Tokyo (AP) -

Un  reactor   din Japonia  are  un nivel ridicat de radiaţii  datorita     impactului cu apa   suferit   cu  ocazia tsunmi-ului   ce a fost im urma  cu  un an ,iar  după o examinare internă, marţi,  expertii   afirma că îşi reînnoiesc  îndoielile cu privire la stabilitatea  reactorului .

Un instrument echipat cu o camera video mica, un termometru, un dozimetru şi un indicator de apă a fost utilizat pentru a evalua daunele în interiorul camerei de izolare nr 2a  reactorului  pentru a doua oară de la tsunami-ul cuprins în Fukushima Dai-Ichi  cu un an în urmă.

Sondarea  făcua t în luna ianuarie nu a reuşit să găsească apă de suprafaţă şi a oferit doar imagini care arata  aburi, piese neidentificate şi suprafeţe metalice ruginite, zguduit de expunerea la radiatii, caldura si umiditate.Datele colectate de la sonde  facute  au aratat  ca  daunele de la dezastru a fost atat de grave, iar  operatorul centralei va trebui să dezvolte echipament special şi de tehnologie pentru a tolera mediu dur .

Tuesday's examination with an industrial endoscope detected radiation levels up to 10 times the fatal dose inside the chamber. Plant officials previously said more than half of melted fuel has breached the core and dropped to the floor of the primary containment vessel, some of it splashing against the wall or the floor.

Particles from melted fuel have probably sent radiation levels up to dangerously high 70 sieverts per hour inside the container, said Junichi Matsumoto, spokesman for Tokyo Electric Power Co.

"It's extremely high," he said, adding that an endoscope would last only 14 hours in that condition. "We have to develop equipment that can tolerate high radiation" when locating and removing melted fuel during the decommissioning.

The probe also found the containment vessel — a beaker-shaped container enclosing the core — had cooling water up to only 60 centimeters (2 feet) from the bottom, far below the 10 meters (yards) estimated when the government declared the plant stable in December.

Finding the water level was important to help locate damaged areas where radioactive water is escaping.

He said that the actual water level inside the chamber was way off the estimate, which had used data that turned out to be unreliable. But the results don't affect the plant's "cold shutdown status" because the water temperature was about 50 degrees Celsius (122 Fahrenheit), indicating the melted fuel is cooled.

Three Dai-ichi reactors had meltdowns, but the No. 2 reactor is the only one that has been examined because radiation levels inside the reactor building are relatively low and its container is designed with a convenient slot to send in the endoscope.

The exact conditions of the other two reactors, where hydrogen explosions damaged their buildings, are still unknown. Simulations have indicated that more fuel inside No. 1 has breached the core than the other two, but radiation at No. 3 remains the highest.

The high radiation levels inside the No. 2 reactor's chamber mean it's inaccessible to the workers, but parts of the reactor building are accessible for a few minutes at a time — with the workers wearing full protection.

Last year's massive earthquake and a tsunami set off the worst nuclear accident since Chernobyl, sending three reactor cores to melt and causing massive radiation leaks. The government said in December that the reactors are safely cooled and the plant has stabilized, while experts have questioned its vulnerability.

During a recent visit by a group of journalists including The Associated Press, the head of the plant said it remains vulnerable to strong aftershocks and tsunami and containing contaminated water and radiation is a challenge. Radioactive water had leaked into the ocean several times already.

Workers found the fresh leak of 120 tons from a water treatment unit this week from one of its hoses, with estimated 80 liters (20 gallons) escaping into the ocean, Matsumoto said. Officials are still investigating its impact.

Fukukushima's accident has instilled public distrust and concerns about nuclear safety, making it difficult for the government to start up reactors even after regular safety checks. All but one of Japan's 54 reactors are now offline, with the last one scheduled to stop in early May.

**sursa :

Associated Press – Tue, Mar 27, 2012