December 27, 2013

One of the incorrectly used terms often used concerning the Fukushima accident is “hot particle”. It was first applied to Fukushima by America’s inimitable antinuke Arnie Gundersen a few weeks after it all began, when a few traces of Plutonium were found in the environs very near the nuke station. It was picked up by many noted prophets of nuclear energy doom, like Michio Kaku and Helen Caldicott, and continues to be part-and-parcel to many Fukushima scare-stories posted on the Web to this day. What is missing, in every case, is a definition of the term/phrase. It unquestionably has an alarming sound to it, but what does it really mean? By examining its most-possible meaning, we find the application of the phrase to the atmospheric releases from Fukushima is entirely inappropriate.
Perhaps the earliest use of the term “hot particle” was during the United Kingdom’s nuclear weapon’s tests in Marlinga and Emu, South Australia, from 1953 to 1963.1. Microscopic shards of pulverized materials containing radioactive isotopes produced by the explosions were called hot particles. When the bombs detonated, massive clouds of microscopic material from the earth beneath the blasts erupted high into the air. The dust was exposed to the intense neutron field spawned by the blast as it mushroomed vertically. Neutrons are the only type of radiation that can cause other, non-radioactive substances to become radioactive. The neutron field made the dust in the cloud radioactive.

About 99% radioactive isotopes produced (by volume) in a weapon’s detonation are not fashioned by the fissioning that occurs inside the fuel cores of nuclear power plants. 2. Most of these bomb-only isotopes are contained in tiny dust particles carried by the plume which we call fallout. Each of the particles contain many different neutron-activated materials. The half-lives of the predominant isotopes (…of Sodium, Manganese, Iron and Cobalt) are relatively short and measured in hours or days, so they are not around very long…they are literally “burned out” a few weeks after the blast. The bomb-spawned dust particles also contain small quantities of Uranium and (depending on the bomb’s core) Plutonium which have long half-lives and persist. A smaller-yet fraction of the bomb’s radioactive isotopes are fission fragments, similar to those made in reactors, but have long-enough half-lives to persist in the environment and be detected. However, the hot particles containing this buffet of isotopes from are not soluble…a key aspect of definition. They fall from the sky when they can no longer be held aloft by the post-blast meteorology…fallout!

The US Nuclear Regulatory Commission extended the hot particle definition to nuclear reactors in 1987. 3. They said the concept can be applied to “degraded fuel and neutron-activated corrosion and wear products.” They stress in 1987 (and other subsequent publications on the topic) that hot particles are not water soluble. Specifically, the NRC says hot particles can come from fuel bundles inside reactors that have cracks in their tubing which release fuel isotopes directly into the water flowing through the fuel core. These are not high-volumes being released into the power plant’s water system. Only a tiny fraction of the isotopes, those very near the edge of the fuel pins, ever leave the fuel itself. The high density of the fuel pins is a very effective primary containment. In addition the kinds of cracks in the tubing that contains the fuel pins are primarily microscopic, and the frequency of this cracking in vanishingly small. A quite effective secondary containment. Further, because of their insolubility and great atomic mass, NRC-defined hot particles cannot travel very far and will rapidly precipitate out of the air in the unlikely event they escape the plant’s multiple protective barriers…the tertiary level of containment, if you will. But, nowhere in the NRC document are individual fission products, like radioactive Cesium, included in the definition. In other words, the vast majority of radioactive isotopes released at Fukushima – Cesium, Iodine, Strontium, – should not be called hot particles.

It should be noted that the date of the NRC notification came the year after the Chernobyl nuclear accident in the Ukraine in 1986. Because of the unique plant design and accident situation involved with Chernobyl (see The Chernobyl Disaster in the left-hand menu), a considerable amount of hot particles were generated and deposited within a few kilometers of the calamity. For all intents and purposes, the reactor at Chernobyl was blown apart and microscopic pieces of the tanks surrounding the fuel core, support structures, and fuel-itself inside the reactor compartment (they had no pressure vessel around the core) were ejected into the near-environment for the better part of 10 days. It should also be noted that the NRC’s application of hot particle protection was probably influenced by a passing mention of England’s 1957 Windscale fire in the IAEA document (above). The IAEA report also includes fissile materials at nuclear production facilities for nuclear-weapon programmes in their definition.

We should also keep in mind that all reputable sources emphasize that hot particles are all Beta (β) radiation emitters. There is no mention of gamma (ɣ) radiation emitters. This adds yet another reason why applying the notion to individual isotopes like Cesium-134 and Cs-137 cannot be correct. The same goes for Strontium-90. Why? Because all three isotopes are β and ɣ emitters. Because hot particles are only β emitters, they are primarily (but not exclusively) external hazards with high concentrations found in locations near bomb blasts, such as Hiroshima/Nagasaki, and living near Chernobyl in 1986. But none of the recognized hot particles can be correctly, appropriately applied to the radioactive releases of the accident at Fukushima Daiichi…except for the traces of Plutonium found very near the nuke station.

While there is no universally-agreed-upon definition of “hot particles” 4., there seems to be a reasonable meaning that can be gleaned from the bunch…hot particles are small, discrete, highly radioactive particles capable of causing extremely high doses to a localized area in a short period of time. Our inquiry further shows that the term can only be correctly used in reference to one nuclear power plant accident in the world…Chernobyl. Arnie Gundersen cavalierly used the term with Fukushima when traces of Plutonium were found in the near-station environs to F. Daiichi. Plutonium is one of many long lived isotopes found in multi-element, bomb-spawned hot particles.

As is his modus operendi, Gundersen extended and confabulated the kernel of truth by applying it to all radioactive isotopes from Fukushima. He has also done this with his use of trace Cesium levels from nuclear weapon’s detonations to the total Cesium presumed to be in the F. Daiichi spent fuel pools, then positing there’s a massive number of Hiroshima bombs at F. Daiichi waiting to happen. He’s a snake oil salesman of fear, and he’s eminently successful at exploiting the myths and misconceptions common to the world’s nuclear-averse demographic. Gundersen, and those of his ilk, demonstrate that exploitation of the Hiroshima Syndrome’s prime causality – confusion between reactors and bombs – is effective and profitable!


  1. Danesi, Piero Roberto; Hot Particles & The Cold War; IAEA Bulletin; April, 1998.
  2. Operation Redwing: Project 2.63: Characterization of Fallout; March 15, 1961; ppg 222-223.
  3. Control of Hot Particle Contamination at Nuclear Power Plants; US Nuclear regulatory Commission Information Notice 87-39; August 21, 1987.
  4. Hansen, Rick; May 19, 2010.