Increased Scrutiny of Power Plant Seismic Hardening

In recent years, the Japanese government has become much more cognizant of the threat posed by earthquakes to nuclear plants. The Nuclear and Industrial SafetyAgency (NISA), the former nuclear regulatory overseer that was abolished after the 3.11 disaster, had directed that geological surveys be conducted at six nuclear plants and facilities, Higashidori, Mihama, Monju (FBR), Oi,

49 The plants were the Onagawa Plant in Miyagi Prefecture struck by the August 2005 Miyagi earthquake, the Shika Plant in Ishikawa Prefecture struck by the March 2007 Noto earthquake, and the Kashiwazaki Kariwa plant in Niigata Prefecture struck by the July 2007 Chuetsuoki earthquake. In each case, the maximum ground motion caused by the earthquake was greater than the seismic design criteria for the nuclear power plants. This implies that these plants lacked adequate earthquake design standards.

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Shika and Tsuruga.⁵⁰ The surveys, however, were entrusted to the plant operators. NISA had often delegated oversight duties to the operators, including periodic inspections of the plants. In many instances, the operators conducted self-inspections with no government supervision. Reports on the Fukushima disaster including the Diet report indicate that at times operators falsified records or made no record of abnormalities. Even when government officials were present at some inspections, minor misconduct apparently was condoned (National Diet, 2012).

Since the Nuclear Regulation Authority (NRA) took over oversight responsibility in September 2012, six panels of experts have been formed to investigate the geologic faults at the six

aforementioned nuclear facilities. They have concluded so far that faults at Oi and Shika were inactive but faults at Tsuruga and Mihama were active. The owners of Tsuruga and Mihama announced in April 2015 that they plan to decommission three reactors at their plants, Tsuruga 1, Mihama 1 and Mihama 2 (See Figure 5.15). In December 2016, Cabinet ministers directed that Monju FBR be decommissioned. The JAEA submitted its decommissioning plan on 13 June 2017 to MEXT (JAEA, 2017). Higashidori was found to be located on an active fault but the operator has challenged the NRA assessment and a final assessment is not available (NRA, 2018).

 It is noteworthy that JNES, which merged with the Nuclear Regulation Authority (NRA) in March 2014, likely was concerned about the links between the earthquakes and nuclear accidents. In its 2012 accident assessment report, JNES mentioned that accidents common to Japanese boiling water reactors (BWRs) and pressurized water reactors (PWRs) during the past 50 years were due to cracking of small pipes and

nozzles from earthquake vibration and shocks, such as the 2007 July Niigata Earthquake.

JNES, nonetheless, made no mention of direct links between nuclear accidents and earthquakes (JNES, 2012b).

As a result of the Fukushima nuclear accident, NRA-sponsored geologic studies, and other economic reasons, the TEPCO CEO told the Fukushima Governor on 14 June 2018 that the company was working toward a decision to decommission all four units of the Fukushima Daini power plant (4 BWRs, 4400 MWe total) (JAIF, 2018a, 2018b). He provided no other details.

Therefore we have not yet included the four reactors in the decommissioning program (See Chapter 8).

In addition to the six nuclear plants that have been reviewed by NRA’s geologic studies , there are a number of other nuclear plants that are widely viewed as vulnerable to earthquake damage. They include Hamaoka 3, 4 and 5, which are believed to be located directly above the epicenter of the Tokai earthquake, Ikata 3, which is located on the median tectonic line in Shikoku, and all or some of the seven Kashiwazaki Kariwa reactors, which are close to various active faults.

50 The Nuclear and Industrial Safety Agency (NISA) was abolished on June 20, 2012 and was replaced by a new agency, the Nuclear Regulation Authority (NRA), under the Ministry of the Environment, in September 2012. On March 1, 2014, the Japan Nuclear Energy Safety (JNES) was integrated into the NRA.

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Figure 5.15 Seismic Risk to Japan’s Nuclear Power Reactor Fleet (best graphic available) Of 57 reactors originally built, 18 are to be decommissioned; 23 are subject to seismic risk.

Source: Created by the authors based on the data provided by the Government of Japan to the OECD. Notes are added by the authors.

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Hamaoka 1 and 2 have been scheduled for decommissioning since 2009. In the aftermath of the 3.11 Fukushima disaster, Prime Minister Naoto Kan on May 6, 2011, also ordered the closure of Hamaoka 4 and 5 because of earthquake risk (Figure 5.16). Hamaoka 3 was closed for regular inspection in November 2010 has not operated since then (JAIF, 2018b).

Figure 5.16 Epicenters of Swarm Earthquakes that Occurred Near the Hamaoka Nuclear Power Plant, August 29, 2015 to September 1, 2015

Note: The asterisk shows where the Hamaoka nuclear plant is located. The dots indicate epicenters of more than 100 earthquakes that occurred near the Hamaoka Nuclear Power Plant from August 29, 2015 to September 1, 2015. The shortest surface distance from the epicenter to the Hamaoka Plant is 2.6 km. The depth of the epicenter is shown by the color of the scale.

Source: Gtogk, 2015.

The Ikata Plant in Shikoku is located in the southern part of the Sadamisaki Peninsula in close proximity to the median tectonic line, which is one of the most prominent in Japan (See Figure 5.17). If an earthquake strikes the area causing the collapse of roads and ports and triggering a nuclear accident, about 5,000 residents living to the west of the plant could become isolated. In Ehime and Yamaguchi prefectures, more than 120,000 people reside within a 30-km radius of the Ikata plant. The operator of Ikata, Shikoku Electric, recently decided to decommission one of the three reactors at the plant. Ikata 1 is a small 566 MW reactor and is almost 40 years old (it was commissioned in 1976). It would require approximately $2 billion to upgrade the reactor to meet new regulations, according to the operator. The decision reverses Shikoku’s earlier position of planning for the restart of Ikata 1 (World Nuclear Industry Status Report, 2016).

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Figure 5.17 Locations of Nuclear Power Plants and Major Fault Lines in Western Japan Sources:

Base map obtained from “Japan Median Tectonic Line,” Wikipedia, 2017b. Notations provided by the authors.

The Kashiwazaki Kariwa plant is also exposed to high seismic risks. As discussed earlier, Professor Ishibashi pointed out that the plant registered abnormally high seismic readings at the time of the Chuetsuoki offshore earthquake on July 16, 2007. Kashiwazaki Kariwa was 19 km away from the epicenter of the magnitude 6.6 Chuetsuoki earthquake. Shaking of 6.8 m/s² (0.69 g) was recorded at the plant in the east-west direction, exceeding the design specification for safe shutdown (4.5 m/s² ) and well above the rapid restart specification for key equipment in the plant (2.73 m/s²). An IAEA team was invited for a four-day inspection in August 2007 and it provided two recommendations, which included a re-evaluation of the seismic safety standard and detailed geophysical

investigations (IAEA, 2007). The Japanese government acknowledged that it was responsible for approving construction of the first Kashiwazaki Kariwa units in the 1970s very close to what is now known to be a geological fault line (See Figure 5.18). The report was presented to the IAEA Senior Regulators' Meeting in September 2007 (WNA, 2016b).

Nonetheless, at the end of September 2013, TEPCO filed an application for safety inspections of Units 6 and 7 at its Kashiwazaki-Kariwa with the NRA, seeking restart of the two reactors. TEPCO argued that reactivation of the two advanced boiling water reactors (ABWRs), with an output of 1,356 MW each, would greatly contribute to the financial rehabilitation of the power company (Citizens' Nuclear Information Center (CNIC), 2013). On 27 December 2017, the NRA announced that Units 6 and 7 met the new regulatory standards (NEI, 2017). Local oppositions to restart of the plants, however, has remained strong. Niigata Prefecture Governor Ryuichi Yoneyama has said he will not discuss restart of the units until TEPCO develops a clear plan for the disposition of

Fukushima Daiichi, which is expected to take several years. The mayor of Kashiwazaki, Masahiro Sakurai, has also called for at least one of the plant's seven reactors to be decommissioned as a precondition to restart of Kashiwazaki-Kariwa Units 6 and 7 (Iiyama, Fukumoto, 2018).

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Figure 5.18 Kashiwazaki Kariwa Plant and its Newly Discovered Fault Lines Note: Lines A, B, C, and D represent active faults.

Source: Wikipedia, 2017c.

Besides seismic risk, the Nuclear Regulatory Authority (NRA) in 2013 initiated a study regarding the monitoring of volcanoes near nuclear facilities and the need for rapid and complete nuclear reactor shutdown capabilities in case of volcanic activities. Based on the study recommendation, NRA set up in March 2016 a Nuclear Reactor Volcano Subcommittee to assess potential

earthquake eruptions and the NRA’s authority to shut down nuclear plants. (Ministry of

Environment (MOE), 2017). Professor Ishibashi points out that earthquakes are caused not only by geologic faults, tectonic plate movements and the movements of slabs, but also by other unknown reasons and causes. He stated that earthquakes could occur even when there are no apparent causes.

Thus, it is prudent for the NRA to monitor volcanic activity and strengthen its regulatory authority over plant safety with respect to these types of indicators.

(Ishibashi, 2002).