Contaminated Water Issues Remain at Fukushima

by ThinkReliability Staff

High levels of contaminated water leaving the highly damaged reactors at the Fukushima Daiichi nuclear power plant in Japan are creating issues for the personnel on site, who are working frantically to keep the reactor safe and working towards decommissioning and closing down the site.  Additionally, there is continued concern for the ongoing safety of the site, as the high volume of water could potentially threaten the safety of the reactors.

We can look at these issues in a Cause Map, or visual root cause analysis.  With a Cause Map, the first step is to determine how the issue impacts the organization’s goals.  In this case, we can consider the goals from the perspective of the utility company that owns the power plant.  There is an impact to the safety goal because of the potential risk for another accident, according to the Chairman of the Nuclear Regulatory Authority.  The leakage of contaminated water is an impact to the environmental goal.  There is concern about the lack of a comprehensive plan by the utility, which can be considered an impact to the customer service goal.  The massive construction efforts required to install tanks to store the water are an impact to the property goal and the efforts by the workers to control the flow are an impact to the labor goal.

Once the impacts to the goals have been determined, the next step is asking “Why” questions to determine the cause-and-effect relationships that led to the incident.  In this case, the issues resulting in the high rate of contaminated water needing to be stored are that high rates of water are entering the reactor, becoming contaminated due to the damage inside the buildings from the earthquake and tsunami on March 11, 2011, and the water has to be removed from the building.

The water is entering the buildings because the plant is in the groundwater flow path from the mountains to the ocean and there is insufficient protection to prevent the water accessing the plant.   Severe cracking in the reactor buildings from the earthquake/tsunami are unable to be repaired due to the high residual levels of radioactivity.  The utility rejected plans to build a wall to protect the reactor.  It is believed this is because the utility had planned to dump the water into the ocean.   Additionally, according to the Japan Atomic Energy Commission, the issues from the water weren’t something that were thought of, as the focus was on the nuclear issues.  All involved in the cleanup, including the utility, have had their hands full, so it’s likely something as benign-seeming as water just wasn’t on the list of immediate concerns.

The contaminated water must be pumped out of the building to avoid swamping the cooling systems, which are still needed to remove decay heat that continues to be produced even after the reactors are shut down.  It appears that the original plan was to filter the water and dump it into the ocean, but even after filtering, a high level (about one hundred times the level released from a healthy plant) of tritium would remain.  Public outcry has ended the possibility of being able to dispose of the water that way.  Wastewater pits originally built for this purpose were found last month to be leaking, necessitating the installation of hundreds of tanks for water storage.

For now, the utility workers continue to install tanks to hold the radioactive water.  The task is so overwhelming, it’s not clear if there are any other plans to try and slow the tide of contaminated water.  However, outside experts are attempting to provide assistance.  The International Atomic Energy Agency completed its initial review of the decommissioning plans last month.  The final team report is expected later this month.

To view the Outline and Cause Map, please click “Download PDF” above.  Or click here to read more.