Another radiation hotspot has been found at the Fukushima Daiichi site - again in part of the emergency venting and filtration system.
Yesterday an extremely high reading of 10,000 millisieverts per hour was announced as having been found in pipework leading to an exhaust stack. Today that was followed by a reading of over 5000 millisieverts per hour inside one of the buildings.
Both of the readings were taken from parts of the Standby Gas Treatment System (SGTS), through which steam was vented to relieve reactor pressure during the accident in March. In that sense, it is highly likely that Tokyo Electric Power Company will make several more findings of radiation hotspots as it conducts stabilisation work inside the power plant buildings.
The first hotspot was detected in a part of the SGTS pipework immediately before the exhaust stack shared by units 1 and 2. The latest one is on the second floor of unit 1's turbine building, near the entrance to a room related to the SGTS.
Each reactor building has an SGTS which maintains slightly lower air pressure during normal operation to reduce the possiblity that potential contamination could exit the plant building through any tiny holes. It has air intakes and components on several floors. Should contamination be present in the buildings for any reason, the SGTS is there to filter the air before release through the stack. It also provides the filtered route for venting from the reactor system, as used during the accident.
The radiation levels indicated by these off-the-scale readings mean that no worker can approach to within a few metres of the areas to take detailed manual measurements. Instead, levels were estimated using gamma cameras mounted on robots.
Researched and written
by World Nuclear News