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Japan: nuclear scandal widens and deepens

Nuclear Monitor Issue: 

(October 4, 2002) The scandal affecting the Japanese nuclear industry has widened to include utilities Chubu Electric, Tokohu Electric and Japan Atomic Power Co., which have also failed to report faults in their reactors. Meanwhile, for Tepco, the utility originally affected, the scandal has grown deeper, with allegations that a 1992 test of the leak rate of a reactor containment vessel was faked.

(574.5441) WISE Amsterdam - After it was revealed that Tepco had falsified inspection reports at three of its nuclear power plants for years (see WISE/NIRS Nuclear Monitor 573.5436, "Japan: whistleblowing turns into tornado"), other utilities began to investigate if they too had failed to mention defects in reports. Soon, two utilities, Chubu Electric and Tokohu Electric, reported that they too had left out details of faults in their inspection records.

Chubu is Japan's third largest power company, and halted all its reactors after admitting it had failed to report signs of cracking in water pipes of reactors 1 and 3 at its Hamaoka plant to the authorities. The largest of these, in Hamaoka-3, was 60 millimeters long and 3 millimeters deep, in a pipe around 40 millimeters thick.

The failure of Chubu to notify the authorities of the crack indications in water pipes is all the more worrying because of recent incidents involving pipes at Hamaoka. Last year, a water pipe at Hamaoka-1 exploded, releasing radioactive steam into the containment building (see WISE News Communique 558.5339, "Japan: a 'grave situation' at Hamaoka BWR"). This year, sixteen workers were irradiated after a water pipe leak at Hamaoka-2 (see WISE/NIRS Nuclear Monitor 569.5411, "Japan: More problems at Hamaoka").

In addition, inspections at another Hamaoka reactor revealed a 45-centimeter crack in the core shroud - a steel cylinder surrounding the reactor core of a boiling water reactor (BWR). The core shroud is the same location where cracks were found in Tepco reactors and covered-up - sometimes literally, with vinyl sheets (!) - in the past.

Cracks in core shrouds could lead to a catastrophic scenario in the case of an earthquake (see WISE News Communique 483/4.4802, "Nuclear power and earthquakes"). When an earthquake shakes the reactor, it can dislodge steam bubbles that are forming on fuel rods. Their place is then taken by extra cooling water, which acts as a moderator, slowing down neutrons so that they can cause fission of additional uranium-235 atoms. This leads to a power surge, which normally can be stopped by a "scram" (automatic insertion of control rods into the reactor). However, if a core shroud is cracked, the earthquake could cause it to break and prevent the control rods inserting properly, leading potentially to a meltdown.

Citizens' groups are pushing for the closure of Hamaoka, which lies at the center of the seismic source area of the anticipated Tokai Earthquake. The recent revelations of core shroud cracking make this situation even more urgent, and will lead to pressure on Chubu not to restart any of the four Hamaoka reactors.

Tohoku Electric, Japan's fourth largest power company, announced on 20 September that they had failed to report cracks found in recirculation piping at Onagawa 1 back in 1988. Not only that, but during the reactor's refueling and maintenance outage beginning 8 September, twelve cracks were found in the core shroud, the longest of which is 14 centimeters long.

Onagawa-1 suffered a power surge in a 1993 earthquake (see WISE News Communique 483/4.4802, "Nuclear power and earthquakes"). In 1993, the scram was successful, with the control rods inserting when the resulting power surge reached 118%. However, if a similar event occurred with cracking present in the core shroud, the results could have been disastrous.

Japan Atomic Power Co. (JAPC) acknowledged that cracks in the core shroud of Tsuruga-1 had been covered up, following inspections carried out by General Electric in 1994,1996 and 1998. Tsuruga was the scene of an accident in 1999 where 50 tons of primary coolant leaked from reactor 2, and radiation levels inside the reactor building reached 11,500 times permitted levels (see WISE News Communique 515.5057, "Tsuruga-2: Large leak of primary coolant water").

Tepco scandal deepens
While cover-up scandals have broadened to include other Japanese utilities, the allegations against Tepco, the original utility affected, have become more and more serious. They affect all 10 BWRs at Fukushima, plus some of the 7 at Kashiwazaki-Kariwa.

Cracks were covered up not just in core shrouds - the original focus of the investigation - but also in a whole variety of other reactor components. These include steam dryers (which dry the steam before it leaves the reactor), access hole covers, and components associated with the jet pumps, which circulate cooling water inside the reactor. In these cases, the inspections had been carried out by General Electric International Inc.

Later, they revealed that there were also flaws in recirculation pumps - primary cooling water pumps located outside the reactor - and their piping. In these cases, the inspections whose results had been covered up were carried out not by General Electric, but by Hitachi and Toshiba.

More serious than this - indeed, potentially criminal in some cases - were the secret repairs carried out of various components, such as the core shrouds. Nevertheless, Tepco might avoid criminal prosecution since they have since replaced the shrouds with new ones, and the Ministry of Economy, Trade and Industry (METI) did not recommend prosecution.

Another clandestine repair involved a core spray sparger (spray head) at Fukushima I-1. This forms part of the emergency core cooling system, and its correct functioning is important for the safe shutdown of the reactor in an emergency. Here again, METI has recommended against criminal prosecution.

Faked pressure test
Yet in the most serious case of all, Tepco officials are alleged to have faked a pressure test designed to test the integrity of the containment building. The test involves pumping nitrogen gas into the building to increase the pressure to about three times atmospheric pressure, then taking pressure readings to measure the leak rate.

Regulations state that the leak rate must be less than 0.45% per day. However, at Fukushima I-1 in 1992, the company conducted its own tests before the government inspectors turned up, and discovered that the building might not pass the test. One source quoted in the Daily Yomiuri said that leak rates fluctuated from 0.3% to 2.5% per day.

Documents found at Hitachi by Tepco's own investigative team describe a method to fake the test by secretly pumping in extra air from the main steam isolation valve. At the time, Hitachi had a contract to check Tepco equipment. It is alleged that Tepco officials followed this procedure when the government inspectors were checking the leak rate.

High containment leak rates have been an issue in France, where the containment vessels of 1300MW and 1450MW PWRs lack the steel liners usually found in other countries (see WISE News Communique 487.4832, "Generic problems at EDF NPP?").

IAEA criticism
Things have got so serious in Japan that IAEA officials have expressed concerns. Even the IAEA's Director-General, Mohamed ElBaradei, has been quoted as suggesting that on-going probes by the Japanese authorities might not be enough to provide reassurance.

The IAEA's criticism of Japan contrasts notably with its positive-sounding review of Bulgaria's Kozloduy 3 and 4 in July - reactors previously described by a former U.S. Nuclear Regulatory Commission official as amongst the most dangerous in the world (see NIRS Nuclear Monitor, June 1999, "A Visit to the Most Dangerous Reactors in the World").

The Japanese cover-up scandal has nixed Japan's MOX program, at least for the time being (see box "Cracks and MOX" in WISE/NIRS Nuclear Monitor 572.5431, "Japan: Tokaimura Hibakusha group files a lawsuit").

On 26 September 2002, the Fukushima governor formally rescinded prior approval for the Pluthermal (MOX) program in Fukushima. He stated, "On this occasion, we should rethink [Japan's] nuclear power policy itself, taking it back to the starting point."

The Asahi news web site reported on 26 September that it is now certain that there will be a push for reconsideration of the nuclear fuel cycle in Japan.
E-mail from Aileen Mioko Smith, Green Action

However, Japan's relationship with the IAEA has been a bitg frosty in recent years. The last time the IAEA sent and Operational Safety and Review Team (OSART) to Japan was in 1995. According to Nucleonics Week, visiting experts who took part in the OSART missions said that utility executives at Tepco and Chubu strongly resisted the recommendations voiced by IAEA experts.

According to one IAEA official, the message the IAEA received from Japanese utilities was: "We want your technical information and we want to hear about good practices, but Japan is different and so we don't want you to tell us to make changes in organization."

Even the Tokai-Mura criticality accident in 1999, which left two workers dead and a number of people injured, did not stop the Japanese nuclear industry's attempts to present an image of perfection to the world.

Nuclear experts from other countries have sometimes expressed their doubts about the claims of the Japanese nuclear industry. Representatives from other countries were surprised when Japan told parties to the International Nuclear Safety Convention last April that in the 14 plant safety reviews done in Japan during the last 3 years, no significant corrective actions were recommended.

The image of the Japanese nuclear industry now lies in tatters amid all the stories of cover-up and falsification. Yet in a sense, the real surprise is perhaps that the Japanese nuclear industry has for so long been seen as an exception to the reputation for cover-up that is common to nuclear industries in many other countries.

Indeed, it is ironic that the story has broken just as MOX fuel falsified by BNFL has returned to Britain to an uncertain future. Now first Japan's MOX program, then the future of Japan's nuclear industry itself have been thrown into question by its own, home-grown nuclear falsification scandal.


  • Dow Jones Tokyo, 20 September 2002
  • Mainichi Daily, 9 September 2002
  • Nucleonics Week, 26 September 2002
  • Daily Yomiuri, 26 September 2002
  • Asahi Shimbun, 30 September 2002
  • AFP, 17 September 2002

Contact: WISE Japan