| Summary: | A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013. === In this study a dose assessment is used to demonstrate conformance to national
and international dose limits for workers and meets the Necsa ALARA goals for a
radiological repair task. The dose assessment methodology is based on
international standards, principles and criteria and involves the process of
determining radiological dose, through the use of exposure scenarios, bioassay
results, monitoring data, source term information, and pathway analysis.
The radiological task is the replacement of the leaking steam coil on the
radioactive effluent evaporator facility at Necsa. The effluent treatment facility, its
operation, the origin of the radioactive effluent and hazards associated with the
leaking coil are discussed.
The dose assessment is supported by measurement of actual radiological
conditions in the area where the task will be performed using suitable and
calibrated instrumentation. The assumptions were limited to the physical
phenomena associated with the behaviour of materials and available from national
and international studies. The importance of proper planning of all the tasks
associated with the replacement task as well as sources of inaccuracy and
uncertainty associated with the calculated doses are discussed.
The results of the assessment are evaluated in terms of ALARA, namely the safety
fundamental principles of justification, optimisation and limitation of facilities
and activities. Other dose reduction options, such as personal protective clothing
and equipment, were considered to show that the doses conform to the ALARA
objectives of Necsa and other operation optimisation measures.
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