JAPAN | Gov’t calls TEPCO radiation exposure standards ‘overly optimistic’

Posted on June 15, 2011

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JAPAN | MAINICHI | June 15, 2011

Workers install a pressure sensor inside the No. 1 reactor building at the Fukushima No. 1 Nuclear Power Plant on June 3, in this photo provided by Tokyo Electric Power Co.

Workers install a pressure sensor inside the No. 1 reactor building at the Fukushima No. 1 Nuclear Power Plant on June 3, in this photo provided by Tokyo Electric Power Co.

As the number of workers exposed to high levels of radiation at the crippled Fukushima No. 1 Nuclear Power Plant increases, the government is accusing plant operator Tokyo Electric Power Co. (TEPCO) of slack radiation dose calculations.

“From the start, the way TEPCO calculates internal radiation exposure has been overly optimistic,” a senior Ministry of Health, Labor and Welfare official stated.

On June 14, Health, Labor and Welfare Minister Ritsuo Hosokawa directed TEPCO to withdraw any worker exposed to more than 100 millisieverts of internal radiation at the disaster-stricken plant, sparking a dispute between the company and the government over radiation dose calculation standards, and delaying the implementation of worker safety-first policies at the plant.

Meanwhile, with work at the Fukushima plant — where three reactors have melted down — projected to go on for some time, uncertainty over exactly how high a dose workers there are subjected to may impact TEPCO’s public timetable for resolving the nuclear crisis.

On May 30, TEPCO revealed that two of its Fukushima No. 1 plant workers had been exposed to a higher radiation dose than the 250 millisievert emergency upper limit, though the firm did not state how much of that exposure had been from radioactive materials taken into the body.

The labor ministry had demanded that TEPCO calculate workers’ cumulative radiation exposure starting from March 12, when a hydrogen explosion destroyed the plant’s No. 1 reactor building. However, TEPCO rejected the government demand, stating, “It’s impossible to say when any internal radiation exposure occurred. If workers were on the job until the end of March, then cumulative radiation calculations should be made starting March 21, about half way between the day of the earthquake and the end of the month.”

In this May 15, 2011 photo released Friday, June 10, 2011 by Tokyo Electric Power Co. (TEPCO), workers take break in a temporary rest area at Fukushima Dai-ichi nuclear power plant. (AP Photo/Tokyo Electric Power Co.)

In this May 15, 2011 photo released Friday, June 10, 2011 by Tokyo Electric Power Co. (TEPCO), workers take break in a temporary rest area at Fukushima Dai-ichi nuclear power plant. (AP Photo/Tokyo Electric Power Co.)

Internal radiation doses are measured with a device called a “whole body counter,” which measures not only current exposure but sums up a person’s total dose over time. As such, TEPCO’s insistence on calculating total radiation doses starting from March 21 has resulted in significantly lower exposure figures than those the government is using.

“We tried to persuade TEPCO to use a rigorous calculation method but the company wouldn’t give in. In fact we’re still at odds over the issue,” the labor ministry’s standards bureau told the Mainichi.

However, TEPCO’s exposure estimates are only “provisional,” and the utility leaves precise calculations to a radiology research laboratory that uses the government’s dosage calculation standard. According to the lab, the two workers revealed on May 30 were exposed to 540-590 millisieverts of radiation internally, and 643-678 millisieverts in total.

TEPCO accepted the lab’s conclusion, and submitted a revised report of worker radiation exposure totals on June 13. In that report, six more workers were revealed to have exceeded the emergency maximum exposure limit.

However, while the utility may have accepted the lab’s, and thereby the government’s, dosage standards, Hosokawa’s 100 millisievert internal exposure limit has little scientific foundation and was a purely political decision.

Just after the revelation of the first two cases of workers exposed to radiation doses higher than the emergency limit, the labor ministry directed TEPCO to take internal radiation exposure measurements of the some 130 workers doing similar jobs. The results, reported on June 3, showed none of the 130 tested had exceeded the emergency upper limit, but there were three people who almost certainly had internal doses over 100 millisieverts. The ministry directed TEPCO to pull the three from the Fukushima plant.

The ministry furthermore stated that TEPCO’s revised radiation dose calculations from June 13 “closely reflected actual conditions.” In addition to the six workers who exceeded the maximum allowable exposure level revealed by the new figures, six more workers were shown to have doses over 200 millisieverts. Just to be on the safe side, labor ministry administrators also directed these six to be withdrawn from operations at the plant.

In this May 10, 2011 file photo released by Tokyo Electric Power Co., workers check the status of the water level indicator at the Unit 1 reactor building at the Fukushima Dai-ichi nuclear power plant in Okuma town, Fukushima Prefecture, northeastern Japan.(AP Photo/Tokyo Electric Power Co., File)

In this May 10, 2011 file photo released by Tokyo Electric Power Co., workers check the status of the water level indicator at the Unit 1 reactor building at the Fukushima Dai-ichi nuclear power plant in Okuma town, Fukushima Prefecture, northeastern Japan.(AP Photo/Tokyo Electric Power Co., File)

However Hosokawa, apparently fixated on his first June 3 directive ordering workers with internal doses exceeding 100 millisieverts be pulled from plant work, changed the administrative decision on the six workers. The change could be seen as a sign of worry that Hosokawa was pulling back set maximum dosage standards. However, a senior labor standards bureau official told the Mainichi it was “a political decision, based at least in part on TEPCO’s tendency to be slow to take action.”

Meanwhile, an attorney for former nuclear plant workers suing TEPCO has called Hosokawa’s 100 millisievert internal radiation exposure limit “too high.”

“That there hasn’t been an internal radiation exposure limit before is also a major problem,” said attorney Atsushi Suzuki, adding, “There are cases of multiple myeloma (a cancer of plasma cells, a type of white blood cell) from exposure to 70 millisieverts of annual external radiation, and cases of leukemia caused by just 5 millisieverts. The internal radiation doses Fukushima plant workers have been exposed to just leave me at a loss for words.”

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