Ro­bot snaps pics of melted re­ac­tor de­bris

Northwest Arkansas Democrat-Gazette - - BUSINESS & FARM -

MARI YA­M­AGUCHI

TOKYO — An un­der­wa­ter ro­bot cap­tured im­ages of so­lid­i­fied lava­like rocks Fri­day in­side a dam­aged re­ac­tor at Ja­pan’s crip­pled Fukushima nu­clear plant, spot­ting for the first time what is be­lieved to be nu­clear fuel that melted six years ago.

Plant op­er­a­tor Tokyo Elec­tric Power Co. said the ro­bot found large amounts of lava­like de­bris ap­par­ently con­tain­ing fuel that had flowed out of the core into the pri­mary con­tain­ment ves­sel of the Unit 3 re­ac­tor at Fukushima. The plant was de­stroyed by a huge earth­quake and tsunami in March 2011.

Cam­eras mounted on the ro­bot showed ex­ten­sive dam­age caused by the core melt­down, with fuel de­bris mixed with bro­ken re­ac­tor parts, sug­gest­ing dif­fi­cult chal­lenges ahead in the decades­long de­com­mis­sion­ing of the de­stroyed plant.

Ex­perts have said the fuel melted and much of it fell to the cham­ber’s bot­tom and is now cov­ered by ra­dioac­tive wa­ter as deep as 20 feet. The fuel, dur­ing melt­down, also likely melted its cas­ing and other metal struc­tures in­side the re­ac­tor, form­ing rocks as it cooled.

Power com­pany spokesman Takahiro Ki­moto said it was the first time a ro­bot cam­era has cap­tured what is be­lieved to be the melted fuel.

“That de­bris has ap­par­ently fallen from some­where higher above. We be­lieve it is highly likely to be melted fuel or some­thing mixed with it,” Ki­moto said. He said it would take time to an­a­lyze which por­tions of the rocks were fuel.

In an ear­lier sur­vey Wed­nes­day, the ro­bot found se­vere dam­age in the ves­sel, in­clud­ing key struc­tures that were bro­ken and knocked out of place.

The ro­bot, nick­named “the Lit­tle Sun­fish,” on Fri­day went in­side a struc­ture called the pedestal for a closer look. The power com­pany plans to send the ro­bot far­ther down in hopes of find­ing more melted fuel and de­bris.

Ex­perts have said the melted fuel is most likely to have landed in­side the pedestal af­ter breach­ing the core.

Ki­moto said the ro­bot probe in its two mis­sions has cap­tured a great deal of use­ful in­for­ma­tion and im­ages show­ing the dam­age in­side the re­ac­tor, which will help ex­perts even­tu­ally de­ter­mine a way to re­move the melted fuel, a process ex­pected to be­gin some­time af­ter the 2020 Tokyo Olympics.

“It’s still just the be­gin­ning of the [decades­long] de­com­mis­sion­ing. There is still a long way to go, in­clud­ing

de­vel­op­ing the nec­es­sary tech­nol­ogy,” he said. “But it’s a big step for­ward.”

Lo­cat­ing and an­a­lyz­ing the fuel de­bris and dam­age in each of the three wrecked re­ac­tors is cru­cial for de­com­mis­sion­ing the plant. The search for melted fuel in the two other re­ac­tors has so far been un­suc­cess­ful be­cause of dam­age and ex­tremely high ra­di­a­tion lev­els.

The sub­mersible ro­bot, about the size of a loaf of bread, is equipped with lights, ma­neu­vers with five pro­pel­lers and col­lects data with two cam­eras and a dosime­ter. It is con­trolled re­motely by a group of four op­er­a­tors. It was co-de­vel­oped by Toshiba Corp., the elec­tron­ics, nu­clear and en­ergy

com­pany charged with help­ing clean up the plant, and the In­ter­na­tional Re­search In­sti­tute for Nu­clear De­com­mis­sion­ing, a gov­ern­ment­funded con­sor­tium.

AP/SHUJI KAJIYAMA

A newly de­vel­oped ro­bot for un­der­wa­ter in­ves­ti­ga­tion at Ja­pan’s Fukushima nu­clear plant’s dam­aged re­ac­tor moves in the wa­ter at a Toshiba Corp. test fa­cil­ity in Yoko­suka in early sum­mer.

AP/EU­GENE HOSHIKO

Tokyo Elec­tric Power Co. shows an im­age cap­tured by an un­der­wa­ter ro­bot in­side the Unit 3 re­ac­tor at Fukushima nu­clear plant dur­ing a news con­fer­ence Fri­day in Tokyo.

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