Section 325.5016. Definitions Re to Ro.

(1) "Recording" means producing a permanent form of a radiographic image resulting from x-ray or gamma-ray photons.

(2)       "Rem" means the absorbed dose in rads multiplied by appropriate modifying factors which are determined by the quality of radiation and the conditions of exposure and is the special unit of dose equivalent. For the purpose of these regulations, each of the following is considered to be equivalent to a dose of one rem:

(a)     An exposure of 1 roentgen of 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.

* If it is more convenient to measure the neutron flux, or equivalent, than to determine the neutron absorbed dose in rads, 1 rem of neutron radiation may, for purposes of these regulations, be assumed to be equivalent to 14 million neutrons per square centimeter incident upon the body; or, if there exists 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 the following table:

Neutron Flux Dose Equivalents

Neutron Energy (Mev)

Number of neutrons per square centimeter for a dose equivalent of 1 rem

Average flux to deliver 100 millirem in 40 hours (neutrons/cm2 per second)

                                                    (neutron/cm2)                                                                                    

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
10.0	24	x	106	17

10 to 30   14

x       106      10

(3)     "Research and development" means theoretical analysis, exploration or experimentation; or the extension of investigative findings and theories of a scientific or technical nature into practical application for experimental and demonstration purposes, including the experimental production and testing of models, devices, equipment, materials and processes. This definition does not apply to human use.

(4)      "Response time" means the time required for an instrument system to reach 90% of its final reading when the radiation-sensitive volume of the instrument system is exposed to a step change in radiation flux from zero sufficient to provide a steady state midscale reading.

(5)      "Restricted area" or "controlled area" means an area access to which is controlled by a licensee or registrant for purposes of protection of individuals from exposure to radiation or radioactive materials. It does not include an area used for residential quarters, although a separate room in a residential building may be set apart as a restricted area.

(6)        "Roentgen" means 2.58 x 10-4 Coulombs/kilogram of air and is the special unit of exposure.

History: 1954 ACS 85, Eff. Dec. 3, 1975; 1954 ACS 98 Eff. Mar 9, 1979.