Risk Based Approach to NORM

1
Risk Based Approach to NORM

• Dr. Brian Heaton

2

• 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.

3
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.

4
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.

5
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.

6
Difference between Oil and Gas Operations

• Care must be taken making doserate measurements
  in gas operations because many doserate
  instruments are based on Geiger tubes which do
  not measure the gamma photon given off by
  lead-210 very efficiently and give a lower
  reading than the correct value.

7
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.

8
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.

9
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.

10
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.

11
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.

12
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.

13
Risk in Practice

• Inhalation and ingestion easily controlled by
  either normal hydrocarbon gas protection or
  wearing a P3 grade face mask.

14
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.