Curso De Refresco De Rt

IRPA12 Refresher Course RC-20

Radiation protection in industrial applications of
Radiation
radioactive sources:

Prevention of Accidents in
Gammagraphy
John Croft
Consultant
Former Head of Emergency Response
Health Protection Agency
UK

Introduction: Why this subject?
Introduction:
•

Prone to accidents and leaving orphan sources
Dominant usage in UNSCEAR list of accidents
―Many instances of orphan sources
― Radiation injuries and fatalities
―

•

Terminology
Gammagraphy = gamma (ɣ)radiography
― Industrial radiography = X- and ɣ-radiography
―

River Tyne, 1972

4088

Contents
Contents
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•
•
•
•

Types of radiography and equipment
Common causes of accidents
Examples of serious accidents
Mechanisms to learn lessons
Roles of thedifferent “Players”
Emergency response
Guidance material and training

Types of radiography (1)
Types
Enclosure radiography
• Purpose built (?) shielded enclosure
“temporary” nature of some
― Non-standard use
―

•
•
•

Installed safety systems: warning lights and
interlocks (?)
Should be inherently safer: maintenance an
issue
Problems with open topped enclosures

Types ofradiography (2)
Types
Mobile radiography
•
•
•
•
•

Within temporary barriers
Portable warning and safety systems
Adverse working conditions
Often away from supervision
Access control can be difficult
―
―

•

Multi-level
Need to liaise with site management and contractors

Heavy reliance on procedures

Inherently more Hazardous

X-Radiography
•

Typically 100 to 300 kV and3 to 15 mA
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―
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Need for automatic fail-safe safety and warning
systems
Integral part of design of enclosures
―
―

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Outputs 30 to 300 mGy.min-1 at 1 m
At 10 cm: 3 to 30 Gy.min-1
Collimation

Emergency stop buttons/ pull cords
Search and lock up

Typical accidents from:
poor design and maintenance of safety systems
Lack of awareness and poor proceduresLinear accelerators
Linear
•
•
•
•

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Typically up to 8 MeV
Outputs ~ 4 Gy.min-1 at 1 m
Specialist uses
High quality (multiple redundancy) safety
systems
Higher degree of knowledge and training for
operators

Typical radiography sources
Typical
Radionuclide

Energy
(MeV)

Source output at 1m
(mGyh-1 per 37 GBq)

Half
Life

Typical use for
steel of
thickness (mm)Cobalt-60

1.17 and
1.33

13.0

5.3 y

50–120

Ir-192

0.2–1.4

4.8

74 d

10–70

Se-75

0.12–0.97

2.03

120 d

4–28

Yb-169

0.008–0.31

1.25

32 d

2.5–15

Shutter type container
Shutter
Operating handle
Source

Tin front
window
“Beam port”
Shielding

Source
holder

Radiation injury from
Radiation
Shutter type container

“Torch” typecontainer
High cumulative doses
due to proximity

Misuse leading to
radiation burns to
the fingers

Projection type / remote exposure
Projection
containers

Projection type / remote exposure
Projection
containers

Source “pigtail”
Source

Commonest direct cause of accidents
Commonest
FAILURE TO ADEQUATELY
MONITOR

Typical radiation injuries
Typical

EffectiveControl

Increased Risk of
Loss of Control

Authorisation/licencing

Illegal importation / acquisition

Purchase/installation

Long term storage before use

Normal usage

Poor training /safety /security

Increased risk modalities

Poor maintenance
Use of mobile sources

Challenging events

Fire, explosion, unexpected event
Lack of emergency preparedness

Maintaining knowledgeLoss of key staff
Bankruptcy

Disused sources

No clear future
Disposal costs
Dismantling of plant

Planned authorised disposal

Orphan
sources

Root Causes
Root
•

Lack of, or ineffective
Regulatory body
― Regulations
― Regulatory enforcement
― Radiation protection services
― Training of workers and management
― Commitment by management to safety
― RP programme in...