jrSN T 0 GtAMQY15 DE IPS TIED -DLYE 33b3gg sikl Aw ercah 1 ocKvvievl-l-S HS DECLASSIFIED 81 2 0 1 121 Y x8ys-- ' '- I r1 - - rte NATIONAL ACADEMY OF SCIEI CES COMMITTEE ON ATOI IC FISSION N M v Frank B J ewett President National Academy of Sciences AUTHQ E @11901 2101 Constitution Avenue Washington D C Dear President Jewett ----- J9 - JTS%FrMML-i V I -a 29 which The committee of the National Academy of Sciencesoftoatomic military aspects you have referred the matter of possible April 30 with Dr Briggs' fission held a meeting in Washington Uranium Committee and a second meeting in Cambridge May 5 Further conferences were held by mail and wire with question b of your 7de have been concerned primarily all things considered letter of appointment as-to whether pressure indicated in larger funds and facilities and more knowledgeare and the probability the light of our present scientific with national defense problems of applications useful in connection the next 6 months Our primary recommendation is that during be spen on is proZem a stro intensified effort should Dr Briggs on behalf This is in accord with the view urged by opinion of the other of his committee and with the unanimous qualified persons with whom we have consulted by that It now appears probable that the results obtained with regard to time will show the need for a large scale program possible that on the contrary the atomic fission It remainsthat vigorous effort will no longer results will then indicate on the attenbe justified in view of other urgent military demands with a successful associated tion of physicists The possibilities such importance and are so outcome of the work are however ofmust not risk giving an enemy inuninent that in our opinion we nation the advantage of first putting atomic fission to military use involve sharply increased Intensive immediate effort will work and means for facilitating appropriations in support of present the efficient use of the men qualified to Work in this field For accomplishing these objectives specific recommendations are presented in the final section of this report that the use of nuclear fission It would seem to us unlikely within less than two yews though can become of military importance it would appear that some of the British experts anticipate applicathe ct ain reaction can tions more prompt than this If however rapidly become a determining be produced and controlled it may to a struggle which may confactor in warfare Looking therefore important that we gain the lead tinue for a decade orThat more it is nation which first produces and controls in this development the process will have an advantage which will grow as its applications multiply -6 k4sk Doc DE'I PS IED DOE 8803 rv'e V kS A - -ica - bo - q - ewf- zA- HS DECIAS0llIED $1 2C f possible hilitary Applications Applications of military importance in connection with atomic fission are based upon the expectation of producing a nucIn this reaction when a U23 atom combines lear'chain reaction with a slow neutron it divides with great energy the process of When fission emitting rays among which are fast neutrons these neutrons are slowed down by collision with other atoms such as deuterium beryllium or carbon they may be captured This is the chain by other U235 atoms which in turn divide reaction continuing as long as a sufficient number of U235 atoms The energy thus and atoms of the slowing agent are present liberated per atom of U235 is about 130 000 000 times that developed per atom from such a chemical reaction as combustion of carbon in oxygen or about 2 000 000 times as much per pound of U235 as per pound of carbon burning in oxygen It is anticipated that under suitable conditions the reaction will be under control with respect t6 speed of development but that under other conditions it may proceed with explosive violence Proposed military applications of a uranium fission reaction include a Production of violently radioactive materials to be used as missiles destructive to life in virtue of their ionizing radiations For this purpose the function of the central installation for producing the chain fission reaction would be to produce the artifically active materials These might then be carried by airplanes to be scattered as bombs over enemy territory Whi 0 this might be the most promptly applicable military use of the method because of the hazards that will necessarily be involved it could hardly be applied within less than twelve months from the first successful production of a chain reaction This would mean not earlier than 1943 b As a power source on submarines and other ships This is perhaps the most straightforward use of atomic power but because of the engineering difficulties involved and the necessary protection against hazards it can hardly have important application within less than three years from the time of production of the first chain reaction c Violently explosive bombs It would now appear that a strong concentration of urani- m 235 or of some other element which is subject to fission on capturing thermal neutrons will be required in order to produce an explosive atomic reaction The destructive power of such an explosion should be enormous as compared with that from chemical explosives Optimistic estimates of the time required for separation of adequate amounts of uranium isotopes would be from three to five years It is possible that element 94 usable for this purpose may be produced abundantly by the chain fission reaction If this is true such atomic bombs might become available within twelve months from the time of the first fission chain reaction Because of the hazard in its use however some years will be required for development This means that atomic bombs can hardly be anticipated before 1945 --R A sk r-AeY oc A Y e%ri co v b o c- K v e- n4-S DE-1 AS 'FIED DOE 8gb3 L A NS DECLPSFIFIED S 11 In making these time estimates we have been guided by normal high pressure development of scientific and engineering processes It is possible that with luck the times would in cer- tain cases be appreciably reduced It seems to us more likely however that the effectiveness of the methods concerned will become most evident at later dates than those here indicated On the other hand it should be kept in mind that the outcome of a new process such as this will certainly open new possibilities now unthought of Some of these may be of prompt application but most of them will only gradually be realized Progress toward Securing a Chain reaction The calculations seem to make it clear that a chain reaction of atomic fission should easily be produced with a sufficiently large quantity of the 235 isotope of uranium The separation of this isotope is possible but according to present indications can be achieved in quantity only by the installation of large expensive plants whose suitable design has not yet been determined In time this may become a most important aspect of the problem and cork now under way in studying the methods of isotope separation must therefore be continued Those working on the fission problem are however agreed that the probability of obtaining a chain reaction with the normal mixture of uranium isotopes is good To make this process a success involves the use of an agent to slow down the fast neutrons liberated at the time of fission to a speed so low that they will not readily be captured by uranium 238 The-best estimates indicate better than even chances that continued work along the lines now being followed will effect this reaction If given sufficient support adequate tests of these methods should be completed the reaction perhaps obtained within 18 months and The time and cost required to complete the tests needed now estimated as follows to produce the chain reaction if the method is practicable is a Mixtures of uranium and carbon 1 Intermediate experiment now in hand at Columbia University Details are given in the attached report by George B Pegram Cost - materials 117 000 Salaries 33 000 Incidentals 24 000 174 000 Time of completion about July 1 1942 Anticipated results Definite evidence whether uraniumcarbon mixture can give chain reaction and reliable data from which to determine amount of material required to produce such reaction Present status about 1 60 000 worth of material on order 33 11 45k boc LA rri2 DOE vA -s Voc wten4-s Aw erI ca DE-1 4S-FIED 2g03y2A- N5 DECLASSIFIED i I've N 1_ 9 2 Production of chain reaction with carbon and uranium is complete -en y p anne unil experiment This cannot be in e i te 120 tons of graph As now anticipated it will require at least The cost of this stage will and the erection of suitable housing probably be between _500 000 and 1 000 000 The uranium-carbon experiment is the most immediately applicable of the proposed methods This is because the materials is estimated by Fermi required are immediately available ItItdoes not appear as hopeful to have an even chance of success as methods b and c mentioned below Because of its immediate applicability however and the importance of learning what the chain reaction will do it is important to go ahead now with the intermediate stage 1 of this experiment b mixtures of uranium with beryllium or beryllium oxide Be and BeO seem to have advantages over C as slowing agents neutrons to rest iB because 1 the path required to bring the the shorter and 2 additional neutrons are released within Time will be BeO is available in suitable quantity beryllium required to produce metallic Be t of Be 1 Intermediate experiment on relative effectiveness y un vers xperlmen s now in nanu a ac en s BeO and C as s own of Chicago See attached report by S K Allison Cost- materials including 2 tons BeO and 250 pounds Be 35 000 22 500 Salaries 1 15 000 50 percent 65 000 7 500 Incidentals Completion date of experiment December 1 1941 Result Knowledge of comparative value of beryllium and carbon as slowing agent for neutrons and an estimate of relative amount of beryllium beryllium oxide or carbon required to produce a chain reaction Lvui c 2 Determinative uranium-beryllium experiment This will involve use of larger quantities of t e materials The design at of the experiment will depend upon the state of the problem rggard to th e time It should give definite information amount of materials required to produce the reaction Its completion can will probably be limited by the rate at which the materials be supplied but should not be later than July 1 1942 Probable cost about 430 000 additional 3 Chain reaction with beryllium oxide and uranium On for used the basis of present rou eat mates comparable with those20 tons above this experiment will require some experiment a-2 of uranium oxide and 00 tons of beryllium oxide Total cost should - tfrc0 l-e--Gi ' 1 et C ---l fi' sJ ° 1--A t -r t ii J r rf V - r may i1 1- 1 1 r--rrt-i vpR - ocLA rvte v AvvA -rlca bocKw evbt DECLAS'NED -DOE yy HC --i 8-- g80312A-1S 111x DECLASSIFIED S r Allison suggests that plans should be made now for an experiment using about 1 cubic meter of BeO 3 to 4 tons some 200 lbs of Be metal and 2 to 3 tons of uranium oxide or metal Arranging the uranium in 2 concentric shells filled with beryllium he believes a definite answer to the possibility of a chain reaction by this method can be given and the amounts required definitely determined There would be perhaps some chance of securing at once the chain reaction if the uranium and the metallic beryllium is borrowed from the carbon experiment the material cost would be confined to that of the beryllium oxide roughly 50 000 This would replace experiments bl and b2 ere indicated - -5 k L o c t t r% % e v% -S Avv ericah Doc v ejs DECIPS TIED si -pct 88b3_1 zA NS yZ 1r Y t HC__ ' DECISSSIFIED 31ac1S uranium carbon of the corresponding be roughly somewhat less than that data based upon uncertain experiment This however is whether be possible to choose reliablythus By July 1942 it should is preferable and beryllium slowing agent the carbon or the It will probably not be desirexperiment select able to taeither expboth at that -3 mixtures of uranium with pure heavy water See e rey agent is the most promising The use of heavy water as a slowing ususe however awaits Itsneffective method now on the horizon thalve q separation of the necessary methods even though the expensive than the other ly it may be less results and at lower initial other methods may be the first to give separating deuterium heavy hydrogen cost The most promising method of exchange reaction between water the chemical is according to Urey a countercurrent is fed through system hydrogen and and hydrogen in which the water this converting then catalyst sstem containing y through the catalyst y n attached f eeding the ahydrogen back catalyst and of the construction Studies of the appropriate system are now in progress of a pilot fractionation water The plant may Larce scale roduction oof-heav eavy water should 1 e ars on on or a an cost a half m As a rough estimate and '25 000 per ton cost between 110 000 the fission chain reaction 2 several tons will be required for effecting water mixtures Preliminary 3 Tests of uranium and heav using ngland been performea by Ha an in encouraging tests of this type Havewater - The and re 'su t was very 120 kilograms of heavy reaction physicists that the chain convinced tFhe-British has apparently not however clear The experiment is can be produced by this method with perhaps a ton of heavy water before out and needs repitition itself can be reaction experiment the conditions for the chain for making this test-may Materials available definitely formulated be available by July 1942 uranium and heavy water This experi4 Chain reaction with at a oost in addition e not titer t an poss ment should separation plant of from building of the deuterium -_ to that for the 200 000 to 400 000 Recommendations Budget the intermediate experiment on uranium We understand that partially financed as is also a pilot and graphite is already of pure heavy water plant for the production In addition to giving -B 14s 1 DOGitr- e v -DOE Aw ecUY% boc- r eh 4-S DE'I PS-FIED DECLASSIFIED $86314izA- MS $1 2a 1g By vi HC1 these two projects full support wd would urge emphasis on the beryllium project to the extent of approximately the X65 000 for the next six months indicated above The other work on the separation of uranium isotopes should also be kept active although it does not need the urgent emphasis that should be placed upon the use of normal uranium There should thus be made available for the next six months a o a a ou 000 n s is as ar as the committee a eves Iorma on justifies definite plans na present Toward the end of this 6 month period i e about November 1941 the results should however be reconsidered by a committee similar to the present one If the indications are favorable one or both of the following projects should then be carried through a The next stage of the beryllium experiment at a cost of about j130 000 and b the construction of the separation plant for producing heavy water at a cost of perhaps 000 000 It would now seem that acomparable expenditure Burin g th following year may be required in order actually to produce t he chain reaction in usable form It is doubtful whether the cost atomic be reduced much below a total of two million dollarsx without so can prolon ing the experiments that we should be trailing the work done in other countries F e recognize that this is a heavy demand on the funds able for national defense research We believe however that availthe military possibilities of atomic fission are so vast and the dangers of its neglect until some other nation has outdistanced serious that if necessary a request should be made for us are so a special appropriation to cover this work iithin a half dozen years the consequepces of such investigations may be crucial in determining the nation's military position It is noteworthy that our emphasis on its high importance reflects the seemingly unanimous judgment of those in this country and England who have studied intimately the possibilities of atomic fission This includes all of the individual members of the Uranium Committee as well as the investigators with whom we have conferred peal th Pecdally nutas- o -the-I'a3r_ 5aeetl f fur- ommitZEe Personnel question of employing on this problem scientific men i g eht ht be more useful at other national defense problems has irno m b een considered This aifficulty is not as serious a s woui d at first appear for two reasons 1 The greater part of the expense does not g o int o e employment of physicists but rather into the 4-1 supp 1 ying of the expensive materials required 2 The physicists xIt may be noted that the market value of the material purchased will be a consider abl e f ruc t ion of this cost I fir s DocLA re V- Aw ev-i cav baLt e v 4s DE 14S-FIED CE S363 q XA - IFS 05-H c DECLASSIFIED i 5120 s mfr 1 7 to be used on this project are and will continue to be for the most part those whose qualifications do not fit -them for important positions in other national defense projects This applies to most of the physicists andwchemists now employed at Columbia and Chicago with the exce p tion of Mr P egram and Mr Allison In order to insure the rapid and efficient progress of these studies we would recommend I 1 The formation of a sub-dommittee called perhaps the Research Committee o the Uran um Comm ttee consist n o YS K Allison G Breit E rermi G Pe ram and H C re As its chairman Coolidge Slater and ompton favor Allis on V an Vleck favors Urey and Lawrence favors either Ure or Allis on It would be the function of this sub-committee 1 toy plan carry through the research program 2 to confer continuouslyand the developments as they occur 5 to see that newly obtainedoninformation is promptly available to those investigators that need it and 4 to rep ort as may b e desired to the central uranium committee 2 We consider it vital that every effort be made to insure th a t th ose f orking on the uranium problem at the request of the uranium committee be kept acquainted with the advances made by other investigators and be encouraged to confer upon their mutual problems Experience indicates that only thus can rapid progress be made and rapid progress is in the present instance of-first importance 3 In order to progress most rapidly it will be of value to bring immediately by air to the United States Mr Halban now at 1work on this problem in Cambridge England x He has information that will greatly aid our investigations and can take back to England such information as we may have obtained that may be of value in their study of the same problem We wish to congratulate the Uranium Committee on the excellent progress that h as thus f ar been made We would-encourage the Defense Research Committee to give even more complete supportNational to the capable men now engaged upon this research This we believe can best be done by giving prompt and adequate financial support along the lines indicated above Arthur H Compton ' ' ith the expressed approval of the following members of the committee 17 D Coolidge E 0 Lawrence J C Slater J H Van Vleck Because of illness r Bancroft Gherardi has taken no part in the committee's discussions py C it is suggested that such an invitation be routed through l 'r Coekcrnft_ -