SAFERIB 2002
RADIATION PROTECTION
IN A CLASS "A" TYPE LABORATORY
A. DORSIVAL
SAFERIB 2002
1
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
A. DORSIVAL
SAFERIB 2002
2
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)
A. DORSIVAL
SAFERIB 2002
3
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

A. DORSIVAL
RS 814.501 Annex 3, columns 4 and 5
SAFERIB 2002
4
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

A. DORSIVAL
RS 814.501 Annex 3, columns 12
SAFERIB 2002
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The Swiss Ordinance : workplaces

Workplace classification
Laboratory type
Activity
Class C
1 < LA < 100
Class B
1 < LA < 10000
Class A
1 < LA < upper permitted limit
Activity used per operation and per day
(RS 814.501 Article 69)

A. DORSIVAL
SAFERIB 2002
6
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
A. DORSIVAL
SAFERIB 2002
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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)
A. DORSIVAL
Isolde release measurement
SAFERIB 2002
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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
A. DORSIVAL
SAFERIB 2002
9
Class A laboratories :
basic requirements
CEA-Marcoule-Atalante
Photos: Th. FOULON
A. DORSIVAL
SAFERIB 2002
10
External exposure risks

External exposure
– Time, distance, shielding
» Hot cells with lead-glass and remote manipulation
CEA-Cadarache-Chicade Photo: E. Joly
A. DORSIVAL
SAFERIB 2002
CEA-Marcoule-Atalante
Photo: Th. FOULON
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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

A. DORSIVAL
RS 814.501.43 Annex 10
SAFERIB 2002
12
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
A. DORSIVAL
SAFERIB 2002

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CAi
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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
A. DORSIVAL
SAFERIB 2002
14
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
A. DORSIVAL
SAFERIB 2002
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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
A. DORSIVAL
SAFERIB 2002
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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
A. DORSIVAL
SAFERIB 2002
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“Frequently Asked Questions”
A few examples of radiation exposure
Source: CEA
A. DORSIVAL
SAFERIB 2002
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