TOKYO, Oct 10 (Reuters) - Radiation levels in seawater justoutside one of the damaged Fukushima reactors spiked this weekto the highest level in two years, the operator of the crippledJapanese nuclear plant said on Thursday.
Radiation levels on Wednesday, the day six workers wereexposed to highly radioactive water, jumped 13 times theprevious day's reading, the highest levels since late 2011.
A massive quake and tsunami hit the power station, operatedby Tokyo Electric Power Co, also known as Tepco, inMarch 2011, causing three reactor meltdowns and hydrogenexplosions.
Tepco, which is pouring hundreds of tonnes of water to keepreactors cool, has struggled to contain the build up ofradioactive water at the plant.
In the latest incident, a worker on Wednesday mistakenlydetached a pipe connected to a treatment system, releasing seventonnes of highly radioactive water.
The accidents at the Fukushima Daiichi plant, 220 km (130miles) north of Tokyo, are adding to the crisis and stirringdoubt over Tepco's abilities to carry out a complex cleanupwidely expected to take decades.
Tepco said combined Cesium-134 and Cesium-137 readings justoutside the damaged No. 2 reactor spiked to 1,200 becquerels perlitre on Wednesday, more than 13 times the level on Tuesday.
Cesium-134 readings were 370 becquerels per litre whileCesium-137 was 830/litre within a silt fence right outside thereactor building. Regulatory limits for Cesium, which emits astrong gamma radiation and is harmful to the human body, is 90bq/litre for Cesium-137 and 60 bq/litre for Cesium-134.
A Tepco spokesman said the sudden spike in radiation wascaused by construction work near the No. 2 building.
Workers are injecting chemicals to harden the ground on theseaside of the Fukushima reactor buildings to preventcontaminated water from flowing out to the ocean. The pressurefrom pumping chemicals into the ground pushed some contaminatedsoil out into the port area, the spokesman said.
Tepco also said Cesium-137 readings just outside the siltfence next to the No.2 reactor rose to 160 bq/litre, also abovethe regulatory limit and almost double the previous day's level.
The readings were taken right next to the Fukushima plantbut hundreds of meters from the port entrance that connects tothe Pacific Ocean.
Radiation from water leaking from the facility is mostlyconfined to the harbour around the plant, officials have said.
Last week, Tepco said 430 litres (113 gallons) ofcontaminated water had spilled out of a storage tank atFukushima and probably flowed to the ocean.
Cesium readings further out in the Pacific Ocean remainnon-detectable and officials say there is no environmentalthreat to other countries as radiation will be diluted by thesea.
In September, Prime Minister Shinzo Abe promised theInternational Olympic Committee that radioactive water problemsat Fukushima were "under control" and any contamination islimited to the harbour next to the Fukushima plant.
Japan's Nuclear Regulation Authority last week ordered Tepcoto draft in additional workers and report within a week on itsmeasures to tackle the hazardous clean-up.
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