Transcript IAEA Training Material on Radiation Protection in Radiotherapy

IAEA Training Material on Radiation Protection in Radiotherapy
Radiation Protection in
Radiotherapy
Part 17
Protection of the Public
Public Exposure

IAEA Safety Series 120 and glossary of
BSS: “Exposure incurred by members
of the public from radiation sources,
excluding any occupational or medical
exposure and normal background
radiation but including exposure from
authorized sources and practices from
intervention situations.”
Radiation Protection in Radiotherapy
Part 17: Protection of the public
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Context of part 17


BSS Appendix III
Other important context:


Radiation Protection in Radiotherapy
Part 7 (“shielding”) of the
present course
Part 16 (“discharge of
patients”)
Part 17: Protection of the public
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Objectives
To understand the concept of ‘public
exposure’ in the context of a
radiotherapy facility
 To identify potential routes of exposure
of the public through radiotherapy
 To be able to optimize protection of the
public and ensure relevant dose
constraints are not exceeded

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Part 17: Protection of the public
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Contents
1. Radiotherapy and the Public
2. Potential routes of public exposure
3. Measures to minimize radiation
exposure of the public
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Part 17: Protection of the public
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1. Radiotherapy and the Public

Public:
People living around a radiotherapy facility
 Visitors to the department
 Relatives, friends and other persons who
may be in contact with patients


Not necessarily: Partners and nonoccupational persons who are involved
in care or comforting the patient - this is
“Medical Exposure” (compare part 9)
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…public could also be:
Staff from other departments/divisions
 Contractors

electricians
 painters
 plumbers

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Responsibilities for Public Exposure
BSS Appendix III.2. “Registrants and licensees shall be
responsible, with respect to the sources under their
responsibility, for the establishment, implementation
and maintenance of:
(a) protection and safety policies, procedures and
organizational arrangements in relation to public
exposure in fulfilment of the requirements of the
Standards;
(b) measures for ensuring:


(i) the optimization of the protection of members of the public ...
(ii) the limitation of the normal exposure of the relevant critical
group, …”
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In radiotherapy
Requires a radiation safety program
 Written policies and procedures



These should include all potential areas of
exposure - e.g. in the handbook for outside
contractors some information on radiation
must be included.
Most likely a radiation safety committee
and a radiation protection officer
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2. Potential for Public Exposure
in Radiotherapy
2

1
External:
Facility shielding for outside world
(1)
 Discharge of
patients with
radioactive
implants (2)
 Radioactive waste

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Potential for Public Exposure in
Radiotherapy

Internal:
Facility shielding for visitors
 Radioactive waste

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Exposure of the Public to
External Irradiation
BSS Appendix III.6. “Registrants and licensees
shall ensure that, if a source of external
irradiation can cause exposure to the public:
(a) prior to commissioning, the floor plans and equipment
arrangement for all new installations and all significant
modifications to existing installations utilizing such
sources of external irradiation be subject to review and
approval by the Regulatory Authority;
(b) specific dose constraints for the operation of such a
source be established to the satisfaction of the
Regulatory Authority;”
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In radiotherapy practice



Close collaboration
with relevant
authority
Shielding checked
already in planning
phase
Verification of the
dose constraints
used in calculations
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Dose Limits for Public Exposure

BSS Schedule II (and ICRP 60)
Effective dose 1mSv/year
 Under special circumstances 5mSv/year
(but not more than 5mSv/5years)
 Equivalent dose to eye: 15mSv/year
 Equivalent dose to skin: 50mSv/year


May be different in your country!!!
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In radiotherapy practice

Close collaboration
Contributions
to exposure can
comewith
from relevant
many sources - therefore
designs
of a facility must be
authority
shielded to restrict dose more than
 Shielding checked
required by the dose constraint
already
in planning
(typically:
1/3)

phase
Verification of dose
constraints
Radiology
Radiation Protection in Radiotherapy
Part 17: Protection of the public
Nuclear
Medicine
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Means to minimize public
exposure

Designation of areas as:
public
 supervised
 controlled


Compare part 8 on occupational
exposure
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Controlled Area
A controlled area is an area where procedural
controls are required in order to restrict
radiation exposures.
Restriction of Access
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Controlled Area Requirements
Work in a controlled area should
be carried out in accordance
with a written set of local rules.
These apply not only to
occupationally exposed persons
but also to others, such as
contractors. Therefore they must
be in writing, easily accessible
and regularly reviewed.
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Supervised Areas
A supervised area is one that does not
require classification as a controlled area,
but where exposure conditions should be
kept under review. It could be accessible
for the public, however, it requires:
a
delineated area
 routine monitoring
 work to be undertaken in accordance
with local rules
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Means to prevent public
exposure
Access restriction
 Shielding
 Warning signs
 Lights
 Interlocks (e.g. door)
 Written information

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Means to prevent public
exposure






Access restriction
Shielding - see part 7 of the course
Warning signs
Lights
Interlocks (e.g. door)
Written information - for staff and members of
the public who could be at risk of exposure
(e.g. contractors, allied health professionals)
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Issues for public exposure:
 Discharge
of patients
 Radioactive waste
 Old
teletherapy sources
 Old brachytherapy sources
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Discharge of patients with
radioactive implants
Dealt with in part 16
 Rules are designed to keep
public exposure limited
 Written information must be
available to the patient

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Radioactive Waste
BSS appendix III.8: “Registrants and
licensees shall: (a) ensure that the activity
and volume of any radioactive waste that
results from the sources for which they are
responsible be kept to the minimum
practicable, and that the waste be managed,
i.e. collected, handled, treated, conditioned,
transported, stored and disposed of, in
accordance with the requirements of the
Standards and any other applicable standard”
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The problem of waste in
radiotherapy
Mainly a problem with radioactive
sources no longer used for treatment.
 These could be:

teletherapy sources (60-Co, 137-Cs)
 old and no longer usable brachytherapy
sources with long half life (226-Ra, 137-Cs)
 short/medium lived sources with activity
too low for treatment

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Old teletherapy
sources




High activity
Regulatory authority must be informed
Requires specialized transport and storage container
Disposal



could be very costly
should be part of initial purchase or source replacement
contract with manufacturer
documentation (i.e. source certificate) essential
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Watch depleted uranium which
may have been used as shielding
material in telecurie treatment
units
Example: schematic
drawing of treatment
head of a 60-Co unit
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Long lived brachytherapy
sources
May leak
 Disposal pathway MUST be approved
by authority
 Documentation essential

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Short/medium half life
brachytherapy sources




Examples: 198-Au, 192-Ir, 125-I, 103-Pd
A protocol must be in place for disposal
Store in suitable location until activity below
the prescribed limit value
Return to manufacturer - may be required by
law to accept the sources
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Waste - unsealed isotopes
 Not
part of this training course
 Covered in the companion course
on Radiation Safety in Nuclear
Medicine
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3. Measures to minimize radiation
exposure of the public
Thinking ahead - what could happen
 Shielding and safe design
 Access restriction and sign posting
 Procedures and a radiation safety
program
 Information sheets for public

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Visitors = general public

BSS Appendix III: PUBLIC EXPOSURE deals
explicitly with “CONTROL OF VISITORS”: III.5.
Registrants and licensees, in co-operation with
employers when appropriate, shall:
(a) ensure that visitors be accompanied in any controlled area
by a person knowledgeable about the protection and safety
measures for that area;
(b) provide adequate information and instruction to visitors
before they enter a controlled area so as to ensure
appropriate protection of the visitors and of other individuals
who could be affected by their actions; and
(c) ensure that adequate control over entry of visitors to a
supervised area be maintained and that appropriate signs be
posted in such areas.
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Information for visitors
Written information and signs
 May be accompanied by trained staff at
all times when visiting a patient with
radioactive implants in place


the same applies to other hospital staff
(e.g. maintenance, porters, catering,…)
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Transport and storage of sources
Covered in part 14
 Within the hospital:

Secure storage (locks, interlocks)
 When in transport (e.g. from hot lab to
treatment area or operating theatre)
sources MUST be under constant
surveillance.

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Monitoring of Public Exposure
BSS appendix III.13: “Registrants and licensees shall, if
appropriate:
(a) establish and carry out a monitoring programme
sufficient to ensure that the requirements of the
Standards regarding public exposure to sources of
external irradiation be satisfied and to assess such
exposure;
(b) establish and carry out a monitoring programme
sufficient to ensure that the requirements of the
Standards for discharges of radioactive substances
to the environment … be satisfied.”
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Monitoring
Relevant areas (at least all
controlled and supervised
areas) must be regularly
monitored for radiation
exposures
 Contractors may be subject
to temporary personal
monitoring

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Monitoring
Monitor and document
workload
 All outgoing radioactivity
must be accounted for monitor compliance

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BSS Appendix III. 13: PUBLIC
EXPOSURE (cont.)

MONITORING OF PUBLIC EXPOSURE

“Registrants and licensees shall, if
appropriate:
(c) keep appropriate records of the results of the
monitoring programmes;
(d) report a summary of the monitoring results to the
Regulatory Authority at approved intervals;
(e) report promptly to the Regulatory Authority any
significant increase in environmental radiation fields or
contamination that could be attributed to the radiation
or radioactive discharges emitted by sources under
their responsibility;”
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BSS Appendix III. 13: PUBLIC
EXPOSURE (cont.)

MONITORING OF PUBLIC EXPOSURE

“Registrants and licensees shall, if
appropriate:
(f) establish and maintain a capability to carry out
emergency monitoring, in case of unexpected
increases in radiation fields or radioactive
contamination due to accidental or other unusual
events affecting sources under their responsibility; and
(g) verify the adequacy of the assumptions made for the
prior assessment of radiological consequences of the
discharges.”
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A last note on all monitoring
Done prospectively and with a purpose
 Is quantitative
 Is documented
 Action levels are usually established
 Potential actions are thought of
beforehand and they are documented

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A note on action levels
Without them monitoring would be less
useful
 Need to be established and discussed
by all people involved
 Helps tremendously to speed up a
reaction

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Summary
If a radiotherapy department is
designed well, the risk of public
exposure is usually very small
 Procedures must be established and be
available in writing
 Information of staff and the public about
potential risks is essential.

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Where to Get More Information
Parts 7 (shielding), 8 (occupational
exposure) 14 (transport) and 16
(discharge of patients)
 BSS appendix III

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Any questions?
Question:
Discuss why the dose constraint for
public exposure is smaller than for
occupational exposure.