Ask HN: Nazi “atomic pile” criticality in WWII? | Hacker News Reader

Ask HN: Nazi “atomic pile” criticality in WWII?

2 pointszunzun6 comments

I had seen on a television documentary where men with radiation detectors entered an overgrown tunnel entrance in a German forest, and in the tunnel the radiation levels became extremely high. I had seen photos of Allied dismantling of a prototype Nazi power reactor on Wikipedia here:

https://en.wikipedia.org/wiki/German_nuclear_weapons_program#/media/File:German_Experimental_Pile_-_Haigerloch_-_April_1945.jpg

however this photo appears to show an industrial prototype and not a physics experiment, and criticality had not been achieved at this facility. So, I wondered if the underground radiation was from the original research prototype.

WWII nuclear scientists from Germany were secretly recorded conversing after after the defeat of the Nazis, and of course they were unaware of the U.S. "atomic pile" criticality at the University of Chicago. In the transcripts of their discussions, they refer to an "engine" which seems to be their term for a power reactor. I see the following statement on page 12 of the transcripts at http://germanhistorydocs.ghi-dc.org/pdf/eng/English101.pdf

"History will record that the Americans and the English made a bomb, and that at the same time the Germans, under the HITLER regime, produced a workable engine."

which tells me they were all aware of a research reactor having achieved criticality. Does this seem correct?

There's a museum in the Haigerloch beer cellar where the prototype reactor was built. https://www.haigerloch.de/de/Tourismus/Atomkellermuseum/Der-... says that the B8 attempt did not reach criticality.

Last paragraph:

> Der Vermehrungsfaktor (das Verhätnis Voll- zu Leermessung) ergab sich etwa zu 7. Damit war der Haigerlocher Reaktor nicht kritisch geworden. Berechnungen ergaben, dass etwa die eineinhalbfache Reaktorgröße notwendig gewesen wäre. Eine Vergrößerung war im April 1945 nicht mehr möglich, weil weder weiteres Uran noch Schweres Wasser vorhanden war.

Google Translate:

> The multiplication factor (the ratio of full to empty measurement) was about 7. Thus, the Haigerlocher reactor was not critical. Calculations showed that about one and a half times the reactor size would have been necessary. An enlargement was no longer possible in April 1945, because neither more uranium nor heavy water was available.

It makes sense that the nuclear physicists involved actually meant that history would record they "desired to produce" or "hoped to produce" - their spoken German was probably not very good.

The "WEIZSÄCKER" here is Carl Friedrich von Weizsäcker. Quoting https://en.wikipedia.org/wiki/Carl_Friedrich_von_Weizs%C3%A4...

> Born in Kiel, Schleswig-Holstein, he was the grandson of Karl Hugo von Weizsäcker, the Prime Minister of the Kingdom of Württemberg. His grandfather was ennobled in 1897 and raised to the hereditary nobility with the title of Baron (Freiherr) in 1916. As such, the four-year-old Carl Friedrich Weizsäcker became Baron Carl Friedrich von Weizsäcker. Since 1919, noble titles have legally been considered parts of the family name.

> Weizsäcker was raised in Stuttgart, Basel and Copenhagen. Between 1929 and 1933 Weizsäcker studied physics, mathematics and astronomy in Berlin, Göttingen and Leipzig, supervised by and working with Heisenberg and Niels Bohr, among others. The supervisor of his doctoral thesis was Friedrich Hund.

I therefore cannot believe that his "spoken German was probably not very good."

That Wikipedia link gives a further description

> the "Farm Hall Transcripts" also revealed that Weizsäcker had taken the lead in arguing for an agreement among the scientists that they would claim that they had never wanted to develop a German nuclear weapon. This story was at least untrue to the extent that the detainees also included scientists actively engaged in eager attempts to build a nuclear bomb, namely Kurt Diebner and Walter Gerlach.[14] Max von Laue later called this agreement "die Lesart" (the Version).

Thus, I think you should see this as an attempt to create a narrative that likely didn't exist.

Thus, I was being mildly sarcastic about the German scientists ability to speak German.

It came across as a comment by someone very ignorant of the history around the German nuclear program.

Not only was it nonsensical for Weizsäcker specifically, Heisenberg was attacked by proponents of the "Deutsche Physik" movement, who had a particular hatred of the "Jewish physics" which turned out to be so useful for nuclear weapons development. They believed Heisenberg wasn't German enough - a 'White Jew'. See https://en.wikipedia.org/wiki/Deutsche_Physik

Your sarcastic comment also suggests that the physicists on the German nuclear project weren't German enough to even speak German well.

For anyone who knows the history, your attempt at humor instead comes across as a continuation of the anti-Semitic smear attack on Heisenberg.

Since that isn't what you meant, it means that you don't know anywhere near enough of the history to be at the point where you should be comfortable in making sarcastic comments.

Consider me to have been properly and most righteously chastised.

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