Radiation science

1. Individual Monitoring
Musa Y. Dambele
Nuclear Medicine Unit/ Radiation Protection and Dosimetry Unit
Dept. of Medical Radiography
Bayero University, Kano
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2. Legal requirements
Regulation 47
-(1) Every employer shall ensure that –
(a) in respect of each of his employees who is
designated as a classified person, an assessment is
made of all doses of ionizing radiation received by
such employee which are likely to be
significant; and
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3. Regulations 47 (2):
For the purposes of paragraph (1) of this regulation,
the employer shall make suitable arrangements with
one or more authorised dosimetry service providers
for -
(a) the making of systematic assessments of such
doses by the use of suitable individual measurement
for appropriate periods or, where individual
measurement is inappropriate, by means of other
suitable measurements; and
(b) the making and maintenance of dose records
relating to each classified person.
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Legal requirements

4. Regulations 47:
(3) For the purposes of paragraph (2) (b) of this
regulation, the arrangements that the employer shall
make with the authorised dosimetry service provider
shall include requirements for that service to –
(a) keep and submit to the Authority, quarterly
records made and maintained pursuant to the
arrangements or a copy thereof until the person to
whom the records relates has or would have attained
the age of 75 years or for at least 50 years from when
they were made, whichever is earlier;
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Legal requirements

5. What is Personnel Monitoring Program
• A systematic process for monitoring, recording, evaluating, and
reporting the radiation doses received by occupationally exposed
individuals

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Purpose of Personnel Monitoring
• To ensure compliance with established dose limits
• To keep radiation doses as low as reasonably achievable (ALARA)

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Monitoring Criteria
 Any occupationally exposed individual who is likely to receive a dose
in excess of 10% of any applicable limit
 Any occupationally exposed individual who is likely to receive an
intake of radioactive material in excess of 10% of the annual limit on
intake (ALI)
 Any person entering a high radiation area or very high radiation area

8. 8
Individual monitoring
• Individual dose monitoring shall be undertaken
for workers who are normally exposed to
radiation in controlled areas:
• Radiographers, radiologists, medical physicists, the
RSO, and nurses
• Other frequent users of X Ray systems and those
working regularly in supervised areas, or occasionally
in controlled areas should have personal doses
assessed such as endoscopists, anaesthetists,
cardiologists, surgeons etc., as well as ancillary workers
who frequently work in controlled areas, shall also be
monitored.

9. Individual monitoring
Twocategories ofpersonalmonitoring:
•External: the measurement of dose
due to sources outside the body
•Internal: the measurement of dose
due to sources inside the body
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10. Personal Dosimeters – (External monitoring)
Types of external personal dosimeters
 Passive dosimeters:
o Photographic Film
o Thermoluminescence
o Optically Stimulated Luminescence
o Nuclear Track Emulsions etc
 Active dosimeters:
o Electronic Dosimeters
o Pocket Dosimeters
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11. 11
Personal dosimetry
Several personal
dosimeters are
recommended
From: Avoidance of radiation injuries from interventional procedures. ICRP draft 2000

12. whole
body extremity
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Use of personal alarm and TLD

13. Personal Alarms
• Real time read-out of dose
• Audible alarm at pre-set levels (dose or dose rate)
• Used where potential dose rates are high, eg radiography, radiation
emergencies, source replacement
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14. Internal Dosimetry
• Assess intake
• Calculate dose
• Biological dosimetry
• Whole body monitoring
• Thyroid monitoring
• Personal air sampling
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15. Assessing intake
• Direct measurement of
intake
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16. Dosimeter placement
The dosimeter should be placed in a position
representative of the most highly exposed part of
the surface of the torso.
• Normally on the front of the body
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17. Dosimeter placement
 Body locations representing skin and whole
body are usually not the same.
 When fields are highly non-uniform,
additional dosimeters on other parts of the
body may be useful.
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18. Dosimeter placement
• In special situations (eg. medical
radiology where protective
clothing such as lead aprons are
used), more than one dosimeter
may be used:
• one under the protective apron, and
• one on unshielded parts of the body
to provide information on the
exposure to the unshielded part of
the body (skin, eye, etc).
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19. Dosimeter placement
 When protective clothing is worn, the
dosimeter should be worn at the position
where the skin is likely to be most seriously
exposed (i.e. either under the clothing or at
the unprotected part of the body).
 If the exposure is inhomogeneous, it may be
necessary to use more than one dosimeter.
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20. Exposure to the lens of the eye
 HP(3) can be assessed from the indication of
HP(10) and HP(0.07).
 Dosimeters used for this purpose should be
worn near the eyes (e.g. on the forehead or
on a cap).
 If HP(10) and HP(0.07) are below the relevant
dose limits, the value of HP(3) will nearly
always be below the dose limit for the lens of
the eye (150 mSv).
Dosimeter placement
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21. 21
Individual monitoring
when a lead apron is used
• The dosimeter should be worn under the apron
for estimating the effective dose
• The other body areas not protected by the apron
will receive higher dose
• One dosimeter worn under the apron will yield a
reasonable estimate of effective dose for most
instances
• In case of high workload (interventional radiology)
an additional dosimeter outside the apron should
be considered by the RSO

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Individual monitoring
when a lead apron is used
• When expected doses are high, two dosimeters are required:
• 1 under the apron at waist level
• 1 over the apron at collar level
• The effective dose E is given by:
E = 0.5 Hw + 0.025 Hn
where:
• Hw : dose at waist level under the apron
• Hn : dose recorded by a dosimeter worn at neck level over the
apron
• Note: The thyroid shielding allows 50% reduction of the E
• The dosimeter worn over the apron at collar level gives also an
estimation of thyroid and eye lens doses

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Special aspects of individual monitoring
• In case of loss of a dosimeter, the dose estimation may be carried out
from:
• recent dose history,
• co-workers dose
• or, workplace dosimetry
• Individual monitoring devices should be calibrated
• Laboratory performing personnel dosimetry should be approved by
the regulatory authority

24. Individual monitoring Objectives
• control of radiation exposure
• assesses ALARA
• identifies high doses
• assessment of working practices
• Fulfilling legal requirements
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25. Demonstration of good working practices,
including adequacy of:
u supervision
u training
u engineering standards
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Individual monitoring Objectives

26.  Estimation of the actual radiation exposure
of workers, to demonstrate compliance with
legal requirements.
 Evaluation and development of operating
procedures.
 Provision of information that may help
motivate workers to reduce exposure.
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Individual monitoring Objectives

27.  Provision of information for evaluation of
dose following an accident.
 Data for medical purposes.
 Provision of data for use in epidemiological
studies.
 Risk-Benefit analyses.
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Individual monitoring Objectives

28. Health surveillance
• Objectives
• to assess fitness of workers for radiation work
• to provide baseline of information
• to support management of overexposed workers
• Periodic medical reviews
• Health Records
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29. Personal monitoring period
 Depends on the exposure situation.
 A week to a month is often convenient.
 More than 1 month may be undesirable,
since it is more difficult to determine
the reason for an exposure with time.
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30. Personal monitoring period
 For people who usually do not receive a measurable
dose, a 3 month monitoring period may be suitable.
 Direct reading dosimeters should be worn in addition
to the official dosimeter, if daily monitoring is required.
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31. Record keeping
• Records of dose received to be kept
• Records to include:
- Personnel data (gender, age, ...)
- Nature of work
- Dose information and means of assessment
- Dates and relevant employer
- Doses received during emergencies to be identified
Must exchange information when employee exposed to
source under another employer’s control)
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32. Dose records
• Must be available to
- Worker
- Supervisor of health surveillance programme
- Regulatory authority
- New employer
• After the employee’s working life
- Records to be kept to 75th Birthday, or to 30 years
from cessation of radiation work.
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33. 33
Dose Assessment
• Evaluation of dose is an important aspect of
radiation protection
• It is important that workers return dosimeters on
time for processing
• Delays in the evaluation of a dosimeter can result
in the loss of the stored information
• Licensees should make every effort to recover any
missing dosimeters

34. Reference levels
Reference level - predetermined value for: any of
the quantities, which requires a certain course of
action if, the value of the level for a quantity is
exceeded.
Reference levels often refer to effective dose, but
may apply to other quantities
These are called derived reference levels
A reference level is not a limit in itself.
The reference level action may range from just
recording the value to intervention.
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35. Reference levels
l Recording level
l Investigation level
l Action level
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36. Recording level
Value of dose equivalent, detected activity
above which a result should be retained
The recording level should be based on:
1/10 of the fraction of the annual limit,
corresponding to the period of time of which
the individual monitoring measurement refers
about 0.17 mSv for monthly monitoring
periods
A result smaller than the recording level may
be discarded and treated as zero in
assessing the dose
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37. Investigation levels
l Investigation level - a value of dose
equivalent or intake, usually for a single
measurement, above which the result
justifies further investigation.
l It is often appropriate to set the
investigation level at 3/10 of the fraction
of the relevant annual limit corresponding to
the individual monitoring period.
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38. Investigation levels
l For monthly monitoring or exchange periods,
IL= 20 mSv x 0.3 / 12 = 0.54 mSv
l Below the investigation level, further review is
not needed.
l It may be necessary to change investigation
levels, for example as conditions in a workplace
change.
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39. Action level
l Level that for remedial or protective action.
l Applies to chronic exposure or emergency exposure
situations.
l Action levels often serve to protect the public.
l Have occupational exposure relevance in chronic exposure
situations.
l Particularly relevant to workplace radon exposure.
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40. Employer
The employer should:
l Provide workers access to information in
their own exposure records;
l Provide access to the exposure records by
the supervisor of the health surveillance
programme, the Regulatory Authority and
the relevant employer; and
l Facilitate the provision of copies of
workers' exposure records to new
employers
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41. Worker
l Usually through his employer
l A simplified version of the full dose record
is appropriate. Partly because the
transcript may contain unrecognizable
computer terminology
l On termination of employment, a summary
of the dose record may be given to the
worker
l Covers the period of last employment and
dose information transferred from previous
employment
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42. Organizations
Dose reporting may be required to:
l Employer (radiation safety
officer/management)
l Radiation worker
l Local safety inspector
l Medical officer
l National legal
authorities/inspectorates.
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43. Summary
• Controlled areas
• Supervised areas
• Local Rules
• Supervision of the work (RSO)
• Use of radiation monitors
- dose rate, contamination
- Testing, record keeping
• Individual monitoring – external exposure
• Individual monitoring – intakes
• Individual monitoring objectives
• Record keeping & Dose assessment
• Reference levels
• Health Surveillance
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44. Conclusion
Personal Monitoring ensures:
• control over individual dose to be exercised
• abnormally high doses to be identified
• changes in working conditions to be identified
• poor working practices to be identified
• legal evidence to be provided
• security and confidence
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45. Conclusion
Personal monitoring is an essential Technical Service:
• to authorized radiation users
• to the Regulatory Authority
Accredited Dosimetry Service provider should be
engaged
Dosimeter should be worn Properly
Dose Record Analysed properly
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