Dangerous levels of radiation are preventing nuclear workers and emergency responders from safely approaching the facility's four reactors to control fires and assess the extent of damages.

已经达到危险级别的辐射污染使核电站工作人员和紧急反应人员无法安全地接近设施中四座受损反应堆，控制火势和评估危害程度的工作无法进行。

youdao

Professor Links says workers within the nuclear plant are the only people at risk of extremely high doses of radiation.

VOA: special.2011.03.16

The U.S. Nuclear Regulatory Commission limits the exposure of U.S. nuclear workers to no more than 5 rem per year.

WSJ: Japan's Nuclear Crisis Escalates

The annual total radiation exposure for nuclear workers in Japan is 250 milliseiverts (raised from 100 ms just after the earthquake).

FORBES: First Videos From Inside Fukushima Reactor Buildings Show Extensive Damage

With a limited number of trained nuclear workers, TEPCO, the owner of the plant, is rotating workers after far shorter periods.

FORBES: Radiation Dangerously High Inside Japanese Nuclear Power Plant