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This past April, whenthe Japanese governmentand Tokyo Electric Power

Co. (TEPCO) jointly unveiledtheir plan to bring the damagedreactors of the FukushimaDai-ichi nuclear power plant to acold shutdown and gain control of the release of radioactive materials,they set a tentative completiondate for mid-January 2012.

And tentative had to bethe operative word, for theobstacles TEPCO facedand to some extent still doesfaceare challenging in theextreme. They include:

Fuel rod meltdowns in reactors1, 2, and 3 due to loss of coolingsystems following the 11 Marchearthquake and tsunami;

Severe damage to the upper levelsof reactor buildings 1, 3, and 4 andslight damage to building 2, stem-ming from hydrogen explosions;

High levels of radiation and con-taminated rubble, making working

conditions hazardous and di cult;

Thousands of metric tonsof contaminated wateraccumulating on the site andleaking out of the reactors.It appears, however, that the

process is now ahead of sched-ule. Environment Minister GoshiHosono, who is also in charge of the Fukushima nuclear accidentrecovery, told the InternationalAtomic Energy Agencys annualgeneral conference in Vienna

on 19 September that Japan was

now aiming to complete a coldshutdown of the Fukushimaplant by December 2011,instead of mid-January 2012.

Progress was already evidentin July, when Hosono announcedthat workers had completed step1 of the two-step road map onschedule, reducing radioactiveemissions and starting to bringdown the core temperaturesin reactors 1, 2, and 3.

Hosono attributed the suc-cess to the construction of anew cooling system, which had begun pumping water into allthree damaged reactors. In addi-tion to cooling, the system alsodecontaminates the water accu-mulating in the basements of the reactor and turbine build-ings. The contamination is theresult of injected water com-ing into contact with the mol-ten fuel in the pressure vessels.

Critics, however, were quick

to question the stability of thesystem and its ad hoc design.The combination of lteringand decontamination technolo-giesmainly from the Frenchnuclear giant Areva and theU.S. nuclear waste manage-ment company Kurionincludessome 4 kilometers of piping.

The critics have a point. Evenwith the addition of a report-edly more robust system (to beused in parallel or as backup

as needed) from Toshiba and

Shutdown ofFukushima ReactorsIs Ahead of Schedule

uccess in coolin the reactors su ests the plantcould be stabilized by years end

the natural world, the suns energy extractselectrons from a water molecule. The electronsthen reduce CO 2 into fuel (in plants, the fuel takesthe form of carbohydrates). University of Illinoisgraduate student Brian Rosen and other scientistshave invented a device that electroreduced CO 2 to carbon monoxide at a lower voltage thanpreviously achieved. The high voltages usuallyrequired have been a major stumbling blockin the past. Rosens group brought the voltagedown by using a combination of a silver cathodeand an ionic liquid electrolyte that presumablystabilized the CO 2 ion. And, according to RichMasel, who led the research and is CEO of Dioxide Materials, a company working on CO 2 electroreduction with the University of Illinois,this piece of the photosynthesis process couldeventually lead to a way to turn captured CO 2 into syngasa mixture of carbon monoxideand hydrogen used in the petrochemicalindustry to make gasoline and other fuels.

The experiment shows that one canmake syngas e ciently from any sourceof electricity, Masel says. However, large-scale versions of the device probably cant be cooked up until 2018. Presently we havedemonstrated the process on the 1-centimeter-squared scale. We need to go to the millioncm 2 to make signi cant amounts of gasoline.

Work on arti cial photosynthesis has rampedup considerably in recent years. In July 2010,the Department of Energy began funding the

Joint Center for Arti cial Photosynthesis to thetune of $122 million over ve years. The center,with close to 200 members in universities andnational laboratories across California, aimsto build on natures photosynthetic design,

bridging all the disciplines required, fromchemical engineering to applied physics.In an interview earlier this year, the

centers leader, Caltech professor Nate Lewis,told IEEE Spectrum that progress is certainly being made, but it isnt clear yet if the rightcombination of catalysts and light absorbersand everything else that goes into practicalarti cial photosynthetic devices has been found.

Were seeing light in the tunnel, he said.We dont know where the end of the tunnel is.Its a curved tunnel. Dave Levitan

A version of this article appeared online in September.

15 eters he width a flyi g car et wo ld ha e to e to carry a h a si gexisti g aterials a d tech ologies. gi eers at pri ceto ilta 10-ce ti eter rototy e that ro els itself at 1 c /s t o ly ear the s rface.

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IHI Corp., TEPCO admitsthe system underwent39 disruptions between10 July and 8 September.One consequence is that

roughly 100 000 metrictons of water still needto be decontaminated.

Disruptions and remain-ing challenges notwith-standing, TEPCO has beenmaking progress towardstep 2 of the road map: a coldshutdown. According toTEPCO, that means achiev-ing and maintaining a tem-perature of less than 100 Cas measured at the bottom

of a reactor pressure vessel

the steel vessel containingthe fuel rodswhich itself is enclosed inside a protec-tive containment vessel.

A major advance came at

the beginning of September,when TEPCO was able tostart up the core spray linesto cool reactors 1 and 3. Thecore spray lines apply waterdirectly to the cores fromabove, while the systeminstalled in July has beencooling the cores by injectingwater from the bottom.TEPCO has also begunincreasing the amount of water being injected into

reactor 2. The core spray

line could not be used untilrecently because TEPCO

rst had to survey the sub-systems piping and valves.Given the high radiation

in the area, this was dif-cult, but workers com-pleted the job in July andcon rmed the systemsoperability in August.

By late September, as aresult of these e orts, thetemperatures in all threereactors had dropped below 100 C for the rsttime since the accident. Asof 29 September, the tem-peratures for reactors 1, 2,

and 3, respectively, were

77.5 C, 99.7 C, and 78.7 C.We are steadily bringing

the postaccident situationunder control, says Hosono.

To achieve step 2 this year,well move the scheduleforward and do our best.

But Yoshinori Moriyama,deputy director-generalof Japans Nuclear andIndustrial Safety Agency(NISA) is cautious. Weneed to maintain this stateover the midterm, he says.

Temporary lower tempera-tures and the nonrelease of radioactive substances donot immediately mean thatthis is a cold shutdown. Inorder for NISA to declare acold shutdown, the tempera-tures must remain stable and below 100 C into December.So NISA wont o ciallydeclare a cold shutdownuntil near the end of 2011.

Despite these positivedevelopments, nuclearexperts point out thatachieving a cold shutdowndoes not make the troubledplant completely safe,given that even spent fuelcontinues to generateheat for years after use.

And upon achieving a coldshutdown, TEPCO must take

on a new series of challenges.These include nding wherethe injected water is escaping,stopping those leaks, dealingwith the accumulated con-taminated water, removingand storing the thousands of spent fuel rods from the poolsin reactors 1 to 4, and then

guring out a way to removethe melted fuel. The last is atask that could take a decadeor more, according to experts.

John Boyd

Double checkeD: Workers atF k shi a Dai-ichi reactor 1 check awater le el i dicator. I jected waterhas cooled the cores, t it has alsocreated co ta i atio at the site.Photo: tEPCo