The initial needs of the Brazilian Government following the discovery of the Goiania accident

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ASSESSMENT OF OCCUPATIONAL EXPOSURE DUE TO
INTAKES OF RADIONUCLIDES
Assessment of Internal Exposure following
Accidents or Incidents
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Assessment of Internal Exposure following
Accidents or Incidents Unit Outline

• Introduction
• Post Event Information Requirements
• Post Event Monitoring
• Follow-up Monitoring

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Introduction
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Accident

• Any unintended event, including operating
  errors, equipment failures or other mishaps, the
  consequences or potential consequences of which
  are not negligible from the point of view of
  protection or safety.
• BSS Glossary

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IAEA Accident response experience

• Under the 1986 Convention on Assistance in the
  Case of a Nuclear Accident or Radiological
  Emergency, the IAEA
• makes available appropriate resources for
  emergency response,
• promptly transmits requests for assistance to
  other States or international organizations which
  may possess necessary resources, and
• may co-ordinate assistance at the international
  level

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IAEA Accident response experience

• Chernobyl was the most serious accident in Agency
  history.
• IAEA has been involved in investigation of a
  number of other accidents involving.
• loss of control or misuse of radioactive sources,
• errors in medical treatment, or
• accidental exposure in irradiation facilities.

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• Several situations contribute to accidents

• Operational error or equipment failure when
  transferring large sources
• Interlock failure on high dose rate equipment
• Radiography sources left unshielded
• Equipment failure or operational errors in
  nuclear facilities.
• Medical misuse of sources and
• Criticalities

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Accidents with clinical consequences

• Persons
• Activity affected
• Nuclear fuel cycle 245
• Industrial uses of radiation 94
• Medical uses of radiation 18
• Tertiary education and accelerators 19
• Other 344
• Total 720
• From 2000 UNSCEAR Report (1975 through 1994)

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Post Event Information Requirements
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Introduction

• There will be situations involving the use of
  radioactive material in which the operational
  controls break down
• Accidents or incidents may result in releases of
  radioactive materials into the working
  environment with the potential for high doses to
  the workforce

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Accidents Medical treatment first

• After an accident, the radiological consequences
  may be complicated by trauma or other health
  effects incurred by workers
• Treatment of injuries, especially those that are
  potentially life threatening, generally takes
  priority over radiological operations
• Post-accident exposure assessment should be
  conducted when the situation has been brought
  under control.

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Post-accident Gather key information

• When exposure assessment starts, get as much
  information as possible
• Example - information is needed on
• Time and nature of the incident
• Radionuclides involved
• Timing of bioassay samples and
• Measurements of body activity

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Post-accident Gather key information

• Information is necessary for
• Exposure assessment
• Medical assessment, to guide medical treatment of
  the victim (which may include chelation therapy
  or wound excision)
  
• Accident reconstruction
• Long term medical follow-up of victims

Debridement
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Internal decontamination
Soon after ingestion
gastric irrigation
Nuclides which are hardly absorbed by
gastrointestinal tract
cathartic
Na?K?FWT
diuretic
FWT
volume water intake
Cs, Rb
Prussian blue?depress reabsoption by small
intestine
I
potassium iodide ? depress absoption by thyroid
Pb, Cu, Zn?Cd, Cr, Mn, Ni
EDTA ? chelator
Actinides
DTPA ? chelator (Ca-DTPA Zn-DTPA)
approx.10 times
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Debridement
This treatment is seldom done for decontamination
recently
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Dose reconstruction
X-ray tube
FOV
Distance from the tube
Pattern ?
Analysis of the behavior pattern
Pattern ?
Pattern ?
Measurement of the dose with the same condition
as the accident
Pattern ?
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Detectors for dose reconstruction
For low energy and high dose rate
5KeV-1.3MeV (Al deposited PET window 3.6µm)
For general energy and low dose rate
25KeV-50MeV (POM window 1mm)
30KeV-50MeV (POM window 1mm)
30KeV-50MeV (PMMA window 1mm)
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Measurement devices for dose reconstruction
Reference hygrometer, barometer and thermometer
Reference ampere meter
hygrometer, barometer and thermometer
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24Na analysis by Ge detector
to estimate thermal neutron flux
23Na(100) 0.531barn 41K(6.73) 1.46barn
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Long term medical follow-up
23 crews of No.5 Fukuryu-maru were exposed by
the nuclear test that had been done in Bikini in
1954 . The purpose of this investigation is to
examine these victims' health conditions for a
long term,and to research the delayed effect. The
exposure type was a mixture exposure and the
estimated dose was 1.7-6.0Gy. 11 survivors are
having their physical condition examined once a
year .
Fishing vessel, from which radioactivity was
detected Fishing vessel and the fish, from which
radioactivity was detected
Bikini Atoll
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Long term medical follow-up
The contrast medium "Thorotrast" of which the
principal ingredient was the thorium dioxide was
used for the angiography in Japan from 1932 to
1945. The number is estimated to be 10,000-20,000
people. Thorotrast deposits mainly on the liver
and the spleen, then causes the internal
exposure for a long term. The purpose of this
investigation is to clarify the relation between
the deposition amount of Th- 232 and the clinical
conditions and also to clarify the influence to
human body by a long-term internal exposure. The
medical examination is done once a year.
Thorotrast
Abdomen image by radiography
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Post-accident information gathering

• Accidents or incidents can result in high
  committed effective doses (? dose limits)
• Individual and material specific data are
  normally needed for exposure assessment
• Necessary data include information on
• Chemical and physical forms of the
  radionuclide(s)
• Particle size
• Airborne concentrations

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Post-accident information gathering

• Necessary data also includes information on
• Surface contamination levels
• Retention characteristics in the individual
  affected
• Nose blows, face wipes and other skin
  contamination levels and
• External dosimetry results

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Post-accident information gathering

• Data may seem inconsistent or contradictory,
  particularly if the intake period is uncertain
• Adequate dose assessments can be made only after
• Considering all of the data
• Resolving the sources of inconsistency as far as
  is possible, and
• Deciding most likely and worst scenarios for
  exposure and magnitude of intake

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Post Event Monitoring
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Recommended procedures for monitoring
NO
Later actions (see below)
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External contamination interference

• Radiological characteristics of the radionuclides
  determine whether direct, indirect, or both
  methods should be used
• If there is external contamination with gamma
  emitters, direct measurements should normally be
  delayed until decontamination
• This 1) prevents interference with the
  measurement and 2) avoids contamination of the
  direct measurement facility

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External contamination interference

• If urgency of assessment precludes complete
  decontamination, wrap the individual in a sheet
  to minimize contamination of the facility
• Such initial direct measurement results are upper
  limits for the body content
• More measurements would be needed after further
  decontamination
• External a or ß contamination wont normally
  interfere with direct measurements, unless
  bremsstrahlung is produced by the betas

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Other concerns

• External contamination will not interfere with
  indirect methods
• However, care must be taken to avoid transfer of
  contamination to excreta samples
• Rarely, intakes may be so high that special
  techniques to avoid interference with equipment
  response, e.g. excessive electronic dead times

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Mobile Direct Measurement Facilities
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Mobile Direct Measurement Facilities
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Analysis of excreta

• Analyses of samples of urine and faeces should be
  considered to verify the intake
• These results may be difficult to interpret,
  because of
• Possible multiple routes of intake and
• Imprecise about radionuclide transfer to the blood

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Analysis of excreta

• Early excreta results are generally not useful
  for intake assessment because of the delay
  between intake and excretion
• Particularly true for faecal excretion
• In addition, rapid early components of urinary
  excretion can be difficult to interpret - not
  fully defined in some models

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Analysis of excreta

• Nevertheless, all excreta should be collected
  following an accident or incident
• Early detection of radioactivity in urine can be
  a useful indication of the material solubility
  and potential for effective treatment
• Excreta analyses can be the only reliable method
  of assessing intakes if large amounts of external
  contamination interfere with direct measurements.

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Blood sampling

• Emphasize non-invasive procedures. Invasive
  procedures such as blood sampling are usually
  justified only in accident situations in which
  large intakes may have occurred
• Blood sampling can provide data on the solubility
  and biokinetics
• Has limited value for quantitative intake
  estimates because of rapid clearance of most
  radionuclides to other tissues

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Workplace monitoring samples

• Workplace monitoring samples, e.g.
• Air filters
• Surface contamination wipes,
• Should be analysed to determine
• Radionuclides involved
• Isotopic ratios, and
• Physicochemical characteristics

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Follow-up Monitoring