Operation Hardtack - Project 2.7, Nuclear Radiation from a Detonation at Very-High Altitude (Deleted)

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Nuclear Radiation from a Detonation at Very-High Altitude U.S. Naval Research Laboratory This is an extract of ITR-1624, Operation HARDTACK, Project 2.7. Approved for public release; distribution is unlimited. Extracted version prepared for DEFENSE NUCLEAR AGENCY BEST COPY AVAILABLE

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Destroy this report when it is no longer needed. Do not return PLEASE NOTIFY THE DEFENSE NUCLEAR AGENCY, ATTN: STTI, WASHINGTON, DC 20305-1000, IF YOUR ADDRESS IS INCORRECT, IF YOU WISH IT DELETED FROM THE DISTRIBUTION LIST, OR IF THE ADDRESSEE IS NO LONGER EMPLOYED BY YOUR ORGANIZATION.

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REPORT DOCUMENTATION PAGE a REPORT SECURITY CMSSIFICATION lb RESTRICTIVE MARKINGS 3 DISTRIBUTION/ AVAIIASILITY OF REPORT Approved for public release; distribution m NAME OF PERFORMING ORGANIZATION 6b OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION U.S. Naval Research Laboratory Defense Atomic Support Agency PROGRAM PROJECT T/# WORK UNIT ELEMENT NO. No. ACCESSIONNO. Detonation at Very-High Altitude, Extracted Version 3a. TYPE OF REPORT 13b. TIME COVEREO 14. OATE OF REPORT (Yw,ti/~Y) S. PAGE COUNT 16 SUPPLEMENTARY NOTATION This report has had sensitive mi litary information removed in order to provide an unclassified version for unlimited distribution. The work was performed by the Defense Nuclear Aqency in support of the DoD Nuclear Test Personnel Review Proaram. ‘7 COSATI COOES 18. SUBJECT TERMS (Continue on reverse If necesswy lnd hfWfY by blocknumbd FIELD GROUP I SUB-GROUP Hardtack The objective of this project was to measure the neutron spectrum and total prompt-gamma-ray flux produced by the detonation of a nuclear device of low yield at an altitude of about 90,000 feet. This information was to be obtained by suitable detectors in the vicinity of the nuclear device and telemetered to the ground to be recorded and subsequently analyzed. The theory and “instrumentation for measurement of neutron spectrum and total prompt-gammaray flux from a nuclear device detonated at an altitude of 85,000 feet is described. The balloon system left nothing to be desired in ease of launching and getting instrumentation of this type to altitude. The difficulties encountered with the command and telemetering systems could certainly be corrected by adequate testing in an environment including tests in the 100,000 ft. altitude range, and if repeated with thoroughly tested systems, should offer an excellent chance of success. 20 OISTt{l@UrlON/AVAlLA81LlTf OF ABSTRACT 21 A@STRACT SECURITY CLASSIFICATION All other ed$tlam we obsolete SECURITY CLASSIFIOTIONOF THIS PAGE

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Classified material has been removed in order to make the information available on an unclassified, open publication basis, to any interested parties. The effort to declassify this report has been accomplished specifically to support the Department of Defense Nuclear Test Personnel Review (NTPR) Program. The objective is to facilitate studies of the low levels of radiation received by some individuals during the atmospheric nuclear test program by making as much information as possible available to all interested parties. The material which has been deleted is either currently classified as Restricted Data or Formerly Restricted Data under the provisions of the Atomic Energy Act of 1954 (as amended), or is National Security Information, or has been determined to be critical military information which could reveal system or equipment vulnerabilities and is, therefore, not appropriate for open The Defense Nuclear Agency (DNA) believes that though all classified material has been deleted, the report accurately portrays the contents of the original. DNA also believes that the deleted material is of little or no significance to studies into the amounts, or types, of radiation received by any individuals during the atmospheric nuclear test program.

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NUCLEAR RADIATION FROM A DETONATION AT VERY -HIGH ALTITUDE Erneet A. Pineon, Coi, USAF Commader, Tack Unit 7.1.3 (-’$ObA. Chirnent, Maj, USA

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other militery-effeot projeots caa be obtalnd from ITR-166% the %mmary Report of the Commuxler, Task IhMt 9.” This teohnbal aunmxy fnohldes: (1) tables Mung eaoh detion with ita yield, &pe, environment, metaombgiaal comtitioM, eto. ; (2) maps ehowing shot lCMXUOM;(9) dhousdons of rewlta by p~; (4) summaries of objeoUves, procedures, results, etc. for all projeota; - (5) a listing of projeot reports for

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‘l’heobjective was b measure the neutron spectrum ad totalPrompt gamma ray fluxproduced by the detonation of a nuclear device of low ylelci at m altitude of shout 90,000 feet. l“hfs information wae to be obtahMd by euitahle detectors in the vicinity of the nuclear device and telemetered to the ground to be recorded sad subsequently The theory ad inetrum ntation for measurement of neutron ~ sxi total prorcptgamma-ray flux from a nuulear device detonated at an altltufje of 85,000 feet 1s descfibed. Measurement of neutron time of flight with a IA% sclnUUator-photodiode detector, with a simtlar LiI detector for gamma-ray correction of the Li~ detector, was pkaned. The measurement waa to have extended to plus 120 meet. A Cal ecfnU.Ilationdetactor, whose output wa.a integrated for the first 10 peso afta the zero time, sad a XBr oryetal, wbss &kening was meaaured as a function of the for 120 mew aftar zero time, wexwto tm used to detect gamma flux. The detector outputs were ta have been electronically encoded ad recorded on a magnetic-tape recorder programmed to record for 120 msec after zero time, reduce its speed to 1/16of the recording speed, and continuously play back tbe data. The recorder output modulated a 70-Icc volxe+ontrolled oscillator used in a standard frequencymcdulated telemetering system. A ground etation received and recorded the sigmal, The Bendix command system shared by this project end Projects 1.10 and 8.2 failed, and no data was obtained.

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wae done hy the Nuoleonics Dfvlaion personnel who participat$xi in the field, the timeAy completion of the printed ciroultry and the solution of oircult problems could not have oo - curred without the aid of the Xmtrumentatton Branch of the Radiation Division of Naval Research Lahoratog (NRL). In parthxdar major contributions were made by G. Wall,

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Tho objeotive was to rneuure theneutron epeotrurnandtotal prompt gamma ray flux p*wOd by the detonation of a nuolear detioe of low yield tianeltitude of about 90,000 feet. TbM tiO=on W to be obtafhed by suitable dei4wtora h the ticidw of ~ m@ear *OO and teleared to the ground to be reoorded mid imbDuring Opertion Teapot, neutron flux from a devioe ddmated at 38,600 feet above mean eea level (=ot 10) me measured by meena of threshold fledon end aotlvation detectore in canfders dropped from the delivery airoreft. Gqnma rays were meaeured with doaimetar fihne, DT/60/PD service doaimetere, silver phom glaos and uhemid doeimeters. Several flsdaMhreehold deteotore with threaholda at 200 ev, 1,000 ev, 700 kev, and 1300 kev were ueed. The differences in flux given by these deteotorfi were plottad ae a hfetogram (Raferenoe 1). A rough picture of the apeotrum wae given. Threshold deteotirs do not permit a detailed analyda of the epeotrums for reaeone dieoueaed in Reference 1. Time-of-flight methode can give good energy-epeotrum meaeuremente if the geometry ie good (neutrone eoattered hho the detetotor are exoluded or oegifgibie) and if the time duration of neutron production 1s short, compared to the mean time of flight. At tlte altitude planned for the very-high-altitude burst (Shot Yucca), the air denally is approximately 1 percent of the atr denad~ at aea level. For this small denul~ and for small ranges, the time-of-flight method for meaaurementa of neutron-energy epeotra becomes feadble. The neutron-threehold data from Shot 10 of operation Teapot wae used to calculate the condttione for the meauuremeat. Originally, it wee planned to use a “real time” telemeter link, i.e. , the telemeter would transmit the eignal inetan~eously. It was noted, however, that the blaat data telemeters in the near caaiet8rs during 9hot 10 of Operation Teapot were inoperative for a period in the order of 8eoomie, caueed by absorption of the telemetering @@ @ the intense gamma-ray ionization produced by the nuclear device. The theory of this attenuation waa inadequatefor the calculation of the attenuation in the very-high-altitude caae. It waa not possible to chooee either operating frequency or transmitter power without detded knowledge of the attenuation. Therefore, meamuementa of attenuation were made in the X bad range during Operation Redwing (Reference 2). Although the mea.eurementa were successful, they were made at only one frequeoc y ad one range. On the bads of the Redwing data, a real-time link might be successful. To enlarge the data and to field teet telemeter technique, fur-

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results idicated that a red-ti- W would nothe feadhle for w reaanable frequenoy or trexumitter power. The plana for Shot Yuooa then nece-arlly included nwane for data etorage eo that data traaemisdon could take plaoe after the ionization had cleared up. Aa attriotive proaedure for meammlng the enerw epeotmn ofanatrwa eouroe is the puleed neutron beema and mobanimlly ohopped reaotor beams. Shoe the neutrone reulting from a nuolear deti!mtlon are all emittad in 8 reiativdy 8hort Ume, the method is edaptahle here also; but a rdatlvoly long peth length 1s neoesury, *O x of M fiadon neutmne are very energotio. la addition, the extremdy high pulhle flux wailahle makes posdble a detaotor wstom that need not oount idividud events, mat largs df-es from the eouroe. Suppose the deteotor is a didanoo 1 fmm the noutsoa aouroo, ad at fht lot us ne~ observed neutrons trwel dhotly from eouroo to dsteotor, there is a eimple re14Uon between time of arrival ofs neutron (t) and it8 ermm (*): The detector racorda the number of neu@one reaohlng the deteotor per unit of time, q(t). Then, if N(E) is the number of neutrons per unitof energy emitted, the following simple reiationahip holde, with E ad t connected by Equation 1: In the present experiment, 1 = 834 metere. Some typical neutron delay timee are ae follows (initial y rays arrive at t = 2.78 Kseo): The interpretation of the actual experiment is, of course, complicated by two effects: interaction of neutrons with the air and variation of detector efficiency with ener~. In

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that the neutrons undergo during collision with the air can be negleoted. l’his enerw degradation is small for most of the neutrone, shoe the mead number of aoattmrings experienced by a neutron is small. If A(E’ ) in the atUmuaUon of the direot be- of ene~ TMS is an inhomogeneous intagral equation for the desired qusntfty N(E), the eouroe intensity per unit of energy. The integral represents the tital effeot of all in.eoattered neutrone of energy higher h E’, hence capable of being confused with direot neutrons of The problem of data reduction from a high-altitude detonation then is reduced to: (1) an evaluation of the kernel K(E, t’), which represents geometrical and physical properties of the atmosphere end its interaction with neutrons of all energies; (2) a calculation of the quanti~ Q(E); and (3) solution of the foregoing integral equation. Problem 3 seems rpost sueoeptible to a stapwise numerical procedure, begfnntng with the higheet energy groupe and working downward. Experimental values of I(t’) are Inserted, and successively Iower values of E’ are reached. Problem 2 is essentially solved by the work on detector, recorder, snd electronic calibrations given elsewhere in thlIs report. assuming single sc~fi~ of he neutrons ~, agtin, aSEUX@ no enerw degradation due to scattering in the air. The vaiidi~ of thts assumption and its appl.lcabllity in the present case might well be questioned, but as a tempor~ expedient it seemed WCrtb-

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In Formula s ad the subsequent deflnitio~ the tlUM of artivd, t’, is rneaeured in unite x = a variable of integration

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Ground To Ground Figure 1.1 Coordinate eyetem for scattering calculation. b reliable out to P = 3 E. This memo, for example, that correction can be made for the In an attempt to overcome the inherent Mnitationa of the eingle scattering approxiterested in this problem. The hope 16 to develop a “workable” Monta4arlo type of

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The inetrumentatton oanieters d nuolear device were mspeded from a large plaatic balloon, launohed at 1126:06, 28 April 1968, from the flight &ok Of the U- Boxer (CV8-21). Detonation ooourred at 1440, 28 April 1958 at 86,000 feet at LaUtude 12 degrees 37 minutes north sd Lon@tude 163 degrees 013 minutes east, in b Eniwetok tude had been reaohed, as well u telemetering reoaiving - reoordng fscffltiea, were provided by Projeot 1.10’8 “grou# ctation on the fli@t deok of the U8S Boxsr. Projeot 2.7 inetmmen tath wu aontatned in a premurlzed alwninurn Vaseel, 22 laohes high ad 81Alnohes in dlametsr, oompridng the upper half of the Canitir 6. The _ tors were mounted in the top of the half camitir, with the more maadve aompcmentain the bottom. 2%0bwer half of Csaieter 6 end the other four oaniaters oontained inatxwmentatlon ueed by Projeote 8.2 and 1.10. Control ad telemetering for Projeot 2.7 were aocomphhed by equipment mounted in the lower half of Cant8ter 5, serving both PmjeotS 2.7 and 1.10. At the time of detonation, Canister 5 wae 2,760 feet from the nuoleu dwiuet or at an altitude of about 824260 feet. A time-of-flight neutron measurement wu seleoted. Two sotntlllation detaotors were used, one with a Lit crystal and one with a normal MI myetd. The MI ad LPI orystah should reapoxd to gamma rayt in the same way. By comparimm of their outputs, the neutron component can be isolated. ‘IWOgamma-ray detectors were employed. The flrti used a CSI oryatal a8 a soinUllator, the second, a KBr crystal in whlah the darkening produced by gamma radtation was measured. The CSI detector channel was designed to measure the integral of the gamma radiation during the period from O to 10 gsec after detonation. The KBr deteotor is inherently an integrating device and would provide, at any time after detonation, the inteIn the low+enslty air at 90,000 feet, it was believed that the five canisters might hang in a straight line, sinoe there would probably be little wind shear in the 3,000 feet between the nuclear device and Canister S. This would interpose the mass of the upper four canisters be~een the device and the deteotirs used by Projeot 2.7, introducing an unknown tured by Atlantic Reeearoh Corporation, Alexsadria, Virglnfa) producing 40 pounds of thrust for 1 seoond. This was to have been detonated at minus 2 seoonda to produce a OA-g aooeleration of the 80-po~ r. I The resuiting deflection of the cant-r would have been approximately 30 feet at zero time and continued to about 90 feet at plus 7 The outputd of the four detectors were enooded electronically and recorded sixnultaneously on four psral.lei tracks of a magnetic-tape recorder having a recording time of about 120 msec. On completion of the recording operation, the tape speed was reduced to ?/10of the recording speed and the data played out, one channel at a time, into a stand-

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reoolxkl by the ground StaUm. . The deteotors ueed h thts experiment were dedgned to give a quantitativemeaeure— malt of the ebeolute mutzwn elmotmm ead the gamma-ray doeage produoed by the nuolear moo the ehot wee to take plaao eta very-h@ aitlblde (abut 90,000 feet), itwas known effeot of the atmosphere for neutron energies in exoeea of 0.1 Mm, is emall at theee altitudes. The ~-ray flux - meaeured in * ways-the doeege in the inttlal pulee, …