Radiation Protection is an applied discipline. The purpose is to define the limits within which some human activities with potentially harmful consequence may safely be carried out.
All classified workers should have valid licence / certificate issued by, Radiation Protection Department of Ministry of Health. At least two classified persons should be employed on every radiography job (One radiographer and the other an assistant with sufficient knowledge in safe working).
The protection against exposure to source of radiation depends upon the following factors:
A) Keeping longer safe working distance from the source of radiation as far as possible.
B) Minimise the duration of radiation exposure by careful planning & execution.
C) Interposing attenuating (protective) high dense barriers such as lead sheet, steel objects etc… between the source of radiation and the operator during exposure.
MAXIMUM PERMISSIBLE DOSE (MPLS)
EXPOSED PART OF THE BODY | RADIATION WORKERS (CLASSIFIED) (DESIGNATED) | NON-RADIATION WORKERS (ASSOCIATED WORKERS-Students, Trainees between age 16-18) |
Whole body | 20 mSv (2rem) per year, Averaged over 5 yrs. Not exceeding 50mSv(5 rem) in any one year Except females (13mSv or 1.3 rems / calendar) quarter | 6 mSv (0.6 rem) |
Lens of the eyes single or with other organs | 150 mSv (15 rem) | 50mSv (1.5rem) |
Skin (100cm) single or with other organs | 500 mSv (50 rem) | 150 mSv (15 rem) |
Hands, Forearms feet and ankles single or with other organs | 500 mSv (50 rem) | 150 mSv (15 rem) |
The maximum permissible dose listed above applies to a person of age 18 years or above
In case of radiation workers it is based on the life time dose of the individual where:
D = 5(N - 18)
D = Dose (expressed in rems) absorbed by Tissue
N = Age in years
It will be noted that an individual may receive a relatively high dose of 20 mSv (2 rem) averaged over 5 years but must not exceed an accumulative dose in excess of 50 mSv or 5 rem in any one year. Dose limit for radiation worker in
STANDING INSTRUCTIONS:
The following instructions are to be rigidly adhered to by "Classified" users of "Radiography Equipment".
- Classified worker should check for the following prior to the Radiography work: Type of work, location, quantum of work, type of radiation source available & its strength, radiation monitoring, warning devices & tools such as remote operated Cee Vee tongs, transport containers to face any emergency.
- Film badges and dosimeters are to be worn at all times while handling or operating radiography equipment.
- Dosimeters readings are to be checked (prior to and following exposure to radiation), by the person(s) who is/are handling or operating the radiography equipment.
- Dosimeters readings are to be checked weekly by Inspection Engineer (Svcs) and a record kept of all such readings.
- A survey of camera and guide to be taken after each exposure to make sure that the source is in its shielded position.
- Use collimators whenever possible to reduce the useful beam to minimum size necessary for work. This is an important device for reducing the radiation dose.
- Should a dosimeter reading in excess of 0.1 rems be noted after any Radiography Equipment operation or at the end of working week, it is to be reported to Inspection Engineer (Svcs)
- When a dosage in excess of 0.1 rems is recorded, the person concerned shall cease, forthwith, to use the Radiography Equipment for an appropriate period of time (until the month end if it is with in the monthly dose limit 160 mr). Such a period will depend on the excess dosage received and determined by Preventive Medical Services.
- In case a person receives a single dosage of 3 rems or more, arrangements will be made through Health & Environment Team to get that person medically examined at Hospital. Also the film badge of the person should be sent immediately to Radiation protection department (RPD) to process & verify the dose received by the radiographer. RPD's advice to be followed.
- All classified workers who are authorized to carry out radiography work will be referred through Preventive Medical Services to Hospital for blood examination at six-month intervals and for physical examination every year.
- The radiation level at the boundary of defined barricaded (cordon off area) area must not exceed 2.5µSv / hr (0.25 m rem/hr)
- It is forbidden for personnel using radiography source to leave the equipment unattended.
- All vehicles used for the transportation or Radiography source or equipment shall have Warning Notice posted on the sides & back.
- On completion of radiography operations and before returning the source to X-Ray room pit (Safe Storage location) it is to be ensured that it is securely locked and there is no radioactive leakage in the area.
- Leakage tests shall be carried out for the radiography camera involved in any fall or damage during transportation or work to make sure the camera is safe for further use.
- Extra care shall be taken by the authorized personnel, while transferring newly acquired isotopes from "sealed storage" to "Operational Container".
- A monthly record of source movement along with used film badge will be sent to the Radiation Protection Dept., Ministry of Health before every 5th of the month, with a copy marked to Inspection & Corrosion Team.
- In case of emergencies involving radiation accidents Inspection Engineer (Svcs), TL Inspection & Corrosion (S&E), HSE team to be informed. Once the emergency has been recognized, the next step is to call the radiation protection department for assistance.
SAFE WORKING DISTANCE: THE INVERSE SQUARE LAW states that the intensity (dose rate) is inversely proportional to the square of the distance from the radioactive source. The safe distance for a classified (radiological) worker is that distance where the dose rate does not exceed 10 µSv / hr (205 mrh). For associated workers the dose rate must not exceed 0.75 mrh.
This is the distance at which three dimensional control barriers must be set up for any situation involving unclassified workers.
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