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Abstract
Objective
In order to understand the complete scenario of the effectiveness of radiation protection practice in the workplace, especially in the industrial radiography and also to analyze the trends with other related studies, epidemiological studies and legal purposes, the assessment and register of the effective dose plays a significant role. Therefore, efforts have been given in the assessment of collective effective dose, mean effective dose, prediction of lifetime cancer risk, and contribution of different age group workers in the collective effective dose.
Methods
The occupational radiation exposures for 472 workers were investigated in industrial radiography throughout Bangladesh from 2015 to 2018 by using thermoluminescent dosimeter (TLD). By using a Harshaw TLD reader (Model-4500), the effective dose was measured in a quarterly basis throughout the year. Based on the value of personal dose equivalent Hp(10), database was prepared and recorded.
Results
The collective effective dose was 36.1, 40.7, 28.8 and 37.5 man·mSv among 105, 102, 100 and 165 radiation workers in 2015, 2016, 2017 and 2018, respectively. The maximum effective dose received by radiation workers was 6.0, 7.1, 6.9 and 19.9 mSv in 2015, 2016, 2017 and 2018, respectively, which remained within the stipulated dose limits imposed by Nuclear Safety and Radiation Control (NSRC) Rules-1997, Bangladesh and International Commission on Radiological Protection (ICRP-103).
Conclusion
This kind of monitoring would help to construct a national database that will be used by the end users to improve their implementation of optimization in occupational radiation protection in industrial radiography.
Keywords
Occupational exposure
Effective dose
Collective effective dose
Radiation protection
Thermoluminescent dosimetry
Industrial radiography
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© 2021 National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.
- The Radiation Protection Act and the Radiation Protection Ordinance specify dose limits for the general population and for occupationally exposed persons.
- Dose limits do not constitute a dividing line between hazardous and harmless radiation exposure. Rather, exceeding a limit value means that the probability of health effects (in particular cancer) exceeds a value that is defined as acceptable.
- The limit value for the effective dose aimed at protecting members of the public is 1 millisievert in a calendar year (§ 80(1), Radiation Protection Act).
- Medical applications of radiation are excluded from these limitations.
The Radiation Protection Act and the Radiation Protection Ordinance specify dose limits for the general population and for occupationally exposed persons. In general, any application of ionising radiation must be justified and the radiation exposure must be kept as low as possible even when below the limit values.
Limit values and health risks
Dose limits do not constitute a dividing line between hazardous and harmless radiation exposure. Rather, exceeding a limit value means that the probability of health effects (in particular cancer) exceeds a value that is defined as acceptable. The limit values are laid down by the legislative or regulatory authority.
As there is no dose value below which it is possible to rule out a health risk due to ionising radiation, a certain – albeit minor – risk also exists below the limit values which increases with increasing dose. Therefore, any radiation exposure, even at levels below the specified limit values, should be avoided if possible and, failing this, kept to a minimum (principle of optimisation). In practice, this principle means that in the vast majority of cases radiation exposure is far below the legally specified limit values.
Limit values for exposure of the general public
The limit value for the effective dose aimed at protecting members of the public is 1 millisievert in a calendar year (§ 80(1), Radiation Protection Act).
This value refers to all radiation exposures to which members of the public may be exposed due to nuclear and other facilities for the generation of ionising radiation, as well as the handling of radioactive substances. This means that the limit value applies to the sum of radiation exposure from direct radiation and radiation exposure due to discharges from nuclear facilities. At the same time, the radiation exposure from an individual facility via the exposure pathways of waste water and exhaust air must not exceed 0.3 millisievert per year for either pathway (§ 99(1), Radiation Protection Ordinance).
Medical applications of radiation are excluded from these limitations. There is currently no legal dose limit for radiation from natural sources.
The limit values for the organ equivalent dose ("organ dose") for the general public are specified in § 80(2) of the Radiation Protection Act. They are equal to 15 millisieverts in a calendar year for the lens of the eye and 50 millisieverts in a calendar year for the skin.
In addition, limit values for radiation exposure resulting from the release of radioactive substances into the environment must be taken into account in the planning of protective measures against incidents at a nuclear power plant (see § 104 of the Radiation Protection Ordinance).
Limit values for occupationally exposed persons
The limit value for the effective dose in order to protect occupationally exposed persons is 20 millisieverts in a calendar year (§ 78(1), Radiation Protection Act).
In individual cases, the competent authority can allow a value of 50 millisieverts for a single year, but a value of 100 millisieverts must not be exceeded for five subsequent years. Lifetime occupational exposure must not exceed 400 millisieverts (§ 77, Radiation Protection Act).
These dose limits apply equally to women and men. However, for women of childbearing age, the organ equivalent dose (organ dose) for the uterus must not exceed 2 millisieverts per month. For pregnant women, the limit value for the unborn child is 1 millisievert from the time of declaration until the end of pregnancy (§ 78(4), Radiation Protection Act).
For apprentices under the age of 18, the limit value is 1 millisievert per calendar year (§ 78(3), Radiation Protection Act). For educational purposes, the competent authority may specify a limit value of 6 millisieverts for 16- to 18-year-olds if necessary.
The Radiation Protection Act additionally sets limit values for individual organs for protective measures relating to the radiation exposure of specific parts of the body (§ 78(2), Radiation Protection Act).
For further information and details on this topic, please refer to the article “Limit values for occupationally exposed persons”.
Important limit values and typical dose values in comparison
To allow better classification of the limit values, the following table lists some important limit values and typical dose values (effective dose in each case) for comparison purposes.
Effective dose | |
0.01 mSv per year | Calculated order of magnitude of the annual maximum dose for the Germany population due to nuclear power plants in normal operation. (These calculations are based on conservative assumptions
regarding, among other things, location and diet so that the actual exposure values are lower.) |
0.01–0.03 mSv per image | Typical dose range for an X-ray of the thorax |
up to 0.1 mSv per flight | Dose due to cosmic radiation during a flight from Munich to Japan |
1 mSv per year | Limit value (maximum permissible dose) for annual radiation exposure of members of the general public (e.g. resulting from the release of radioactive substances from nuclear facilities) |
1–3 mSv per image | Typical dose range for a cranial CT (head CT) |
2 mSv per year | Average annual dose for a person in Germany from artificial sources, primarily medicine (value for 2015: approx. 1.7 mSv) |
2 mSv in 50 years | Total dose for the period 1986–2036 due to the Chernobyl reactor accident for a person in the foothills of the Alps |
2–3 mSv per year | Average annual radiation exposure from natural sources for the general public in Germany 10–20 mSv per image Typical dose range for a whole-body CT of an adult |
10–20 mSv per image | Typical dose range for a whole-body CT of an adult |
20 mSv per year | Limit value (maximum permissible dose) for annual radiation exposure of occupationally exposed persons in Germany |
250 mSv | Guideline value for an individual when using life-saving measures or to avoid major disasters in Germany |
400 mSv | Limit value (maximum permissible dose) for lifetime occupational dose of occupationally exposed persons in GermanyPersonen der allgemei |
Important thresholds for deterministic radiation effects
The table below contains lists some threshold values for acute radiation damage (deterministic radiation effects) in order to facilitate the classification of dose and limit values.
Dose | |
100 mSv | Lower estimate for the threshold for damage to the unborn child |
1,000 mSv | In the case of acute exposure, acute radiation effects (e.g. headache, nausea, vomiting) occur from this threshold upwards. |
2,000 mSv | In the case of acute exposure, reddening of the skin occurs from this threshold upwards. |
3,000–4,000 mSv | Without medical intervention, this dose results in the death of 50 percent of exposed individuals within 3–6 weeks if the radiation exposure was experienced over a short period of time (LD50). |
>8,000 mSv | Without appropriate medical treatment, there is only a small chance of survival if the radiation exposure was experienced over a short period of time. |
State of 2022.10.13