Iowa Administrative Code › Agency 641 - Public Health Department › Chapter 40 - Standards for Protection Against Radiation › Rule 641-40.2 - Definitions

Current through Register Vol. 47, No. 3, July 24, 2024
(1) For the
			 purposes of this chapter, the definitions of 641-Chapter 38 may also
			 apply.
(2) As used in this chapter,
			 these terms have the definitions set forth below.
"Annual limit on intake (ALI) "
means the
				derived limit for the amount of radioactive material taken into the body of an
				adult worker by inhalation or ingestion in a year. ALI is the smaller value of
				intake of a given radionuclide in a year by the reference person that would
				result in a committed effective dose equivalent of 5 rem (0.05 Sv) or a
				committed dose equivalent of 50 rem (0.5 Sv) to any individual organ or tissue.
				ALI values for intake by ingestion and by inhalation of selected radionuclides
				are given in Table I, Columns 1 and 2, of Appendix B.
"Class (or lung class or inhalation class)"
means a classification scheme for inhaled material according to its rate of
				clearance from the pulmonary region of the lung. Materials are classified as D,
				W, or Y, which applies to a range of clearance half-times: for Class D, Days,
				of less than 10 days, for Class W, Weeks, from 10 to 100 days, and for Class Y,
				Years, of greater than 100 days.
"Declared pregnant woman"
means a woman who
				has voluntarily informed her licensee or registrant, in writing, of her
				pregnancy and the estimated date of conception. The declaration remains in
				effect until the declared pregnant woman withdraws the declaration in writing
				or is no longer pregnant.
"Derived air concentration (DAC) "
means the
				concentration of a given radionuclide in air which, if breathed by the
				reference person for a working year of 2,000 hours under conditions of light
				work (inhalation rate 1.2 cubic meters of air per hour) results in an intake of
				one ALI. DAC values are given in Table I, Column 3, of Appendix B.
"Derived air concentration-hour (DAC-hour)"
means the product of the concentration of radioactive material in air,
				expressed as a fraction or multiple of the derived air concentration for each
				radionuclide, and the time of exposure to that radionuclide, in hours. A
				licensee or registrant may take 2,000 DAC-hours to represent one ALI,
				equivalent to a committed dose equivalent of 5 rem (0.05 Sv).
"Dosimetry processor"
means an individual or
				an organization that processes and evaluates individual monitoring devices in
				order to determine the radiation dose delivered to the monitoring
				devices.
"Inhalation class"
(see "Class.")
"Lung class"
(see "Class.")
"National tracked source"
means a sealed
				source containing a quantity equal to or greater than Category 1 or Category 2
				levels of any radioactive material listed in Appendix H of this chapter. In
				this context a "sealed source" is defined as radioactive material that is
				sealed in a capsule or closely bonded in a solid form and that is not exempt
				from regulatory control. It does not mean material encapsulated solely for
				disposal, or nuclear material contained in any fuel assembly, subassembly, fuel
				rod, or fuel pellet. Category 1 nationally tracked sources are those containing
				radioactive material at a quantity equal to or greater than the Category 1
				threshold. Category 2 nationally tracked sources are those containing
				radioactive material at a quantity equal to or greater than the Category 2
				threshold but less than the Category 1 threshold.
"Nonstochastic effect"
means a health effect,
				the severity of which varies with the dose and for which a threshold is
				believed to exist. Radiation-induced cataract formation is an example of a
				nonstochastic effect. For purposes of these rules, "deterministic effect" is an
				equivalent term.
"Plannedspecial exposure "
means an infrequent
				exposure to radiation, separate from and in addition to the annual occupational
				dose limits.
"Quarter"
means a period of time equal to
				one-fourth of the year observed by the licensee, approximately 13 consecutive
				weeks, providing that the beginning of the first quarter in a year coincides
				with the starting date of the year and that no day is omitted or duplicated in
				consecutive quarters.
"Reference person"
means a hypothetical
				aggregation of human physical and physiological characteristics determined by
				international consensus. These characteristics may be used by researchers and
				public health workers to standardize results of experiments and to relate
				biological insult to a common base. A description of the reference person is
				contained in the International Commission on Radiological Protection report,
				ICRP Publication 23, "Report of the Task Group on Reference Man."
"Respiratory protective equipment"
means an
				apparatus, such as a respirator, used to reduce an individual's intake of
				airborne radioactive materials.
"Sanitary sewerage "
means a system of public
				sewers for carrying off wastewater and refuse, but excluding sewage treatment
				facilities, septic tanks, and leach fields owned or operated by the licensee or
				registrant.
"Stochastic effect"
means a health effect that
				occurs randomly and for which the probability of the effect occurring, rather
				than its severity, is assumed to be a linear function of dose without
				threshold. Hereditary effects and cancer incidence are examples of stochastic
				effects. For purposes of these rules, "probabilistic effect" is an equivalent
				term.
"Weighting factor "
wj for an organ or tissue
				(T) means the proportion of the risk of stochastic effects resulting from
				irradiation of that organ or tissue to the total risk of stochastic effects
				when the whole body is irradiated uniformly. For calculating the effective dose
				equivalent, the values of wTare:
ORGAN DOSE WEIGHTING FACTORS
Organ or Tissue
WT
Gonads
0.25
Breast
0.15
Red bone marrow
0.12
Lung
0.12
Thyroid
0.03
Bone surfaces
0.03
Remainder
0.30a
Whole Body
1.00b
a0.30 results from 0.06 for each of
				5 "remainder" organs, excluding the skin and the lens of the eye, that receive
				the highest doses.
bFor the purpose of weighting the
				external whole body dose, for adding it to the internal dose, a single
				weighting factor, wT = 1.0, has been specified. The use
				of other weighting factors for external exposure will be approved on a
				case-by-case basis until such time as specific guidance is
				issued.