Training in risk assessment when working with sources of ionizing radiation (IR), safety regulations concerning work

with open sources of ionizing radiation and procedures performed when loss of control of IR sources occurs (according to § 26 of regulation No. 307/2002 coll.)

Mgr. Jiří Křivohlávek, supervisor of radiation safety at MU

Theoretical partLegislature

• Collection of laws No. 18/1997 coll., with later changes and amendments, so called „atomic law“

• Regulation No. 307/2002 coll., with later changes and amendments

Current versions at http://www.sujb.cz

Organization structure

Statutory representative of the organization (rector) → supervisor (Křivohlávek) → person with direct responsibility (Marini, Rotrekl, Vaňáčová, Hofr) → radiation worker

Controls SÚJB (State Office for Nuclear Safety), regular controls, possible fine up to 50 million Kc (§ 41. law No. 18/1997 coll.), when safety regulations are not met and also in case of serious offenses against safety rules.

Protection against ionizing radiation (IR)It consists in reducing the radiation dose to the value at which the risk for the human body becomes negligible.

Methods of protection from IR:

• Keeping distance from the radiation source ~ 1 / l2 (important for γ radiation)

• Shielding the radiation (not for α radiation; for β 1-2 cm glass or Plexiglass is enough; for γ lead, reinforced concrete, concrete with barytem (BaSO4))

• Limiting the time spent in the area with sources of IR

Biological effects of IR Basic definitions: Dose D: D = dε / dm [Gy] 

Equivalent dose HT: HT = wR DTR [Sv]

Radiation WR

Photons and electrons of all energy levels 1

Neutrons 10 keV 5

Neutrons 10-100 keV 10

Neutrons 0,1-2 MeV 20

Neutrons 2-20 MeV 10

a radiation 20

Source: ammendment No. 5, Regulation No. 307/2002 coll.

Tissue, organ wT

gonads 0.20

bone marrow 0.12

intestine 0.12

lungs 0.12

stomach 0.12

bladder 0.05

breast 0.05

liver 0.05

gullet 0.05

thyroid gland 0.05

skin 0.01

bone surfaces 0.01

other tissues and organs 0.05

Effective dose Hf: Hf = S wTHT [Sv]

Optimalization of radiation protection

Reasonably achievable level of radiation protection is considered to be sufficiently demonstrated also in those cases where, the radiation activities, or at foreseeable deviations from normal operation, annual effective dose in any of the radiation workers does not exceed 1 mSv and annual effective dose for no other person does not exceed 50 μSv.

Princip ALARA (as low as reasonably achievable)

collective effective dose ES(Sv)

Co

sts

for

soci

ety

X+Y

YX

ES,opt

X – costs of protectionY – costs of health harm due to radiation

Irradiation of humans by natural and artificial sources of ionizing radiation

• Czech Republic in total 3,1 mSv /year• Other places 100 – 300 mSv / year

Ref: http://www.suro.cz

The effects of ionizing radiation is reflected to a greater or lesser extent in all living organisms. The intensity of the effects depends on dose, dose rate and type of organisms.

Direct effects: modification of biologically important macromolecules (nucleic acids) by the direct action of ionizing radiation particles or secondary particles

Indirect effects related to the radiolysis of water (changes caused by radicals, hydrogen peroxide and hydrated electron - dried enzymes show less damage than enzyme solutions)

Specific information and procedures

Radionuclide Half-life Emax

3H 12,3 years 18,6 keV14C 5730 years 156,5 keV32P 14,3 days 1,71 MeV33P 25,4 days 249 keV35S 87,4 days 167,5 keV125I 60,14 days 35,5 keV

Overview of properties of used radionuclides

Rules for working with open radionuclide sources

• All radioactive substances must be stored in the original packaging and only at designated places

• All radioactive substances must be kept in shielded• Income and consumption of radioactive substances must be registered• Work with radioactive materials must be carried out only in designated areas• Packaging material that is not contaminated, can be disposed with the normal waste, but only after removing warning signs and labels

• Contaminated material is stored only in containers for radioactive waste• change into work clothes before working with open radionuclide sources • Use rubber gloves, Plexiglas shields and goggles• For handling use tweezers, forceps, tongs• Use protective walls and enclosures

Finishing your work with open radionuclide sources

• the rest of the emitters returns to the fridge for storage, other unwanted material is put after work into the radioactive waste,

• no radioactive material should remain on the working place• perform the decontamination of used equipment, glassware, tools, work equipment and,

when necessary, of protective tools, clothing and footwear.

When working with open radionuclide sources you must follow these rules:

Radioactive waste management

• Disposal is performed by the central decaying storage in accordance with the operating regulations,

• in the laboratory, a record is kept of waste submitted to the central decaying storage.

Waste• radioactive waste is stored in shielded containers for solid waste with an

disposable PE bag or a bottle for liquid waste• one bag (bottle) can store only material contaminated with the same radionuclide!• after work, the bag or bottle is sealed and marked• The label should say the name of the laboratory, room, date, radionuclide and the

activity of this nuclide processed in the laboratory,• in accordance with the rules of operation of the central decaying storage, the containers

are as soon as possible (the latest the following morning) emptied by a worker of the central decaying storage and taken to the storage for decaying,

• laboratory glassware is washed only in a chemical sink, from which liquid chemical waste is diverted into a collecting tank in the basement.

Monitoring

Monitoring is performed in the laboratory on the following areas:• laboratory tables• hood• laminar box• floor• sink

Class of radionuclide

Reference levelsRecording[Bq/cm2]

Investigation[Bq/cm2]

Intervention[Bq/cm2]

125I 0,1 1 332P 0,1 10 30

33P, 35S 0,1 10 300

Reference levelsThe recording levels are the minimum surface activity measurable by the used counter ofsurface contamination. Investigation levels correspond to the expected values of surface contamination on work surfaces, under normal operating conditions. Finally, the intervention levels are chosen as indicative values for surface contamination with radioactive nuclides

Ensuring emergency preparedness

It is considered loss of control over an ionizing source when this occurs:• spilling, splashing or spraying of radioactive substances during handling• loss or theft of radioactive emitter In these cases, the procedure is to follow the intervention instructions for each individual case. Whoever finds a loss of control over the source of ionizing radiation, is obliged to immediately inform the person with direct responsibility for radiation protection, the head of the department and the supervisor, who are appointed to manage the execution of these instructions to reestablish normal working conditions.

INTERVENTION INSTRUCTIONS IN CASE OF LOSS OF CONTROL OVER THE SOURCE (SELECTION) • Control by dosimetry whether any person has been contaminated• Perform decontaminationDECONTAMINATION PROCEDURES Decontamination of the working place:• Carry out decontamination in rubber gloves• Absorb the maximum amount of radioactive substance with cellulose cotton• Wash the affected area with a suitable decontamination agent (eg citric acid)• Check success of decontamination by dosimetry• Discard waste produced during decontamination (cotton, gloves) to a PE bag

properly labeled (date,nuclide) to be stored at the central decaying storage

In case of contamination of hands, eyes and clothing:• Gently with a cellulose cotton absorb the radioactive substance from the contaminated

areas of the skin• Wash the skin with warm water and soap• When failing to decontaminate the skin this way, use complexing agents, such as 1%

solution of citric acid• Do so carefully, not to damage the skin• Carry out dosimetric control continuously• Repeat until the values drop to background readings of the used monitoring counter

INTERVENTION INSTRUCTIONS IN CASE OF LOSS OR THEFT OF RADIATION SOURCES

• Notify the loss or suspected loss of radiactive emitters to the Police Department of the Czech Republic

• Give the police a description of the radioactive emitter and information of the properties of the radioactive substance, emitted radiation a description of dangerous properties

ContactsTelephone numbers of involved persons and organizations:Supervisor (Mgr. Křivohlávek) tel. 549 493 150

mobil 776 205 729 SÚJB RC Brno fax 515 902 760Director, RNDr. Urbančík tel. 515 902 773 Inspector of Radiation Safety, RNDr. Vrbanová tel. 515 902 789 Police of the Czech Republic tel. 158Firemen tel. 150

Tests at http://www.rect.muni.cz/nso/ to be sent to fractal@mail.muni.cz