Section 325.60601a. Definitions.

Rule 1a.  Definitions applicable to these rules.

(1)      "Radiation" includes alpha rays, beta rays, gamma rays, x-rays, neutrons, high-speed electrons, high-speed protons, and  other   atomic particles; but the term does not include sound or radio waves, visible light, or infrared or ultraviolet light.

(2)         "Radioactive material" means any material which emits, by spontaneous nuclear disintegration, corpuscular or electromagnetic emanations.

(3)     "Restricted area" means any area access to which is controlled by the employer for purposes of protection of individuals from exposure to radiation or radioactive materials.

(4)      "Unrestricted area" means any area access to which is not controlled by the employer for purposes of protection of individuals from exposure to radiation or radioactive materials.

(5)     "Dose" means the quantity of ionizing radiation absorbed, per unit of mass, by the body or by any portion of the body. When the provisions in these rules specify a dose during a period of time, the dose is the total quantity of radiation absorbed, per unit of mass, by the body or by any portion of the body during such period of time. Several different units of dose are in current use. Definitions of units used in these rules  are set forth in subrules (6) and (7) of this rule.

(6)     "Rad" means a measure of the dose of any ionizing radiation to body tissues in terms of the energy absorbed per unit of mass of the tissue. One rad is the dose corresponding to the absorption  of   100  ergs  per  gram  of tissue (1 millirad (mrad) =

0.001 rad).

(7)     "Rem" means a measure of the dose of any ionizing radiation to body tissue in terms of its estimated biological effect relative to a dose of 1 roentgen (r) of x-rays (1 millirem (mrem) = 0.001 rem). The relation of the rem to other dose units depends upon  the   biological    effect   under

consideration  and  upon   the  conditions   for  irradiation.    Each  of   the  following  is considered to be equivalent to a dose of 1 rem:

(a)    )  A dose of 1 roentgen due to X- or gamma radiation.

(b)     A dose of 1 rad due to X-, gamma, or beta radiation.

(c)     ) A dose of 0.1 rad due to neutrons or high-energy protons.

(d)     A dose of 0.05 rad due to particles heavier than protons and with sufficient energy to reach the lens of the eye.

(e)       If it is more convenient to measure the neutron flux, or equivalent, than to determine the neutron dose in rads, as provided in subrule (7)(c) of this rule, 1 rem of neutron radiation may, for purposes of these rules, be assumed to be equivalent to 14 million neutrons per square centimeter incident upon the body; or, if there is sufficient information to estimate with reasonable accuracy the approximate   distribution  in energy of the neutrons, the incident number of neutrons per square centimeter equivalent to 1 rem may be estimated from table G-17:

TABLE G-17--NEUTRON FLUX DOSE EQUIVALENTS

Neutron energy   (million electron volts (Mev))	Number of neutrons per square centimeter equivalent to a dose of 1 rem (neutrons/cm2 )	Average flux to deliver 100 millirem in 40 hours (neutrons/cm2 per sec.)
Thermal	970 x 106	670
0.0001	720 x 106	500
0.005	820 x 106	570
0.02	400 x 106	280
0.1	120 x 106	80
0.5	43 x 106	30
1.0	26 x 106	18
2.5	29 x 106	20
5.0	26 x 106	18
7.5	24 x 106	17
10	24 x 106	17
10 to 30	14 x 106	10

(8)   For determining exposures to X- or gamma rays up to 3 Mev., the dose limits specified in these rules may be assumed to be equivalent to the "air dose." For the purpose of these rules "air dose" means that the dose is measured by a properly calibrated appropriate instrument in air at or near the body surface in the region of the highest dosage rate.

History: 2009 AACS.