23. Risk and control of ionizing radiation (ionizing radiation monitoring). Main principles of protection.

Risks of Ionizing Radiation

• Somatic effects: ARS, cancer, cataracts, infertility, skin injuries

• Genetic effects: Heritable mutations

• Environmental risks: Contamination, radioactive waste

Monitoring of Radiation

• Individual monitoring:

  • Personal dosimeters (e.g. film badges, TLDs)

  • Worn on trunk → gives whole-body dose in mSv/month

• Area monitoring:

  • Radiation detectors in workplaces

  • Ensures environmental radiation is within safety limits

Main principles of protection

1. ALARA principle

2. Protection from external exposure and closed sources

3. Protection from Unsealed (Open) Radioactive Materials

4. Radiation-Specific Protections

5. Timing of Effects

ALARA Principle

As Low As Reasonably Achievable
Minimise radiation dose using the 4 key factors:

(mnemonic- SDTS)

• Source Activity:

  • Dose ∝ source intensity (e.g. mA in X-rays)

  • stronger the radiation source = higher the dose

  • lower the source output to the minimum required amount

• Distance: Dose

  • ∝ 1 / distance²

  • if you double the distance = dose reduces by a factor of 4

  • Keeping a safe distance is the most effective way of reducing exposure

• Time:

  • Dose ∝ Exposure time

  • Reduce the amount of time spent near a radiation source.

  • Shorter exposures = less accumulated dose.

• Shielding:

  • Dose ↓ exponentially with the thickness/absorption of material

  • lead, concrete or specialised clothing

  • thicker or more dense the shielding = the greater the dose reduction

Protection from External Exposure & Closed Sources

• Decrease source activity

  • Limit device power during construction

  • Avoid multiple sources or prolonged activation

• Increase distance

  • Especially useful for X-rays and penetrating radiation

  • Elevated rooms reduce secondary radiation

• Minimize exposure time

  • Short exposures (e.g., 1–2 sec for radiographs)

  • “Doctor in the dark” principle (step out during exposure)

• Use shielding

  • Material selection depends on radiation type

  • Interaction reduces exposure

Protection from Unsealed (Open) Radioactive Materials

• Facility design

  • Minimize contamination

  • Easy decontamination

  • Adequate ventilation and shielding

  • Provide changing/ washing areas

• Work control

  • Use minimal quantities

  • Isolate procedures

  • Monitor workspaces

  • Use appropriate systems and PPE

Radiation-Specific Protections

• X-Rays:

  • Shielded rooms (concrete)

  • Staff use lead coats, gloves

• Neutron Radiation:

  • Triple-layer shielding:

    1. Water/ concrete – slow down (moderate) fast neutrons

    2. Cadmium/borax – absorb slow neutrons

    3. Lead – blocks secondary gamma rays

  • Ventilation, hermetic (sealed) rooms, telemetric controls (remote)

• Open Sources:

  • Hermetically sealed rooms

  • Mask/glove use

  • Auto pipettes

  • Patient & waste safety emphasized

• Protection against neutron radiation

  • Three levels of shielding are used:

• 1st

  • slows down fast and very fast neutrons (water, concrete)

• 2nd

  • captures slow neutrons (cadmium and borax are used)

  • neutron absorption

• 3rd

  • is build to accept secondary gamma radiation (Pb).

What is decontamination?

Decontamination is the process of removing or reducing radioactive substances from:

• Surfaces (equipment, floors, walls)

• Environment (air, water, soil)

• Human skin and clothing

The goal is to reduce contamination to safe levels or eliminate it entirely.

How is decontamination done?

The process used is called deactivation, which involves:

• Physical methods: brushing, washing, vacuuming, ventilation

• Chemical methods: using detergents, acids, or chelating agents

• Mechanical methods: scraping or removing contaminated materials

The method chosen depends on the material being treated:

• Skin: gentle washing with soap and water

• Metal: chemical solutions

• Porous materials (e.g., fabric, concrete): often harder to decontaminate completely

Principle rules in performing decontamination

1. The deactivation must be done immediately after the contamination

   • to prevent permanent fixation of radioactive substances to the surface or material.

2. Always wear protective gloves and work clothes.

   • Use tools that allow distance between the person and the contaminated object (e.g., push-button devices).

3. The decontamination methods used must not damage the treated material or skin.

4. The effectiveness of the decontamination should be checked using a dosimeter.

5. All waste generated during decontamination must be treated and disposed of as radioactive waste.

Decontamination of hands

• The epidermis has a main role in the protective function of the skin.

• Start with double washing

  • with water, soap and soft brush

  • until the appearance of abundant foam.

• After rinsing, the hands are wiped with a personal napkin

  • and are checked on the dosimeter device

  • to check the remaining radioactivity.

• If the washing is not effective then other washing means are used

Skin contamination

• Sites of contamination should be washed or scrubbed gently using warm water, soap and a soft nail brush

• Do not break the surface of the skin or allow contamination to enter the bloodstream

• Ensure uncontaminated cuts or sores are covered with a waterproof dressing prior to washing

Persistent skin contamination

• Use 4% solution of potassium permanganate and allow to dry.

• Brown staining removed with 5% solution sodium metabisulphite.

• Dry and monitor

Cleaning of body skin

• Decontamination is done in the sanitary bathroom.

• Mouth, nose, throat, and ears should be rinsed with a potassium permanganate (KMnO4) solution.

• Do not use organic solvents, as they increase skin absorption of radiation.

• Hand-washing water should be below 37°C.

  • Hot water opens skin pores and increases blood flow

  • which can enhance absorption of contaminants.

• Bathing water should be between 45–50°C.

work clothing decontamination:

• Contaminated work clothes are cleaned in special laundries.

• Sorting is done based on:

  • Type of radiation (alpha, beta, etc.)

  • Level of contamination

  • Type of fabric (e.g. cotton, polyethylene)

• Cotton white coats:

  • Washed in 80–90°C water

  • Boiled in soap-soda solution

  • Then starched to help with future decontamination.

Minor spills on benches and floors

• Demarcate the affected area

  • Mark boundaries to prevent the spread and access

• Wear PPE

  • Use disposable gloves and overshoes.

• Contain the spill

  • Place paper towels/tissues over the spill to absorb and prevent spreading.

• Clean the spill (decontamination)

  • Mop from the periphery inward to prevent the contaminated area from spreading.

  • Place all used towels in sealed plastic bags.

• Monitor and repeat if needed

  • Use a radiation monitor to check for remaining contamination.

  • Repeat cleaning until levels are safe.

• Report the incident

  • Inform the Radiation Protection Supervisor (RPS) who will assess the extent and cause.

• Update records

  • Document and account for disposed material in the radioisotope logbook.

principles of protection

• Optimization (ALARA): All exposures should be kept as low as reasonably achievable, taking into account economic and social factors.

• Dose Limitation: Individual exposure must not exceed the dose limits recommended by regulatory bodies.

Personal monitoring

• Individual dosimeters are used to record the exposure dose of the people operating the equipment

What is a dosimeter?

• types

A device used to measure a person’s exposure to ionising radiation over time.

• it is a container that holds:

  • Detectors – these detect and measure the amount of radiation.

  • Filters – these help identify the type and energy of the radiation by selectively allowing certain radiation through.

• worn by people who work with/ around radiation

• monitors and limits their exposure.

Types

• Film dosimeter

  • contains photographic film that darkens depending on how much radiation it absorbs

• Thermoluminescent dosimeter

  • radiation causes the crystals inside to store energy

  • when heated, the crystals release light

What is the personal protective equipment ?

• wearing of protective clothing

• use of respiratory protective equipment if appropriate

What is the medical care ( prevention ) ?

why is it important?

• risk groups

  • not permeated to work in a condition of ionizing radiation

• list of disease with which workers are not allowed working in a conditions of ionizing radiation

  • People under 18 years of age

  • Pregnant and breastfeeding women

  • People with specific medical conditions

    • Blood disorders (e.g. anemia, leukemia)

    • Skin diseases (e.g. chronic eczema, psoriasis)

    • Nervous system disorders

    • Endocrine diseases (e.g. uncontrolled diabetes)

    • Severe cardiovascular disease

    • Kidney and liver failure

    • Malignancies (cancers)

• To protect individuals who are more vulnerable to radiation damage.

• To prevent occupational illnesses caused/ worsened by exposure.

how to monitor radiation workers?

All radiation workers must undergo regular medical surveillance

• before employment

• during their work period

• after leaving the job.