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18/04/23 radiation safety - level 5 2
ContentsContents
atomic and nuclear physics (1) interaction with matter (3)
o sources and x-ray equipment (2)o shielding (3)o detection (4)o radiobiology (6)
• objective risk of radiation (6)• subjective risk acceptation (6)
quantities and units (5) regulations (7)
o practical health physics (8 - 10)o waste (11)
18/04/23 radiation safety - level 5 3
DosimetryDosimetrysource constant and inverse square lawsource constant and inverse square law
dose is proportional to the activity and to the irradiation timedose decreases with the square of the distance from the source
D = A t / r2
the constant in this equation is called "source constant"it makes it possible to convert activity to external dose
E / 7 Gy m2 MBq-1 h-1 (E in MeV)
18/04/23 radiation safety - level 5 4
DosimetryDosimetrysource constant and inverse square lawsource constant and inverse square law
nuclide (Gy m2 MBq-1 h-1) T½22Na 0.33 2.6 j60Co 0.36 5.3 j99mTc 0.023 6.0 h125I 0.034 60 d131I 0.066 8.0 d137Cs 0.093 30 j192Ir 0.14 74 d201Tl 0.017 73 h241Am 0.017 430 j
18/04/23 radiation safety - level 5 5
DosimetryDosimetryrules of thumbrules of thumb
at 1 m from a -source of 1 MBq dose rate 10 µGy/h
at 1 m from a -source of 1 MBq dose rate E / 7 µGy/h
at 1 m from an x-ray tube dose rate 10 mGy/min
a -contamination of 1 kBq per cm2
skin dose rate rate 2 mGy/h
18/04/23 radiation safety - level 5 6
DosimetryDosimetryeffective dose coefficienteffective dose coefficient
E(50) = e(50) A
the "effective dose coefficient" e(50) depends onradiotoxicity of the nuclidechemical composition of the radioactive substancecontamination route (ingestion, inhalation, injection, wound, skin)
it makes it possible to convert activity to internal doseespecially tritiated water can penetrate skin and even gloves
18/04/23 radiation safety - level 5 7
DosimetryDosimetryeffective dose coefficienteffective dose coefficient
nuclide e(50)inh (Sv/Bq) T½3H (H2O) 1.810-11 12.3 j14C (CO2) 6.510-12 5730 j22Na 2.010-9 2.6 j32P 2.910-9 14.3 d35S 1.210-10 87.5 d45Ca 2.310-9 163 d99mTc 2.910-11 6.0 h125I 7.310-9 60 d131I 1.110-8 8.0 d226Ra 1.210-5 1600 jnatural Th 6.210-5 1.41010 jnatural U 5.710-5 4.5109 j
18/04/23 radiation safety - level 5 8
Safety measuresSafety measuresnominal working hoursnominal working hours
8 hours per day5 days per week 40 hours per week50 weeks per year 2000 hours per year
18/04/23 radiation safety - level 5 9
Safety measuresSafety measuresorganisational measuresorganisational measures
maintain a correct administration system for sources and devicesmark each source and device with a warning sign when in usestore unused sources in a vaultremove the key of an x-ray device when not in use
18/04/23 radiation safety - level 5 10
Safety measuresSafety measuressealed sourcessealed sources
protection against external radiationuse as little activity as possible (ALARA)reduce exposure timeincrease working distance (inverse square law)apply shielding (lead, lucite)measure the dose rate
periodic leak testtake regular smear tests (limit is 185 Bq)direct activity measurent with a contamination monitor is pointless
18/04/23 radiation safety - level 5 11
Safety measuresSafety measuresx-ray devicesx-ray devices
protection against external radiationdo not irradiate more often than necessary (ALARA)reduce exposure timeincrease working distance (inverse square law)apply shielding (lead apron)use a dose rate meter that is sensitive at low energy
check the equipment periodicallycheck filter and leakage radiationleave maintenance to the supplier of the equipment
watch out for scattered radiationreduce exposed area (diaphragm, light visor)
18/04/23 radiation safety - level 5 12
Safety measuresSafety measuresopen radioactive substancesopen radioactive substances
protection against external radiationsee sealed sources
protection against internal contaminationuse as little activity as possible (ALARA)prevent spreading (containment, splash tray)remove air born activity (ventilation, fume hood)prevent intake of activity (work discipline, protocol)
check for contamination by periodic laboratory surveysimmediately warn responsible radiation expertevacuate laboratory and check workers when leavingdetermine extent of contamination (dose rate meter is useless)decontaminated surface (limit is 4 Bq/cm2)
18/04/23 radiation safety - level 5 13
Safety measuresSafety measuresopen radioactive substancesopen radioactive substances
principle of "containment"glas tube, beaker glas, splash tray, fume hood, radionuclide laboratory
18/04/23 radiation safety - level 5 14
Safety measuresSafety measuresopen radioactive substancesopen radioactive substances
avoid oral uptakedon't eat at the work placedon't drink at the work placedon't smoke at the work placedon't apply make-up at the work place
18/04/23 radiation safety - level 5 15
Safety measuresSafety measuresopen radioactive substancesopen radioactive substances
avoid uptake via lungsrisk of aerosol formation while
shaking and vortexingcentrifugingopening bottlessanding
risk of tritium vapourtritium in condens is released when defrosting a refrigerator
risk of iodine vapouravoid formation of iodine vapour (keep pH > 4)iodine in condens is released when warming up a "cold room"keep lid on waste bin
18/04/23 radiation safety - level 5 16
Safety measuresSafety measuresopen radioactive substancesopen radioactive substances
avoid direct uptake in blood systemdon't work with open woundsavoid uptake of 3H via skin (use double gloves)
18/04/23 radiation safety - level 5 17
Radionuclide laboratoryRadionuclide laboratoryregulationsregulations
work with open radioactive substances is only permitted in a radionuclide laboratory
there are B-, C- en D-laboratories
building requirements are most stringent for a B-laboratorybuilding requirements are least stringent for a D-laboratory
maximum allowed activity is largest in a B-laboratorymaximum allowed activity is smallest in a D-laboratory
18/04/23 radiation safety - level 5 18
Radionuclide laboratoryRadionuclide laboratoryguideline radionuclide laboratoriesguideline radionuclide laboratories
there are two different opinions1.the risk is determined by regular uptake of small quantities of radioactive substances (National Health Council, 1985)2.the risk is determined by incidents (HARAS-report, 1997)
the Guideline Radionuclide Laboratories is based on opinion 1
18/04/23 radiation safety - level 5 19
Radionuclide laboratoryRadionuclide laboratoryguideline radionuclide laboratoriesguideline radionuclide laboratories
Amax = 0.02 10 p+q+r / e(50)inh
Amax = maximum allowed activity in Bqp = dispersion parameterq = laboratory parameterr = local ventilation parameter (note that r q)e(50) = dose conversion coefficient in Sv/Bq
18/04/23 radiation safety - level 5 20
Radionuclide laboratoryRadionuclide laboratoryguideline radionuclide laboratoriesguideline radionuclide laboratories
p application
-4 highly splashing substancepowder in open system
-3 labelling using volatile nuclideboiling liquid in closed system
-2 labelling using nonvolatile nuclidesimple chemical work (RIA)
-1 short, very simple work with liquidstorage of waste in working area
18/04/23 radiation safety - level 5 21
Radionuclide laboratoryRadionuclide laboratoryguideline radionuclide laboratoriesguideline radionuclide laboratories
q work place
0 outside radionuclide laboratory
1 D-laboratoryancillary space of radionuclide laboratory
2 C-laboratory
3 B-laboratory
18/04/23 radiation safety - level 5 22
Radionuclide laboratoryRadionuclide laboratoryguideline radionuclide laboratoriesguideline radionuclide laboratories
r local ventilation
0 no ventilation
1 fume hood (not NEN-NE 14175)
2 fume hood (NEN-NE 14175)
3 closed system (glove box)
18/04/23 radiation safety - level 5 23
RegulationsRegulationsradioactive wasteradioactive waste
radioactive waste is waste in whichboth the activity concentration exceeds the exemption leveland the activity exceeds the exemption level
radioactive waste is also waste that looks like radioactive waste no radioactivity stickers in normal industrial waste
disposal is expensive (in 2005 about € 1300 per 100 liter)
only COVRA is allowed to collect radioactive waste
18/04/23 radiation safety - level 5 24
RegulationsRegulationsrradioactive wasteadioactive waste
avoid waste productionuse as little activity as possibleuse short-lived nuclidesif not active, dispose as normal industrial waste
separate wastedry and liquid wasteorganic and inorganic wastelong-lived and short-lived wastecounting vialscadaverssealed sources
hand waste over to COVRA in standard drums
18/04/23 radiation safety - level 5 25
RegulationsRegulationsradioactive wasteradioactive waste
radioactive substances may be handed over to another person provided
either the activitity concentration is less than the exemption levelor the activity is less than the exemption level
18/04/23 radiation safety - level 5 26
RegulationsRegulationsradioactive wasteradioactive waste
nuclide concentration (Bq/g) activity (Bq)3H 106 109
14C 104 107
32P 103 106
35S 105 108
99mTc 102 107
125I 103 106
131I 102 106
226Ra 1 104
238U 10 104