Occupational Radiation Exposure Monitoring

Purpose

The work on Occupational Radiation Exposure Monitoring contributes to the fulfillment of the following statutory responsibilities of the Agency:

To provide for the application of the Agency's radiation safety standards (the Standards) to its own operations as well as to operations under its control or supervision
To provide for the application of the Standards, at the request of a State, by rendering appropriate radiation safety services
To provide guidance and assistance for the strengthening of occupational radiation protection infrastructures in Member States

The focus is on developing and maintaining the operational services for radiation safety of the Agency and ensuring the quality of its Radiation Protection Testing Laboratory to enable the Agency's Radiation Safety Regulations, derived from the BSS, to be implemented in an effective and consistent manner. High priority is also assigned to the development, supervision and implementation, mostly under the Agency's Technical Co-operation programme, satisfaction of regulatory and operational needs and provision of services for the application the Agency's Safety Standards. The work is divided into two main areas:

Assessment of occupational exposure by individual monitoring

A testing laboratory is in place with the following objectives:

To assess the occupational exposure due to radiation of IAEA staff and Technical Co-operation experts, on the basis of individual monitoring
To assist Member States in the field of individual monitoring
To provide, in the framework of the Technical Cooperation Programme, on-the-job training and scientific visits on individual monitoring
To carry out these objectives two specialized service laboratories are available: an External Dosimetry laboratory and an Internal Dosimetry laboratory

Assessment of occupational exposure due to external sources of radiation

The External Dosimetry laboratory, managed by one professional, two technicians and a clerk, is used for processing measurements made by the Dosimeters that are used by our Customers.

Customers are workers who are normally employed in a controlled area or who occasionally work in a controlled area and may receive significant occupational external exposure. The nature, frequency and precision of individual monitoring is determined with consideration of the magnitude and possible fluctuation of exposure levels and the likelihood and magnitude of potential exposure. This concerns:

IAEA staff with duty station at Vienna Headquarters, Regional Office in Tokyo and Toronto, Seibersdorf and Monaco Laboratories
Any other worker for whose occupational monitoring the Agency is responsible in the light of the relevant parts of the Basic Safety Standards, i.e. Technical Co-operations experts and members of safety missions

Assessment of occupational exposure due to intakes of radionuclides

The Internal Dosimetry Laboratory is used to obtain measurement data on levels of radionuclides in the whole body, in organs or other tissues and of their rates of excretion, to be used as a basis for assessing intakes and for calculating committed tissue or organ equivalent doses and committed effective doses.

The Internal Dosimetry Laboratory operates a Whole Body Counter a chemical treatment laboratory and a spectrometry laboratory for urine analysis. In a low background chamber (250x180x220 cm), made of 18 cm thick steel, 1 cm Pb and 1 mm electrolytic Cu. Several detector system have been operational over few years, namely:

Four NaI(Tl) detectors for high energy photon detection replaced in 1998 by four HPGe detectors
Two "Phoswich" detectors (5"x2") with 1 mm Be window and 3 mm thick NaI(Tl) crystal, for low energy (6-100 keV) photon detection
During 2003 two Broad Energy HPGe detectors replaced all those detectors for measuring with different electronic setting the low energy and high energy photons.

A set of phantoms for the calibration of the facility is available, among them: the BOMAB, thyroid, Livermore and the knee phantoms.

The Agency's Urine Analysis Laboratory is equipped for the treatment and measuring of urine samples for gamma, alpha and beta content emitters, in three separate laboratories installed at Seibersdorf:

The gamma emitters detection is performed on urine samples, collected in one liter plastic bottles, by means of two HPGe detectors of 15 and 50 % relative efficiency relatively, in 10 cm lead shielding. Each detector is connected to a Spectrum Master Gamma Spectroscopy Workstation controlled by a PC
The alpha emitters detection is performed after chemical sample treatment. This includes alkaline earth phosphate precipitation, mineralization and separation with extraction chromatography. The source preparation is using lanthaneflorid co-precipitation and filtration on a membrane filter. A microwave digestor is used all over the process. The measurement is done by means of ion-implanted silicon detectors (3x8), in vacuum chambers of the Alpha Spectroscopy Workstation
The beta emitters detection is performed by an automatic Liquid Scintillation Counter. An aliquot of urine sample (2ml) is taken and mixed with the liquid scintillation cocktail in a 20 ml low diffusion plastic vials. The measurement is performed over 100 minutes

For further information please contact Rodolfo Cruz Suarez