The Hiroshima High Court ruling judged that if Mt. Aso, an active volcano located about 130 kilometers from Ikata NPP Unit 3, erupts cataclysmically, pyroclastic flows may reach the NPP, and that Shikoku Electric Power failed to prove the safety of the reactor in such a situation. The Japanese Nuclear Regulation Authority (NRA) had confirmed that Ikata Unit 3 complies with the new safety regulations concerning the influence of volcanic events, but the High Court ruling judges the NRA’s confirmation illegitimate and ruled that Unit 3 should be suspended. The ruling nevertheless states that the new safety regulations are legitimate concerning measures against earthquakes and terrorist attacks and that Unit 3 complies with the regulations concerning those risks. The High Court ruling thus supported the NRA’s approval of Unit 3 in these respects.
The Ikata NPP is located on Ehime Prefecture’s Cape Sata Peninsula, facing the Seto Inland Sea, in the southwestern part of Japan. The plant originally had three reactors, and among them, Unit 1 (PWR, 56.6 kW), which started operations in September 1977, discontinued service in May 2016 and is scheduled to be decommissioned. The plant currently has two operable reactors: Unit 2 (PWR, 56.6 kW, start of operation March 1982) and Unit 3 (PWR, 89.0 kW, December 1994). Unit 3 is one of the five reactors whose operations restarted earliest in Japan after the Fukushima Daiichi NPS accident. The reactor restarted in August 2016, loaded partially with MOX fuel.
In response to the forthcoming restart of the Unit 3 reactor, residents living within 100 kilometers of Ikata NPP (including those living in Hiroshima City and Matsuyama City) filed a petition for a temporary injunction to suspend its operations with the Hiroshima District Court in March 2016, citing the dangers of the Ikata NPP and questioning the legitimacy of the NRA’s new regulations. The Hiroshima District Court turned down the petition in March 2017, and the residents filed an immediate appeal to the Hiroshima High Court.
Concerning the date of expiry to the period of suspension set by the High Court, the plaintiff attorneys say that the other lawsuit at the Hiroshima District Court has just started and that there is almost no possibility that any ruling will be issued before the expiry of the suspension period, and that therefore the High Court ruling is illegitimate in this respect. Temporary injunctions seeking the suspension of Ikata Unit 3 have also been filed in Ehime, Oita and Yamaguchi Prefectures along with Hiroshima, and this recent ruling at the Hiroshima High Court will influence the ensuing rulings.
In response to the Hiroshima High Court ruling, Shikoku Electric Power has taken judicial actions seeking the overturning of the ruling, including filing for a stay of the execution of the temporary injunction and an objection to the temporary injunction. Ikata Unit 3 had entered a regular inspection period in October 2017 and was scheduled to restart at the end of January 2018, but is currently in a state of standstill.