Dose Quantities: Operational ICRU v' Protection ICRP Quantities

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Dose QuantitiesOperational (ICRU) v. Protection
(ICRP) Quantities

• Daniel J. Strom
• Pacific Northwest National Laboratory
• Richland, Washington USA
• strom_at_pnl.gov 1 [phone]
• Battelle operates Pacific Northwest National
  Laboratory for
• the U.S. Department of Energy under Contract No.
  DE-AC05-76RLO 1830

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Relationships among Physical, Operational, and
Protection Quantities (ICRP 74, 1996)

• ICRU ICRP are at odds over some quantities and
  values.

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ICRP and ICRU are working together to build a
coherent set of quantities and units for
radiation protection
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Absorbed Dose, D

• Average ionizing energy per unit mass m deposited
  in matter or tissue
• For x and g radiation, 1 R ? 1 rad 0.01 Gy 10
  mGy
• The rad was originally defined as 100 ergs/gram

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Mean Absorbed Dose

• The mean absorbed dose in a specified tissue or
  organ T is
• where mT is the mass of the tissue or organ, and
  D is the absorbed dose in the mass element dm
• a.k.a. organ dose
• Can be specified for various types of radiation,
  R DT,R

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For Limitation Purposes 2007Equivalent Dose

• The equivalent dose in a tissue or organ is

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Tissue Equivalent Dose, HT

• Equivalent Dose (Absorbed Dose) (Radiation
  Weighting Factor)
• Thus 1 R of x or g ?1 rad 1 rem
• for neutrons, 1 rad 10 rem
• for a, 1 rad 20 rem

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Quality Factors, Q or Radiation Weighting
Factors, wR
Q replaced by wR in recommendations and
international regulations.
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ICRP 2007 Recommendations wR
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ICRP Quality Factors versus Unrestricted LET

• ICRP 26 60

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Quality Factor versus Lineal Energy (1 mm)

• ICRU 40 (1986)

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Calculated values of Q vs. photon energy under
conditions of charged-particle equilibrium

• ICRU 40 (1986)

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Calculated values of Q for the entire range of
alpha particles of given initial energy

• ICRU 40 (1986)

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Calculated values of Q vs. neutron energy under
conditions of charged-particle equilibrium

• ICRU 40 (1986)

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Neutron wR versus Energy

• ICRP 60 (1991)

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ICRP 2007 Recommendations wRneutron
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Fluence

• The number of particles that pass through a
  sphere of unit cross-sectional area
• ? number/area, m?2
• The number of particles that pass through a
  sphere of unit cross-sectional area per unit time
• ? number/area, m?2 s?1

Fluence Rate
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Neutron Dose Equivalent per Unit Fluence
McDonald et al. 1998
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Combining Doses to All Tissues from Different
Kinds of Radiation
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For Limitation Purposes 2007Effective Dose

• The effective dose is
• where wT is the tissue weighting factor
• Accounts for non-uniform irradiation

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Tissue Weighting Factors, wT

• a1977 each of 5 highest dose organs included in
  remainder with 0.06 weighting factors stomach,
  liver, small intestine, upper and lower large
  intestine each count as 0.06 if receiving high
  doses.
• b1985 skin was added total no longer 1.00.
• c1990 remainder included adrenals, brain, upper
  large intestine, small intestine, kidney, muscle,
  pancreas, spleen, thymus, and uterus.
• d1977 not listed.
• e2005 Adipose tissue, adrenals, connective
  tissue, extrathoracic airways, gall bladder,
  heart wall, lymphatic nodes, muscle, pancreas,
  prostate, si wall, spleen, thymus, and
  uterus/cervix.
• f2007 Adrenals, extrathoracic (ET) region, gall
  bladder, heart, kidneys, lymphatic nodes, muscle,
  oral mucosa, pancreas, prostate (?), small
  intestine, spleen, thymus, uterus/cervix (?).

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Total Effective Dose

• TED emphasizes the summation of doses from
  internal and external irradiation
• Suppose a worker receives
• an equivalent dose of 1.00 mSv to the whole body
• a committed equivalent dose (CED) of 10.00 mSv to
  his thyroid
• a CED of 3.00 mSv to his bone marrow
• What is his TED?
• Answer TED 1(1.00) 10(0.04) 3 (0.12)
• 1.76 mSv

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A Quantity That Never Occurred to the ICRP
Total Effective Dose (Equivalent)

• USA regulators explicitly named the sum of doses
  from external sources and committed doses from
  intakes of radionuclides TEDE
• USA regulators also explicitly named the implicit
  whole body tissue weighting factor (w(T whole
  body) 1)
• also have cumulative or lifetime TEDE

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IAEAs Total Effective Dose, ET

• IAEA SS 115 (1996) for verification of
  compliance with dose limits, use
• where the sums are over radionuclides j, ing
  means ingestion, and inh means inhalation
• intakes I and personal dose equivalent Hp, are
  within a specified time period, e.g., 1 y
• looks like an operational quantity

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Groupings of Radiation Quantities
equilibrium factor
equilibrium equivalent exposure
number of transitions
activity
activity concentration
potential a energy concentration
Radioactive Material
decay constant l
specific activity
unattached fraction
air kerma rate constant
potential a energy
equilibrium equivalent concentration
Photons
S/r, Scol/r, Srad/r
exposure rate
cross section
potential a energy exposure
particle size
Radon Progeny
m/r, mtr/r, men/r
radiation chemical yield
linear energy transfer, lineal energy
fluence, energy fluence rate
Neutrons
specific energy
energy deposit, energy imparted
energy per ion pair
energy dose-like quantity dose-rate-like
quantity interaction of radiation with
material biology or risk other
kerma rate
absorbed dose rate
cema rate
Indirectly Ionizing Radiation
Directly Ionizing Radiation
equivalent dose rate
effective dose equivalent rate
a, b, recoils
IRF
SEE
AF
retained quantity
fraction deposited
e(t)
hT(t)
wT
Q, wR
intake is implicitly dose-like due to
retention
f1
F, M, S
Biology or Risk