field testing - the physical proof of design principles

Field TestingThe Physical Proofof Design Principlesby Bob Campbell, Ben Diven, John McDonald, Bill Ogle, and Tom Scolmanedited by John McDonald

For the past four decades, LosAlamos has performed full-scalenuclear tests as part of the Labo-ratory’s nuclear weapons pro-

gram. The Trinity Test, the world’s firstman-made nuclear explosion, occurred July16, 1945, on a 100-foot tower at the WhiteSands Bombing Range, New Mexico. Theactual shot location was about 55 milesnorthwest of Alamogordo, at the north endof the desert known as Jornada del Muertowhich extends between the Rio Grande andthe San Andres Mountains.

The actual detonation of a nuclear deviceis necessary to experimentally verify thetheoretical concepts that underlie its designand operation. In particular, for modernweapons, such tests establish the validity ofsophisticated refinements that explore thelimits of nuclear weapons design. In addition,occasional proof tests are conducted of fullyweaponized warheads before entry into thestockpile, and from time to time weapons arewithdrawn from the stockpile for confidencetests. Also, tests characterized by a highdegree of complexity are conducted to studymilitary vulnerability and effects.

Information from test detonations assuresthat weapons designs which match theirdelivery systems can be produced in a man-ner consistent with the availability of fissilematerial and other critical resources. The

164

interplay of field testing and laboratory de-sign is orchestrated to optimize device per-formance, to guarantee reliability, to analyzedesign refinements and innovations, and tostudy new phenomena that can affect futureweapons.

The advent of versatile, high-capacitycomputers makes it possible to model thebehavior of nuclear weapons to a high degreeof similitude. However, subtle and im-perfectly understood changes in designparameters, such as small variations in mass,shape, or materials, have produced unex-pected results that were discovered onlythrough full-scale nuclear tests. Whereas thesymmetry and compression of mock fissilematerial can be studied by detonating highexplosives in a controlled laboratory en-vironment without producing a nuclear yield,the actual performance of a weapon,particularly one of the thermonuclear type,cannot be simulated in any conceivable labo-ratory experiment and must be done in anactual nuclear test.

Field testing is the culmination of theimposing array of scientific and engineeringeffort necessary to discharge the Labora-tory’s role in developing and maintainingnuclear weapons technology to support theUnited States national security policy ofnuclear deterrence. Embedded therein is theparadox: How do you test a bomb, un-

disguisedly an instrument of destruction,without hurting anyone?

From the beginning, field testing of nu-clear weapons has followed commonsenseguidelines that accord prudent and balancedconcern for operational and public safety,ob ta in ing the maximum amount ofdiagnostic information from the high-energy-density region near the point of explosion,and meeting the exacting demands of engi-neering and logistics in distant (and some-times hostile) environments. The extremeboundaries of the arena of nuclear testingencompass tropical Pacific atolls and harshAleutian islands, rocket-borne reaches intothe upper atmosphere, and holes deep under-ground. Since 1945, tests have occurred atoptowers, underwater, on barges, suspendedfrom balloons, dropped from aircraft, liftedby rockets, on the earth’s surface, and under-ground. The locations evoke the words of aonce-popular song, “Faraway Places withSt range-sounding Names’’—Bikin i ,Eniwetok, Amchitka, Christmas Island; andnearer to home, at the Nevada Test Site(NTS), Frenchman Flat, Yucca Lake, andPahute Mesa, among others. These names,no longer so strange sounding, have becomefamiliar parts of the test community’s lan-

guage.At various times between June 1946 and

November 1962, atmospheric and under-

Winter/Spring 1983 LOS ALAMOS SCIENCE

Aerial view of subsidence craters from underground nuclear tests in Yucca Flat at theNTS. The so-called Yucca Lake is in the background, and the Control Point complexis to the right of the dry lake.

ground tests were conducted by the U.S.principally on Eniwetok and Bikini Atolls inthe Marshall Islands and on ChristmasIsland and Johnston Atoll in the PacificOcean; at the Nevada Test Site; and over theSouth Atlantic Ocean. Since November1962, even before the atmospheric test bantreaty of 1963 came into effect, all U.S.nuclear weapons tests have been under-ground, most of them at the NTS, as part ofan ongoing weapons program. Three under-ground tests were conducted on AmchitkaIsland in the Aleutians. Some tests for safetystudies, peaceful uses of nuclear energy, andtest detection research were conducted onthe Nellis AFB Bombing Range in Nevada,and at other locations in Colorado, Nevada,

New Mexico, and Mississippi. The accom-panying table summarizes testing activities.

A nuclear test moratorium initiated in

LOS ALAMOS SCIENCE Winter/Spring 1983

1958 was ended abruptly in August 1961when the Soviets resumed atmospheric test-ing. During the period of nontesting, the U.S.made substantial progress in its mathemati-cal modeling capability, but becausesubstantial preparations for atmospherictests had not been made, it was not until thelate spring of 1962 that atmospheric nuclearexperiments could be fielded. Undergroundtests had been resumed in the early fall of1961.

In conjunction with ratification of theLimited Test Ban Treaty (LTBT) in October1963, the Joint Chiefs of Staff defined foursafeguards, which, with the strong support ofCongress, were to have significant impactupon the Laboratory.

The first safeguard was, in effect, apromise that the nuclear weapons labora-tories would be kept strong and viable. The

second called for a strong underground testprogram. The third concerned maintenanceof the capability to return to testing in the“prohibited environments’’—the atmos-phere, underwater, and space—should thatbe necessary, and the fourth recognized theneed to monitor carefully the nuclear testactivities of other nations.

The first two safeguards provided newjustification for underground testing, includ-ing tests purely scientific in nature. The thirdsafeguard led to nonnuclear atmosphericphysics tests in Alaska, northern Canada,and the Pacific region. The facilities andcapabilities held in readiness for nuclear testswere used in many scientific endeavors,including solar eclipse expeditions andauroral studies. The fourth safeguard wasresponsible for triggering Laboratory ac-tivity in space, as Los Alamos developed asatellite test-monitoring capability that arosefrom the Vela program. This in turn has ledto a number of first-rate scientific spaceprograms.

At present, the Los Alamos test programis carried out by approximately 385 Labora-tory employees from the Test OperationsOffice and various divisions, including WX,P, ESS, MST, INC, M, X, and H. Theirefforts are supplemented by about 740 con-tractor employees of the DOE’s NevadaOperations Office working at the NTS.Notable among the contractors are theReynolds Electrical Engineering Company(REECo) for drilling and field construction,EG&G for technical support, Holmes andNarver (H&N) for construction architectureand engineering; and Fenix and Scisson(F&S) for drilling architecture and engineer-ing. The dedicated efforts of all these peopleare necessary to execute nuclear tests as avital element of the Los Alamos weaponsprogram.

Diagnostics and Testing Technology

Before the Trinity test, estimates of itsyield varied from zero to 20 or more kilo-

165

NUCLEAR WEAPONS TEST OPERATIONSa

AnnouncedU.S. Nuclear

Operation Testsb Dates Location

Trinity 1 Alamogordo New MexicoJuly 1945June - July 1946April - May 1948January - February 1951April - May 1951October - November 1951April - June 1952October - November 1952March - June 1953February - May 1954February - May 1955April 1955November 1955- January 1956May - July 1956April 1957May - October 1957December 1957February - March 1958April - August 1958August - September 1958September - October 1958September 1961- June 1962April 1962- October 1962July 1962- November 1962July 1962- June 1963August 1963- June 1964July 1964- June 1965July 1965- June 1966July 1966- June 1967July 1967- June 1968July 1968- June 1969July 1969- June 1970October 1970- June 1971July 1971- May 1972July 1972- June 1973October 1973- June 1974July 1974- June 1975September 1975- August 1976November 1976- September 1977October 1977- September 1978November 1978- September 1979November 1979- September 1980October 1980- September 1981October 1981- September 1982November 1982-

Bikini AtollEniwetok AtollNevada Test SiteEniwetok AtollNevada Test SiteNevada Test SiteEniwetok AtollNevada Test SiteBikini and Eniwetok AtollsNevada Test SiteEast PacificNevada Test SiteEniwetok and Bikini AtollsNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteEniwetok and Bikini Atolls; Johnston IslandSouth AtlanticNevada Test SiteNevada Test Site; Carlsbad, New MexicoChristmas and Johnston IslandsJohnston IslandNevada Test SiteNevada Test Site; Fallon, NevadaNevada Test Site; Hattiesburg, MississippiNevada Test Site; Amchitka, AlaskaNevada Test Site; Hattiesburg, MississippiNevada Test Site; Dulce, New MexicoNevada Test Site

World War II were August 5 and 9,1945,

Nevada Test Site; Grand Valley, Colorado; Amchitka, AlaskaNevada Test SiteNevada Test Site; Amchitka, AlaskaNevada Test Site; Rifle, ColoradoNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteNevada Test SiteNevada Test Site

respectively.b All tests before August 5, 1963, and after June 14, 1979, have been announced.

166 Winter/Spring 1983 LOS ALAMOS SCIENCE

Field Testing

Schematic of a pinhole imaging experiment.

tons. Even if the yield had been known inadvance, estimates of the effects of theexplosion were based on speculation plussome extrapolation from a 100-ton shot ofhigh explosive, This rehearsal shot, consist-ing of 100 tons of TNT laced with fissionproducts, was made prior to Trinity toprovide calibration of blast and shock meas-urement techniques and to evaluate fallout.The yield of Trinity was measured by ob-servation of the velocity of expansion of thefireball as photographed by super-high-speedmovie cameras, by radiochemical analysis ofthe debris, and by observation of blastpressure versus time and distance. If theyield had been disappointingly low, the mostimportant diagnostic for understanding thereason for failure would have been measure-ment of the generation time, that is, thelength of time spent in increasing the fissionreaction rate by a given factor. Effectsmeasurements were needed to predict thedamage that would be done to the enemy byblast and radiation and also to evaluatepossible damage to the delivery aircraft.

The Trinity measurements were amaz-ingly successful considering it was the firstshot observed. The photographic coveragewas superb. The fireball yield technique wasconfirmed by radiochemical data. The gen-eration-time data were successfully recorded


on the only calibrated oscilloscope fastenough to make the measurement. Observa-tions of debris deposition patterns led to thefirst fallout model. Dozens of other experi-ments, such as blast pressures versus dis-tance, neutron fluences in several energyranges, gamma-ray emissions, and thermalradiation effects, also gave useful data.

Postwar tests had the same general re-quirements for diagnostics as Trinity, butallowed more time for diagnostic develop-ment to improve the original techniques andto add new measurements. Yield is stillmeasured by radiochemical techniques thatwere pioneered for Trinity, although theyhave been greatly improved upon since then.In addition, for as long as atmospherictesting was done, fireball measurements gavereliable yield determinations. Methods weredeveloped to obtain the yield from accuratemeasurements of the spectrum of neutronsfrom the devices by careful observations ofthe emerging gamma rays, and, for under-ground shots, where a fireball cannot beobserved, from the transit velocity of theshockwave through the ground. Generation-time measurements that covered only a smallinterval of the complete reaction history ofthe Trinity explosion have been expanded tocover changes in reaction rate and gammaoutput over as many as 17 orders of magni-

tude. Detectors and recording equipmenthave been developed to follow the later fasterreacting devices. Methods have been de-veloped to observe the flow of radiant energythat emerges from a device in the form oflow energy x rays by observation of the x-ray spectrum as a function of time. Alongwith development of the various diagnosticdetectors have been improved methods oftransmitting data from detector to the re-cording stations. In addition to use of coaxialcables. which were first used at Trinity, wenow use modern instrumentation that in-cludes fiber optics, digital systems, andmicrowave transmission.

Photographic coverage of atmosphericevents, starting with Trinity, reached a peakof perfection in the art of high-speed datarecording, calling on the combined intellec-tual and technical resources of the Labora-tory as well as a number of contractors,notably Edgerton, Germeshausen and Grier,who made significant contributions in os-

cilloscope and photographic technology, andthe Naval Research Laboratory and theUniversity of California Radiation Labora-tory, who were successful in carrying outhighly complex experiments. The innova-tions born of this expertise have proliferatedbeyond nuclear weapons testing to find ap-plication in many scientific activities requir-ing high-speed data resolution, ranging fromendeavors as separate as studies of transientphenomena of interest in fusion energy re-lease for civilian power to picosecondcameras used in studies of photosynthesis.

As a more detailed example of an experi-ment on a weapons test, consider a veryuseful diagnostic tool developed during at-mospheric testing and modified and refinedfor underground use. A pinhole camera isused to take a picture of the actual shape andsize of the fissile material of a fission bombas it explodes or of the burning fuel in athermonuclear bomb. A tiny pinhole througha thick piece of shielding located between theexploding device and a detector projects animage of the device onto the detector.

167

Gamma rays and neutrons from the reactingmaterial are transmitted through the bombparts, such as high explosive and bomb case,and reach the detector (for example, a fluor)and cause it to light up with a brightnessproportional to the intensity of incidentradiation. The resulting image is a two-dimensional picture of the reacting fuel, asseen through the bomb debris. The brilliantlight and x rays from the bomb surroundingsare eliminated by a thin screen of metalbetween the bomb and the fluor. A TVcamera then transmits the picture to a re-cording station. It is even possible by use ofvarious schemes to produce gamma rays orneutron pictures of selected energies or to getseveral frames of motion of the reactingregion separated by a few billionths of asecond.

We were presented with new challengeswhen, in 1963 as a result of the LTBT, alltests had to be conducted underground.Underground emplacement of a nuclear de-vice at the Nevada Test Site occurs in one oftwo basic modes: in a vertical shaft or ahorizontal tunnel, with appropriate arrays ofdiagnostics for weapons development testsor for weapons effects and vulnerabilitystudies. Of course, when any test is con-ducted for whatever reason, as many experi-ments and diagnostics measurements areadded as can be accommodated in thelimited volume of subsurface placement tomake optimum use of the device’s uniqueand costly output. Diagnostic informationtypically is obtained with sensors that “look”at the test device through a line-of-sight(LOS) pipe or by close-in sensors whoseoutput is transmitted over coaxial or fiberoptics cables to remotely located high-data-rate recorders. A variety of techniques isused to protect diagnostic equipment longenough to obtain and transmit data beforebeing engulfed in the nuclear explosion.

During atmospheric testing, we measuredyield, radiation, blast, and thermal effects,but we also studied weapons phenome-nology: how the weapons’ outputs interacted

168

DNA Auxiliaryclosure

Cooperation between Los Alamos and the military services in weapons effects testingbegan soon after the close of World War II. The damage from atmospheric,underwater, and surface detonations was assessed by positioning a variety of militaryhardware at various distances from the device. When above-ground tests wereprohibited, effects tests were transferred to horizontal tunnels deep underground. The

figure shows a typical modern-day Defense Nuclear Agency effects test arrangement.A Los Alamos (or Livermore) supplied device is located in the Zero Room, which isconnected to a long, horizontal line of sight (HLOS) containing several test chambers.Various rapid closure mechanisms in the HLOS allow radiation generated by thenuclear device to reach test chambers but prevent the escape of debris and radioactivegases. Following the test, military hardware and components that have been placed inthe test chamber are retrieved and the effects of radiation exposure are evaluated atDNA contractor laboratories. The radiation output from the device provides a uniquesource for answering physics questions of interest to weapons designers. Occasionallysuch physics experiments are mounted simultaneously with effects tests. Usually theadd-on experiments consist of one or more line-of-sight pipes with appropriatedetectors as shown near the Zero Room in the figure.


Field Testing

Typical Weapon Development Test

Recording

Control Point


with the environment and the effects ofweapons-generated electric and magneticfields. Information on these subjects gleanedfrom early tests has been extremely helpfulwith respect to present problems, specifi-cally, the interference of electromagneticpulse (EMP) signals with power grids, com-munication links, and satellites, and typical

Diagram at left: Most weapons develop-ment tests are conducted in verticalshafts drilled deep into the ground. Arack holding the device, the associatedfiring components, and the diagnosticsdetectors and sensors is lowered into theemplacement hole and the she@ isbackfilled with a combination of sand,gravel, concrete, and epoxy that stemsthe hole to ensure containment of thenuclear explosion. The test is fired bysending a specific sequence of signalsfrom the Control Point to the “RedShack” near Ground Zero. (The RedShack houses the arming and firingequipment.) The diagnostics instrumentsdetect outputs from the nuclear deviceand the information is sent upholethrough cables. Usually within a fractionof a millisecond following the detonationthe sensors and cables will be destroyedby the detonation, but by that time thedata have been transmitted by cables torecording stations a few thousand feetfrom Ground Zero or by microwave tothe Control Point. Photograph: Aerialview of Ground Zero rack tower,diagnostic cables, and diagnostic-record-ing trailer park. Final test preparationsinclude emplacing miles of cable down-hole. The cables will transmit vital testinformation to the diagnostics trailers inthe foreground of the picture. A rackcontaining instrumentation to go down-hole is assembled in the tower at the topof the picture.

169

This photo contrasts the information capacity of fiber opticsA device diagnostics rack suspended from a crane prior tobeing installed inside the Ground Zero rack tower. Themodular rack tower is erected over the emplacement hole toprovide protection against wind and weather while diagnosticsequipment is installed and prepared for the test. Finally therack and the device canister are lowered into the hole, the racktower is disassembled, and the hole ispropriate stemming material.

other weapons effects associated withprompt radiation and blast. While we can’tstudy all of these problems underground,many weapons effects can still be observed.The Defense Nuclear Agency of the Depart-ment of Defense funds very complex tests ofthis nature and Los Alamos participates inthese shots, frequently supplying and firingthe nuclear explosive as well as makingmeasurements of weapons effects.

From the time of the first nuclear ex-plosion, there was speculation about non-military uses for these devices. Among thefirst scientific applications were contribu-

tions to seismology and meteorology.Knowledge of the exact time and location ofnuclear explosions is particularly useful inobtaining information complementary to

170

backfilled with ap-

cables (orange) with those of coaxial cables (black). A singlebundle of fiber optics cables (orange cable at lower right)carries data in the form of light signals from the undergrounddiagnostics rack at Ground Zero to a photomultiplier stationwhere the light signals are converted to electrical impulses.The coaxial cables exiting from that station transmit the datato the recording stations in the background. These stationshouse oscilloscopes that record the data on photographic film.

that from earthquakes. New chemical ele-ments have been produced by nuclear ex-plosions: specifically, the elements einstein-ium and fermium were discovered in 1952 inthe debris from a high-yield Los Alamosthermonuclear device. Los Alamos scientistshave also applied nuclear tests to the meas-urement of nuclear physics data concerningreact ions of nucle i wi th neut rons ,particularly on those isotopes whose self-radioactivity tends to mask the data gener-ated from the lower fluxes available in thelaboratory.

When the Limited Test Ban Treaty of1963 resulted in all of our nuclear tests beingconducted underground, the necessary engi-neering developments were made whichproduced a line of sight from a deeply buried

bomb to the ground surface. This line ofsight remained open long enough for neu-trons and gamma rays from the bomb toreach the surface, but was closed off by avariety of shutters and valves and groundshock before any radioactive debris couldescape. With this system, a very nicelycollimated beam of neutrons could beproduced that was ideal for study of neutron-induced reactions. From 1963 to 1969, eightof these experiments were performed andproduced a mass of useful physics data.

Except for state-of-the-art improvementsin solid-state electronics, digitization of data,and miniaturization, some test diagnosticshave changed relatively little since earlytesting experiments. which bears witness tothe ingenuity of pioneers at the Pacific and


Field Testing

A fiber optics cable compared to three types of NTS coaxial cable. The two smallercoaxial cables (RF-19 and RF-13) are used downhole and the larger cable (RF-16) isused only for horizontal surface transmission. Each coax cable provides a single datachannel; the fiber optics cable provides eight data channels. Depending on the qualityof fiber used, the cost per fiber data channel is 1/3 to 1/6 the cost of the cheapest coax(RF-13) shown here. The fiber provides a bandwidth (data capacity) far exceedingthat of coax cable. Fiber can provide a bandwidth above 1 GHz for a I km length;RF-13 cable can achieve 1 GHz over a 50 m length. The fiber cable is much lighterand smaller than the coax. Since it is nonmetallic, it precludes coupling of electricalinterference from the test into sensitive recording instrumentation. Inside a ruggedplastic sheath, layers of stranded Kevlar protect and strengthen the inner bundle offibers. Each fiber is in a small plastic tube (8 in all) and each tube is filled with a gelmaterial. A central strength member provides most of the tensile strength. This designtotally precludes transfer of radioactive gas along the cable while providing excellentprotection for the delicate fibers inside.

Interior of a diagnostics recording station with oscilloscopes and cameras.

Nevada proving grounds. It is a tribute ofconsiderable magnitude to realize that someof the gear fielded at Trinity represented anew branch of technology that was bornessentially full grown.

Engineering, Construction, andLogistics

Early testing experience established amode of operation, largely followed by LosAlamos participants ever since, that grewout of a habit of broad discussions amongthe experimenters and theoreticians leadingto an agreed course of action. The earlytests, apart from Trinity, were done on ornear isolated islands in the Pacific. It was anenormous task to provide the necessaryequipment, laboratory and shop facilities,spare parts, transportation, communications,living accommodations, and everything elseneeded to conduct test operations underdifficult conditions on tight schedules farfrom home. Pacific operations atypically re-quired planning over a two-year period be-cause they presented extraordinary situ-ations compared to most scientific and engi-neering undertakings. Some of the ad hocsolutions to vexing and unique problemsestablished precedents that have proved ad-mirably sound in the light of subsequentcritical examination.

One specific engineering task was theconstruction of towers to support the testdevices above ground. Our appetite for shottowers that could support bigger loads atgreater heights was insatiable. Early towersneeded only to support the device itself, somefiring hardware, and perhaps a few detectorsand coaxial cables, but we continued to addshielding and collimator loads as ourdiagnostics techniques developed. By the endof the atmospheric testing period, we wereroutinely accommodating tower loads of 100tons distributed on any two of the four legs.Our desire for higher towers was driven bythe operational problems created by theTrinity shot when activated or contaminated

LOS ALAMOS SCIENCE Winter/Spring 1983 171

particulate matter was engulfed by the fire-ball and entrained in the resulting cloud. TheTrinity shot was fired on a 100-foot tower.We progressed to 200 feet for Sandstone,300 feet for Greenhouse, 500 feet for Teapot,and 700 feet for the Smoky shot of thePlumbbob series.

There are many true and untrue talesregarding towers. The tower for GreenhouseGeorge was heavily loaded, but the storythat you couldn’t withdraw a bit after drillinga hole in the tower leg because the weightcaused the hole to immediately become ellip-tical is not true. It is true, however, that usersof the taller towers reported very perceptiblemotion at the top on windy days. whichproduced little enthusiasm for working undersuch conditions. People did get stuck inelevators when winds whipped cables aboutand once technicians even disconnected thepower needed to fire the device while theywere removing the tower elevator after the

device was armed.Towers were necessary for shots with

elaborate diagnostics. but there were othershots whose purpose could be satisfied by airdrops from military aircraft, although wewere not always skillful enough to buildtargets that the Air Force could hit. In thePlumbbob series, several tests were con-ducted with devices suspended from tetheredballoons in a system engineered and oper-ated by Sandia Corporation. The balloonscould not be inflated in high winds, but theysignificantly reduced the operational prob-lem of fallout by allowing us to fire as highas 1500 feet above ground level.

Beginning with the Castle series of 1954,we were able to repeatedly fire large-yielddevices in Pacific lagoons near fixeddiagnostic stations on land by placing thedevices on barges moored at the four cornersto anchors on long scope. By adjusting theindividual winches on each corner, we couldhold barges to within a few feet of theirrequired positions. Mercifully, the tidal varia-tions at Eniwetok and Bikini are slight.

Power was a problem both in the Pacific

172

A test device mounted on a 500-foot tower at the Nevada Test Site. Taller and tallertowers were built (to as high as 700-feet) to minimize entrainment of ground debris bythe fireball and thereby reduce fallout resulting from the test.

and Nevada. At NTS, power was generated a bit risky. In the Pacific, power was usuallywell away from the shot areas, but both the generated by diesel-driven generators near

above- and below-ground distribution sys- the point of use. The diesel engines would

terns were subjected to ground shock which loaf along for hours under low loads and

tended to make counting on postshot power then die when the required large loads were


Field Testing

This photo of a balloon-carried test configuration was taken around 1957. The deviceis suspended from the balloon and the balloon is tethered to the ground by steel cables.With the balloon at the desired altitude (perhaps 1500 feet) the device was fired bysending electrical signals through the firing cables that connected the device with thefiring system on the ground.

An early barge-mounted test configuration at the Pacific Proving Grounds. Thenuclear device is housed in the shot cab (white structure).

imposed minutes before shot time. Ex-perimenters were plagued at both sites by thequality of the power and by the effects of thetest-generated EMP carried on the powerdistribution system. EMP shielding rangedfrom continuously soldered solid-copper lin-ing of the recording rooms, to screenedrooms, to no screening except that providedby reinforcing bars in the structural con-crete—each according to the tenets of theindividual experimenter. Power and timingsignals were sometimes brought in on in-sulated mechanical couplings (with a motoror relay outside the shielded volume coupledmechanically to a generator or relay inside).Continuity of power was sought by severalstratagems that included replacing fuzes withsolid wire. Breakers in substations werewired closed to prevent ground motion orEMP from operating them, Automaticsynchronizing and transfer equipment wasdesigned to run generators in parallel andpass the load back and forth as necessary.This proved to be unreliable. so we ended uprunning several generators, each of sufficientsize to carry the whole load and eachcarrying a dummy load, each of which couldbe dropped if any one or more of thegenerators running in parallel failed.

Concrete was a problem in the Pacific,since the only available aggregate was coraland we had to use salt water. Several mixeswere invented, some to provide the requiredstrength for recording stations and some tomatch the strength of normal constructionconcretes so that we could have valid effectstests on typical military and civilian struc-tures. At both sites we learned to calculateand design shielding for collimators and theirrecording equipment. The resultant design ofmassive structures tended to err on theconservative side. The high-density concretemade by loading the mix with limonite ore,iron punchings, and the like gave densitiestriple that normally encountered, but wasrough on mixing equipment and difficult toemplace. On some stations that had tofunction in close proximity to megaton-class


devices, the center-to-center spacing of rein-forcing steel approached its diameter andpresented a very difficult job for the con-struction worker. There was a legend, neverconfirmed. that some iron bars which hadbeen included for shielding in the design of astructure near Ground Zero were omitted inthe construction because the superintendent“knew very well that the structure wouldstand without them.”

Our initial experience in drilling the deepemplacement and postshot sampling holeswas instructive. It must be the custom in thedrilling industry to do whatever the manpaying the bills asks, and not proffer anysuggestions, for we were permitted to rein-vent a number of existing drilling techniques.

particularly in postshot drilling for radio-chemical samples. Once Fenix and Scisson,Inc., came aboard as drilling and miningarchitect-engineer (A-E) and REECo tookover enough of the drilling previously doneby contract drillers to provide continuity, ourlot improved. Big-hole drilling techniqueswere developed which are now accepted

throughout the industry. We learned to ex-tract postshot samples of device debriswithout releasing radioactivity to the at-mosphere. Drilling times have improved eventhough the diameters of emplacement holeshave increased from two to eight feet, andpostshot operations that once took morethan a month are now done in a safer andcontained fashion in less than a week.

None of this work could have been donewithout the complete cooperation of thecontracting officers and the sometimesheroic efforts of the architect-engineers andconstructors in support of the laboratories.A real “can-do” attitude on the part of allconcerned has been the trademark of theweapons testing community since Trinity.

For the earliest tests, namely Trinity andCrossroads, engineering and construction ofscientific facilities, camps, utilities, com-munications, and the like were accomplishedby military forces. For Sandstone, ArmyEngineers were used by the AEC because

174

A multimegaton barge shot on Eniwetok in 1958,

there wasn’t time to obtain private contrac-tors, but much of the building design andspecifications were done by the firm ofJohnson and Moreland. Liaison betweenthese two parties was done by the SandiaLaboratory. whose engineers handled manydetails for Los Alamos. The Santa Fe Opera-tions Office (SFOO), Office of Engineeringand Construction, employed Holmes and

Narver (H&N) as architect-engineer (A-E)and constructor for Greenhouse; and allsubsequent Pacific testing and liaison withthe AEC and its contractors became theresponsibility of a small group, J-6, at LosAlamos. For logistics of construction forRanger, SFOO employed the Reynolds Elec-trical Engineering Company (REECo) in ajoint venture with R. E. McKee and Brown-


Field Testing

A modern large-diameter drill bit, weights, and rigging used to drill deviceemplacement holes. Holes typically range from 600 to 3000 feet in depth and from 4 to8 feet in diameter.

Olds. For Buster-Jangle, SFOO employed in Areas 7, 9, and 10. For the Tumbler-H&N as A-E although some of the later Snapper series, REECo returned in the sameengineering was done on site by Haddock type of arrangement as before, while main-Engineering. At NTS, Haddock built Con- tenance work was done by the Nevadatrol Point Buildings 1 and 2 as well as the Company. a Haddock subsidiary. Duringrequired construction work for Buster-Jangle this time. Haddock built the first structure at


Camp Mercury—plywood hutments. REE-

C O did construction and maintenance onUpshot-Knothole and all subsequent Nevadaoperations. Silas Mason served as A-E foroperations Tumbler-Snapper throughTeapot. REECo provided A-E support inaddition to doing the construction for Pro-jects 56 and 57. Holmes and Narver re-turned as A-E for Plumbbob and subsequentoperations.

Firms and people have come and gone,but the fact that they sometimes had reasonto believe our requests were unusual neverreduced their fervor to help us field anoperation. They, too, were pioneering toproduce the facilities we needed to conductthis totally new business of testing nuclearweapons.

Readiness

Halloween night of 1958 saw an abrupthalt to the weapons tests that had continuedmore or less regularly since Trinity. Duringthe test moratorium, which was agreed to bythe U. S. and the Soviet Union in order topromote arms control and disarmamentnegotiations, no preparations for test re-sumption were authorized in the U. S. Never-theless, when the Soviets resumed testingwithout notice in 1961, the test organization

and the laboratories responded heroically;only ten days later they were able to tire thefirst United States underground test since the1958 moratorium.

More difficult to accomplish than thebomber-dropped air bursts that comprisedmost of the early atmospheric tests afterresumption of testing was the renewal ofhigh-altitude testing, which employed rocketsfired from Johnston Island to carry a varietyof weapons to a wide range of altitudes,mainly to explore the effects that had onlybeen hinted at during the last days of theHardtack atmospheric operation. In 1963the Limited Test Ban Treaty (LTBT)prohibited tests in the atmosphere, under-water, and in outer space, but it left under-

175

ground testing unrestricted so long as noradioactive debris crossed internationalborders. Underground testing continues. lim-ited by the Threshold Test Ban Treaty(limiting yields to 150 kilotons) which isobserved although not ratified. The presenttesting activity provides some technologicalcontinuity that was not available when itbecame necessary to resume testing in 1961.

Maintenance of the capability to resumetesting in the prohibited environments re-quired not only continued training of a cadreof test personnel but also upkeep and mod-ernization of extensive and sophisticated in-strumentation, hardware. and facilities.Capabilities provided. for example, by opera-tion of the NC-135A “flying laboratory”aircraft and the small-rocket range in Hawaiiwere periodically utilized to address ques-tions about high-altitude detonations thatwere raised as a result of the 1962 at-mospheric tests.

Experiments of a purely scientific nature.such as a series of solar eclipse observationsfrom the aircraft, resulted in original scien-tific achievements while attracting otherLaboratory scientists to the testing environ-ment and preserving the scientific credentialsof the base test cadre.

Our mandate to monitor international nu-clear testing led to the birth of a spaceinstrumentation and space science capabilitywithin the Laboratory. Beginning from de-

sign and fabrication of instruments for satel-

lite-based test detection, this activity hasevolved over the years to include a broadlybased scientific space observation programwith worldwide recognition,

Safety Considerations

Throughout the entire history of testing.operational and public safety have alwaysbeen principal concerns. While the govern-ment agencies—first the Manhattan Engi-neer District, then the Atomic Energy Com-mission, later the Energy Research and De-velopment Administration, and now the De-

The USAF NC135A-369 containing the Los Alamos Airborne Diagnostics Labora-tory. This plane, part of the atmospheric test readiness program, was available andready to measure device performance in the event that atmospheric testing wasresumed. Used during the 1960s and 1970s for several test readiness exercises andnumerous purely scientific missions (solar eclipse, cosmic ray, auroral, and other), thisplane is now retired.

A Thor missile, with gantry to the left, used in an ICBM weapon system simulationtest on Johnston Atoll, August 1970. Some Los Alamos personnel served in anadvisory role to the Task Force commander, while others aboard the Los Alamosflying-diagnostic-laboratory aircraft observed the missile launching and flight. Thisreadiness exercise served as a very valuable and effective checkout of the missilesystem.

176 Winter/Spring 1983 LOS ALAMOS SCIENCE

Field Testing

View of surface Ground Zero during the emplacement operation showing emplace-ment hardware and diagnostic cable bundle that connects the downhole equipmentwith the recording trailers. The small cylinders on the cables are gas blocks thatprevent the flow of downhole gases through the cables to the atmosphere.


partment of Energy-have the responsibili-ties for the safe conduct of test operations,the Laboratory has always played an activerole in safety matters. Because nuclearenergy was totally new. every question re-lated to nuclear hazards had to ‘be for-mulated before instrumentation could bebuilt to gather the necessary data. This wasas true for safety matters as for weaponsdiagnostics. In retrospect, the effort devotedto public safety. particularly as one notes theprofusion of problems and unknowns. is veryimpressive. Pressure was applied from withinthe Laboratory to learn as much as possible,but to be very conservative in experimentaldesign. As a result. the testing communityhas accumulated an outstanding safety rec-

ord. In fact. the record is unique for a new,evolving technology.

As additional experience was gained, thequestion “How can we reduce fallout?”became increasingly important for all tests.The first nuclear test at Trinity was con-ducted near the earth’s surface. but then toreduce fallout we went to taller towers, thenair drops. balloons, and tunnels. and now tocompletely contained underground ex-plosions,

Our first experiments in underground test-ing were done in 1957, initially using onlyhigh explosives. The first underground nu-clear test. Pascal A, was in a three-foot-diameter hole at a depth of 485 feet. In lieuof completely filling the hole, a combinationplug-collimator was placed near the bottomof the hole. Fired at 1:00 a.m., Pascal Aushered in the era of underground testingwith a magnificent pyrotechnic Roman can-

dle! Nonetheless. the radioactive debris re-leased to the atmosphere was a factor of 10less than what would have resulted had thetest been conducted in the atmosphere. The-oretical models were constructed concerningpossible containment schemes and 20 under-ground nuclear tests had been conductedbefore the in tervent ion of the tes tmoratorium. Theoretical work continuedduring the moratorium ( 1958- 1961) and

177

when testing resumed, additional contain-ment experience was obtained from a num-

ber of underground tests. By 1963, contain-ment was sufficiently well understood topermit the U. S. to sign the LTBT withconfidence that required tests could be con-tained underground—including those withextended lines of sight. The language of thetreaty text prohibits detectable radiationlevels beyond national borders.

The U. S.-assumed necessity to preventeven gases from escaping into the at-mosphere at test time spawned entirely newdisciplines in containment, and prompted thedevelopment of a number of specialtechnologies to help achieve complete con-tainment. With the exception of a few re-leases (none since 1970), the containmentrecord of U. S. nuclear testing has beenexcellent since the LTBT was initiated inOctober 1963. No off-site radiation ex-posures exceeding national guidelines havebeen experienced.

There were some diagnostic cable relatedseeps and some sizable leaks associatedmainly with LOS pipes. There were also afew prompt ventings; however, in no in-stance did off-site radiation levels violateguidelines. Only the close-in areas wereevacuated for test execution. Containmenteffort was largely on an ad hoc basis and hadlittle effect on operations.

After the Baneberry event of December18, 1970, in which a large prompt ventingproduced off-site radioactivity. but not ex-ceeding guidelines, the admonition became“not one atom out!” A more formal contain-ment program was initiated, and the subse-quent containment has been virtually perfect.Containment Evaluation Panel (CEP)procedures are more rigorous and formal.The Los Alamos containment program isextensive and involves about 35 employeesin the Laboratory, plus NTS support. Thereare detailed geologic site investigations. De-vices are buried deeper. Gas-blocked cablesand impervious stemming plugs are used. All

178

Postshot drilling blowout preventer, a device used to preclude the escape of radioactiveproducts into the atmosphere during postshot operations. This is a direct adaptationfrom oil field technology.


Field Testing

added expense and operational complica-tions, they have provided increased con-

Aerial view of the formation of a postshot subsidence crater at the moment of collapse.This collapse may occur from a few minutes to many hours after a shot fired. Notethe dust caused by falling earth.

operations are more conservative, and any- preparation, and the DOE approval process.thing new or different that has any con- Emplacement and stemming time and ex-ceivable effect on containment must be well pense have increased. All of the NTS northunderstood and justified. Longer lead times of the Control Point is evacuated for everyare required for geologic studies, document event. Although these steps have resulted in

fidence in complete containment of radioac-tive debris and the overall safety of testoperations.

Conclusion

Nuclear testing has always been and willcontinue to be a vital element in the LosAlamos weapons program. Only with full-scale tests can the validity of complex designcalculations be confirmed and refined. In asimilar manner, only in the nuclear crucibleof weapons tests can the physical behavior ofweapons materials and components be in-vestigated. Without testing, it would be dif-ficult if not impossible to maintain a comple-ment of knowledgeable weapon designersand engineers. Possible stockpile degradationcould go undetected. Innovative solutions tonational security problems would remainonly paper designs, without proof of theirvalidity in nuclear tests. As long as theUnited States national security is dependentupon nuclear deterrence, the weapons pro-gram will need nuclear tests to maintain itscredibility. The Los Alamos history of suc-cessful and safe nuclear testing over the past40 years is strong evidence that the programcan remain a vital element of the nationalnuclear weapons program without detrimentto the citizens of the United States or theworld.

For any participant in the testing pro-gram, indelible impressions remain. Amongthose are the unique elements of romanticismand camaraderie associated with “where itwas at’” and the excitement of successfullymeeting difficult objectives and schedules.Another is the strong and consistent mili-tary-civilian partnership that grew through-out the 1950s to become an integral part ofthe testing philosophy and operation. Notthe least of them, however, is the sense ofpurpose and accomplishment that comesfrom the conviction that we are doing some-thing good for our country. ■


field testing - the physical proof of design principles

Documents