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information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise

About lead and dosimeters (Follow-up)

July 24, 2012


Lead used to show less radiation
Probe targets ploy to shield dosimeters

Jiji, Kyodo



KORIYAMA, Fukushima Pref. — The Health, Labor and Welfare Ministry said Tuesday it is investigating whether dosimeters worn by workers trying to contain the crisis at the Fukushima No. 1 nuclear plant were manipulated to underreport their radiation exposure and may pursue prosecution.


The ministry meanwhile told Tokyo Electric Power Co. to have all workers, including subcontractors, whose dosimeter readings were suspiciously low to come in for checks to determine their actual radiation exposure.

The announcement of the new probe followed recent revelations that five employees of Build-Up, a subcontractor based in Koriyama, Fukushima Prefecture, used lead shields at the Fukushima No. 1 plant to cover their dosimeters late last year, as Build-Up apparently tried to make their radiation readings appear lower than the actual figures.

Build-Up executive Teruo Sagara told reporters Monday in Koriyama, however, that he had no intention of having the workers use the lead shields so their dosimeters would give lower radiation readings than what they were actually exposed to, contrary to a Saturday report indicating otherwise.

The investigation into whether attempts were made to manipulate the dosimeter readings will be carried out by the health ministry's regional labor bureau in Fukushima Prefecture.

If the probe turns up violations of the industrial safety and health law, the ministry said it will send the cases to the Fukushima District Public Prosecutor's Office.

"Any law violation will be strictly dealt with," Health, Labor and Welfare Minister Yoko Komiyama told reporters.

"This is an issue that shakes the foundation of the management of workers' radiation exposure," she said, adding that if manipulations did occur, such actions would be unforgiveable.

The Nuclear and Industrial Safety Agency, which started an inspection of Fukushima No. 1 on Tuesday, said it will also check how radiation exposure is monitored and instruct Tepco to take measures to prevent any dose-reading manipulations. NISA is under the Ministry of Economy, Trade and Industry.

At a separate news conference, METI chief Yukio Edano condemned Build-Up's alleged attempt to manipulate the radiation exposure readings.

Build-Up executive Sagara, 54, claimed Monday he only wanted to reassure workers as much as possible by delaying when the dosimeters beeped frequently, warning of high radiation exposure. He added that he was among the five and that they discarded the lead shields because they were ineffective.

Sagara said that when he visited the Tepco plant in late November, he feared radiation doses there may exceed the government-set limit of 50 millisieverts per year right away.

He instructed several workers to fashion 12 covers out of lead sheets that had been disposed of at the plant.

On Dec. 1, the five worked for 30 to 40 minutes near reactor 1 with the lead-encased dosimeters in their chest pockets.

With no change in the frequency of the beeps, Sagara said he found them meaningless. He said he discarded all 12 dosimeters with lead covers in the metaldisposal site for the plant's reactors 5 and 6 on the following day.

Sagara said using the covers was his idea, and they were not used on any other day. This contradicts Saturday's report that a Build-Up executive, who was not named, again told workers last spring to use lead-encased dosimeters, and that they refused.

Sagara emphasized that he did not force any workers to use dosimeters with lead covers. He said he did not allow three employees who declined to use them to work at the site. He said this was only because he was worried they would not obey his instructions.

The workers wore backup glass badges, which measure the cumulative radiation doses during their work.

Tokyo Energy and Systems Inc., which has contracted to do work at the nuclear plant and used Build-Up, said separately that the maximum gap was 1.3-fold between the cumulative doses measured by glass badges and those based on readings of the shielded dosimeters.

"No major differences were detected," an official of the company said.

Tepco uses dosimeters to decide how long workers at the Fukushima plant can work without exceeding the government-set exposure limit of 100 millisieverts a year.

Lead is one of the major materials to shield against radiation. In the case of Build-Up, it is believed the lead shields were of a thickness that would have only reduced the radiation reading by 15 percent.

Lead covers meant to hide radiation exposure not effective, TEPCO subcontractor says




KORIYAMA, Fukushima -- The lead covers for dosimeters that several workers at the crippled Fukushima nuclear power plant used were in fact not effective in hiding their exposure to radiation, the executive of a company who instructed the workers to cheat on radiation exposure revealed on July 23.

Teruo Sagara, a director of Buildup, a Fukushima Prefecture-based construction company, told a news conference that he had decided not to use the lead covers for dosimeters after he and his workers used them once and found they were ineffective in shielding radiation. He implied, however, that he would have continued to use the lead covers if they were effective in hiding radiation exposure, saying, "If they were effective, we would have gone in the wrong direction." At the news conference, he apologized: "I am sorry for having caused you trouble."

When Sagara visited the work site with his workers in preparation for the actual task to help bring the Fukushima No. 1 Nuclear Power Plant under control on Nov. 28, 2011, he was "upset" by the warning sounds of the alarm pocket dosimeters (APDs), he said. "In order to dispel workers' concerns," he had looked for lead vests that could shield radiation, but he decided not to use them because they were too heavy. Then he thought of lead covers.

On Nov. 30, 2011, six people including Sagara himself made 12 lead covers out of radiation-shielding lead plates at the original contractor's storehouse. Sagara instructed the workers to attach them to their dosimeters on that evening.

Sagara said that he had told those workers who voiced worry, "You won't be able to work if radiation doses rise." On the morning of Dec. 1, 2011 -- the first day of their work -- Sagara removed three workers who refused to use the lead covers from the project and left them at their lodging facility. Five people including Sagara attached the lead covers to their dosimeters and carried out their work in a high-dose area. But because the lead covers were made without measuring the size of the dosimeters properly, they did not fit into the APDs. Therefore, after checking the actual radiation exposure following the day's work, the lead covers were found to be ineffective, Sagara said.

After the news conference on July 23, Sagara and Buildup President Takashi Wada visited the Tomioka labor standards inspection office in Iwaki, Fukushima Prefecture, to report what had actually happened.

Ikuro Anzai, honorary professor at Ritsumeikan University, said, "It is possible that similar things are taking place in other places. The government should deal with it as an issue related to work safety and strictly check whether actual radiation exposure is deliberately underestimated."



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