Early in the Fukushima nuclear crisis, as the Self-Defense Forces were
flying helicopter water-bombing missions over the overheating reactors,
the Prime Minister’s Office informed the Defense Ministry that the
government would raise the upper radiation exposure limit for nuclear
crisis personnel to 500 millisieverts.

The hike in the exposure limit would ultimately be rejected, but the
fight over the proposal also highlights the chaos that reigned in
government circles as Japan faced one of the most serious crises in the
history of nuclear power.

The new policy, delivered on March 17 and titled "Regarding Raising the
Upper Radiation Dose Limit," came just three days after the government
had raised the exposure limit from the usual 100 millisieverts to 250.
The proposed doubling to 500 millisieverts would have brought the
emergency upper limit in line with that recommended by the International
Commission on Radiological Protection (ICRP).

Hydrogen explosions had ripped through two of the Fukushima No. 1
Nuclear Power Plant’s reactor buildings just days before, and working in
a radioactive environment was unavoidable if the disaster was to be
brought under control.

The 250 millisievert limit was already as high as the Ministry of
Health, Labor and Welfare thought it was safe to go. Then prime
ministerial aide Goshi Hosono, however, told Akihisa Nagashima, a former
parliamentary official for the Defense Ministry, that no real work could
be done at that exposure limit, adding, "We have to get all the
government offices in line on this." Nagashima took Hosono’s demands
verbally to the ministries and agencies concerned.

On March 15, Fukushima plant operator Tokyo Electric Power Co. (TEPCO)
pulled all but 50 workers from the crippled power station. An infuriated
Prime Minister Naoto Kan contacted TEPCO executives, telling them to
become “a suicide unit.” Soon after, Kan told people around him that a
complete withdrawal from the station would invite direct U.S.
intervention to resolve the nuclear crisis.

The response at the Defense Ministry to the March 17 letter from the
Prime Minister’s Office was ambivalent, with some wondering if it was
truly an official demand. With Self-Defense Forces personnel on the
front lines of operations to get the Fukushima reactors under control,
Defense Minister Toshimi Kitazawa called an emergency meeting on the 500
millisievert exposure limit with senior ministry officials and Self
Defense Force chiefs.

At more than 250 millisieverts of radiation exposure, a person’s white
blood cell count will dip temporarily. At 500 millisieverts, lymphocyte
counts in the bloodstream drop significantly, weakening the immune
system. With this in mind, the reaction at the Defense Ministry meeting
to doubling the already raised exposure limit was emphatically negative.

"Cancer rates rise at a 500 dose. There’s no way we’re going through
with such a stupid plan," one attendee apparently said, with another
pointing out that "raising the limit to 500 just after setting it at 250
will make people wonder what’s really safe. On-site personnel won’t know
what to believe anymore."

Meanwhile, after receiving the policy notification from the Prime
Minister’s Office, a senior official with the Ministry of Economy, Trade
and Industry’s Nuclear and Industrial Safety Agency (NISA) told staff to
"be prepared to raise the upper exposure limit to 500 millisieverts at
any moment." NISA also began coordinating with the Ministry of
Education, Culture, Sports, Science and Technology to have the
ministerial ordinance governing the radiation limit amended by a
radiation commission under the science ministry’s jurisdiction.

At just past 6 p.m. on March 17, Kan and Hosono met with Kitazawa,
Minister of Health, Labor and Welfare Ritsuo Hosokawa and Minister of
Economy, Trade and Industry Banri Kaieda to talk over the exposure limit.

“So, can we raise the limit to 500 millisieverts?” Kan asked the
assembled men, to which Kitazawa said, "A hasty jump would not be a good
idea."

Under ICRP recommendations, exposure of up to 500 millisieverts should
only be risked to save lives in emergencies.

"If down the road a major explosion happens or is possible, then that
situation needs to be communicated to the Japanese people," read a
message sent to the Prime Minister’s Office summarizing the Defense
Ministry’s position on the exposure limit. "If there is no such risk,
then the ministry believes there is no need to raise the radiation dose
limit."

The Prime Minister’s Office denied there was any risk of further
explosions at the plant. And thus, in the end, the 500 millisievert
limit never became a reality for the workers struggling to tame the
Fukushima reactors.

The struggle over the 500 millisievert dose, however, highlights the
terrible confusion and disorder within the government during the
unprecedented nuclear crisis. In fact, resolving this confusion came to
displace the safety of workers on-site as the central concern of the
government.

Mainichi Shimbun , July 25, 2011
http://mdn.mainichi.jp/mdnnews/national/archive/news/2011/07/25/20110725p2a00m0na009000c.html