RADIATION PROTECTION IN A CLASS "A" TYPE LABORATORY

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RADIATION PROTECTIONIN A CLASS "A" TYPE
LABORATORY

• SAFERIB 2002

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Overview

• Regulations
• A few definitions, guidelines and limits
  extracted from the Swiss ordinance ORaP
• Workplace equipment
• What are the basic equipments in a class A type
  laboratory
• Exposure risks
• How to measure and reduce external and internal
  radiation exposure

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Vocabulary

• Unsealed source
• Source that does not meet the definition of a
  sealed source and can cause a contamination
• A sealed source is any radioactive material
  encased in a capsule designed to prevent leakage
  or escape of the material
• Radioactive contamination
• Undesired radioactive material that is deposited
  on the surface of or inside structures, areas,
  objects or people
• Can be loose (indirectly measurable with a
  smear)
• Can be fixed (directly measurable on surface
  with a probe)

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The Swiss Ordinance

• The licensing limit LA
• Activity (Bq) derived from the committed
  effective dose by inhalation
• The intake by inhalation of 1 LA gives a
  committed effective dose of 5 mSv
• RS 814.501 Annex 3, columns 10
• The incorporation dose factors einh and eing
• For the considered isotope, the inhalation or
  respectively ingestion of 1 Bq causes the given
  effective dose
• Source Directive Euratom 96/29
• RS 814.501 Annex 3, columns 4 and 5

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The Swiss Ordinance guideline values

• The concentration of activity CA
• The air inhalation with 1 CA concentration of
  activity during 40 hours per week and 50 weeks
  per year (persons occupationally exposed to
  radiation) causes an effective dose of 20 mSv
• CA Bq/m3 0,02 / (einh 2400)
• RS 814.501 Annex 3, columns 11
• The surface contamination CS
• Expressed in Bq/cm2, this guideline value is the
  most conservative result of 3 calculation modes
  and applies for material leaving controlled
  areas
• Skin irradiation, Ingestion, Inhalation
• RS 814.501 Annex 3, columns 12

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The Swiss Ordinance workplaces

• Workplace classification
• Activity used per operation and per day
• (RS 814.501 Article 69)

Laboratory type Activity
Class C 1 lt LA lt 100
Class B 1 lt LA lt 10000
Class A 1 lt LA lt upper permitted limit
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Class A laboratories basic requirements

• General characteristics
• Located away from circulation
• Isolated from other workplaces
• Grouped to form a unit (controlled area)
• Hierarchically organized following risks
• Ventilation
• Minimum air renewal 5 h-1
• Hierarchic depression
• Absolute filtration
• Release chimney
• Control system (radioactivity, flows, pressures)
• Backup power supply

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Class A laboratories basic requirements

• Radioactive storage area
• Low background for contamination measurements
• External exposure reduction
• Radioactive release management
• Gas and aerosol monitoring
• Liquids monitoring (backup reservoir)

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Class A laboratories basic requirements

• Collective equipment
• Fume cupboards (dynamic confinement)
• Glove box (static confinement)
• Appropriate radiation protection monitors
• Radioactive waste containers
• Decontamination facilities
• Hot and cold changing rooms
• Individual equipment
• Working clothes (overall, gloves, special shoes
  or overshoes)
• Breathing protection device

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Class A laboratories basic requirements
CEA-Marcoule-Atalante Photos Th. FOULON
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External exposure risks

• External exposure
• Time, distance, shielding
• Hot cells with lead-glass and remote manipulation

CEA-Marcoule-Atalante Photo Th. FOULON
CEA-Cadarache-Chicade Photo E. Joly
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Internal exposure risks

• Internal exposure
• The intake of radioactive substances can reach
  the human organism through 4 different ways
• Inhalation, ingestion, skin absorption, wound
• Concentration measurement
• Activity deposited on a filter (aerosol)
• Circulation in a differential chamber (gas)
• Exposure threshold (mesure de tri)
• when this threshold is exceeded, it is mandatory
  to measure incorporation and to determine the
  committed effective dose
• Expressed in Bqhm-3
• RS 814.501.43 Annex 10

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Internal exposure risks

• Exposure measurement
• The exposure is the integration of the
  concentration of activity for a given time
• Exposure Bqh/m3 ? A(t) dt
• Sampled activity Bq Fs ? A(t) dt
• Inhaled activity Bq Fi ? A(t) dt
• With Fs sample flow, Fi inhalation flow
• Example the aerosols exposure can be deduced
  from the activity deposited on a filter divided
  by the sample flow
• Mixtures of radio nuclides
• Example of additive rule for CA

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Working methods

• General rules involving unsealed sources
• Work should be conducted in a tray lined with
  absorbent paper and at least in a fume cupboard
• Use the smallest quantity of radioactivity
  compatible with the objective of the experiment
• Make a plan and test it if necessary
• Know how to react in case of spill or a personal
  contamination
• Work carefully, and monitor regularly the work
  area to avoid accidental contamination
• All radioactive waste must be placed in marked
  containers
• Never work alone! Ask for RP supervision

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Working methods

• Example
• Sealed removal of waste or material from glove
  box
• Put the object in the bag
• Check welding on a test bag
• 3 welds at close intervals
• Cut in the middle one
• Monitor gloves, scissors
• Put the sealed object in a second bag and weld it

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Working methods

• Critical operations
• Caution undressing (mask, overall and gloves
  removal)
• Combination of external and internal exposure
  wearing heavy protections may extend the time of
  intervention
• Is there a benefit?
• Small traps glasses, phone, watch, long hair...

CEA-Brennilis-Liquids Treatment Station Photo
A. Gonin
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Working methods

• How to react in case of incident
• Minor spills involving no radiation hazard to
  persons
• Confine the spill immediately
• Notify all the other persons in the room
• External decontamination
• Incidents with presumed incorporation
• Vacate the room
• Wear appropriate protection before re-entering
  the room (for emergency measures)
• External decontamination
• Nasal sample, anthropogammametric scan (whole
  body, thyroid), urine and/or feces analysis

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Frequently Asked Questions
A few examples of radiation exposure
Source CEA