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RADIATION APPRECIATION
COURSE
THE USE OF IONISING RADIATION FOR
Types of radiation sources & Biological effects of radiation
Typical equipment used on site
Emergencies & protection
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LEGAL REQUIREMENTS
Ionising Radiation Regulations 1999
Working with Ionising Radiation ACOP 1999
Radioactive Substances Act 1993
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TYPES OF RADIATION SOURCES
& BIOLOGICAL EFFECTS
TYPES OF RADIATION
(RADIOACTIVE DECAY) X-RAY
ALPHA BETA GAMMA
Yb 169Se 75Ir 192Co 60
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UNITS OF RADIATION
There are three principle units we need to be aware of:- Activity - which is the measure of quantity of a radioactive source
defined in terms of the number of nuclear transformations per second
and is expressed as the Bequerel - 1 disintegration / second.
Absorbed Dose - which is a measure of energy deposited in aparticular material from radiation and is expressed as the
Gray - 1 joule / kilogramme
Dose Equivalent - which is the absorbed dose modified by a quality
factor (Q) to take in the different biological effect of different types of
radiation and is expressed as the Sievert - Gray X Q.
For the type of radiation we are concerned with the Gray and Sievert
are the same.
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Radiation Travels In Straight Lines
Radiation Travels At The Speed Of Light
IONISING RADIATION KEY FACTS
Radiation Penetrates Matter
Radiation Can Impair Or Destroy Living Cells
Radiation Can Not Be Detected By Human Senses
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RADIATION EFFECTS ON BIOLOGICAL TISSUE
DEPOSITS ENERGY IN CELLS
99% DISSIPATED AS HEAT
(NEGLIGIBLE RISE IN
TEMPERATURE)
1% CAUSES CHEMICAL
CHANGES.
(RESULTS IN DAMAGE TO
CHROMOSOME PROTEIN etc)
DESTROYS
CELLS
DAMAGES
CELLS
CAN IMPAIR THE CELLS ABILITY TO REPRODUCE
ITSELF. THIS CAN BE MORE CRITICAL IN CELLS
THAT REPRODUCE RAPIDLY, SUCH AS THOSE IN
BLOOD FORMING ORGANS
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DOSES IN PERSPECTIVE (SPECTRUM OF DOSES)
Spectrum of Doses Approximate Dose
Annual Dose Limit for Classified Workers 20 mSv/YearAverage Radiation worker 4 mSv/Year
Annual Dose Limit for Other persons 1 mSv
Background (Natural), UK 1.9 mSv/Year
Back round, Other laces in the World 0.5mSv to 260 mSv/Year
(0.5 mSv average 260 mSv Ramsar Iran)
Typical dose from a chest X-Ray 0.3 mSv
Detectable damage to Chromosome 100 mSv
Detectable blood count change 300 mSv
Radiation sickness > 1 Gray (Body)
Death > 3 Gray (Body)
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TYPICAL EQUIPMENT USED FOR
RADIOGRAPHY ON SITE
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TYPICAL ISOTOPE SOURCE HOLDER
The radioactive isotope
is usually disc shaped
and is typically 2mm
diameter and 2mm in
.
This radioactive disc is
welded into a precision
made tungsten holder
Source
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GAMMA RADIOGRAPHY PROJECTOR SYSTEMS
Source Guide Tube Source Projectors Control Unit
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TYPICAL EQUIPMENT USED FOR RADIOGRAPHY
Equipment includes:-
Isotope container
Guide tube
Control mechanism
Collimation(Shielding)
Radiation monitor
TLD
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HUMAN SENSES
Radiation Can Not Be Detected By Any Of The Human
Senses
Radiation Monitors Are The Eyes And Ears Of The
Radiographer
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RADIATION (SURVEY) MONITORS
The radiation monitor is the
eyes and ears of the
radiographer.
They contain a Geiger-Muller
or similar tube, which detects
.
They also measure the
radiation dose level.
The monitor has a graduated
scale and an audible indicator
(clicker).
Monitors also have a battery
test button which indicates
that the batteries are OK.
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RADIATION (SURVEY) MONITORS
The scale is a graduated
logarithmic scale.
In this case the range is
from zero to 1000 Sv
per our.
The dose rate at a
barrier for site
radiography must be
less than 7.5Sv/hr
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RESTRICTION OF ACCESS TO CONTROLLED AREAS
Because of the dangers
site radiography is
conducted in a restricted
(controlled) area.
e area s emarca e
by barriers and boards.
The area will be
monitored throughout to
ensure the dose levels
outside are safe, lessthan 7.5Sv/hr.
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RESTRICTION OF ACCESS TO CONTROLLED AREAS
On site radiography
often requires barriers
to be established at
different levels on a
,
level at which the workis being done.
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GAMMA ALARM
When the Alarm is switched on
radiation below threshold
7.5Sv/hr is indicated by a
amber flashing lamp.
Radiation above the threshold is
indicated by a red flashing
lamp.
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EMERGENCIES
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EMERGENCIES INVOLVING RADIOGRAPHY
Incidences involving damage to radiography equipment resulting in
loss of containment of the radioactive isotope are extremely rare. We
are not aware of any such incidents in recent history.
However, should such an instance occur the priority of the emergency
serv ces wou e or t e sa ety o t e pu c an t en property.
Because of the nature of the work requiring other personnel to be
excluded from an area, it is highly unlikely that other personnel would
be in the vicinity of the radiographic equipment.
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ACCIDENTS INVOLVING INDUSTRIALRADIOGRAPHY
Equipment is regularly maintained and Radiographers conduct weekly
check and before use , but from time to time things can go wrong.
Most accidents which happen are the result of equipment damage or
malfunction. However, such accidents result in the potential for higher
dose levels and not contamination or loss of containment.
Procedures called Contingency Plans are in place to deal with any
foreseeable incident.
Radiographers are trained to implement the Contingency Plan if an
incident occurs.
The law requires that radiographers receive adequate refresher training
and that Contingency Plans are rehearsed on an annual basis.
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EMERGENCIES AND CONTINGENCY PLANS
Following any incident, the approach to recovery of the equipment
would be dependant on the circumstances.
Any company involved in work with Ionising Radiation most have
contingency arrangements for dealing with emergencies.
These contingency arrangements involve;
Measuring dose levels and setting safe distances Access, restriction of personnel to the vicinity
Planning a course of action for recovery
Telling relevant people what the plan is and how we will proceed
Replacing the equipment into suitable container for removal
Calling for external assistance if required
Keeping the area clear of unauthorised personnel until it is safe
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THE PRINCIPLES OF PROTECTION FROM IONISINGRADIATION ARE
TIME, DISTANCE & SHIELDING
TIME, the shorter the length of time a person is exposed to a radiation
source, the smaller the dose received.
DISTANCE, the further a person is away from a radiation source, the
smaller the dose received. Radiation obeys the inverse square law
which, in simple terms means, if you double the distance away from
the source the dose will be reduced by a quarter.
SHIELDING, materials absorb radiation, by shielding people from the
source dose levels are significantly reduced.
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EMERGENCIES AND CONTINGENCY PLANS
SITE INCIDENTS WHEN SOURCE IS IN USE
CONTINGENCY PLAN
If a fire alarm or toxic alarm sounds when working with a source on site, the first priority
is THE RADIOGRAPHERS OWN SAFETY
If the source can be returned to a container without danger then it SHOULD BE
If the operator can remove a container without danger then HE SHOULD
If the operator is in any doubt, the container should be left where it is, AT THE FIRST
OPPORTUNITY THE RADIOGRAPHER SHALL REPORT THE SITUATION TO
THE CONTROL ROOM OR RESPONSIBLE PERSON. MAKING SURE THAT FIRE
FIGHTERS OR RESCUE PERSONNEL ARE AWARE OF THE EXACT LOCATION
OF THE BARRIERS AND THE CONTAINER. THEY SHOULD GIVE AS MUCH
DETAIL AS THEY CAN REGARDING DOSE LEVELS IN THE AREA.
They shall offer any assistance or advice they can.
The radiographer should inform their RPS at the first available opportunity.
The radiographer should remain available in case additional information or assistance is
required.
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EMERGENCIES AND CONTINGENCY PLANS
CONTAINERS DAMAGED BY FIRE OR COLLAPSE
CONTINGENCY PLAN
If a container is caught in a fire or structural collapse the radiographers initial
responsi ility is for, THEIR OWN SAFETY FIRST.
THEY SHOULD REMOVE THEMSELVES TO A PLACE OF SAFETY AND
INFORM THE APPROPRIATE PERSONNEL. They should make themselves available
to offer any assistance or advice they can.
They should inform their RPS at the first available opportunity.
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ISO:3999 SPECIFICATION FOR APPARATUS FORGAMMA RADIOGRAPHY
All radiography equipment is produced to the highest standards and
licensed in accordance to rigorous requirements, which includes fire
and impact resistance, also resistance to puncture.
Should the equipment be involved in a fire, it is unlikely that the
emergency services would be exposed to dangerous levels of radiation,
however it would be appropriate if monitoring was carried out where
practicable.
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ACCIDENT IN THE USA IN 1979
In California in 1979 a radioactive source holder had become detached
from its container, the radiography crew were unaware of this and the
source holder was left at site.
An unsuspecting worker had found it and put it in his pocket, it was
left there for about 45minutes.
,
the man noticed a burning sensation and reddening of the buttock.
After two days the man went to his doctor, who thought it was an
insect bite.
The burn got worse and after seventeen days the man was hospitalised.
After three days of questioning by the doctors the man recalled having
the object in his pocket, at this point the Doctors realised that he had a
radiation burn.
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ACCIDENT IN THE USA IN 1979
About fifty days after
the incident a skin flap
was sewn over the
burn to close it.
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ACCIDENT IN THE USA IN 1979
About six months
after the incident a
secondary burn had
developed away from
.
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ACCIDENT IN THE USA IN 1979
A second skin flap
had been added 19
months after the
accident, but the
fully healed.
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Radiation Incident
February 20th, 1999
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Incident Synthesis
Location
Hydroelectric Construction Site in Yanango.
Distance from Lima: 300km (East)
District: San Romn De artment of Junn.
What Happened
A non-authorised person removed the screws of the security
lock to free the radioactive source of a Gammagraph.
No key is needed to remove the source, it can be done with a
screwdriver.
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Equipments Characteristics
Security
Lock
Type: SPEC T-2
Radionucleid: Ir192
Activity Max: 3.7 TBq
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Equipments Characteristics
With a screwdriver, the safety
lock can be removed to make the
source accessible
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Welder
- 4:00 pm: A worker (welder) finds the source of gammagraphy (192 Ir)abandoned in a water pipe. He puts it in the back pocket of his trousers.
- He works for six hours with the source in his pocket and his assistant nearby
Chronology
- 10:00 pm: He leaves work, takes a bus and travels home (he felt little pain in hisright leg). During his return, he travelled for 30 minutes with 15 people.
- He thinks that the red skin is due to an insect sting.
- His wife sat on the trousers for 10 minutes to feed their baby. Two children slept
nearby.
- 11:00 pm: The welder, takes the trousers off in the room.
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Operator
- 10:30 pm: The operator makes a gammagraphy. The radiation detector doesntdetect any readings. He assumes the equipment is not working well and stops to
have dinner.
Chronology
- 00:00 am: He enters the water pipe, checks the gammagraphy equipment and
finds no screws or radioactive source. They start looking for the source.
- 1:00 am: They find the welder in his house (February 21st). He comes out with
the source in his hands. The operator slaps the welders hand knocking the source to
the street and puts a stone to cover it.
- The source is recovered and secured in a container with iron walls 2 thick.
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What was done?
Initially, the welder was hospitalized in the Cancer Centre
of Lima.
Chronology
He was then sent to the Military Hospital Precy de ClaartGrave Burns Treatment Centre in France.
C
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Consequences
Severe Radiation Exposure To 1 Person and
Minor Exposure to 18 Other People
Effects on Leg
(13:00pm 2/21/99)
16 Days After
the incident
3/8/99
Effects on Leg
(70 days after the
incident 5/3/99)
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Consequences
Leg Amputation
(10/18/99)
Severe Infection
12/14/99
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