Code of Maine Rules › 10 - DEPARTMENT OF HEALTH AND HUMAN SERVICES › 144 - DEPARTMENT OF HEALTH AND HUMAN SERVICES - GENERAL › Chapter 220 - Rules Relating to Radiation Protection › Part A - GENERAL PROVISIONS › Section 144-220-A-13 - The International system of units (SI)

Current through 2024-29, July 17, 2024
The Metric Conversion Act of 1975 (PL 94-168) urged
					 the increasing awareness and use of the International System of Units (SI). The
					 generally accepted regulatory values in the narrative portions of this document
					 are followed by the SI equivalents in parentheses. Where appropriate, schedules
					 and appendices are provided, with notes concerning conversion factors. The
					 inclusion of the SI equivalent is for informational purposes only unless
					 otherwise specified.
A. Units of
				  Exposure and Dose
(1) Absorbed dose. The unit
				  of absorbed dose is the gray (Gy) which is equal to 1 joule per kilogram. One
				  rad is equal to 1 x 10-2 gray. Sub-multiples
				  included in this document are the milligray (mGy) and the microgray
				  (µGy).
(2) Dose equivalent.
				  The unit of dose equivalent is the sievert (Sv) which is equal to 1 joule per
				  kilogram. The dose equivalent in sievert is equal to the absorbed dose in gray
				  multiplied by the quality factor. One REM is equal to 1 x
				  10-2 sievert. Submultiples included in this document
				  are the millisievert (mSv) and the microsievert (µSv).
(3) Exposure. The unit of exposure is the
				  coulomb per kilogram (C/kg). One roentgen is equal to 2.58 x 10-4
					  coulomb per kilogram of air. Submultiples of this unit are the
				  millicoulomb per kilogram (mC/kg) and the microcoulomb per kilogram
				  (µC/kg).
(4) Quality factors.
				  As used in this rule, the quality factors for converting absorbed dose to dose
				  equivalent are shown in Table I.
TABLE I
Quality Factors and Absorbed Does
					 Equivalencies
Type of Radiation
Absorbed Dose Quality Factor
Equal to a Unit Dose (Q)
Equivalenta
X, gamma, or beta radiation and high-speed
								  electrons
1
1
Alpha particles, multiple -charged particles,
								  fission fragments and heavy particles of unknown charge
20
0.05
Neutrons of unknown energy
10
0.1
High-energy protons
10
0.1
aAbsorbed dose in gray equal to
					 1 Sv or the absorbed dose in rad equal to 1 rem.
(5) If it is more convenient to measure the
				  neutron influence rate than to determine the neutron dose equivalent rate in
				  sievert per hour or rem per hour, as provided in A.13.A(4), 0.01 Sv (1 rem) of
				  neutron radiation of unknown energies may, for purposes of this rule, be
				  assumed to result from a total influence of 25 million neutrons per square
				  centimeter incident upon the body. If sufficient information exists to estimate
				  the approximate energy distribution of the neutrons, the licensee or registrant
				  may use the fluence rate per unit dose equivalent or the appropriate Q value
				  from Table II to convert a measured tissue dose in gray or rad to dose
				  equivalent in sievert or rem.
TABLE II
MEAN QUALITY FACT0RS, Q, AND FLUENCE PER UNIT
					 DOSE EQUIVALENT FOR MONOENERGETIC NEUTRONS
Mean Quality Factors Q, and Fluence Per Unit Dose
					 Equivalent for Monoenergetic Neutrons
Neutron Energy (MeV)
Qualitya Factor (Q)
Fluence per Unit Dose
									 Equivalentb (neutrons
									 cm-2 rem-1)
Fluence/Unit Dose
									 Equiv.b (neutrons-2 cm
									 Sv-1)
(thermal)
2.5E-8
2
980E+6
980E+8
1E-7
2
980E+6
980E+8
1E-6
2
810E+6
810E+8
1E-5
2
810E+6
810E+8
1E-4
2
840E+6
840E+8
1E-3
2
980E+6
980E+8
1E-2
2.5
1010E+6
1010E+8
1E-1
7.5
170E+6
170E+8
5E-1
11
39E+6
39E+8
1
11
27E+6
27E+8
2.5
9
29E+6
29E+8
5
8
23E+6
23E+8
7
7
24E+6
24E+8
10
6.5
24E+6
24E+8
14
7.5
17E+6
17E+8
20
8
16E+6
16E+8
40
7
14E+6
14E+8
60
5.5
16E+6
16E+8
1E+2
4
20E+6
20E+8
2E+2
3.5
19E+6
19E+8
3E+2
3.5
16E+6
16E+8
4E+2
3.5
14E+6
14E+8
a
Value of quality
					 factor (Q) at the point where the dose equivalent is maximum in a 30-centimeter
					 diameter cylinder tissue-equivalent phantom.
b
Monoenergetic
					 neutrons incident normally on a 30-centimeter diameter cylinder
					 tissue-equivalent phantom.