Satellite image on 16 March 2011 of the four damaged reactor buildings at Fukushima.

New research shows that corrosion of reactor pipes currently being used to pump water into the reactors in an attempt to cool the melted fuel may compromise those pipes long before TEPCO plans to stop injecting water. This same corrosion may be doing considerable damage to metal parts in the spent fuel pools.

TEPCO injected seawater early in the disaster in a last ditch attempt to cool the reactors. This introduced large amounts of salt into the pipes and the spent fuel pool. TEPCO currently uses a portion of the existing reactor pipes and spray rings to pump in water.  If those fail there is no replacing them, humans can not enter those portions of the reactor and robots capable of such work do not exist.

The spent fuel pools also are at risk. TEPCO pulled two unused fuel assemblies out of unit 4′s spent fuel pool. They had moderate corrosion, older used fuel assemblies and other sections of the pool may not be faring so well. The pools have considerable sediment.

TEPCO has made some efforts to clean and remove salt from the water being used to cool the reactors. Salt remained in these systems for an extended period of time and salt deposits may still remain in places with limited water flow. Other out of spec water chemistry continues to corrode pipes and other metals involved.

The worst case scenario gives as little as 3 years before pipe failure, even using the worst corrosion factor on a new pipe (Daiichi’s are 34-42 years old) only gave it up to 7 years before failure. More investigation is needed to establish more exact failure ranges and those are ongoing. What this does highlight is the drastic failure potential currently going on and as usual TEPCO is mostly ignoring the issue.  

The 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 Corrosion At Fukushima Daiichi PDF

Photo by Digital Globe under Creative Commons license.