Traces of radioactive iodine linked to quake-hit Japan's nuclear power plant have been found in rainwater samples taken last week in Massachusetts, US.However, what the story doesn't cite is the plutonium seeping into water & ground. Plutonium (alpha emitter) can decay into far more deadly materials after after a short period of time. Plutonium-241 can decay into Americium-241, which is a gamma-ray emitter.
The low level of radioiodine-131detected in Massachusetts rainwater samples is comparable to the amounts found in California, Washington and Pennsylvania.
What are alpha emitters? From Princeton:
An alpha particle consists of two neutrons and two protons ejected from the nucleus of an atom. The alpha particle is identical to the nucleus of a helium atom. Examples of alpha emitters are radium, radon, thorium, and uranium.So, those workers at the plants are dead ducks. And everything leaking into the ground & water could mutate into gamma emitters.
Because alpha particles are charged and relatively heavy, they interact intensely with atoms in materials they encounter, giving up their energy over a very short range. In air, their travel distances are limited to no more than a few centimeters. As shown in the following illustration, alpha particles are easily shielded against and can be stopped by a single sheet of paper.
What are gamma emitters? From Idaho State University:
After a decay reaction, the nucleus is often in an “excited” state. This means that the decay has resulted in producing a nucleus which still has excess energy to get rid of. Rather than emitting another beta or alpha particle, this energy is lost by emitting a pulse of electromagnetic radiation called a gamma ray. The gamma ray is identical in nature to light or microwaves, but of very high energy.
Like all forms of electromagnetic radiation, the gamma ray has no mass and no charge. Gamma rays interact with material by colliding with the electrons in the shells of atoms. They lose their energy slowly in material, being able to travel significant distances before stopping. Depending on their initial energy, gamma rays can travel from 1 to hundreds of meters in air and can easily go right through people.
It is important to note that most alpha and beta emitters also emit gamma rays as part of their decay process. However, their is no such thing as a “pure” gamma emitter. Important gamma emitters including technetium-99m which is used in nuclear medicine, and cesium-137 which is used for calibration of nuclear instruments.