Two weeks after a tsunami from Japan’s biggest earthquake in 140 years wiped out backup generators at the Fukushima Daiichi nuclear plant, efforts to restore power to reactors are progressing while radiation from them continues to raise alarm.

The plant’s common spent-fuel tank, in a separate building from the reactors, was connected to outside power Thursday, according to Japan’s Nuclear and Industrial Safety Agency. Photos from plant operator Tokyo Electric Power Co. also showed the control room of unit 1 with its lighting restored, a day after the lights came on in the shared control room of units 2 and 3.

(Video shows the Fukushima Daiichi plant soon after it was hit by a 40-foot tsunami wave triggered by the March 11 earthquake.)

TEPCO indicated it plans to restart the cooling system in unit 3 as soon as today. Recent progress in testing systems and repairing cooling equipment before switching on the power from AC lines recently run to all six units has come at a cost. According to NISA, 17 workers now have received radiation doses in excess of 100 millisieverts, with three exposed to more than 170 millisieverts. (See our Sievert to Rem Conversion Chart here.) Kyodo News, quoting TEPCO and NISA, reported that the three men with the highest doses – all subcontractors in their 20s or 30s – were laying cables at unit 3’s turbine building. Two were hospitalized after receiving beta ray burns on their feet while standing in a puddle without boots. Radiation readings at the puddle’s surface and in the air nearby were recorded at 400 millisieverts and 200 millisieverts per hour, respectively, Kyodo reported. Afterward, workers evacuated the unit’s basement and ground floor.

Japanese authorities raised the maximum permitted dose at the plant from 50 millisieverts per year to 250 millisieverts following the accident. Reports indicate no worker has exceeded the larger amount. A dose of 100 millisieverts is the lowest at which research indicates an increased risk of cancer.

In Tokyo, concerns in the last few days about radioactive elements in tap water have eased some. After tests at water plants in recent days showed levels of radioactive iodine at levels considered a potential long-term health risk for infants, the latest tests indicate those levels are back within safe limits. In nearby Chiba prefecture, though, new reports emerged of tap water with radioactive substances above healthy levels for infants. Testing Wednesday in the city of Matsudo detected 220 becquerels of iodine-131 per liter, according to the Xinhua News Service.

Scientists continue to monitor radioactive elements in seawater and food, as well. The IAEA reported measurable levels of iodine-131 and caesium-137 18 miles off shore. Kyodo also reported Thursday that cesium had been detected at 1.8 times allowable levels on vegetables in a Tokyo research facility.