34


Analytical Instrumentation


Dirty Bombs and Liability Exposure in the Petroleum Industry


Ray R. Fleming and Robert C. Tisdale* Email: drtisdale@gmail.com


Globally, the petroleum industry continues to employ tens of thousands of radioisotopes in activities that range from exploration and production to distribution. The presence of these radioisotope sources, in such vast numbers, represents a statistically significant opportunity for theft and subsequent misuse. Governments worldwide now regard radiological terrorism, through the use of radiological dispersive devices (RDD) - often called “dirty bombs,” to be far more likely than use of a nuclear explosive device. In the context of the recent Deepwater Horizon Incident in the Gulf of Mexico, it is incumbent on the petroleum industry to evaluate liability exposure relative to its radioisotope inventory. Whether protecting the customer base or corporate shareholders, technology now exists to largely mitigate the risk associated with previous generation isotope-based technologies.1


Radioisotope Threat


Whether for radiography, gauging or compositional analysis, a variety of radioisotopes (see Table 1) have been routinely employed in the petroleum arena for many decades. For example, americium-241\beryllium (241


Am\Be), cesium-137 (137 Cs) and californium-252 (252 Cf)


have all been employed for well logging of oil and gas wells, with respective half-lives (t½


Ir), and cobalt-60 Am or 137 ) of 432, 30 and 2.6 years.


Co), with half-lives of 74 days and 5.3 years respectively. Level and density gauges are used throughout petrochemical plants typically employ 60


Radiography devices for x-raying welds on pipelines and petrochemical plants use iridium-192 (192 (60


Co, 241 Am/Be neutron sources and/or 137 Cs.


Moisture/density devices used in construction contain smaller 241


Cs sources.


Analytical instrumentation, used for mea surements such as positive material identification, may also contain 241


or some other less common or less hazardous isotopes. 241


Am\Be produces neutrons when the 241 Am, Am emits an


alpha particle that is absorbed by the beryllium, producing an unstable carbon isotope that decays emitting a neutron. It also emits low energy gamma rays that are not very hazardous. Alpha radiation is very hazardous if inhaled or ingested. Beryllium is also highly toxic if inhaled. The hazard is such that first responders, responding to an RDD event using an alpha emitter, must wear respiratory protection as they can exceed the US Environmental Protection Agency’s Protective Actions Guidelines (PAGs) at levels that they cannot measure with the typical radiation meter that they may carry.2


The U.S. has been out of the 241 Am business for many


years and thus has created a shortage. That shortage is now at least partially being filled from Russia. The shortage will become even more critical in the future as many of the sources are over 30 years old and their special form certificates which allow them to be shipped inexpensively, are going to expire between now and November 30, 2014. Many of the companies that made the most common 241


Am\Be sources are no longer in business, so it is not clear if the certificates can be renewed. It is also not clear if they should be. One of the leading source manufacturers assigns a 15 year life, extendable to 30 years for this type of source and declines to seek a new special form certificate when sources are quite old. In the mean time, 252


Cf is being evaluated as an alternative


source since it is a very strong neutron emitter. It emits neutrons via prompt fission and, unfortunately, happens to be one of the isotopes with the lowest critical mass for fission in the metallic form, less than Uranium-235 (235 Plutonium-239 (239


U) and Pu).3 The other common well logging isotope is 137 Cs, which


emits a beta (β) particle and then a high-energy gamma ray (0.662 MeV from a 137


Ba decay intermediate).


Commonly available as a chloride salt, it is readily soluble in water, making it easy to spread but exceedingly difficult


Americium-241 Californium-252 Cesium-137 Cobalt-60 Iridium-192


430 2.6 30


5.3 0.2 (74 d) 3.5


540 88


1,100 9,200


α


α (SF, EC) ß, IT


ß ß, EC Isotope


Table 1: Basic Radiological Properties of 5 Potential Radionuclides for RDDs4 Half-Life (Years) Activity (Ci/g) Decay Mode


Alpha


5.5 5.9 - - -


Radiation Energy (MeV) Beta


0.0056


0.19, 0.065 0.097


Gamma


(α)(ß)(γ) 0.052


0.033


0.0012 0.662


1.17, 1.33 0.256 - 0.672 0.317, 0.468


SF = spontaneous fission; IT = isomeric transition; EC = electron capture. A hyphen means the decay mode does not produce that type of radiation. The radiation energies for cesium-137 include the contributions of barium-137 metastable (Ba-137m).


Suffice it to say that an abundance of radioactive


sources are in the petroleum industry inventory, at activity levels ranging from less than 1 curie (Ci) to more than 150 Ci, which is high enough to be used to effect terror and economic disruption on a large scale. To further put the situation into perspective, as of 2008 in the United States alone, companies have reported losing track of almost 1,700 radioactive sources in the previous decade. Of the very large number of sources in use at any one time, in the United States, an average of 430 sources are lost or stolen each year.5


Mass Disruption


A radiological dispersive device combines a conventional explosive device with radioactive material. It is designed to scatter dangerous but typically sub-lethal amounts of radioactive material over a general area. Such RDDs appeal to terrorists because they require limited technical knowledge to build. The primary purpose of terrorist use of an RDD is to cause psychological fear and economic disorder, leading to the popular classification of RDDs as Weapons of Mass Disruption.6


Some devices could cause


fatalities from exposure to radioactive materials. Depending on the speed at which the area of the RDD detonation was evacuated, or how successful people were at sheltering-in-place, the number of deaths and injuries from an RDD might not be substantially greater than from a conventional bomb explosion.7


effects of a theoretical RDD. Using a 16 curie 241 Am\Be


source as an example, one can easily model the effects. A ground explosion was assumed with the following parameters: one pound (TNT equivalent) charge, wind speed of 4.47 mph, neutral wind stability (Class D), a 1000 meter mixing lid (an atmospheric layer that caps the rise of the plume), and all of the 241


Am particles spread by the


device were fine enough to be respirable. The resulting radiation exposure area, exceeding 1 REM, extended out 25 km with a maximum width of 3km. This exposure is about four times the average exposure to the public from natural and medical sources of radiation, and it also equates to the EPA PAG for the first years exposure.9,10


Liability Scenarios


While it is believed that immediate human casualties associated with a radiological dispersal event (RDE) would be low, and mostly attributed to the detonation and not radioactivity, such an event is particularly dangerous in that it has the potential to cause major economic disruptions. In a potential RDE scenario in Manhattan, involving the dispersion of the amount of americium-241 used in well-logging equipment, a region two kilometers long and covering sixty city blocks was modeled to be contaminated in excess of EPA safety guidelines. As reported in a 2002 study, the Federation of American Scientists estimated that the decontamination and rebuilding costs for this situation might exceed $50 billion.11


to remediate. Radiography sources, including 192 60


Ir and


Co, are the most dangerous if used in a Radiological Exposure Device (RED) as they are quite deadly if left


unshielded. Both are high-energy gamma ray (γ) emitters: 192


Ir principally emits gamma radiation at 0.317 and 0.468 MeV and 60Co at 1.17 and 1.33 MeV. However


they are usually not deadly at distances of 10 meters or more, assuming short exposures, and are generally easy to shield and recover if left in a capsule. Both are usually distributed in a solid metal form, but can easily be made usable in a RDD.


The size of the affected area, and the level of destruction caused by an RDD, would depend on the sophistication and size of the conventional bomb, the type of radioactive material used, the quality and quantity of the radioactive material, and the local meteorological conditions. The area affected could be placed off-limits to the public for an extended period during cleanup efforts.8


A publicly available software program from The National Atmospheric Release Advisory Center (NARAC), called HotSpot, may be used to quickly determine the


June/July 2010


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