The old rusty pipes at Daiichi? They may not last the entire decade TEPCO says they need to cool the melted fuel. The SimplyInfo.org research team looked at various factors involved in the accident and the long term use of out of balance water to cool both the reactors and the spent fuel pools.
TEPCO's best case scenario to remove all the fuel from the spent fuel pools is ten years. Two unused fuel assemblies removed from unit 4's spent fuel pool showed signs of moderate corrosion. Older used assemblies and other parts of the pool may not be even faring that well as various factors such as circulation and sediment cause uneven corrosion within the pool.
The research found accelerated corrosion from the injected seawater, age of the metal in the reactors (34-42 years) and the ongoing out of range water chemistry. This could cause metal pipes or other critical metal parts to fail in as little as 3 years under certain circumstances.
Since TEPCO can not send human workers deep into the reactors now or at any point in the near future, replacing reactor vessel pipes is not possible. Degraded metal on fuel assemblies or other critical parts of the spent fuel pools could drastically increase the risks and complexity of trying to remove the used fuel from the pools.
While TEPCO has taken steps to lower the salt levels in the water being used to cool the reactors and fuel pools, extremely high salt levels existed for a considerable amount of time. Other factors of the water chemistry remain seriously out of spec adding to the ongoing degradation.
The SimplyInfo.org research team has issued a new set of papers on corrosion factors at Fukushima Daiichi.
The main paper “Spent Fuel Pools At Fukushima; Follow On Report – Corrosion“ looks at corrosion factors in the spent fuel pools at Fukushima Daiichi, it also looks into the ongoing corrosion of pipes still in use to cool the melted down reactors. This paper also looks at the factors such as the long term impact of sea water injection at the plant and the ongoing uncontrolled water chemistry. For a more basic overview of how corrosion happens within the systems at Fukushima Daiichi, the companion paper “Corrosion At Fukushima Daiichi Explained” is included.
The corrosion issues at Fukushima Daiichi are concerning and merit more immediate action to mitigate the potential consequences.
Both papers can be found at the links provided or a complete PDF of both papers can be downloaded here
SimplyInfo.org Corrosion At Fukushima Daiichi
TEPCO has found themselves overwhelmed by the disaster and in many cases has done the bare minimum needed to save money or deal with limited manpower issues. TEPCO knows corrosion is a problem. They either have not grasped the magnitude of this problem or hope to ignore it until it can no longer be ignored as they have with other issues at Daiichi.