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Monju inspection a "long drawn-out process"

 July 21, 2013


Govt's nuclear fuel cycle policy teeters on edge as onsite Monju inspection completed



An expert team investigating geologic faults below the Monju prototype fast-breeder reactor has announced that the deliberations will be a drawn-out process, casting further uncertainty on the national government's nuclear fuel cycle policy.

Among the five-person panel appointed by the Nuclear Regulation Authority (NRA), four members spent two days investigating the activity of shattered zones, or zones of crushed rock, and whether they could possibly shift in the future.

The panel will wait for its fifth member, Chiba University professor Takahiro Miyauchi, to complete an onsite visit since he was unable to participate in the two-day inspection. An assessment meeting will then be convened as early as late August.

NRA Commissioner Kunihiko Shimazaki, who heads the panel, hinted that the process is expected to take time. "This is not a situation where we will be able to draw a quick conclusion," he said.

The Monju prototype fast-breeder reactor -- a central pillar of the government's nuclear fuel cycle policy -- is subject to the same new safety standards as other nuclear reactors. As such, key facilities are prohibited from being installed above active faults.

Eight shattered zones have been found directly beneath the Monju reactor. One of them runs for 250 meters directly underneath an auxiliary facility housing equipment that exchanges the sodium used to cool down the reactor. In the latest survey, the expert panel inspected the shattered zones that appeared in a ditch dug nearby, and also collected clay from the site.

Panel members have said, however, that the sample available to them is insufficient in identifying the timeline when the faults were active -- a crucial factor in determining whether the faults remain active today. Consequently, they have called for an expansion of the inspection site.

The panel also inspected an active fault called the Shiraki-Nyu fault that runs north and south some 500 meters from the western edge of the Monju. Experts have pointed out the possibility that this active fault could move together with the shattered zones within the Monju grounds. Because the Shiraki-Nyu fault slants underground, it runs below Monju about 850 meters below the surface of the ground.

Panel head Shimazaki said, "One of the challenges we face will be to determine whether the facility can tolerate the shocks from an earthquake (caused by this active fault)."

Among additional surveys the panel will carry out, seabed investigations in waters surrounding Monju are expected to take a particularly long time to complete. A fixed fishing net has been installed in the spot designated for inspection, and will not be removed until November at the earliest.

The existence of active faults has been a key factor in deciding whether nuclear plants will be reactivated.

This past May, the NRA acknowledged that a fault running directly underneath the No. 2 reactor of the Tsuruga Nuclear Power Plant in Fukui Prefecture, operated by the Japan Atomic Power Co. (JAPC), was active. In response, JAPC filed an objection based on the Administrative Appeal Act.

"We will promptly handle the additional investigations that have been suggested, and prove that the fault is not active," Monju deputy director Makinori Ikeda said.

Even if the NRA concludes that the faults are active, the Japan Atomic Energy Agency (JAEA) is likewise expected to respond with an all-out defensive, delaying any hope of a swift resolution even further.

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