KOEBERG like many Pressurised Water Reactor (PWR) nuclear plants, produces emissions of radioactive isotopes. The resulting ‘effluent’ is routinely released into the environment where it makes its way into the food chain. Annual allowable emissions known as the ‘Annual Authorised Discharge Quantity’ are all authorised by the Department of Energy. In some instances emissions have included unwanted radionuclides, breaching minimum emissions standards. The department monitors ‘some sixty-five radioisotopes found or expected to be found in Koeberg “effluent”

Tritium, a radioisotope of Hydrogen with a half-life of 12.3 years, is relatively abundant within the plant. According to the Nuclear Industry Association of South Africa (NIASA): “The greatest source of radioactivity in the reactor coolant circuit is, however, irradiation of the coolant itself. Neutron bombardment of nitrogen dissolved in the water gives rise to carbon-14. Moreover, irradiation of boron dissolved in the coolant water creates hydrogen-3, i.e. tritium, the radioactive isotope of hydrogen.”

NIASA boldly claims: “Even if all were discharged at the maximum (AADQ) allowed, and in the impossible event that the critical paths for all the isotopes in the liquid and gaseous effluent irradiate the same local resident, that individual would still receive less than the permitted 0.25 millisievert per year.”

The association further claims “Caesium-137 and sometimes strontium-90 are detected at levels consistent with the background attributable to global nuclear weapons testing largely in the 1960s”.

This contradicts their own findings and studies conducted by independent environmental professionals which have detected long-lived fission products such as the radioisotopes iodine-131 and caesium-137 in plant and sea-life around the installation. Both isotopes do not occur naturally and are produced as a byproduct of nuclear fission. Iodine-131 in particular is a result of fission not weapons testing, and the prevalence of these particles around the plant and not the rest of the country raises questions.

In 2010, 91 workers were contaminated with radioactive Cobalt-58. According to NIASA: “radioisotopes such as cobalt-58, cobalt-60 and silver-110m arise as a result of wear or corrosion of reactor components. They become radioactive due to neutron bombardment as they circulate through the reactor with the primary circuit cooling water.”

These radionuclides are not fission products as such, since the plant was not designed to produce them, and should rather be termed contaminants.

Radionuclides, due to their instability produce radioactivity, resulting in alpha, beta and gamma particle emission. High-energy beta particles disrupt molecules in cells and deposits energy in tissues, causing damage.

The presence of Cobalt radionuclides is particularly concerning since it points to issues which may require the decommissioning of the plant. Cobalt-58 for instance is achieved by irradiation of Nickel, and thus points to the breakdown of stainless steel components within the plant due to increased radiation levels. The decision to extend the life of the plant which was commissioned in 1984 appears to have been made on the basis of a ‘business case’, and not a scope of plant safety issues moving forward.

NIASA explains the effluent and contaminants from the plant : “The radioisotopes in the Koeberg effluent are of two types, fission products and activation products. Traces of uranium (‘tramp’ uranium) may remain on the outside of new nuclear fuel assemblies on arrival at the power station. Moreover, minute leaks may develop in the fuel in the course of operation. Both sources may contribute to fission product isotopes in the reactor cooling water, particularly the more mobile radioisotopes iodine-131 and caesium-137.”

As argued by Koeberg Alert, these fission products bio-accumulate up the food chain, via our wheat, shellfish and dairy. While iodine-131 collects in the thyroid gland, caesium-137 is bone-seeking, (it loves calcium) and may end up in the bone marrow. Eskom disclaims any responsibility for increases in leukaemia and blood cancers caused by exposure to low-dose, long-term emissions from the plant. In addition NIASA fails to explain the cumulative impact of emissions of long-lived radionuclides and appears to operate under the false assumption that every year represents a clean slate.

Half-life is the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay. Thus after that interval, a sample originally containing 8 g of cobalt-60 would contain only 4 g of cobalt-60 and would emit only half as much radiation. After another interval of 5.26 years, the sample would contain only 2 g of cobalt-60 and so on.

The annual allowable emissions from the plant are reported to have been scheduled upwards by the Minister, in order to accommodate Koeberg plant emissions and exceed European Safety Standards.

Here is information on some of the 65 radioisotopes associated with Koeberg and acknowledged by the Nuclear regulator.

CAESIUM-137

Caesium-137 is significant because of its prevalence, relatively long half life (30 years), and its potential effects on human health. Caesium-137 emits beta particles as it decays to the shortlived barium isotope, Ba-137m (half life = 2.6 minutes). Barium itself, has been linked to hyperkalemia by the US Dept of Health. Barium is a “competitive potassium channel antagonist that blocks the passive efflux of intracellular potassium, resulting in a shift of potassium from extracellular to intracellular compartments. The net result of this shift is a significant decrease in the potassium concentration in the blood plasma.”

Radioactive isotopes of caesium are a greater health concern than stable caesium and demonstrate a wide range of haematological effects. The most important exposure routes are external exposure to the radiation emitted by the radioisotope and ingestion of radioactive caesium-contaminated food sources.
Once radioactive caesium is internalized, it is absorbed, distributed, and may be excreted in the same manner as stable caesium.

The short-range beta radiation produces a localized dose while the more penetrating gamma radiation contributes to a whole body dose. “Molecular damage results from the direct ionization of atoms that are encountered by beta and gamma radiation and by interactions of resulting free radicals with nearby atoms. Tissue damage results when the molecular damage is extensive and not sufficiently repaired in a timely manner.”

CARBON-14

Carbon-14 is a low beta emitter with a half-life of 5730 years. It has low penetrating power which causes radiation stress mainly due to internal irradiation, if the 14C is incorporated. Carbon-14 is interesting from a radiobiological standpoint because it is integrated in cellular components (proteins, nucleic acids), particularly cellular DNA (Le Dizès-Maurel et al., 2009). The resulting DNA damage, involving molecular breaks, may lead to cell death or induce potentially inheritable mutations.

COBALT-60 & COBALT-58

Cobalt-60 is a radioactive isotope of cobalt with a half-life of 5.2713 years. Cobalt-58 on the other hand is a short-lived radionuclide with half-life of 70.86 days. Primarily a gamma and beta emitter, requiring protection and shielding. CDC says “Being exposed to radioactive cobalt may be very dangerous to your health. If you come near radioactive cobalt, cells in your body can become damaged from gamma rays that can penetrate your entire body, even if you do not touch the radioactive cobalt. Radiation from radioactive cobalt can also damage cells in your body if you eat, drink, breathe, or touch anything that contains radioactive cobalt. The amount of damage depends on the amount of radiation to which you are exposed.”

IODINE-131

Exposure to I-131 with half-life of 8.0197 days can cause thyroid cancer as shown conclusively by the 1986 nuclear accident in Chernobyl, which resulted in high level exposure for many people. The NCI dose reconstruction model indicates that the level of exposure to I-131 was sufficient to cause and continue to cause excess cases of thyroid cancer. Because of uncertainty about the doses and the estimates of cancer risk, the number of excess cases of thyroid cancer is impossible to predict except within a wide range.

TRITIUM

Naturally occurring tritium, with half-life of 12.32 years, is extremely rare on Earth. The atmosphere has only trace amounts, formed by the interaction of its gases with cosmic rays. The NRC therefore “agrees with national and international radiation protection regulatory agencies that any exposure to radiation could pose some health risk. This risk increases with exposure in a linear, no-threshold manner. Lower levels of radiation therefore have lower risks. The health risks include increased occurrence of cancer. Since it is assumed that any exposure to radiation could pose some health risk,” it makes sense to keep radiation doses as low as reasonably possible.

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DECOMMISSION KOEBERG NOW. NO SAFE DOSE OF CAESIUM-137, NO SAFE DOSE OF IODINE-131, NO SAFE DOSE OF COBALT-58, NO SAFE DOSE OF TRITIUM OR CARBON-14.

Tag: Emissions