Effective dose commitments

The collective effective dose committed by an event, a decision or a finite portion of a practice k, 5, is given by ... 

Absorbed dose, organ dose, equivalent dose, effective dose, committed equivalent dose, or committed effective dose, depending on the context. The modifying terms are often omitted when they are not necessary for defining the quantity of interest. 

Radionuclides Effective dose commitment/ jiSv External Ingestion Inhalation Total exposure... 

Globally dispersed activities and corresponding world average effective dose commitments for the period of 1970-1997. The energy produced was 3,860 GWy, the reprocessed fuel was equivalent to 420 GWy... 

Release radioactivity/PBq Radionuclides Reactor Reprocessing Total Average annual effective dose commitment/nSv... 

The general principles for exen tion are reformulated by requiring that radiation risks to individuals and the collective radiological impact are both "sufficiently low as not to warrant regulatory control". In addition, it is stated that practices and sources may be exempted "without further consideration" provided that individual doses do not exceed 10 ftv/y and the collective effective dose committed by one year of the practice is no more than about 1 man.Sv. Compliance with these conditions allows for "automatic exemption". 

Exemption may be granted if the regulatory body is satisfied that the justified practices or sources within practices meet the exemption principles and criteria specified in Schedule I of the BSS, the exemption levels specified in Schedule I of the BSS or other exemption levels as specified by the regulatory body on the basis of the exemption criteria specified in Schedule I of the BSS. The criteria for exemption are that (a) the effective dose expected to be incurred by any member of the pubUc due to the exempted practice or source is of the order of 10 gSv or less in a year, and (b) either the collective effective dose committed by one year of performance of the practice is no more than about 1 man Sv or an assessment for the optimization of protection shows that exemption is the optimum option (Ret [1], para. 1-3). 

The second radiological criterion for exemption set out in Schedule I of the BSS concerns the collective effective doses associated with a practice (see para. 2.8 of this Safety Guide). The collective effective doses likely to be associated with the exemption and clearance of materials have been evaluated in a number of studies [5, 13]. It has generally been concluded that the individual dose criterion will almost always be limiting and that the collective effective dose commitments from one year of the practice will usually be weU below 1 man Sv. 

Food item Transfer factors 241 Am concentration4 Committed effective dose ( lSv) from241 Amb ... 

Occupational - the committed effective dose equivalent (Internal) and annual effective dose equivalent (external) combined... 

The Annual Limit of Intake (ALI) for any radionuclide is obtained by dividing the annual average effective dose limit (20 mSv) by the committed effective dose (E) resulting from the intake of 1 Bq of that radionuclide. ALI data for Individual radionuclides are given in ICRP (1991b). 

The dose of radiation delivered by an internally deposited radionuclide depends on the quantity of radioactive material residing in situ. This quantity decreases as a function of the physical half-life of the radionuclide and the rate at which the element is redistributed or excreted (i.e., its biological half-life). Because the physical half-life is known precisely and the biological half-life can be characterized within limits for most radionuclides, the dose to a tissue that will ultimately be delivered by a given concentration of a radionuclide deposited therein can be predicted to a first approximation. The collective dose to a population that will be delivered by the radionuclide—the so-called collective dose commitment—serves as the basis for assessing the relevant long-term health effects of the nuclide. 

Kendall, G.M., Kennedy, B.W., Greenhalgh, J.R., Adams, N. Fell, T.P. (1987) Committed doses to selected organs and committed effective doses from intake of radionuclides. Report GS7. National Radiological Protection Board. Chilton, Oxon. 

Hadditional dose commitment by a risk coefficient and a value of individual (collective) dose. The life-long risk coefficient characterizes reduction of the duration offull-valuelifeby 15 years (on average) per one stochastic effect (due to fatal cancers, serious hereditary effects and non-fatal cancers with similar-to-fatal-cancer consequences). 

Current federal and state regulations limit radiation workers doses to a total effective dose equivalent (TEDE) of 5 rem/year and a committed dose equivalent to any organ, other than the lens of the eye, of 50 rem/year (EPA 1988c USNRC 1995a). These limits apply to the sum of external and internal doses. The limits are upper limits, and an important philosophy in radiahon protection is to keep radiation doses as low as reasonably achievable (ALARA). 

The ALI is the activity of a radionuclide that can be taken into the body in a year, by inhalation or ingestion, without exceeding a committed effective dose equivalent (CEDE) of 5 rem/year or a committed dose equivalent to any organ of 50 rem/year, whichever is more limiting. The total effective dose equivalent TEDE is the sum of the CEDE and any penetrating external dose (10 CFR 20). If any external dose is present the ALI must be reduced by a proportional amount to ensure that the dose limits are not exceeded. For example, if a worker received an external dose of 1 rem/year, the ALI would have to be reduced by 20% to ensure that the TEDE did not exceed 5 rem/year. 

The SITP is a quantity derived from the Annual Limit on Intake (ALI), an internationally accepted concept that has been acknowledged by the Government s Radioactive Waste Management Committee (RWMAC) as a valid method of establishing equivalent hazards of different waste types. The ALI is a derived limit for the permissible amount of radioactive material taken into the body of an adult radiation worker by inhalation or ingestion in a year. The ALI is the smaller value of intake of a given radionuclide in a year by the reference man that would result in either a committed effective dose equivalent of 0.05 Sv or 0.5 Sv to any individual organ or tissue. 

Table 3.3 summarizes the radiation exposure doses due to the industrial exploitation of phosphate rock, expressed in terms of collective effective dose equivalent commitments resulting from the decision to use a unit mass of marketable ore to accomplish a defined purpose, as reported by UN Scientific Committee on Effects of Atomic Radiation (United Nations, 1982). 

Collective effective dose equivalent commitments per unit of marketable phosphate ore (10 man Sv t" )... 

F. Radiation Dose (committed dose equivalent, committed effective dose)... 

After an elapsed time T following an intake of radioactive substances, the committed effective dose is defined as ... 

For the purpose of demonstrating compliance with dose limits, the sum of the personal dose equivalent from external exposure to penetrating radiation in the specified period and the committed equivalent dose or committed effective dose, as appropriate, from intakes of radioactive substances in the same period shall be taken into account. 

The committed effective dose per unit intake following ingestion of Zr is 9.5 X 10 Sv Bq for adults > 17 years of age (IAEA, 1996). However, due to its relatively short physical half-life, the major environmental impact of Zr is likely to be short-term external irradiation. 

Handl et al. (2000) reported measured transfer factors for silver in pasture grass ranging from 0.009 to 0.065. This range is slightly higher than the rather limited collection of soil-plant transfer factors quoted by lUR (1989) of 0.00027 for lettuce, 0.0008 for tomato, and 0.0013 for radish. Ng et al. (1982) quoted a transfer factor value of 0.15 for Ag in unspecified plant material. The committed effective dose per unit intake following ingestion of " "Ag is 2.8 x 10- Sv Bq for adults older than 17 years of age (IAEA, 1996). 

Effective dose equivalent (He) is the sum of the products of the tissue weighting factors (Wr) applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to the corresponding organ... 

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