Occupational Protection against Exposure to Radioactive Sources and Electromagnetic Fields in the Offshore Petroleum Industry
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The objective of the Master Thesis has been to provide an overview of the radioactive sources and Electromagnetic fields (EMF), existing on offshore petroleum installations from the Norwegian continental shelf (NCS). It has also been of interest to describe how offshore workers handle these radiation sources, which are the associated health hazards and which are the most efficient protection measures against exposure. The report contains a literature research of the most recent national and international publications relevant for the topic; a collection of interesting data from the literature study, from the interviews of various experts within Health, Safety and Environment, and from a workshop where the participants have shared their personal experiences with radiation protection offshore. Moreover, the literature research also provides an overview of important radiation concepts, of measuring units used in the assessment of exposure, of statutory requirements and means of identifying and prioritising protection measures. The thesis is accompanied by two digital databases that have been created in conjunction with the data collection realised. One of the databases provides the mapping of radioactive sources used in the offshore petroleum industry, while the other one includes a similar mapping for the EMF. Both of the databases contain significant information from the literature study and from the workshop attended about: the properties of almost 40 mapped radiation sources, efficient protection measures and interesting practical experiences. Moreover, the databases have been sent to experts for quality assurance and new inputs. Furthermore, the results from the data collection have been thoroughly discussed in order to highlight the most critical radiation sources on the NCS and efficient barriers against exposure. The results show that among the most hazardous radioactive sources on the NCS there are: industrial radiography, well logging by use of neutron and gamma radiation, installed gauges, intelligent pigs , radiotracers, as well as the natural occurring radioactive material (NORM) formed in gas and oil equipment. EMF are divided into: Static magnetic fields (SMF), Extremely low frequency electric and magnetic fields (ELF) and Radiofrequency electromagnetic fields (RF). Among the most important sources of ELF, there are: generators, low and high voltage transformers, low-voltage switch gear room, the drive space, as well as power supply cables to or from the shore. RF sources highlighted in the studied literature and by experts are: the X-band and S-band maritime radars and the Radio Link communication antennas, while strong SMF are generated by powerful electric motors. Protection measures against exposure to radioactive sources are based on restricting as much as possible the total dose people receive throughout their lives and thus, the likelihood of developing cancer and genetic damages. Most of the barriers are related to radiation protection principles like: maximising the distance from the radiation source (radiation doses decrease rapidly with the square of the distance), minimising the exposure time and shielding the source. Moreover it is particularly important to avoid inhaling or ingesting radioactive material, such as NORM dust. Barriers against exposure to ELF are mainly based on avoiding acute biological effects, such as the excitation of muscle and nerve cells, with possible but nevertheless, uncertain impact on e.g. the development of Alzheimer s. Protection measures are also aimed at avoiding health effects such as the increased risk for leukaemia caused by long term exposures to high magnetic fields. A possible long term biological effect of strong SMF, is their impact on the expression of certain genes, primarily in mammalian cells. Most of the barriers against exposure to ELF and SMF are based on the radiation protection principles of maximising the distance from the source and minimising the exposure time, since the level of exposure to EMF decrease also with the square of the distance. Strong magnetic fields are normally difficult to shield. Protection measures against exposure to RF are related to biological effects such as tissue damages after a temperature increase in the body of 1-2 oC, caused by extremely high exposure levels. There are several hypotheses about the RF s exact short term and long term health effects but none of them is well established. Thus, most of the barriers are based on a precautionary strategy, and they are primarily related to the principle of minimising the exposure time to avoid tissue heating, maximising the distance from the source, and to design solutions such as directing the transmission of antennas away from manned areas. Radiation protection is a wide subject, thus, there are many possible recommendations one could give with respect to efficient protective measures. One strategy that applies for both radioactive sources and for EMF is: to use radiation sources only if they are justified and to restrict the exposure levels as much as reasonably achievable. Apart from keeping in mind these three factors: distance, time and shielding against the radiation source, one should always make sure that workers have adequate training and that there is maintained a good level of communication, experience exchange and risk awareness within the organisation and across the industry. Moreover, priority should be given to design and organisational barriers at the source and the use of personal protective equipment must be always considered as a last resort.