In Which I Use Scientific Reasoning to Doubt the Thorium-Powered Car

While I was away at Dragon*Con, stories about a possible thorium-powered car popped up in the news. From the write-up at Txchnologist:

Charles Stevens, an inventor and entrepreneur, recently revealed that his Massachusetts-based R&D firm, Laser Power Systems (LPS), is working on a turbine/electric generator system that is powered by “an accelerator-driven thorium-based laser.” The thorium laser does not produce a beam of coherent light like conventional lasers, but instead merely heats up and gives off energy.

There’s a whole lot of science word salad in that paragraph — what does it even mean to have a laser that isn’t actually lasing and producing coherent light? So let’s detangle it and see if the proposed thorium-powered car makes sense.

The first thing to know is that there’s been a lot of work done on using thorium for fuel in a nuclear reactor. Thorium-232, the kind you dig up out of the ground, is only weakly radioactive and won’t undergo fission by itself. What you can do, however, is bombard it with slow neutrons from uranium or plutonium. That turns thorium into uranium-233, which is fissile and can be used in a nuclear power plant. That means you can use thorium as breeder fuel to produce the fissionable material you really want.

Thorium has several benefits over uranium-235, the usual nuclear reactor fuel. For one, thorium ore is about three or four times as prevalent in the Earth’s crust as uranium ore. For another, you can use all of the thorium you mine. Only 0.7% of uranium is 235U. The rest of it is 238U, which isn’t useful for nuclear reactors. That makes thorium far more abundant for nuclear power purposes.

There are downsides, of course. As the World Nuclear Associate fact page dryly puts it, “Despite the thorium fuel cycle having a number of attractive features, development has always run into difficulties.” There aren’t any commercial thorium reactors yet.

However, if you read carefully what Charles Stevens is saying, he’s not claiming to be using thorium in a nuclear reactor. The WardsAuto article on Stevens states, “Stevens agrees, emphasizing his system is ‘sub-critical,’ which means no self-sustaining nuclear reaction within the thorium creating significant amounts of radioactivity.” So what is he doing?

Unfortunately his two websites currently have very little information. To find out more we have to look at the 2009 version of his webpage and exerpts from that same page. Back then he talked about laser-driven cars in which a “Hybrid Solid state Free Electron laser” heats up thorium, which releases even more heat to turn water into steam and drive a turbine. Also an accelerator may be involved. And according to what he told WardsAuto, “1 gm of thorium equals the energy of 7,500 gallons (28,391 L) of gasoline Stevens says. So, using just 8 gm of thorium in a car should mean it would never need refueling.”

Right, let’s try and make sense of this, starting with one gram of thorium equaling the energy of 7,500 gallons of gas. This a question of energy density: how much energy can you extract from a given amount of fuel?

I have no clue what process Stevens is claiming to use that lets you bombard thorium with a laser and get energy out, especially since he said it’s sub-critical and thus not a nuclear fission reaction. Instead I’ll pretend he is doing nuclear fission, since that’s one of the more energy-productive reactions we can do and will set a good estimated upper bound on how much energy Stevens could extract from thorium. I’ll also assume 235U fission, since we don’t have a thorium reactor yet.

Uranium in a reactor produces about 20 terajoules of energy per kilogram. For comparison, gasoline gives you about 48 megajoules per kilogram. That means uranium gives us about 425,000 more power per kilogram than gas. Let’s assume thorium will give us roughly the same ratio. That means one gram of thorium would be like 425 kg of gas. Gas has a density of about 2.7 kg per US gallon, so that 425 kg of gas is equivalent to 156 gallons.

That’s way short of Stevens’s claim of 1 gm of thorium being equivalent to 7,500 gallons of gas. For that to be true, his laser-induced power output has to be fifty times more energy efficient than nuclear fission. That is an extraordinary claim, to put it mildly, and he’s offered no proof and precious few details.

Looking through his other claims, it sounds as if he glued together actual science together as if making a collage for kindergarten, regardless of whether the results made sense or not. You could in theory make an actual thorium laser, though that’s not what he’s doing. You can use a particle accelerator to drive a nuclear reaction by knocking neutrons out of other particles, though again that’s not what Stevens is doing despite him adding “accelerator-driven” to the description of his process. You can even induce nuclear reactions using super-powerful lasers, but Stevens says he’s not inducing fission.

So to sum up: Stevens isn’t claiming to have made a nuclear-powered car. He’s claiming to have made a steam-powered car where the steam is heated up when he shines a laser on thorium. I don’t know of any physical process that would let you get more heat energy out of the thorium than you’d spend on making the laser go. For his process to be so awesome that it would power a car for some 200,000 miles on a single gram of thorium, he’d have had to come up with something that’s fifty times more powerful than a nuclear reactor. And he hasn’t released any papers, only press releases. That’s 3 out of 3 red flags for the research not being real.

Sorry, world. If we’re going to have a laser-powered car, it sounds like this isn’t it.

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7 Comments

  1. Sean B
    on September 16, 2011 at 1:53 pm | Permalink

    “For his process to be so awesome that it would power a car for 300 miles on a single gram of thorium”?
    300 miles isn’t very much.
    Especially if he claims 1 gm thorium = 7500 gallons of gas
    7,500 gallons of gas to go 300 miles?

  2. on September 16, 2011 at 2:00 pm | Permalink

    Cut-and-paste error. In one article it talks about cars going 300k miles on a gram of thorium, though I expect 200k is more like it. I’ve updated the post. Thanks!

  3. Tom Bedlam
    on October 9, 2011 at 12:27 am | Permalink

    It’s worse than you think – he’s now violating Bedlam’s First Law of Cranks by invoking Tesla. The way he’s extracting energy from the thorium has been revealed as “Tesla Technology” that increases the decay rate of the thorium by several thousand times using a Tesla coil. This causes insanely energetic emission of beta and alpha particles which pump the laser, which heats the water, instead of, say, just having the particles do it directly.

    I knew Tesla would end up coming into this somewhere.

  4. on October 9, 2011 at 3:36 pm | Permalink

    That does sound even more unlikely.

  5. on December 19, 2011 at 4:38 pm | Permalink

    SONO I POLITICI ILLUMINATI CHE DEBBONO SALVARE IL PIANETA INCENTIVANDO LA SOSTITUZIONE DEI MOTORI INQUINANTI ALIMENTATI DAI DERIVATI DEL PETROLIO. DOPO IL SUCCESSO DEL MOTORE ELETTRICO DELLA TESLA, CHE CON UNA CARICA PERCORRE 450 KM., UN NUOVO GRUPPO DI RICERCATORI AMERICANI HA INVENTATO UN MOTORE CHE SI ALLINEA AI GIGANTESCHI PROGRESSI INFORMATICI DELLA NOSTRA ERA. CON 8 GRAMMI DI TORIO FA PERCORRERE AD UN’ AUTO CIRCA 500.000 KM. CHIEDIAMO AL PRESIDENTE BARAK OBAMA,IN NOME DELLA DIFFUSA SOFFERENZA UMANA CHE HA PROCURATO E PROCURA L’ INQUINAMENTO DEL MOTORE A SCOPPIO, DI ATTIVARSI DA SUBITO PER ORGANIZZARE LA PRODUZIONE INDUSTRIALE DEL MOTORE AL TORIO AD EMISSIONI ZERO.
    15 dicembre 2011

    Signor presidente BARAK OBAMA, DIFENDERE L’AMBIENTE E FERMARE LA MANO FRATRICIDA DI CAINO CONTRO L’ UOMO SIANO I TEMI PRINCIPALI DELLA SUA CAMPAGNA ELETTORALE.

    Lei e’ il primo Presidente eletto e sostenuto dal Popolo di internet ed ha la libertà di contrastare l’ innalzamento della temperatura e la rovina del pianeta ormai nelle prossimità del baratro della TERZA GRANDE ESTINZIONE se da subito non viene sostituito l’ uso dei prodotti petrolchimici per la mobilità di massa con motori ad energia alternativa ad impatto ambientale zero. Mentre Le scrivo miliardi di dannosi motori a scoppio riscaldano l’ aria e la scaricano inquinata nella biosfera utilizzando solo 14% dell’ energia per la locomozione.

    Oggi, in occasione della Sua seconda campagna elettorale, oltre alla possibilità di promuovere la produzione su scala industriale del motore elettrico ad alta autonomia utilizzato con successo dalla TESLA, ha anche la possibilità di prendere in considerazione il motore ad energia nucleare proposto da un Gruppo di ricercatori della LASER POWER SYSTEM alimentato da un laser al torio in grado di far percorrere ad un veicolo con 8 grammi di torio ben 420800 (quattrocentoventimilaottocento) km, realizzando notevoli vantaggi per la salute e per l’ ambiente nonché risparmi per le famiglie dato l’ alto costo del petrolio.

    Per realizzare i progetti verdi da Lei proposti anche nella precedente campagna elettorale, occasione migliore non poteva capitarLe per dare inizio da protagonista alla svolta energetica. Dopo che i Ricercatori dell’ azienda Laser Power System del Massachusetts Le avranno dimostrato la validità del motore al torio, ne incentivi la produzione industriale utilizzando fondi pubblici e chiedendo nel contempo la sottoscrizione azionaria al popolo americano che da tempo attende un politico illuminato, non colluso con la grande finanza, per essere liberato dal flagello dell’ inquinamento e da quel potere finanziario che trae immense ricchezze imponendo il consumo di derivati dal petrolio.

    Da anni l’ umanità e l’ ambiente subiscono pesanti danni a causa del costo e delle emissioni inquinanti dei derivati del petrolio utilizzati nelle locomozione di massa, fra cui :

    -tre milioni di morti all’ anno ;

    -milioni di ammalati per malattie invalidanti alle vie polmonari ;

    -aumento della temperatura causata del gas serra, che, se non fermata in tempo, farà subire al nostro pianeta sconvolgimenti climatici di tale portata distruttiva da minacciare la nostra estinzione;

    -crisi sui mercati finanziari con la riduzione in miseria di intere comunità per l’ aumento del costo del petrolio;

    -guerre sanguinose per l’ accaparramento di pozzi petroliferi.

    Per l’ empatia inclusiva che caratterizza il rapportarsi con i propri simili nell’ era internettiana, le economie mondiali debbono essere liberate dalla dipendenza del petrolio e ogni cittadino deve poter accedere ad apparecchi capaci di produrre energia in proprio in rapporto alle proprie esigenze.

    Egregio presidente Barak Obama, abbiamo festeggiato con gioia il raggiungimento del primo milione di dollari grazie alle prevalenti donazioni degli abitanti dell’ universo internettiano e sosteniamo la Sua campagna elettorale sicuri che concretizzerà le promesse elettorali e le nostre aspirazioni per il progresso e per contrastare l’ egoismo antisociale del grande potere finanziario che avvelena la nostra vita quotidiana ed il nostro avvenire.

    Durante la Sua campagna elettorale dimostri che è possibile realizzare la rivoluzione energetica ad emissione zero per la mobilità di massa e conquisterà molti consensi. Se porrà fine agli evidenti danni causati alla nostra salute ed al pianeta da parte di chi c’ impone il consumo di idrocarburi, farà apparire in tutta la meschinità la campagna che gli uomini di marketing stanno mettendo in atto per avversarla su committenza del Partito Repubblicano sostenuto dai petrolieri.

    Saluti

    francesco miglino

    segretario del partito internettiano

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  6. on October 17, 2012 at 10:42 pm | Permalink

    I’m guessing that the comment that showed up in my feed reader this morning (by a user named “selling a car”) had at least one commercial URL. Even if it wasn’t spam, I read it at least 3 times and couldn’t parse it. Even after I made the corrections (in my head) that seemed to be what the poster intended to say, it still didn’t make sense. I mean, I’ve seen several cases before where what was written was probably meant to be some common expression (but instead ended up being something completely different which _reminded_ me of the expression but had no meaning as written). This one, though… I couldn’t even tell for certain whether the commenter _agreed_ or _disagreed_ with you.

  7. on October 18, 2012 at 9:46 am | Permalink

    I’m intrigued by the art of putting together those spam sentences, trying to balance them so they sound semi-reasonable as a response to a wide variety of blog posts.