The purpose of radiation shielding is to limit ionizing radiation exposures to employees and members of public to an acceptable level. Radiation shielding and other protective means should be designed and evaluated on the premises project development process. The requirements for such premises are listed in the Lithuanian Hygienic Standards. These requirements are necessary for classification of premises, physical protection, radiation monitoring installations and etc.

The most important requirement is related to barrier thickness, which protect employees and members of public from the ionizing radiation. Planning concept involves the use of shielding options dictated by knowledge of the sources of radiation in a facility, size and purpose of the premises, usage of the adjacent areas, the occupancy and etc.

Information about shielding calculations is given in:
1. Methodical recommendations “Shielding calculations for medical x-ray diagnostic procedure rooms”, author G. Morkūnas, Vilnius, 2001.
2. Lithuania Hygienic Standard: HN 95:1999 “Radiation protection and quality assurance in x ray therapy”.

Shielding calculations for all kind activities related with x-ray usage, is calculated according to recommendations given in “Shielding calculations for x-ray diagnostic procedure cabinet”. These calculations are not simple and should be carried out by qualified experts in radiation protection, well informed about the specifics of these activities and their premises peculiarities.

Radiation Protection Centre (RSC) performs an expertise of the projects in regard of radiation safety. Therefore, calculations presented by applicant are recalculated by RSC specialists in order to evaluate the project’s validity and correctness.
Comprehensive information is need for fast and accurate projects expertise. Information required RSC from applicant:
1. Daily workload;
2. Weekly workload;
3. Operating voltage;
4. Primary radiation beam properties;
5. Exposure rate for residents and workers;
6. Average tube current and exposure time product;
7. Average amount of time spend in the irradiated area during one examination (t, s);
7. Distance from radiation source to scatter;
8. X-ray field area;
9. a - ratio of scattered to incident exposure.
10. Shielding materials, their thickness and densities;
11. Purpose and occupancy of adjacent areas;
12. Distance from radiation source to shielding calculation points;
13. Pb equivalents of shielding for primary and secondary (scattered and leakage) radiations;

If different x-ray radiation sources are being used in the same premises, it is need to evaluate influence of all sources to total exposure. All information used by applicant for shielding calculations is required. Applicant has to write shielding thickness and materials, Pb equivalents and other required information in the Description. It is necessary indicate all other protection means intended to use during work time too. Documents, that secure protection of employees and members of public from the ionizing radiation, should be presented to RSC by general order. These documents are:
1. Calculations witch proves selected solutions;
2. Technical specifications of solutions;
3. Schemes and schemas of solutions.

Last update 15.03.2011