
Effective dose / mSv a-1
Medical diagnostics
Caesium-137
Naturally occurring
radionuclides in food
Radon in indoor air
K in the body
Drinking water problem
Frequent air traveller
Reindeer keepers
Smoker (and
ex. smoker)
Never-smoker
Soil and building materials
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. 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
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 (a, b, g)
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: brange in mm
Electron energy / keV
50
100
500
1 000
Al
0.02
0.07
0.8
2.1
Fe
0.008
0.03
0.3
0.8
Pb
0.009
0.03
0.3
0.7
H-3: 19 keV; C-14: 156 keV; S-35: 167 keV;
P-32: 1711 keV
Plexi
0.04
0.1
1.5
3.8
Radiation safety in the lab
External irradiation: Shielding: g
HVL in mm
Photon energy / keV
50
Al
14
Cu
0.5
Pb
0.09
100
500
1 000
16
30
42
2
10
14
0.12
4.2
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
H-3
T1/2,phys
12 y
T1/2,biol
10 d
T1/2,eff
10 d
C-11
C-14
I-125
20 m
5 700 y
60 d
10-40 d
10-40 d
140 d
20 m
10-40 d
40 d
Radiation safety in the lab
• Classification of radionuclides
• Class A: very high radiotoxicity (ex. aemitters: Pb-210, Pu-238, Cf-252,…)
• Class B: high radiotoxicity (Na-22, Ca-45, Co56, 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, Co58, Zn-65, Y-90, I-123, Tl-201…)
• Class D: low radiotoxicity (H-3, C-11, Tc99m,…)
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
University of Gothenburg
Annhild Larsson
Radiation protection
expert (GU)
Annhild Larsson
Radiation protection
expert (Rad. Phys.)
Mats Isaksson
License 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
SSMFS 2008:51: Dose limits
(mSv)
Worker
Student 16-18 a Public
Yearly effective dose
50
6
1
Effective dose / consecutive 5year period
100
Yearly equivalent dose to lens of
the eye *)
150
50
15
Yearly equivalent dose to skin,
hands and feet
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
Nuclide
N.B. Local
restrictions
concerning
max activity
at
departments
Radiotoxicity
class
Activity/work activity
Arb I
(MBq)
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
Thank you for your patience
www.arbetsmiljo.adm.gu.se
www.studentlitteratur.se/#7403-02 (in
Swedish)
www.stralsakerhetsmyndigheten.se

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