A June 18 New York Times article by Hiroko Tabuchi — “High Levels of Radioactive Strontium Found in Groundwater Near Fukushima Plant” — alerted us that Tepco has found strontium-90 and tritium well above their legal limits in the groundwater at the Fukushima Daiichi site:
Diagram from the Asahi Shimbun
Tokyo Electric Power, the operator of the stricken nuclear power plant at Fukushima, said Wednesday that it had detected high levels of radioactive strontium in groundwater at the plant, raising concerns that its storage tanks are leaking contaminated water, possibly into the ocean. The operator said it had found strontium-90 at 30 times Japan’s safety limit in groundwater near its No. 2 reactor, which suffered a fuel meltdown in 2011. The company has struggled to store growing amounts of contaminated runoff at the plant, but had previously denied that the site’s groundwater was highly toxic. If ingested, strontium-90 can linger in bones, emitting radiation inside the body that can lead, in time, to cancer.
Nuclear expert Dr. Gordon Edwards, president of the Canadian Coalition for Nuclear Responsibility, helps explain the effects of exposure to Tritium and Strontium-90.
During the Fukushima Dai-ichi disaster in March 2011, hundreds of different types of radioactive materials were disseminated into the environment.
Like all material things, radioactive substances are made up of atoms. However, the atoms of a radioactive material are unstable, unlike most of the atoms in most of the materials around us in everyday life, which are stable.
Unstable atoms are particularly dangerous.
Stable atoms don’t change. They stay the same forever. But a radioactive atom will suddenly and violently disintegrate, giving off a burst of subatomic shrapnel called “atomic radiation”.
The unit of radioactivity is “one becquerel”, which indicates that one radioactive atom is disintegrating every second. One thousand becquerels means a thousand disintegrations are taking place every second, or over 3 and a half million disintegrations every hour.
Living cells are injured or killed by the passage of the subatomic projectiles given off by disintegrating atoms, which may be one of three types, called alpha, beta and gamma emissions.
Gamma emissions are like x-rays, but more powerful. They can penetrate right through the human body. Beta emissions are quite different; they are not rays, but electrically charged particles,
and they can only travel a few millimetres in soft tissue. Alpha emissions are also made up of electrically charged particles, but those particles are much more massive and even less penetrating than beta emissions.
Each alpha particle is roughly 7000 times heavier than a beta particle. Alpha particles can be stopped by a single sheet of paper or by the dead layer of skin on the outside of your hand.
So what are the dangers of radioactivity?
The Dangers of Radioactivity
Outside the body, the main danger is from the penetrating gamma radiation. External gamma rays can cause “whole body irradiation”, although some parts of the body may get the bulk of the dose — the hands, the feet, the gonads….
But once radioactive materials get inside the body, because a person has unknowingly breathed contaminated air, or drank contaminated water, or ate contaminated food, then those radio-
active atoms are disintegrating right inside the body. Such inhaled or ingested radioactive materials are called “internal emitters”, because the gamma rays and beta particles and alpha particles
are now being given off internally, directly damaging internal cells. Occasionally, such damaged cells can turn into cancerous growths many years later. If reproductive cells are damaged, the
harmful effects can be experienced by children or grandchildren.
Decades of careful research has revealed that internal alpha emissions are about 20 times more biologically damaging than internal beta or gamma emissions, per unit of energy. In other words, a given internal alpha emission experienced by a given population will cause 20 times more cases of cancer or genetic defects than a comparable internal beta or gamma emission experienced by a similar population. (This factor is called the “relative biological effectiveness” or RBE.)
Research has also shown that in many cases internal beta emissions are more damaging than gamma emissions of similar energy. In such cases the RBE could be 2 or 3 or more, meaning that beta particles can be 2 or 3 times as biologically damaging as gamma rays.
What Do Tritium and Strontium-90 Do?
Tritium (the name given to radioactive hydrogen) and strontium-90, both mentioned in the following article, are beta-emitting radioactive materials. They give off almost no gamma rays, so they are primarily an internal hazard. Since water is essential for all living things, water contaminated with tritium and strontium-90 will be eagerly absorbed into any living organism that drinks that water.
Strontium-90 is chemically similar to calcium, very important for the formation of bones and teeth, and a key nutrient in milk. So when strontium-90 is ingested, the body eagerly stores it up in the bones, the teeth — and in mother’s milk, where it is readily passed on to the nursing infant. Since strontium-90 has a half-life of about 30 years (that’s the time required for just half of the radioactive atoms to disintegrate) it is easy to see that the beta emissions will continue for decades to irradiate the bones and the bone marrow of the contaminated individual, whether adult or infant. This unremitting radioactive exposure will increase the risk of bone cancer and leukemia (cancer of the blood).
To make matters worse, when a radioactive atom of strontium-90 disintegrates, it changes into an atom of yttrium-90 — another beta-emitting radioactive material. Yttrium-90 is not chemically similar to calcium, and so the body moves it around to other organs inside the anatomy, including the gonads, where reproductive damage can be done.
Tritium is chemically identical to ordinary hydrogen, except that it is radioactive. Since hydrogen is one of the basic building blocks of all organic molecules, including DNA molecules, some of the radioactive tritium that is ingested by a person will become “organically bound” as part of larger organic molecules. The long-term medical effects of chronic tritium exposure are still not well understood and remain the source of considerable scientific controversy.
The uncertainty about the danger of tritium is underscored by the raging debate over the so-called “permissible” concentration of tritium in drinking water. In this Japan Times article, it is stated that the contaminated ground water at Fukushima has a tritium concentration [500,000 becquerels per litre] that is 8.3 times higher than the “standard” [which in Japan is 60,000 becquerels per litre.] But in Canada, the “standard” for tritium in drinking water is 7,000 becquerels per litre, and a recent report by the Ontario Drinking Water Advisory Committee (ODWAC) gives scientific grounds for concluding that this “standard” should be drastically reduced to only 20 becquerels per litre.
So the tritium levels in the ground water at Fukushima may be 8.3 times higher than the Japanese standard, but those same levels are over 70 times higher than the existing Canadian standard, and 25 thousand times higher than the standard proposed by the ODWAC Scientific Advisory Committee.
One of the most remarkable things about atomic radiation standards is how non-standard they really are. The reason for this is simple. All these standards are arbitrary, since there is no such thing as a safe level of exposure to atomic radiation.
And it should be borne in mind that there are many dozens of other radioactive materials in the contaminated water at Fukushima, mostly beta-emitters and alpha-emitters, that are not even being mentioned by TEPCO or by the Japanese government.