The first Critmass, December 2, 1942

Seventy one years ago — on December 2, 1942, at 3:25 pm — Enrico Fermi and his team achieved the first controlled, man-made, self sustaining chain reaction in a simple reactor. In recognition of that historical event, several of my nuclear colleagues refer to December 2 as “Critmass” (short for critical mass).

The first nuclear reactor — CP-1 (Critical Pile number 1) — was actually a carefully constructed pile consisting of graphite bricks, uranium oxide pseudospheres, and uranium metal pseudospheres. The pile was built on a 30 by 60 foot squash court located under the stands at Stagg Field, the former home of the University of Chicago’s short-lived, but successful, football program.

The construction period was remarkably brief; the stacking process started on November 16, 1942, slightly more than two weeks before the criticality experiment.

In 2012, the Argonne National Laboratory produced a short history video that included interviews of Harold Agnew and Warren Nyers, two of the atomic pioneers who were part of the team that built the pile and produced the world-changing demonstration. ANL also has a Flickr page of CP-1 related images worth perusing.


At the time of the CP-1 experiment, excitement about the possibility of a self-sustaining chain reaction and the use of uranium 235 as a highly capable replacement for coal and oil had been building for about three years. Even though Ernest Rutherford had once dismissed expectations for the use of atomic energy as “moonshine”, talented physicists and chemists recognized that nuclear energy production was almost inevitable once they learned how neutrons could split uranium atoms and how that reaction itself produced additional neutrons. Atomic fission was first widely recognized in early 1939 when Lise Meitner and Otto Frisch properly interpreted the experimental results that Otto Hahn and Fritz Strassmann had reported.

That wide recognition was delayed by nearly five years from the first inkling of what happens when uranium is bombarded with neutrons. In September 1934, Ida (Tacke) Noddack, a chemist, had published a paper titled On Element 93 stating that Fermi’s claim of having produced new elements heavier than uranium during some experiments conducted in 1933 was not valid based on the test method that he reported. She recommended that future experiments test to see if what Fermi asserted were transuranics were, in fact, isotopes of known lighter elements like barium. Noddack suggested that Fermi’s results of at least five different decay half lives after bombarding uranium could be caused by uranium nuclei breaking in previously unknown ways.

When heavy nuclei are bombarded by neutrons, it is conceivable that the nucleus breaks up into several large fragments, which would of course be isotopes of known elements but would not be neighbors of the irradiated element.

Noddack’s interpretation was dismissed, leading to a series of confusing experimental results. That dismissal might have been because Ida Noddack was a chemist commenting on a physics experiment or perhaps because she was a little known woman in a field dominated by men.

Leo Szilard also anticipated the possibility of creating self-sustaining chain reactions in 1933. He filed a patent on the process, even though he was not sure which elements might split with a release of both energy and neutrons.

It is an unfortunate historical accident that Fermi’s successful initiation of an atomic fire occurred at a time when the world was being threatened by Hitler’s quest for total domination. Like Leo Szilard, many of the scientists who collaborated in a world wide burst of creativity to determine how to predictably release the vast amount of energy stored inside atomic nuclei were initially attracted by the idea of developing nuclear heat as an alternative to burning coal and oil. Though Szilard understood that rapid energy release might have military applications and he took steps to keep that knowledge out of Hitler’s hands, the patent itself shows that he anticipated power production because it describes a pile with a means of extracting heat to produce electrical power.

Since “there was a war on” and since several of the key experimenters — including Otto Hahn and Fritz Strassmann — with atomic energy were known to be actively working inside Germany, there was more immediate interest in secretly developing along the explosive path than in openly developing devices that could use controlled atomic chain reactions to produce reliable energy. Even before Fermi began building CP-1 in 1942, a veil of secrecy had been self-imposed by the mostly European scientists; that veil was made official US government policy as part of the Manhattan Project. Despite all of the prior interest in the possibility that chain reactions in uranium would be the atomic analog of fire, there were no contemporary public announcements of Fermi’s successful critical mass demonstration.

December 2 has been reinforced as an important date in nuclear energy by several additional developments. On December 2, 1957, just fifteen years after the CP-1 demonstration, the Shippingport nuclear power station achieved its initial criticality. On December 2, 1977, just twenty years after that power station first began operating, President Jimmy Carter issued an order to bring the final core of the Shippingport reactor to full power. That final core was known as the Light Water Breeder Reactor a demonstration project that eventually operated for five years and more than 27,000 effective full power hours. At the end of that period of operation, there was more fissile material in the core than there was when the core first started operating.

I now wish you a happy Critmass. I hope that this journey through history has been a pleasant addition to your day and to your optimism for the future of nuclear energy development.

About Rod Adams

49 Responses to “The first Critmass, December 2, 1942”

Read below or add a comment...

  1. Daniel says:

    Now, the next true Critmas is happening next year.

    Why ?

    Elementary my friends.

    The first AP1000 and EPR are going live.

    Where might you ask ?

    Elementary my friends. CHINA

    And then, we start riding the learning curve. And then, the entire planet goes nuclear.

  2. Paul W Primavera says:

    I assume that “Critmass”, meaning “Critical Mass”, is a secular perversion of Christ Mass or Christmas.

    We can promote nuclear energy without perverting the Sacred.

    • Rod Adams says:

      @Paul W Primavera

      Celebrating the incredible gift of fission with a play on words is not a perversion of the sacred, especially compared to the commercialization that has bombarded us for more than a century.

      • James Greenidge says:

        Paul;

        As a churchgoer I have to agree with Rod. There’s really nothing sacrilegious here. I’d much rather get on MTV’s case on how they regularly cheerfully malign (to be lightly) the Gospel to tens of millions of gullible innocents.

        James Greenidge
        Queens NY

    • Brian Mays says:

      Hi Paul,

      If God does not have a sense of humor, then why did he create man — in his own image — with one?

      Puns might be the lowest form of humor, but they are still a part of creation, and still not a sin, last time I checked. ;-)

      • Joel Riddle says:

        I thought fart/methane-related jokes were the lowest form of humor, Brian?

        BTW, I concur with you, James, and Rod. Critmas(s) doesn’t take away from Christmas, and represents a tremendous gift for humanity.

        • Engineer-Poet says:

          Critmass may be too close to the gift of Prometheus for some who want the pre-Christian heritage of the West to be forgotten.

  3. Daniel says:

    And maybe Critmass 2013 won’t be too good. It seems like the EU in Brussels, the european arm of the NRC, is going to refuse the Hickley project in the UK.

    You can watch the UK and all 12 european countries supporting nuclear power go ballistic.

    Do not forget that the EU council in Brussels has refused to consider nuclear as a zero emission source of energy not too long ago. And do not forget that reducing emission is the most important thing on the mind of the EU zombies.

    • Daniel says:

      I am so miffed.

      • Daniel says:

        Britain just announced another loan guarantee for Hitachi on the Wylfa nuclear power station in north Wales.

        If Brussels counters those nuclear deals, there will not only abort the energy future of the UK but their effort to re industrialize as well.

        German chose to de industrialize. So be it. But the UK will walk out the the EU if Brussels intervenes. 75% of Brits want out of the EU.

        Brussels has better be careful.

        • EL says:

          Britain just announced another loan guarantee for Hitachi on the Wylfa nuclear power station in north Wales.

          And Hinkley Point is getting held up at European Commission (here and here).

          Commission promises in-depth review of “complex and novel” deal. “The commission frowns on national governments offering deals to companies that stifle competition and distort the market.” French press cited as “worried,” “rejection” mentioned in article, Olkiluoto got no such aid, analysts at Liberium Capital suggest deal “could prove to be ‘economically insane'” (here), and Oettinger (EU Energy Commissioner) called deal “a throw-back to the ‘Soviet’ era.”

          Not a good start. Battle lines getting drawn with Brussels.

    • Engineer-Poet says:

      Do not forget that the EU council in Brussels has refused to consider nuclear as a zero emission source of energy not too long ago. And do not forget that reducing emission is the most important thing on the mind of the EU zombies.

      Mandate an outcome, then ban the most practical method of accomplishing it… to the point that some nations are already backsliding.

      In the old Soviet Union, there were so many contradictory laws that it was impossible to comply and anyone could be jailed on some pretext.  It looks like the EUSSR is well down the same road, and likely for the same reason.

  4. José says:

    Thank you for this post.

    I first became very interested in nuclear energy by reading a very simple book, ‘Worlds within worlds: the story of nuclear energy’, by Isaac Asimov (http://www.amazon.com/Worlds-Within-Story-Nuclear-Energy/dp/0898750016). It is written in a very straightforward way and yet I found it very interesting. I remember he described the history of that first reactor (‘the Italian navigator has landed”), and how the historical events of the moment (world war II, fight against nazism) prompted and speeded up these advances.

    Greetings from Spain.

  5. Bas says:

    Rod,
    Thank you for this interesting story & video. You know how to bring history into live!

    Daniel, Engineer-poet,
    State subsidies in whatever form, are normally against competition rules.
    This is not strange as otherwise a subsidized industry in one country, competes a not-subsidized industry in another country out of the market, etc.
    So the EU also deemed the French program to stimulate renewable as illegal (so France had/has to invent a more specific program, more linked to temporary innovation or so).

    This ruling also has influence on the German Energiewende. It is one of the reasons that this innovative program is so detailed (a general subsidy is illegal) and grants only temporary subsidies and only based on performance (produced KWh).

    As Hinckley is marginal innovative, I doubt whether the present competition rules (Brussels) allow it. Especially since the subsidies concern ~75% of all costs of Hinckley during a very long period (35years and longer), and are partly not performance based.

    So a rule change is probably necessary and that may become a tough one as Merkel has declared against. Germany is in the fire-line once Hinckley becomes a new Fukushima. But may be Cameron (UK prime minister) has something nice in the pocket for Merkel, or it was just election rhetoric of Merkel (however, her trademark is reliability).

    Note:
    Apart from the strike price of ~$180/MWh in 2023 (2% inflation), the loan guarantee is a subsidy of ~$20/MWh. The insurance also ~$20/MWh, the help for decommissioning?
    So Hinckley cost ~$220/MWh at 2023, going up with ~80% of the inflation .
    While whole sales prices in UK are now at ~$60/MWh levels, going down.
    Especially since solar+wind go down (offshore Wind is already cheaper).

    There is no reason to assume that the EPR will become competitive within a few decades.
    Even the less safe Chinese EPR variant, built by the Chinese, cannot compete here.
    So I really do not see, how this can pass Brussels if the commission is honest. But political pressure can do a lot to forget the rules.
    If so, the decision to allow may be contested in EU court at Luxembourg.

    • starvinglion says:

      Here is Germany’s “visionary” “independent” “solution”

      http://www.umweltbundesamt.de/sites/default/files/medien/376/publikationen/hintergrundpapier_thgnd_englisch_lang.pdf

      “a good proportion of the renewable power will probably be generated outside Germany”

      HAHAHA….

      • starvinglion says:

        “The use of nuclear energy is no longer an option in Germany”

        “For a GHG-neutral Germany to become reality in
        2050, innovations and further development of existing
        technology are indispensible. More research and
        development is needed in this field.”

        “We are aware that for our scenario
        to become reality, innovative technology must
        lead the way in the coming four decades.”

        “Hydrogen is currently not yet used as an energy
        carrier for power generation and transport. Further
        research and development is urgently needed,”

        ————————————-

        The general theme is: send all your money to the deep thinkers in the towers. They are going to save you. And what will their solution be in 2050? A bicycle, a solar panel, and a tent. Meanwhile, the deep thinkers will be in the tropics somewhere laughing.

    • John Tucker says:

      Bas is being the Grinch that stole Critmass.

  6. Mitch says:

    Do we know where the original CP-1 graphite bricks went? There were thousands, right? Some must be laying around somewhere! Are there collectors among the staff and personnel of CP-1?

  7. Joe B says:

    I Havent been here in a while because visiting this site actualy makes me feel hopeless about the human condition. At least after reading a bit I see that it is now at least accepted on this forum that there were indeed 3 melt throughs at Fuk u shima. last time Safe Shutdown! was the triumphant final word shouted back at me without exception.

    And so almost 3 years after the Biggest triple Fuk up so far and 72 years after the first sustained criticality which lead up to this event and 3 days since measuring the highest ever levels of radiation in groundwater outside of containment, here we are in a situation that is getting further out of control by the day.

    Happy Critmass!! what a bizarre concept and certainly not one humanity should be proud of, anyway enjoy “normality” while it lasts because things are going to get rough very soon my friends.

    • Rod Adams says:

      @Joe B

      We have not missed you.

      You did not read very carefully if you believe that it is “accepted on this forum that there were indeed 3 melt throughs at Fukushima.”

      Most of us accept that three cores – the part of a nuclear reactor that contains the actual fuel elements – melted and released a portion of the water soluble and volatile radioactive fission products. The best available evidence indicates that the resulting mass of mostly metallic and ceramic material remains inside the pressure vessel where the cores are installed. Those pressure vessels have some paths where water can leak out, but the now solidified “corium” is not mobile and is not outside of the pressure vessel. Though not everyone agrees that the corium did not leave the pressure vessel, it is widely accepted that the cores did not leave the next layer of public protection known as the containment.

      Measuring hot spots is unimportant. As described several times here, that is especially true when the radiation reading reported is an “on contact” reading of mostly beta emitters.

      http://atomicinsights.com/fear-mongering-over-water-leaks-at-fukushima-dai-ichi/

      Beta radiation is stopped by a few sheets of paper, human skin, and will only travel about a meter in dry air. It has no impact on human health unless it is consumed. Most people are smart enough to avoid drinking sea water or unfiltered ground water from an industrial site.

      Before you dismiss the incredible gift to humanity provided by the nuclear scientists that discovered how to assemble a self sustaining critical mass of fissionable material, please consider the competition. Without the emission free, hydrocarbon free heat provided by fission, what kind of long term future would humanity have? How much low cost petroleum do you think the world would have if we had continued burning oil in power plants in France, Japan, the United States, the UK, Russia, Sweden, Switzerland, South Korea, etc? Every year, critical masses produce as much energy for the world as Saudi Arabia and Iraq combined, and that figure completely ignores the energy produced in submarines and aircraft carriers.

      Sure, fission is not absolutely perfect, but it comes closer than any of the alternatives.

      • Bas says:

        Rod,
        I understood that these reactors were shut down after the quake. So the control rods were in, and the reactor was no longer in production mode at the moment the Tsunami hit ~15minutes later on.

        So if a 200ton plane hits a reactor dome in full production mode, such that all cooling (pumps, leakage in pipes, etc) fails, the temperature rise will go 100times(?) faster, hence the melting starts in 15 minutes?
        Even before the fire brigade arrives to extinguish the kerosene, etc. fire.

        Then the extreme high temperatures in contact with … create hydrogen and we get similar explosion. That may result in something worse than Chernobyl?

        • Mitch says:

          All Bas and ilk have in their arsenal against nuclear energy are nightmares and bunches of “ifs”. Imagine had there been a caveman Bas there at the discovery of fire and the wheel…

        • Rod Adams says:

          @Bas

          No. As soon as the plane hits, the reactor will shutdown. It is likely that the plane will not penetrate the containment dome, though it probably will do some significant damage. (I worked in DC in 2001 and saw the wreckage at the Pentagon. I’ve also seen containment structures.)

          Besides, what makes you think that anyone has the skills to hit a relatively small, rounded containment building? It is a much more difficult target than something like the Twin Towers, the Pentagon or a football stadium.

          • Bas says:

            @Rod,
            It is a much more difficult target than something like the Twin Towers
            Bin Laden decided not to attack a NPP as his in-experienced pilots may miss.
            But for an experienced (e.g. 200ton freight plane) pilot it is rather easy.

            We disagree regarding the impact.
            Compare EPR double dome structure with ‘old’ NPP dome structure, while the EPR is not even garanteed against a 50ton plane (only unarmed F-16 of 11ton).

            Consider that European stress-test was delayed for month due to this issue. At the end only light sportsplane (<1ton?) flying a cruise speed was calculated.

            I did some calculations on my own. Those also show an old NPP such as Borssele has no chance against a 200ton plane. Even if it flies at relative low speed of 300km/hr (experienced pilot will fly ~550km/hr).

            We also disagree about the shut down.
            That will not happen in the first ~70mSeconds of the impact. After that the damage is probably already such that most of the rods cannot fall down and/or will not fall down further.

          • Brian Mays says:

            I did some calculations on my own.

            LOL … please publish.

      • Bas says:

        … what kind of long term future would humanity have?
        A future in which we use near 100% renewable for electricity generation as the first step (some countries reached that already), and
        then migrate towards 100% renewable for all energy consumption (Denmark has explicit target to reach that in 2050).

        Renewable add almost no heat to the atmosphere, while nuclear add huge amounts of new heat. A 1GW NPP adds ~3GW heat to the atmosphere (~2GW waste heat and 1GW heat via the electricity it produces). That also contributes heavily to the warming of the earth.

        • Engineer-Poet says:

          It took fossil energy to make the infrastructure for electricity possible (though much of it, like Niagara Falls, was renewable at the beginning, those resources quickly proved inadequate).

          Renewable add almost no heat to the atmosphere, while nuclear add huge amounts of new heat.

          The direct waste heat of nuclear plants is dwarfed by the greenhouse-trapped heat of the fossil-fired backups required by your “renewables”.  Total human energy consumption is about 0.01% of solar flux, while anthropogenic greenhouse warming is already more than an order of magnitude greater.

      • Joe B says:

        Hi Rod, well yes im sure im not too popular in these parts lol, but i appreciate that you havent censored my posts.

        I must have have misread then, but at least we can agree that the notion of cold shutdown was a lie perpetrated by many who knew better including most on this forum. The fact remains that containment is breached below the ground and the only logical explanation is that the cores have melted through the pressure vessels and outer containment. to what extent is hardly important but it is clearly getting worse all the time.

        BTW in your reply you seem to have got beta mixed up with alpha radiation.

        The IAEA thinks its time to consider dumping all of the stored highly contaminated water into the Pacific, because it cant be stored indefinitely anyway and is just hampering progress.

        Unfortunately the harsh reality is either the tanks are going to rapture or it can be made to look like a controlled event. its going to happen either way.

        But what is really disturbing about that announcement is not the actual release into the environment, It is a declaration of defeat. If that water is released to the ocean then nothing has been contained.

        And thats not even touching on the multitude of things that could and likely will go wrong at any time elsewhere on site.

        The wise words of Douglas Adams:

        “The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.”

        And that is the sorry state of nuclear technology, no effective response protocol when something goes wrong and no solid plan for all the waste that will burden our civilization for eternity. It is no gift to humanity it is the number one existential risk to all life on earth. What did nuclear save in man made carbon emissions? 2% or less.

        It is going wrong and although you choose to keep a positive outlook the Socioeconomic repercussions are going to be huge, as of around now the effects will start to be felt, first around the northern pacific and then globally.

        • Engineer-Poet says:

          at least we can agree that the notion of cold shutdown was a lie perpetrated by many who knew better including most on this forum.

          No, we cannot.  Cold shutdown is when the coolant temperature is some margin (12°F) below the boiling point of water.  The coolant in the Fukushima Dai’ichi reactors is well below that temperature and has been for a very long time.  They ARE in cold shutdown, your denials notwithstanding.

          The fact remains that containment is breached below the ground and the only logical explanation is that the cores have melted through the pressure vessels

          I caught a note which suggested that at least one of the major water leaks was likely due to a broken sprinker (pressure suppression system, I guess) pipe inside the lower torus of one of the containments.  That means the outer pressure vessel is likely still intact, and can be re-sealed and filled with water.  Oh, and your “only logical explanation” is anything but.

          The IAEA thinks its time to consider dumping all of the stored highly contaminated water into the Pacific

          That would be the water AFTER scrubbing out fission products, leaving only tritium in significant quantities.  Tritium’s half-life is 12.3 years, and it does not bio-accumulate.  It’s gone in a century.

          If that water is released to the ocean then nothing has been contained.

          The water could be contained indefinitely by adding it to Portland cement, immobilizing it and its ions for centuries.  It makes no sense to do this.

          And that is the sorry state of nuclear technology, no effective response protocol when something goes wrong and no solid plan for all the waste that will burden our civilization for eternity.

          If your time horizon is so short that a century is equivalent to eternity, you are no environmentalist.

          • Joe B says:

            Steaming piles of rubble that dont hold water and are too radioactive to enter do not fit the official definition of Cold Shutdown. Even Tepco doesnt use those words anymore. the pressure vessels have no pressure in them, are you not following the story?

            The water in those tanks is from the waste/drain channel from the R. O. system which is what carries the filtered particles out, the “clean” water is recirculated through the cooling loop. there is a lot more than just tritium in those tanks. Around 3 times to total cesium content released by Chernobyl by some estimates not to mention the myriad of other elements.

            As for the outer pressure vessels (?) if all three outer containment’s are intact groundwater should not measure 1.3 million becquerels/L and rising.

          • Engineer-Poet says:

            Steaming piles of rubble

            What “piles of rubble”?  Even after the hydrogen explosions all but the upper parts of the reactor buildings remained instact.

            are too radioactive to enter do not fit the official definition of Cold Shutdown.

            The definition of cold shutdown involves the absence of chain reaction and physical temperature of the coolant, period.  Any reactor full of spent fuel is far too “hot” to enter, so by your definition utilities have been lying about the state of their reactors when they pulled the tops of the pressure vessels for refueling.  Your definitions and opinions are baseless and worthless.

            The water in those tanks is from the waste/drain channel from the R. O. system which is what carries the filtered particles out

            Which is not the bulk of the water.  Were it not for paranoia about tritium, even that water could be evaporated leaving the particles and metal ions in a solid state.

            As for the outer pressure vessels (?) if all three outer containment’s are intact groundwater should not measure 1.3 million becquerels/L and rising.

            Leaks in the containments do not mean ruptures or melt-through in the walls.  Piping fractures have been identified as likely sources of leaks, and pipes can be plugged.  Since the experts have been right about so much of this so far and you have been wrong, it’s likely that you are wrong yet again.  We’ll find out.

        • Mitch says:

          Coming home from Thanksgiving I was driving past Brooklyn’s garbage _mountains_ last weekend and thought about all the nuclear waste greens are squealing about! Nuclear waste that’d be lost just in the _foothills_ of garbage mountain! And all this stuff is left outside for all eyes to see and noses to smell!

          Bas, you’re so full of gloom and doom that you think engineers are ass clueless about all the flaws and hazards you see and accounting for them. That’s one condescending attitude you have. Like Rod or someone said here once, greens think they have a monopoly on caring about families and safety.

          To know so many like you are so sealed up in denial and doubt in the face of nuclear power’s record and _reality_ makes me pray for earth’s survival. I keep thinking how many were killed in that Tokyo quake gas and oil explosions that greens didn’t give a hoot about so they could howl instead about zero injuries at Fukushima which doesn’t bother the Red Cross or other major reputable hospitals any.

          Your nuclear hang-up is one pile of stone cold hypocrisy, man! Get a life in reality!

          • Bas says:

            Mitch,
            Do not despair regarding earth’s survival.
            Last year the world installed ~100GW new renewable. This year probably 130GW.

            And those cost far less than nes nuclear such as Hinckley Point C (~$220/MWh in 2023 going up with inflation).
            I still hope engineers are sensitive to costs.

  8. Daniel says:

    Rod,

    Your comment:
    At the end of that period of operation, there was more fissile material in the core than there was when the core first started operating.

    A while back we talked about free energy. Brian and others said it did not exist. But when you witness more fuel at the ned that was put at the beginning, can’t we stretch this into ‘free energy’ ?

    I know you are looking for new slogans, do we have one here ?

    Nuclear done right yields free energy

    • Engineer-Poet says:

      Until reactors and their operation come free, energy from them won’t be free.  But the same is true for the darlings of the greens, wind and solar.