Frisch–Peierls memorandum

The Frisch–Peierls memorandum was the first techni-cal exposition of a practical atomic weapon.[1] Writtenby Otto Frisch and Rudolf Peierls while they were bothworking at the University of Birmingham in England,the memorandum contained new calculations about thesize of the critical mass needed for an atomic bomb, andhelped accelerate British and U.S. efforts towards bombdevelopment during World War II.

1 Background and influence

Given toMarcus Oliphant, Oliphant passed the documenton to Henry Tizard, chairman of the Committee on theScientific Survey of Air Defence who consequently re-quested the setting-up of what was to become the secretMAUD Committee. The memorandum (a copy of whichis held in the Public Record Office at Kew) is datedMarch1940.The two men were the first to calculate that an atomicbomb would require about 1 kilogram (2.2 lb) of theisotope uranium-235.[2] (The estimate of 1 kg turned outto be too low; see Critical mass.) Before it had been as-sumed that the bomb itself would require many tons ofuranium, implying that it was theoretically possible, butnot a practical military device. An earlier letter to Pres-ident Franklin D. Roosevelt, signed by Albert Einstein(but written by Leó Szilárd), had suggested it may needto be delivered by ship but “might very well” not be smallenough to drop from the air.The memorandum helped galvanize both Britain andAmerica down a path which led to a report by theBritish MAUD Committee, the Tube Alloys project, theManhattan Project, and ultimately the atomic bombingsof Hiroshima and Nagasaki.

2 Contents

The memo was written in two parts. The second was anexplanation of the science supporting their conclusions.The first was an elegant and comprehensive outline ofthe implications of their calculations. It included a pro-posal that the best defence against such a weapon wouldbe to develop one before Germany did so. In a few shortpages these two scientists had anticipated the policies ofdeterrence which would later shape ColdWar geopolitics.The memorandum opens with:

Strictly Confidential

Memorandum on the properties of a ra-dioactive “super-bomb”

The attached detailed report concerns thepossibility of constructing a “super-bomb”whichutilizes the energy stored in atomic nuclei as asource of energy. The energy liberated in the ex-plosion of such a super-bomb is about the sameas that produced by the explosion of 1000 tonsof dynamite. This energy is liberated in a smallvolume, in which it will, for an instant, producea temperature comparable to that in the interiorof the sun. The blast from such an explosionwould destroy life in a wide area. The size ofthis area is difficult to estimate, but it will prob-ably cover the centre of a big city.

In addition, some part of the energy set freeby the bomb goes to produce radioactive sub-stances, and these will emit very powerful anddangerous radiations. The effect of these radia-tions is greatest immediately after the explosion,but it decays only gradually and even for daysafter the explosion any person entering the af-fected area will be killed.

Some of this radioactivity will be carriedalong with the wind and will spread the contam-ination; several miles downwind this may killpeople.

3 See also• Einstein–Szilárd letter

• Timeline of the Manhattan Project

• Allied technological cooperation during World WarII

4 References[1] Kelly, Cynthia C. (2004). Remembering The Manhat-

tan Project: Perspectives on the Making of the AtomicBomb and Its Legacy. World Scientific. p. 44. ISBN9812560408. Retrieved 2012-09-30.

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2 5 EXTERNAL LINKS

[2] “The energy liberated by a 5 kg bomb would be equiva-lent to that of several thousand tons of dynamite, whilethat of a 1 kg bomb, though about 500 times less, wouldstill be formidable.” Frisch-Peierls Memorandum, March1940, retrieved 2011-12-04

• World Nuclear Association—Outline History ofNuclear Energy

5 External links• Stanford University—The Frisch–Peierls memoran-dum (PDF)

• Frisch and Peierls’s second memorandum

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6 Text and image sources, contributors, and licenses

6.1 Text• Frisch–Peierls memorandum Source: http://en.wikipedia.org/wiki/Frisch%E2%80%93Peierls%20memorandum?oldid=557197482Contributors: AxelBoldt, Stevertigo, Charles Matthews, Fastfission, Christopherlin, MakeRocketGoNow, AKGhetto, Wiki-Ed, Kjkolb,Rwendland, Jmcc150, Ian Dunster, Gaius Cornelius, Welsh, Petri Krohn, JimmyGuano, Sct72, Cordless Larry, Bdushaw, Sibadd, Chris55,Myasuda, Thijs!bot, Headbomb, Brumnick, Daytona2, Rich257, Hugo999, JulesN, Binksternet, SeaRisk, Snocrates, CapnZapp, Addbot,Yobot, MaxDel, EmausBot, GoingBatty, ZéroBot, KLBot2 and Anonymous: 10

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