Monday, April 22, 2013

On the INL Plutonium Exposure Controversy

Warning! Do not eat the plutonium!
Recently, my mother brought an AP article published in the Idaho Falls Post-Register and the online version of The Oregonian to my attention. The article briefly discusses a complaint filed with OSHA against Battelle Energy Alliance (BEA) by two employees. In 2011, 16 employees, including the two who filed the complaint, were exposed to plutonium contamination at the Materials and Fuels Complex (MFC), which is one of the many facilities at the Idaho National Laboratory (INL) (the official Accident Investigation Report can be found here). Of course, the article actually says that they were exposed to "plutonium radiation", which once again shows that the media has no interest in learning the difference between radiation and radioactive contamination. Anyway, as part of their complaint, the two employees claim that the 2011 incident occurred after they had expressed safety concerns over several different jobs.

Let me start by saying that I don't deny that the employees involved have a genuine complaint with regards to the incident itself. Had they been assigned to work a properly planned and engineered job, the spread of contamination would have been avoided. As a matter of fact, I heard about the incident the day it happened; my first response was "why didn't they just use a glovebox?" I wasn't too surprised when I found that Table C-1 in the official report states that the problem would not have occured if they had done exactly that.

Regardless of the errors made, I have a low tolerance for the perpetuation of inaccuracies or falsehoods with regards to the nuclear field. While I could criticize or question the article's statements (and the employees' complaints if it's assumed that the article accurately reports them) on several of fronts, I want to address a detail that is completely wrong. Specifically, one of the primary examples given of a safety concern that was supposedly ignored by BEA turns out not to have been a safety problem at all in light of the radioactive properties of plutonium. The fact that the workers still believe that it was an issue shows that the January 2012 report's statement that "Workers did not understand the consequences of Pu contamination" apparently remains true. According to the article:
Twice in 2011, BEA allegedly refused to allow Stanton and Simmons to use lead shielding to protect themselves when handling plutonium. Both workers exercised their right to stop the jobs, according to the complaint.
Let me cover a few of the most basic radiation types encountered in nuclear power and then we'll see why this particular claim is entirely baseless.

Alpha Radiation: Alpha radiation or alpha decay is the emission of particles from a radioactive isotope. These particles have two protons and two neutrons and are simply helium nuclei with a significant amount of kinetic energy. However, alpha particles present very little external risk since their kinetic energy is expended after traveling through a few centimeters of air or striking something as flimsy as paper or the dead layer of cells on a person's skin. Once stopped, an alpha particle is rendered harmless. Alpha particles only become dangerous when a strong alpha-emitting isotope enters the body. Internal tissues can become severely damaged since they aren't protected by a dead layer of cells like the skin is.

Beta Radiation: Beta radiation is the emission of electrons or positrons (which have the same mass as an electron but are positively charged) from the nucleus of a radioactive isotope. Beta particles don't have as much kinetic energy as alpha particles, although they have greater penetrating power. A beta particle can be stopped by sheets of metal, plastic, or glass. While beta particles have the potential to penetrate the outer layers of a person's skin, personnel working with a beta-emitting isotope are generally protected by the plastic walls of a glove box or by anti-contamination clothing. Since beta particles can penetrate the cornea, personnel may wear goggles or a face shield to protect their eyes.

Gamma Radiation: Gamma radiation is the emission of high energy photons with high penetrating power. Dense materials such as lead or steel are typically used to shield significant gamma-emitting sources, although a generous layer of water or concrete can perform the same function.

Neutron Radiation: Neutron radiation is the emission of free neutrons that usually occurs as the result of nuclear fission. Neutrons can also be produced by exposing certain light elements such as beryllium to an alpha-emitter. Neutron radiation is only effectively shielded by water or other hydrogenous materials such as oil or polymers.

Here's where the INL workers' complaint about the lead shielding falls apart. The workers claim that they weren't allowed to use lead shielding to protect themselves while working with plutonium. However, as I mentioned above, dense shielding is used to protect against gamma radiation, which is highly penetrating. Plutonium, on the other hand, is an alpha-emitter. Unless you have a critical mass (in which case you've started a lethal fission reaction and anything short of a reactor vessel isn't going to save you), plutonium is only a threat if it gets inside your body. As explicitly stated by the EPA, the external risk presented by plutonium is very small since it emits almost no gamma or beta radiation. BEA did not endanger the two employees by disallowing them from using lead shielding since such shielding is completely unnecessary to protect people from an alpha-emitter like plutonium.

I can understand why BEA would have disallowed its employees from using lead shielding while working with plutonium. Once BEA had conceded to allowing two employees to install useless shielding because it made them feel better, the company would be compelled to use "feel-good" shielding all the time. The allowance would simply perpetuate the myth among employees that lead shielding is effective and necessary for handling plutonium. Personally, I would never engineer a job to use unnecessary shielding for that very reason, although I would make sure to explain my reasoning to the workers to avoid any misunderstandings.

There's a lot more I could say about the article and the complaint filed by the two employees (I actually deleted a third of my draft before posting because it became too long and unfocused). For example, I believe that the purported retaliation didn't necessarily have sinister motivations, although I don't have any inside sources on this matter. The employees' claim that their radiation dosage information was withheld might sound suspicious, but may simply reflect the fact that dose assessments following exposure to an alpha-emitter are very difficult to perform. Page 61 of the accident report acknowledges that the measurements needed to complete the assessment might have to made over a period of months or even years.

Nuclear power has many enemies who latch onto any accusation of safety violations in support of their cause. Much too often, these anti-nuclear groups take advantage of the public's ignorance of the science to get their way. Inaccuracies like those found in the AP article and the employees' complaint are inevitably used to frighten the public away from an effective and safe form of power.

[The above represents my own opinions and does not necessarily reflect the opinions of my employer, BEA, or the INL.]

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