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NORM (Naturally Occurring Radioactive Material)

April 29, 2014
Naturally Occurring Radioactive Materials

Naturally Occurring Radioactive Materials

The material in this post is extracted from Chapter 7 of the book Plant Design and Operations.

NORM is found in many naturally-occurring materials, including some oil and gas deposits. When NORM is transported to the surface in production streams it can precipitate and accumulate inside tubing strings, surface equipment and piping as sulfate and carbonate deposits. NORM can also be found in refinery piping. It has been estimated that, every year, the US oil and gas industry produces roughly 260,000 tonnes of NORM contaminated sludge and scale, and around 18 billion barrels of contaminated waste fluid. NORM-contaminated materials typically contain uranium, thorium, lead and radon, and their respective decay elements (their ‘progenys’). These materials present a risk to workers due to direct gamma radiation exposure and airborne radioactive dust inhalation.

The level of radioactivity can vary significantly, depending on the reservoir rock and the salinity of brine from the well. But in general, the higher the salinity, the higher the NORM levels. Also the standards for NORM, which were set 30 to 40 years ago (and updated since), may not provide sufficient information to understand how this material may affect workers.

NORM is a concern that is outside the normal purview of those working in the process industries — they rarely have to consider radioactive contamination and the appropriate protective measures. In an interview of Scott Hahn by Decomworld (2013) he states, “One of the oil and gas sector’s more dangerous oversights is that naturally occurring radioactive material (NORM) waste can be treated as a ‘low level’ radioactive waste stream. A growing body of evidence indicates that health and environmental impacts of NORM have been well underestimated, and that NORM waste streams are increasing at an unmanageable rate.”

Regulations and Standards

NORM is not federally regulated in the United States. However, some states, such as North Dakota, do have rules covering the handling of the material.

TENORM

Where the concentration of the radioactive materials has been increased during processing, the term Technologically-Enhanced NORM (TENORM) is sometimes used. For example, during drilling the produced fluids can contain radioactive materials such as Radium 226 and Radium 228. As these fluids approach the surface changes in temperature and pressure cause barium and radium sulfates to precipitate out of solution and form scale on the inside, and sometimes the outside, of the tubulars.

Exposure

In general, personnel can work in the immediate vicinity of process equipment and piping containing accumulations of NORM without any significant increased health risk. However, the material may be a health hazard during maintenance when piping and equipment is opened and workers inhale or ingest NORM-contaminated scale, dust or sludge. Therefore, before the work starts, these materials should be disposed of properly, preferably in plastic drums that are resistant to corrosion. If the contaminated dust cannot be removed workers will need to wear respirators.

Treatment

Traditionally, final disposal methods for NORM waste have included spreading it on fields; leaving it in evaporation ponds (to leave a deadly legacy of contaminated soil and air born radioactive particles); or discharging it into the nearshore marine environment (a method still widely practiced). More recently, companies began pumping the waste back down hole and sealing it in abandoned wells, or injecting it into salt caverns.

Water / Dry Blasting

In order to remove NORM the current standard practice is to water blast, but this generates a considerable waste stream in itself, which is costly to store, and for which, in many regions, no appropriate final disposal option exists. An alternative is to use dry blasting which turns the issue of storing cubic meters of waste to liters of waste.

Safe Limits

For nuclear energy workers the allowable radiation “whole body” dose is 50 millisieverts a year. For non-nuclear energy workers, referred to as incidental workers (such as the third-party contractors), and members of the public, the maximum dose is 1 millisievert per year (1 mSv/yr) — representing about 2 to 5 chest X-rays, depending on the individual and strength of the x-ray taken. These are “gamma” exposures from a source of radiation is “known” and therefore can be calculated. NORM radiation contains alpha and beta particles so there is no way of knowing just what the safe limits ought to be.

Protective Measures

A worker exposed to NORM should wear appropriate PPE. The eyes, nose, ears and mouth are mucus membranes and are possible entries into the internal structures of the human body and so should be protected in a NORM-contaminated environment. Cuts and abrasions are also a source of entry for particulate radiation.

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