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Risk Based Approach to NORM. Dr. Brian Heaton. When non specialist staff are responsible for identifying when a hazard exists the areas of concern need to be identified and focussed on. Procedures then need to be established which allow them to carry out this role. What are these?.
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Risk Based Approach to NORM Dr. Brian Heaton
When non specialist staff are responsible for identifying when a hazard exists the areas of concern need to be identified and focussed on. Procedures then need to be established which allow them to carry out this role.
What are these? • External-This is from the radiation field that exists around contaminated items or inside a contaminated vessel. Generally the latter is the highest but there are exceptions.
What are these? • Internal-Follows from the incorporation of radioactive material into the body. The main routes are by inhalation or ingestion. NORM materials are a problem because several of the daughters emit alpha particles.
Difference between Oil and Gas Operations • Only real way of establishing risk is by measurement. • Generally higher external doserates in oil operations because of radium being present in scales.
Are external doserates significant • Industrial Radiographers and Well Loggers are exposed to much higher doserates. These tend to be accepted because they are the responsibility of the contractors and have been used in the industry for many years.
Doses Received • International Standards allow non-classified workers to receive up to 6mSv/y in the course of their work. There are no daily limits. Companies should however set their own daily or yearly dose constraints or action levels. • From operations in the North Sea drilling crew and production maintenance operators receive no recordable external radiation doses. These workers are all non-classified workers.
Doses Received • Vessel cleaning crew can receive up to 2-3 mSv in a year external radiation dose. These workers are generally classified workers and are subject to dosimetry and medical surveillance.
Internal Hazard • NORM is potentially more hazardous than the radionuclides used in Hospitals, Universities and Industry because it contains alpha particle emitting radionuclides. • However the scales and silts/sands that contain the NORM isotopes are generally difficult to dissolve even using strong acids or alkalis.
Internal Hazard • The ingestion hazard is therefore not high. • The inhalation hazard is potentially high particularly for any operation that may produce fine dust particles. • The specific activity of lead/polonium-210 in gas field operations can be very high.
Risk in Practice • Very little of the sands and silts produced are small enough to be breathed in and trapped in the lungs. Only when mechanical grinding is being undertaken are these likely. (Are deposits in produced in waste water lagoons different). • Most items are wet when first breached.
Risk in Practice • Inhalation and ingestion easily controlled by either normal hydrocarbon gas protection or wearing a P3 grade face mask.
Summary • The external risk for most NORM operations is low. When not low the yearly dose received by workers is only a few mSv. • The internal risk is potentially high under some circumstances but is quite easily controlled by following procedures and wearing ppe.
