The first dismantling of a commercial reactor in Japan has started, ushering in a new period of decommissioning but with the same problem that has plagued the nuclear power industry for years.

No one yet has a clear idea about what to do with nuclear waste generated through the decommissioning process.

Work started on March 17 to dismantle the No. 2 reactor of Chubu Electric Power Co.’s Hamaoka nuclear power plant in Omaezaki, Shizuoka Prefecture.

The top lid of the reactor pressure vessel, which had contained nuclear fuel during its service, was removed by a crane that day.

This unprecedented phase in Japan marked the true start of the “age of decommissioning.”

The No. 1 and No. 2 reactors of the Hamaoka plant both use boiling water mechanisms for electricity production.

The No. 1 reactor, with an output of 540 megawatts, started operating in 1976, while the 840-megawatt No. 2 reactor entered service in 1978.

Chubu Electric decided in 2008 to decommission the reactors, citing the huge costs required to meet revised earthquake resistance standards for nuclear power stations.

Preliminary measures for the reactor decommissioning program actually began in 2009.

Spent nuclear fuel within the reactor buildings was transferred to storage pools for the No. 4 and No. 5 reactors on the plant’s grounds. Unused fuel has been removed from the plant site.

Chubu Electric decontaminated equipment and then started dismantling turbines, generators and parts of the reactor buildings in fiscal 2015.

The dismantling of the reactors themselves is the most important phase in the decommissioning program.

Reactor pressure vessels and internal reactor components have high radiation levels that are dangerous to humans. Therefore, robots containing advanced technology will remotely carry out the dismantling work.

Chubu Electric plans to handle the No. 2 reactor first. It will spend about 12 years taking apart both reactors.

The entire decommissioning process is projected to end in fiscal 2042 after the reactor buildings are completely eliminated.

But no decision has been made on where to send the estimated 450,000 tons of metal and concrete, plus other waste, generated through the decommissioning project.

About 20,000 tons of that total will be considered low-level radioactive waste.

Control rods are considered the most contaminated low-level waste, followed by reactor pressure vessel components. Peripheral pipes are the least hazardous.

Low-level waste should be buried underground separately based on their radiation levels and closely monitored over a period ranging from 50 years to several hundred years.

According to Chubu Electric, there is still no permanent disposal site for low-level radioactive waste from the No. 1 and No. 2 reactors. Waste generated during the dismantling work is temporarily being stored inside the reactor buildings.

About 3,770 tons of low-level radioactive waste arose from the Japan Atomic Energy Agency’s small JPDR reactor, the only fully decommissioned reactor in the country. The by-products from this research reactor in Ibaraki Prefecture, whose decommissioning ended in 1996, are still stored at the agency’s facility.

The Federation of Electric Power Companies of Japan is deliberating where to keep the most and second-most heavily contaminated low-level radioactive waste.

However, debate is progressing slowly.

“We cannot disclose any details of our discussions,” said a federation representative.

Waste with extremely low radiation levels can be treated as ordinary industrial residue under the current system, as long as its safety is ensured.

Concrete and metal with a radioactive concentration of less than 100 becquerels per kilogram are classified as “clearance materials” and are eligible for reuse.

The nation’s first corporation to process these clearance materials is expected to be established this summer, with investments from Fukui Prefecture and utilities.

Power companies have decided to shut down 18 reactors (not including those at the wrecked Fukushima No. 1 nuclear power plant). Many of the remaining reactors have been in operation for an extended period.

Decommissioning plans have successively been delayed largely because disposal sites for radioactive waste have not been prepared.

The central government’s rules include “the end of contaminated materials’ disposal” as a condition for completing reactor decommissioning.

This means utilities must secure radioactive waste disposal sites to finish their decommissioning programs, even though nuclear plant operators typically estimate reactor closures take 30 to 40 years to complete.

Against this background, deadlines for several decommissioning plans have been delayed.

The decommissioning of Japan Atomic Power Co.’s Tokai nuclear power station in Ibaraki Prefecture was initially slated for completion in fiscal 2017.

But the project has been postponed four times due to such reasons as designing a storage container for generated waste. The plan’s completion date has been pushed back 18 years to fiscal 2035.

Chugoku Electric Power Co. similarly announced a four-year postponement of its decommissioning plan for the No. 1 reactor at its Shimane nuclear power plant in Shimane Prefecture, citing delays in the opening of a reprocessing factory to accept spent nuclear fuel.

(This article was written by Fumi Yada and Keitaro Fukuchi.)