Basic safety standards for ionizing radiation in Vietnam under TCVN 4397:1987

Regarding this matter, LawNet would like to answer as follows: 

1. What are the basic safety standards for ionizing radiation in Vietnam under TCVN 4397:1987?

According to TCVN 4397:1987, the basic safety standards for ionizing radiation are as follows:

- The basic standards for radiation safety regulate the limits of the dose concentration of radioactive nuclides. In water and air, surface radioactive contamination, etc., in order to prevent or minimize the damage caused by radiation to radiation workers and the general public.

- The limits of dose in this regulation are the maximum values of both external and internal exposure, excluding doses received during medical examination and treatment as well as doses from natural background radiation.

- All radiation exposure to the body can have certain risks because there is no dose threshold considered safe. Therefore, when working with radiation, attention should be paid to the following principles:

+ Do not exceed the dose limits.

+ Avoid unnecessary radiation exposure;

+ Reduce low dose exposure to an acceptable level.

- The subjects exposed to radiation are classified as follows:

+ Subject A: Radiation workers;

+ Subject B: Nearby individuals:

+ Subject C: General public.

- Based on radiation sensitivity, the organs in the body are classified into three vulnerable groups, as follows:

+ Group I: whole body, reproductive organs, red bone marrow:

+ Group II: Organs not belonging to Group I and III;

+ Group III: skin, tissue, bone, hands, wrists, feet, and eyes.

- The dose limits (for both external and internal exposure) for the subjects and vulnerable organ groups are specified in the following table:

Note:

- If an organ is exposed to multiple radioactive nuclides or multiple types of radiation, the total dose received by that organ must not exceed the limits specified in Table 2;

- For subject A, the number of working weeks in a year is calculated as 50 weeks, with each week consisting of 40 hours.

In addition to the above basic standards, TCVN 4397:1987 also includes other basic standards for radiation safety, such as: limits of concentration of radioactive nuclides in water and air, levels of radioactive contamination on surfaces in workplaces, protective equipment, etc.

2. How should radiation facilities be arranged?

According to the regulations in TCVN 4397:1987, radiation facilities should be arranged as follows:

- Prohibit the placement of facilities or departments working with radiation sources in residential areas and facilities serving children.

- Facilities using open radioactive materials must be located downwind from residential areas, facilities serving children, social organizations, recreational areas, nursing homes, healthcare facilities, and sports facilities.

- Around radiation facilities, if necessary, control zones (CZ) or surveillance zones (SZ) must be established to meet the requirements of industrial hygiene standards.

- The size of CZ and SZ (if any) is determined based on the external dose from radioactive dust and gases emitted from the facility, the extent of their penetration into the air, the effectiveness of the exhaust air filtration system, the prospects for upgrading the facility's operations, and meteorological, hydrological, ecological factors, etc.

The standard for determining the size of CZ is the annual limit of intake of radioactive materials through the respiratory tract and the limit of external dose for subject B (see Table A, Appendix 2 of TCVN 4397:1987). The size of SZ is usually 3 to 4 times that of CZ.

- Residential facilities serving children, hospitals, nursing homes, and even industrial facilities unrelated to radiation facilities are not allowed within CZ.

- The use of land within CZ for agricultural purposes (farming) must be permitted by the relevant authorities.

More details can be found in TCVN 4397:1987.

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