In order to minimize the potential risks of biological effects associated with radiation, dose limits and guidelines have been established. Even though there are dose limits and administrative control levels, we strive to keep our radiation dose well below these. The ALARA program and associated work practices further reduces risks to workers by keeping doses well below the limits.
ALARA stands for As Low As Reasonably Achievable.
The ALARA concept is an integral part of all activities that involve the use of radiation or radioactive materials. This includes the design, construction and operations of existing and future research facilities. This concept includes reducing both internal and external exposure to ionizing radiation.
A CLOSER LOOK – What is “reasonable”?
The ALARA concept itself grows out of our assumption that any radiation exposure carries with it some risk. Since work that entails radiation exposure is sometimes part of some beneficial endeavor, the ALARA effort is related to balancing the assumed risks of radiation exposure against the benefit of performing the work. So “reasonable” in this context means that the risk from receiving the exposure is “worth” the net benefit of the activity. An extension of this philosophy would be the statement that “There should not be any occupational exposure of workers to ionizing radiation without the expectation of an overall benefit from the activity causing the exposure.”
In other words, ALARA means preventing unnecessary exposure as well as overexposure.
The implementation of the ALARA concept is the responsibility of all employees. The success of the ALARA program depends on each radiological worker’s attitude and actions. ALARA should be a routine element of your work in radiological areas.
The main goal of the ALARA program is to reduce both the external and internal radiation to a level that is As Low As Reasonably Achievable.
The three basic protective measures used to reduce external exposure are:
Minimizing time in a field of radiation
Maximizing the distance from a source of radiation
Using shielding whenever possible
Methods for minimizing time:
Pre-plan and discuss the task thoroughly prior to entering the area. Use only the number of workers actually required to do the job.
Have all necessary tools before entering the area.
Use mock ups and practice runs.
Take the most direct route to the job site.
Never loiter in an area controlled for radiological purposes.
Work efficiently but swiftly.
Do the job right the first time.
Perform as much work outside the area as possible.
Methods for maintaining distance from sources of radiation:
The worker should stay as far away as possible from the source of radiation.
For point sources, the dose rate follows the inverse square law. If you double the distance, the dose rate falls to ¼. If you triple the distance, the dose rate falls to 1/9.
Be familiar with radiological conditions in the area.
During work delays, move to lower dose rate areas.
Use remote handling devices whenever possible.
Proper uses of shielding:
Shielding reduces the amount of radiation dose to the worker. Different materials shield a worker from the different types of radiation.
Use permanent shielding such as non-radiological equipment/structures.
Use shielded containment (eg: glove boxes, etc.) when available.
Wear safety glasses/goggles to protect the eyes from beta radiation when applicable.
It should be remembered that the placement of shielding may actually increase the total dose (eg: man-hours involved in placement, Bremsstrahlung, etc.).
Temporary shielding (eg: lead or concrete blocks) can only be installed when procedures are used. Once temporary shielding is installed, it cannot be removed without proper authorization.
Additional methods to reduce dose:
Source reduction is another method of reducing radiation doses. Sources reduction normally involves procedures such as flushing radioactive systems, decontamination, etc. to reduce the amount of radioactive materials present in/on a system that contribute to radiation levels in an area. Additionally, the production of radioactive materials may be reduced through careful selection of materials used in and around activation sources and by practicing good housekeeping in radiological areas to prevent inadvertent activation or contamination of materials.