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Nuclear Regulatory Commission § 20.1003

§ 20.1002 Scope. exceed, during the hours an individual The regulations in this part apply to is present in a week, an intake of 0.6 persons licensed by the Commission to percent of the annual limit on intake receive, possess, use, transfer, or dis- (ALI) or 12 DAC-hours. pose of byproduct, source, or special Air-purifying means a res- nuclear material or to operate a pro- pirator with an air-purifying filter, duction or utilization facility under cartridge, or canister that removes spe- parts 30 through 36, 39, 40, 50, 52, 60, 61, cific air contaminants by passing am- 63, 70, or 72 of this chapter, and in ac- bient air through the air-purifying ele- cordance with 10 CFR 76.60 to persons ment. required to obtain a certificate of com- ALARA (acronym for ‘‘as low as is pliance or an approved compliance plan reasonably achievable’’) means making under part 76 of this chapter. The lim- every reasonable effort to maintain ex- its in this part do not apply to doses posures to as far below the due to background radiation, to expo- dose limits in this part as is practical sure of patients to radiation for the consistent with the purpose for which purpose of medical diagnosis or ther- the licensed activity is undertaken, apy, to exposure from individuals ad- taking into account the state of tech- ministered radioactive material and re- nology, the economics of improve- leased under § 35.75, or to exposure from ments in relation to state of tech- voluntary participation in medical re- nology, the economics of improve- search programs. ments in relation to benefits to the public health and safety, and other so- [72 FR 49485, Aug. 28, 2007] cietal and socioeconomic consider- § 20.1003 Definitions. ations, and in relation to utilization of nuclear energy and licensed materials As used in this part: in the public interest. means the energy im- Annual limit on intake (ALI) means parted by per unit the derived limit for the amount of ra- mass of irradiated material. The units of absorbed dose are the and the dioactive material taken into the body (Gy). of an adult worker by inhalation or in- Accelerator-produced radioactive mate- gestion in a year. ALI is the smaller rial means any material made radio- value of intake of a given active by a . in a year by the reference man that Act means the Atomic Energy Act of would result in a committed effective 1954 (42 U.S.C. 2011 et seq.), as amended. dose equivalent of 5 rems (0.05 Sv) or a Activity is the rate of disintegration equivalent of 50 rems (transformation) or decay of radio- (0.5 Sv) to any individual organ or tis- active material. The units of activity sue. (ALI values for intake by inges- are the curie (Ci) and the tion and by inhalation of selected (Bq). are given in table 1, col- Adult means an individual 18 or more umns 1 and 2, of appendix B to years of age. §§ 20.1001–20.2401). Airborne radioactive material means Assigned protection factor (APF) means radioactive material dispersed in the the expected workplace level of res- air in the form of dusts, fumes, particu- piratory protection that would be pro- lates, mists, vapors, or gases. vided by a properly functioning res- Airborne radioactivity area means a pirator or a class of to room, enclosure, or area in which air- properly fitted and trained users. Oper- borne radioactive materials, composed ationally, the inhaled concentration wholly or partly of licensed material, can be estimated by dividing the ambi- exist in concentrations— ent airborne concentration by the (1) In excess of the derived air con- APF. centrations (DACs) specified in appen- Atmosphere-supplying respirator means dix B, to §§ 20.1001–20.2401, or a respirator that supplies the res- (2) To such a degree that an indi- pirator user with breathing air from a vidual present in the area without res- source independent of the ambient at- piratory protective equipment could mosphere, and includes supplied-air

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respirators (SARs) and self-contained (4) Any discrete source of naturally breathing apparatus (SCBA) units. occurring radioactive material, other Background radiation means radiation than source material, that— from cosmic sources; naturally occur- (i) The Commission, in consultation ring radioactive material, including with the Administrator of the Environ- (except as a of mental Protection Agency, the Sec- source or special nuclear material); retary of Energy, the Secretary of and global fallout as it exists in the en- Homeland Security, and the head of vironment from the testing of nuclear any other appropriate Federal agency, explosive devices or from past nuclear determines would pose a threat similar accidents such as that con- to the threat posed by a discrete source tribute to background radiation and of -226 to the public health and are not under the control of the li- safety or the common defense and secu- censee. ‘‘Background radiation’’ does rity; and not include radiation from source, by- (ii) Before, on, or after August 8, 2005, product, or special nuclear materials is extracted or converted after extrac- regulated by the Commission. tion for use in a commercial, medical, Bioassay (radiobioassay) means the or research activity. determination of kinds, quantities or Class (or lung class or inhalation class) concentrations, and, in some cases, the means a classification scheme for in- locations of radioactive material in the haled material according to its rate of human body, whether by direct meas- clearance from the pulmonary region urement (in vivo counting) or by anal- of the lung. Materials are classified as ysis and evaluation of materials ex- D, W, or Y, which applies to a range of creted or removed from the human clearance half-times: for Class D (Days) body. of less than 10 days, for Class W Byproduct material means— (Weeks) from 10 to 100 days, and for (1) Any radioactive material (except Class Y (Years) of greater than 100 special nuclear material) yielded in, or days. made radioactive by, exposure to the is the sum of the indi- radiation incident to the process of vidual doses received in a given period producing or using special nuclear ma- terial; of time by a specified population from exposure to a specified source of radi- (2) The tailings or wastes produced ation. by the extraction or concentration of or from ore processed Commission means the Nuclear Regu- primarily for its source material con- latory Commission or its duly author- tent, including discrete surface wastes ized representatives. resulting from uranium solution ex- Committed dose equivalent (HT,50) traction processes. Underground ore means the dose equivalent to organs or bodies depleted by these solution ex- tissues of reference (T) that will be re- traction operations do not constitute ceived from an intake of radioactive ‘‘byproduct material’’ within this defi- material by an individual during the nition; 50-year period following the intake. (3)(i) Any discrete source of radium- Committed effective dose equivalent 226 that is produced, extracted, or con- (HE,50) is the sum of the products of the verted after extraction, before, on, or weighting factors applicable to each of after August 8, 2005, for use for a com- the body organs or tissues that are ir- mercial, medical, or research activity; radiated and the committed dose or equivalent to these organs or tissues (ii) Any material that— (HE,50 = S wT HT,50). (A) Has been made radioactive by use Constraint (dose constraint) means a of a particle accelerator; and value above which specified licensee (B) Is produced, extracted, or con- actions are required. verted after extraction, before, on, or Controlled area means an area, out- after August 8, 2005, for use for a com- side of a restricted area but inside the mercial, medical, or research activity; site boundary, access to which can be and limited by the licensee for any reason.

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Critical Group means the group of in- one ALI. DAC values are given in table dividuals reasonably expected to re- 1, column 3, of appendix B to §§ 20.1001– ceive the greatest exposure to residual 20.2401. radioactivity for any applicable set of Derived air concentration-hour (DAC- circumstances. hour) is the product of the concentra- Declared pregnant woman means a tion of radioactive material in air (ex- woman who has voluntarily informed pressed as a fraction or multiple of the the licensee, in writing, of her preg- derived air concentration for each nancy and the estimated date of con- radionuclide) and the time of exposure ception. The declaration remains in ef- to that radionuclide, in hours. A li- fect until the declared pregnant woman censee may take 2,000 DAC-hours to withdraws the declaration in writing or represent one ALI, equivalent to a is no longer pregnant. committed effective dose equivalent of Decommission means to remove a fa- 5 rems (0.05 Sv). cility or site safely from service and Discrete source means a radionuclide reduce residual radioactivity to a level that has been processed so that its con- that permits— centration within a material has been (1) Release of the property for unre- purposely increased for use for com- stricted use and termination of the li- mercial, medical, or research activi- cense; or ties. (2) Release of the property under re- Disposable respirator means a res- stricted conditions and the termi- pirator for which maintenance is not nation of the license. intended and that is designed to be dis- Deep-dose equivalent (Hd), which ap- carded after excessive breathing resist- plies to external whole-body exposure, ance, sorbent exhaustion, physical is the dose equivalent at a tissue depth damage, or end-of-service-life renders of 1 cm (1000 mg/cm2). it unsuitable for use. Examples of this Demand respirator means an atmos- type of respirator are a disposable half- phere-supplying respirator that admits mask respirator or a disposable escape- breathing air to the facepiece only only self-contained breathing appa- when a negative pressure is created in- ratus (SCBA). side the facepiece by inhalation. Distinguishable from background Department means the Department of means that the detectable concentra- Energy established by the Department tion of a radionuclide is statistically of Energy Organization Act (Pub. L. 95– different from the background con- 91, 91 Stat. 565, 42 U.S.C. 7101 et seq.) to centration of that radionuclide in the the extent that the Department, or its vicinity of the site or, in the case of duly authorized representatives, exer- structures, in similar materials using cises functions formerly vested in the adequate measurement technology, U.S. Atomic Energy Commission, its survey, and statistical techniques. Chairman, members, officers, and com- Dose or radiation dose is a generic ponents and transferred to the U.S. En- term that means absorbed dose, dose ergy Research and Development Ad- equivalent, effective dose equivalent, ministration and to the Administrator committed dose equivalent, committed thereof pursuant to sections 104 (b), (c), effective dose equivalent, or total ef- and (d) of the Energy Reorganization fective dose equivalent, as defined in Act of 1974 (Pub. L. 93–438, 88 Stat. 1233 other paragraphs of this section. at 1237, 42 U.S.C. 5814) and retransferred Dose equivalent (HT) means the prod- to the Secretary of Energy pursuant to uct of the absorbed dose in tissue, qual- section 301(a) of the Department of En- ity factor, and all other necessary ergy Organization Act (Pub. L. 95–91, 91 modifying factors at the location of in- Stat 565 at 577–578, 42 U.S.C. 7151). terest. The units of dose equivalent are Derived air concentration (DAC) means the rem and (Sv). the concentration of a given radio- processor means an indi- in air which, if breathed by the vidual or organization that processes reference man for a working year of and evaluates individual monitoring 2,000 hours under conditions of equipment in order to determine the work (inhalation rate 1.2 cubic meters radiation dose delivered to the equip- of air per hour), results in an intake of ment.

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Effective dose equivalent (HE) is the States of America, which is an instru- sum of the products of the dose equiva- mentality of the United States, or any lent to the organ or tissue (HT) and the board, bureau, division, service, office, weighting factors (wT) applicable to officer, authority, administration, or each of the body organs or tissues that other establishment in the executive are irradiated (HE = S wT HT). branch of the Government. Embryo/fetus means the developing Gray [See § 20.1004]. human organism from conception until Helmet means a rigid respiratory the time of birth. inlet covering that also provides head Entrance or access point means any lo- protection against impact and penetra- cation through which an individual tion. could gain access to radiation areas or High radiation area means an area, ac- to radioactive materials. This includes cessible to individuals, in which radi- entry or exit portals of sufficient size ation levels from radiation sources ex- to permit human entry, irrespective of ternal to the body could result in an their intended use. individual receiving a dose equivalent Exposure means being exposed to ion- in excess of 0.1 rem (1 mSv) in 1 hour at izing radiation or to radioactive mate- 30 centimeters from the radiation rial. source or 30 centimeters from any sur- External dose means that portion of face that the radiation penetrates. the dose equivalent received from radi- Hood means a respiratory inlet cov- ation sources outside the body. ering that completely covers the head Extremity means hand, elbow, arm and neck and may also cover portions below the elbow, foot, knee, or leg of the shoulders and torso. below the knee. Individual means any human being. Filtering facepiece (dust mask) means a Individual monitoring means— negative pressure particulate res- (1) The assessment of dose equivalent pirator with a filter as an integral part by the use of devices designed to be of the facepiece or with the entire face- worn by an individual; piece composed of the filtering me- dium, not equipped with elastomeric (2) The assessment of committed ef- sealing surfaces and adjustable straps. fective dose equivalent by bioassay (see Fit factor means a quantitative esti- Bioassay) or by determination of the mate of the fit of a particular res- time-weighted air concentrations to pirator to a specific individual, and which an individual has been exposed, typically estimates the ratio of the i.e., DAC-hours; or concentration of a substance in ambi- (3) The assessment of dose equivalent ent air to its concentration inside the by the use of survey data. respirator when worn. Individual monitoring devices (indi- Fit test means the use of a protocol to vidual monitoring equipment) means qualitatively or quantitatively evalu- devices designed to be worn by a single ate the fit of a respirator on an indi- individual for the assessment of dose vidual. equivalent such as film badges, Generally applicable environmental ra- thermoluminescence diation standards means standards (TLDs), pocket ionization chambers, issued by the Environmental Protec- and personal (‘‘lapel’’) air sampling de- tion Agency (EPA) under the authority vices. of the Atomic Energy Act of 1954, as Internal dose means that portion of amended, that impose limits on radi- the dose equivalent received from ra- ation exposures or levels, or concentra- dioactive material taken into the body. tions or quantities of radioactive mate- Lens dose equivalent (LDE) applies to rial, in the general environment out- the external exposure of the lens of the side the boundaries of locations under eye and is taken as the dose equivalent the control of persons possessing or at a tissue depth of 0.3 centimeter (300 using radioactive material. mg/cm2). Government agency means any execu- License means a license issued under tive department, commission, inde- the regulations in parts 30 through 36, pendent establishment, corporation 39, 40, 50, 60, 61, 63, 70, or 72 of this chap- wholly or partly owned by the United ter.

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Licensed material means source mate- air pressure inside the facepiece is neg- rial, special nuclear material, or by- ative during inhalation with respect to product material received, possessed, the ambient air pressure outside the used, transferred or disposed of under a respirator. general or specific license issued by the Nonstochastic effect means health ef- Commission. fects, the severity of which varies with Licensee means the holder of a li- the dose and for which a threshold is cense. believed to exist. Radiation-induced Limits (dose limits) means the per- cataract formation is an example of a missible upper bounds of radiation nonstochastic effect (also called a de- doses. terministic effect). Loose-fitting facepiece means a res- NRC means the Nuclear Regulatory piratory inlet covering that is designed Commission or its duly authorized rep- to form a partial seal with the face. resentatives. Lost or missing licensed material means licensed material whose location is un- Occupational dose means the dose re- known. It includes material that has ceived by an individual in the course of been shipped but has not reached its employment in which the individual’s destination and whose location cannot assigned duties involve exposure to ra- be readily traced in the transportation diation or to radioactive material from system. licensed and unlicensed sources of radi- Member of the public means any indi- ation, whether in the possession of the vidual except when that individual is licensee or other person. Occupational receiving an occupational dose. dose does not include doses received Minor means an individual less than from background radiation, from any 18 years of age. medical administration the individual Monitoring (, ra- has received, from exposure to individ- diation protection monitoring) means uals administered radioactive material the measurement of radiation levels, and released under § 35.75, from vol- concentrations, surface area concentra- untary participation in medical re- tions or quantities of radioactive mate- search programs, or as a member of the rial and the use of the results of these public. measurements to evaluate potential Particle accelerator means any ma- exposures and doses. chine capable of accelerating , Nationally tracked source is a sealed , deuterons, or other charged source containing a quantity equal to particles in a vacuum and of dis- or greater than Category 1 or Category charging the resultant particulate or 2 levels of any radioactive material other radiation into a medium at ener- listed in Appendix E of this part. In gies usually in excess of 1 this context a sealed source is defined megaelectron volt. For purposes of this as radioactive material that is sealed definition, ‘‘accelerator’’ is an equiva- in a capsule or closely bonded, in a lent term. solid form and which is not exempt from regulatory control. It does not Person means— mean material encapsulated solely for (1) Any individual, corporation, part- disposal, or nuclear material contained nership, firm, association, trust, es- in any fuel assembly, subassembly, fuel tate, public or private institution, rod, or fuel pellet. Category 1 nation- group, Government agency other than ally tracked sources are those con- the Commission or the Department of taining radioactive material at a quan- Energy (except that the Department tity equal to or greater than the Cat- shall be considered a person within the egory 1 threshold. Category 2 nation- meaning of the regulations in 10 CFR ally tracked sources are those con- chapter I to the extent that its facili- taining radioactive material at a quan- ties and activities are subject to the li- tity equal to or greater than the Cat- censing and related regulatory author- egory 2 threshold but less than the Cat- ity of the Commission under section egory 1 threshold. 202 of the Energy Reorganization Act Negative pressure respirator (tight fit- of 1974 (88 Stat. 1244), the Uranium Mill ting) means a respirator in which the Tailings Radiation Control Act of 1978

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(92 Stat. 3021), the Nuclear Waste Pol- the amount of leakage into the res- icy Act of 1982 (96 Stat. 2201), and sec- pirator. tion 3(b)(2) of the Low-Level Radio- Quarter means a period of time equal active Waste Policy Amendments Act to one-fourth of the year observed by of 1985 (99 Stat. 1842)), any State or any the licensee (approximately 13 political subdivision of or any political consective weeks), providing that the entity within a State, any foreign gov- beginning of the first quarter in a year ernment or nation or any political sub- coincides with the starting date of the division of any such government or na- year and that no day is omitted or du- tion, or other entity; and plicated in consecutive quarters. (2) Any legal successor, representa- Rad (See § 20.1004). tive, agent, or agency of the foregoing. Radiation (ionizing radiation) means Planned special exposure means an in- alpha particles, beta particles, gamma frequent exposure to radiation, sepa- rays, x-rays, , high-speed elec- rate from and in addition to the annual trons, high-speed protons, and other dose limits. particles capable of producing ions. Ra- Positive pressure respirator means a diation, as used in this part, does not respirator in which the pressure inside include non-ionizing radiation, such as the respiratory inlet covering exceeds radio- or , or visible, infra- the ambient air pressure outside the red, or light. Radiation area means an area, acces- respirator. sible to individuals, in which radiation Powered air-purifying respirator levels could result in an individual re- means an air-purifying res- (PAPR) ceiving a dose equivalent in excess of pirator that uses a blower to force the 0.005 rem (0.05 mSv) in 1 hour at 30 cen- ambient air through air-purifying ele- timeters from the radiation source or ments to the inlet covering. from any surface that the radiation Pressure demand respirator means a penetrates. positive pressure atmosphere-supplying Reference man means a hypothetical respirator that admits breathing air to aggregation of human physical and the facepiece when the positive pres- physiological characteristics arrived at sure is reduced inside the facepiece by by international consensus. These inhalation. characteristics may be used by re- Public dose means the dose received searchers and public health workers to by a member of the public from expo- standardize results of experiments and sure to radiation or to radioactive ma- to relate biological insult to a common terial released by a licensee, or to any base. other source of radiation under the Rem (See § 20.1004). control of a licensee. Public dose does Residual radioactivity means radioac- not include occupational dose or doses tivity in structures, materials, , received from background radiation, groundwater, and other media at a site from any medical administration the resulting from activities under the li- individual has received, from exposure censee’s control. This includes radioac- to individuals administered radioactive tivity from all licensed and unlicensed material and released under § 35.75, or sources used by the licensee, but ex- from voluntary participation in med- cludes background radiation. It also in- ical research programs. cludes radioactive materials remaining Qualitative fit test (QLFT) means a at the site as a result of routine or ac- pass/fail fit test to assess the adequacy cidental releases of radioactive mate- of respirator fit that relies on the indi- rial at the site and previous burials at vidual’s response to the test agent. the site, even if those burials were Quality Factor (Q) means the modi- made in accordance with the provisions fying factor (listed in tables 1004(b).1 of 10 CFR part 20. and 1004(b).2 of § 20.1004) that is used to Respiratory protective device means an derive dose equivalent from absorbed apparatus, such as a respirator, used to dose. reduce the individual’s intake of air- Quantitative fit test (QNFT) means an borne radioactive materials. assessment of the adequacy of res- Restricted area means an area, access pirator fit by numerically measuring to which is limited by the licensee for

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the purpose of protecting individuals Supplied-air respirator (SAR) or airline against undue risks from exposure to respirator means an atmosphere-sup- radiation and radioactive materials. plying respirator for which the source Restricted area does not include areas of breathing air is not designed to be used as residential quarters, but sepa- carried by the user. rate rooms in a residential building Survey means an evaluation of the ra- may be set apart as a restricted area. diological conditions and potential Sanitary sewerage means a system of hazards incident to the production, public sewers for carrying off waste use, transfer, release, disposal, or pres- water and refuse, but excluding sewage ence of radioactive material or other treatment facilities, septic tanks, and sources of radiation. When appropriate, leach fields owned or operated by the such an evaluation includes a physical licensee. survey of the location of radioactive Self-contained breathing apparatus material and measurements or calcula- (SCBA) means an atmosphere-sup- tions of levels of radiation, or con- plying respirator for which the breath- centrations or quantities of radioactive ing air source is designed to be carried material present. by the user. Tight-fitting facepiece means a res- piratory inlet covering that forms a Shallow-dose equivalent (Hs), which ap- plies to the external exposure of the complete seal with the face. skin of the whole body or the skin of Total Effective Dose Equivalent (TEDE) an extremity, is taken as the dose means the sum of the effective dose equivalent at a tissue depth of 0.007 equivalent (for external exposures) and centimeter (7 mg/cm2). the committed effective dose equiva- Site boundary means that line beyond lent (for internal exposures). which the land or property is not Unrestricted area means an area, ac- owned, leased, or otherwise controlled cess to which is neither limited nor by the licensee. controlled by the licensee. Uranium fuel cycle means the oper- Source material means— ations of milling of uranium ore, chem- (1) Uranium or thorium or any com- ical conversion of uranium, isotopic bination of uranium and thorium in enrichment of uranium, fabrication of any physical or chemical form; or uranium fuel, generation of electricity (2) Ores that contain, by weight, one- by a light-water-cooled twentieth of 1 percent (0.05 percent), or plant using uranium fuel, and reproc- more, of uranium, thorium, or any essing of spent uranium fuel to the ex- combination of uranium and thorium. tent that these activities directly sup- Source material does not include spe- port the production of electrical power cial nuclear material. for public use. Uranium fuel cycle does Special nuclear material means— not include mining operations, oper- (1) Plutonium, uranium-233, uranium ations at waste disposal sites, trans- enriched in the 233 or in the portation of radioactive material in isotope 235, and any other material support of these operations, and the that the Commission, pursuant to the reuse of recovered non-uranium special provisions of section 51 of the Act, de- nuclear and byproduct materials from termines to be special nuclear mate- the cycle. rial, but does not include source mate- User seal check (fit check) means an rial; or action conducted by the respirator user (2) Any material artificially enriched to determine if the respirator is prop- by any of the foregoing but does not in- erly seated to the face. Examples in- clude source material. clude negative pressure check, positive Stochastic effects means health effects pressure check, irritant smoke check, that occur randomly and for which the or isoamyl acetate check. probability of the effect occurring, Very high radiation area means an rather than its severity, is assumed to area, accessible to individuals, in be a linear function of dose without which radiation levels from radiation threshold. Hereditary effects and can- sources external to the body could re- cer incidence are examples of sult in an individual receiving an ab- stochastic effects. sorbed dose in excess of 500 rads (5

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grays) in 1 hour at 1 meter from a radi- emission of 1.3×105 MeV of potential ation source or 1 meter from any sur- energy. face that the radiation penetrates. Working level month (WLM) means an NOTE: At very high doses received at high exposure to 1 working level for 170 dose rates, units of absorbed dose (e.g., rads hours (2,000 working hours per year/12 and grays) are appropriate, rather than units months per year=approximately 170 of dose equivalent (e.g., rems and )). hours per month). Waste means those low-level radio- active wastes containing source, spe- Year means the period of time begin- cial nuclear, or byproduct material ning in January used to determine that are acceptable for disposal in a compliance with the provisions of this land disposal facility. For the purposes part. The licensee may change the of this definition, low-level radioactive starting date of the year used to deter- waste means not mine compliance by the licensee pro- classified as high-level radioactive vided that the change is made at the waste, transuranic waste, spent nu- beginning of the year and that no day clear fuel, or byproduct material as de- is omitted or duplicated in consecutive fined in paragraphs (2), (3), and (4) of years. the definition of Byproduct material set forth in this section. [56 FR 23391, May 21, 1991, as amended at 57 FR 57878, Dec. 8, 1992; 58 FR 7736, Feb. 9, 1993; Week means 7 consecutive days start- 60 FR 36043, July 13, 1995; 60 FR 48625, Sept. ing on Sunday. 20, 1995; 61 FR 65127, Dec. 10, 1996; 62 FR 4133, Weighting factor wT, for an organ or Jan. 29, 1997; 62 FR 39087, July 21, 1997; 63 FR tissue (T) is the proportion of the risk 39481, July 23, 1998; 64 FR 54556, Oct. 7, 1999; of stochastic effects resulting from ir- 66 FR 55789, Nov. 2, 2001; 67 FR 16304, Apr. 5, radiation of that organ or tissue to the 2002; 67 FR 20370, Apr. 24, 2002; 67 FR 62872, total risk of stochastic effects when Oct. 9, 2002; 71 FR 65707, Nov. 8, 2006; 72 FR the whole body is irradiated uniformly. 55921, Oct. 1, 2007; 72 FR 68058, Dec. 4, 2007; 74 For calculating the effective dose FR 62680, Dec. 1, 2009] equivalent, the values of w are: T § 20.1004 Units of radiation dose. ORGAN DOSE WEIGHTING FACTORS (a) Definitions. As used in this part, the units of radiation dose are: Organ or tissue wT Gray (Gy) is the SI unit of absorbed Gonads ...... 0.25 dose. One gray is equal to an absorbed Breast ...... 0.15 dose of 1 Joule/kilogram (100 rads). Red bone marrow ...... 0.12 Lung ...... 0.12 Rad is the special unit of absorbed ...... 0.03 dose. One rad is equal to an absorbed Bone surfaces ...... 0.03 dose of 100 ergs/gram or 0.01 joule/kilo- 1 Remainder ...... 0.30 gram (0.01 gray). Whole Body ...... 2 1.00 Rem is the special unit of any of the 1 0.30 results from 0.06 for each of 5 ‘‘remainder’’ organs (excluding the skin and the lens of the eye) that receive the quantities expressed as dose equiva- highest doses. lent. The dose equivalent in rems is 2 For the purpose of weighting the external whole body dose (for adding it to the internal dose), a single weighting equal to the absorbed dose in rads mul- factor, wT=1.0, has been specified. The use of other weighting tiplied by the quality factor (1 rem=0.01 factors for external exposure will be approved on a case-by- case basis until such time as specific guidance is issued. sievert). Whole body means, for purposes of ex- Sievert is the SI unit of any of the ternal exposure, head, trunk (including quantities expressed as dose equiva- male gonads), arms above the elbow, or lent. The dose equivalent in sieverts is legs above the knee. equal to the absorbed dose in grays Working level (WL) is any combina- multiplied by the quality factor (1 tion of short-lived radon daughters (for Sv=100 rems). radon-222: polonium-218, lead-214, bis- (b) As used in this part, the quality muth-214, and polonium-214; and for factors for converting absorbed dose to radon-220: polonium-216, lead-212, bis- dose equivalent are shown in table muth-212, and polonium-212) in 1 liter 1004(b).1. of air that will result in the ultimate

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