Alex Wellerstein on Twitter: "relevant Coster-Mullen footnote… "

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Replying to @BeyondNerva @HopDavid41

I suppose it depends on the reference. I saw the figures 85%-100% enriched uranium was "weapons-grade". But I probably saw that in Wikipedia...

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Beyond NERVA‏ @BeyondNerva Jun 10

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Replying to @nyrath @HopDavid41

Well, we could always ask @Casillic or @NuclearAnthro, they're the experts I know on here.

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Martin “Doomsday” Pfeiffer (⧖) ‏ @NuclearAnthro Jun 10

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Replying to @BeyondNerva @nyrath and

“weapons grade” is what you can make explode. Little Boy bomb used 80% enriched. Below 20% a run away criticality impossible or so goes the lore so LEU vs HEU distinction. I believe for US most appropriate to see 93%ish as weapons grade tho there is context & nuance & such

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Casillic‏ @Casillic Jun 10

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Replying to @NuclearAnthro @BeyondNerva and

Casillic Retweeted Casillic

I’ve seen both 80% and 84% HEU on Little Boy not sure which is actual or how much a difference it makes.https://twitter.com/casillic/status/1040411913606320129?s=21 …

Casillic added,

Casillic @Casillic

Output of Fat Man and Little Boy Devices 1/n https://permalink.lanl.gov/object/tr?what=info:lanl-repo/lareport/LA-UR-13-26113 … pic.twitter.com/iIxR6yxAd7

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Martin “Doomsday” Pfeiffer (⧖) ‏ @NuclearAnthro Jun 10

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Replying to @Casillic @BeyondNerva and

A) note error in Pu mass for FM. B) I think the upper enrichment limit of HEU rings hit toward 90% but not sure- I SUMMON @wellerstein! C) the average enrichment may be technically classified still? (Relates to A)? D) Error? Somewhere? E) it was 84%? But

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Martin “Doomsday” Pfeiffer (⧖) ‏ @NuclearAnthro Jun 10

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Replying to @NuclearAnthro @Casillic and

The math carrie sutherland does jives with 80% IIRC but t may not have been able to differentiate in any case. Bittom line: I tell people 80% but I would now have to go to @wellerstein’s primary docs to double check.

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GeorgeWilliamHerbert‏ @GeorgeWHerbert Jun 10

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Replying to @NuclearAnthro @Casillic and

The rings were lower enriched, the solid chunk in the middle was higher, unless I’m having a brain malfunction. Searching for cite...

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Martin “Doomsday” Pfeiffer (⧖) ‏ @NuclearAnthro Jun 10

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Replying to @GeorgeWHerbert @Casillic and

Both cylinders were hollow. The most enriched was in the center.

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Martin “Doomsday” Pfeiffer (⧖) ‏ @NuclearAnthro Jun 10

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Replying to @NuclearAnthro @GeorgeWHerbert and

Cadmium was used as the neutron absorber to reduce predet. I presume b/c affinity for lower energy Ns and because it becomes saturated more quickly than boron-10?

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GeorgeWilliamHerbert‏ @GeorgeWHerbert Jun 10

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Replying to @NuclearAnthro @Casillic and

https://nuclearweaponarchive.org/Nwfaq/Nfaq8.html … Insert: inner stack of 6 cylindrical rings stationary inside the target assembly “The insert had an enrichment of 86%, the projectile was enriched to 82% for an average enrichment for the core of 83.5%, equal to slightly more than three critical masses.”