ATTACHMENT 12 PRELIMINARY REPORT OPERATION PLUMBBOB NEVADA TEST SITE MAY-SEPTEMBER 1957 PROJECT 2.9 NUCLEAR RADIATION RECEIVED BY AIRCREWS FIRING THE MB-1 ROCKET HEADQUARTERS FIELD COMMAND. ARMED FORCES SPECIAL WEAPONS PROJECT SANDIA BASE, ALBUQUERQUE, NEW MEXICO 1 This is a preliminary report based on all data available at the close of this project's participation in Operation PLUMBBOB. The contents of this report are subject to change upon completion of evaluation for the final report. This preliminary report will be superseded by the publication of the final (WT) report. Conclusions are recommendations drawn herein, if any, are therefore tentative. The work is reported at this early time to provide early test results to those concerned with the effects of nuclear weapons and to provide for an interchange of information between projects for the preparation of final reports. When no longer required, this document may be destroyed in accordance with applicable security regulations. When destroyed, notification should be made to: AEC Technical Information Service Extension P.O. Box 401 Oak Ridge, Tenn. DO NOT RETURN THIS DOCUMENT 2 ITR-1418 OPERATION PLUMBBOB-PROJECT 2.9 NUCLEAR RADIATION RECEIVED BY AIRCREWS FIRING THE MB-1 ROCKET Kermit C. Kaericher, Capt, USAF James E. Banks, 1st Lt. USAF Air Force Special Weapons Center Kirtland Air Force Base Albuquerque, New Mexico Issuance Dates October 11, 1957 G.C. Facer, CDR, USN Director, Program 2 K.D. Coleman, Col. USAF Test Group Director, Programs 1-9 3 ABSTRACT Three F-89 interceptor aircraft participated in the delivery of a live MB-1 air-to-air rocket and were instrumented to measure the total gamma and neutron exposure received by the aircrew members. Neutron dose was measured by fission-foil detectors, gold and sulfur threshold detectors, chemical dosimeters, and the Los Alamos human counter. Gamma radiation dose was measured by chemical dosimeters, NBS film badges, and Rad-Safe film badges. Gamma dose rates were also measured in an initial-gamma-versus-time recorder that had been installed in the aircraft. Complete data and an analysis thereof appear in ITE-1414. The values recorded by each of these instruments and devices were evaluated and interpreted in order to yield the most reliable estimate of the total exposures. These were then compared with values predicted on the basis of previous full-scale nuclear test operations. Neutron and gamma doses did not exceed 5 rep 3 r, respectively. Neutron exposures compared well with the predicted values, whereas gamma exposures were found to be somewhat lower than the predicted values. Part of the latter difference can be attributed to shielding by the airframe. There is no doubt that an MB-1 rocket can be fired from an F- 89 interceptor aircraft at an attitude of 19,000 feet MSL with a radiation dose to the delivery aircrew that is within acceptable 5 FOREWORD This report presents the preliminary results of one of the 43 projects comprising the Military Effects Program of Operation Plumbbob, which included 28 test detonations at the Nevada Test Site in 1957. For overall Plumbbob military-effects information, the reader is referred to the "Summary Report of the Director, DOD Test Group (Program 1-9)," ITE-1445, which includes: (1) a description of each detonation, including yield, zero-point location and environment, type of device, ambient atmospheric conditions, etc.: (2)_ a discussion of project results; (3) a summary of the objectives and results of each project; and (4) a listing of project reports for the Military Effects Program. 6 CONTENTS ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 CHAPTER 1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . .9 1.1 Objective . . . . . . . . . . . . . . . . . . . . . . .9 1.2 Background and Theory . . . . . . . . . . . . . . . . .9 CHAPTER 2 PROCEDURE. . . . . . . . . . . . . . . . . . . . . . 10 2.1 Operations. . . . . . . . . . . . . . . . . . . . . . 10 2.2 Instrumentation . . . . . . . . . . . . . . . . . . . 10 2.3 Description of Required Data. . . . . . . . . . . . . 11 CHAPTER 3 RESULTS AND DISCUSSION . . . . . . . . . . . . . . . 13 CHAPTER 4 CONCLUSIONS. . . . . . . . . . . . . . . . . . . . . 15 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . 16 TABLES 3.1 Summary of Gamma Doses. . . . . . . . . . . . . . . . 14 3.2 Comparison of Predicted and Measured Doses. . . . . . 14 7-8 Chapter 1 INTRODUCTION The MB-1 rocket has become operationally available to the Air Defense Command of the United States Air Force. The MS-1 is an air-to-air rocket that carries a nuclear warhead. Only limited information was available from past test operations from which to predict the radiation dose to which the crew of an aircraft delivering an MB-1 would be subjected. 1.1 OBJECTIVE The objective of this project was to measure the radiation dose, both from neutrons and gamma rays, received by an aircrew delivering an MG-1 rocket. Secondarily, the same type of measurements were made at locations other than the crew compartments and on other aircraft in the delivery array. 1.2 BACKGROUND AND THEORY Whenever a new weapon becomes available for operational use, its characteristics be known and available to potential users. Before committing the MB-1 to use, an ILLEGIBLE commander must have information on the radiation dose to be received by the delivery aircrew, as well as the blast effect on the delivery aircraft. The Joint Chiefs of Staff approved the conduct of a test as a part of Operation Plumbbob in order to obtain the necessary experimental measurements. In order to be of value, radiation exposure and blast effects must be experienced under conditions as nearly like the operational situation as possible. Although ample data are available to document radiation as a function of distance for surface and low- altitude detonations, the unknown effect of the air-ground interface necessitated that a test be conducted at a relatively high altitude. Experience in past test operations has shown the difficulty of establishing accurately positioned instrument stations at altitude. One satisfactory method had been found to be the use of aircraft that are tracked and positioned by MSQ-LA radar. This being the case, it was concluded that the best plan for this test would be an actual firing of an MB-1 rocket at a preselected point in space. The delivery aircraft, as well as any other participating aircraft, would serve as instrument stations for radiation measurements. Data from previous test operations have been used to predict the exposure to be received by an aircrew during the delivery of an MB-1. The data, as well as the predictions made therefrom, are contained in References 1, 2, and 3. Since most of the data was obtained on the ground, the presence of the air-ground interface introduces an uncertainty into these predictions. The delivery of an MB-1 could be expected to provide an experimental check point that would increase the degree of confidence in the theoretical computations or point out the need for additional information. 9 Chapter 2 PROCEDURE The activities of this project were limited to Shot John, which was the MB-1 rocket test. 2.1 OPERATIONS Modifications to the aircraft required for the installation of the instruments were made by the 4925th Test Group (Atomic) several weeks before the actual test. The instruments themselves were installed during the night prior to the test. After the detonation and the return of the aircraft to Indian Springs AFB, all instruments were removed at the earliest possible moment. The fission-foil neutron detectors and neutron threshold detectors were flown immediately to the counting facilities established at the Nevada Test Site by Project 2.3. All of the fission foils were counted at least once by H + 58 minutes. The crews of the delivery and alternate delivery aircraft were flown to Los Alamos Scientific Laboratories (LASL) for counting in the human counter. This counting was accomplished by H + 5 hours. Inasmuch as no time limitation existed, the other instruments were evaluated at a later time. The chemical dosimeters were read by Project 39.5 during the afternoon of shot day. The National Bureau of Standards (NBS) film packs were returned to Air Force Special Weapons Center (AFSWC). They were processed and interpreted on shot day. The results from Rad-Safe film badges were received through the normal Rad-Safe channels during the afternoon of shot day. 2.2 INSTRUMENTATION The three aircraft that participated in the MB-1 delivery were instrumented. Identical sets of instruments were installed in four locations on each aircraft. In the delivery and alternate delivery aircraft, these four locations were the rear cockpit, left and right wingtip tanks, and tail section of the fuselage. In the blast-effect aircraft, they were the rear cockpit, right wing-tip tank, tail section, and nose section of the fuselage. Each pilot and radar observer carried an NBS film badge, a Rad-Safe film badge, and a set of chemical dosimeters in the pockets of his flight suit. Instruments that recorded gamma dose rate as a function of time were installed in each aircraft by Project 2.5. A detailed gamma-time history, as well as a discussion of predicted gamma doses for the delivery aircraft, is reported in ITR-1414. The location of primary interest was the crew compartment, since the objective of this project was to measure the radiation exposure of the flight crews. The additional instrument locations were chosen in an attempt to gain some information on the degree of shielding afforded by the airframe. Fission-foil and threshold neutron detectors were furnished by Project 2.3. These detectors, as well as the associated counting apparatus, were calibrated at LASL prior to the beginning of the test operation. Details of this calibration can be found in Reference 4. Chemical dosimeters were obtained from Project 39.5 through the USAF School of Aviation Medicine, Randolph Field, Texas. For the purpose of mixed irradiation dosimetry, 10 ILLEGIBLE phase and half-phase dosimeters were exposed simultaneously. The single-phase system yielded the gamma and fast-neutron dose, while the half-phase system yielded the gamma dose only. Some of these dosimeters were placed in lithium shields fabricated by the Oak Ridge National Laboratories. The purpose of this was to render the dosimeters independent of energy down to about 90 key and to eliminate the response to thermal neutrons. These devices were calibrated extensively before the test operation began. Details of this calibration and further information on the functioning of the dosimeters can be found in Reference 5. Two standard types of personnel film-badge dosimeters were used to measure the gamma-radiation exposure. The National Bureau of Standards film badges were obtained from Project 2.5. There were calibrated with gamma radiation from a 10-curie Co source at AFSWC. Rad-Safe film badges were furnished by the Nevada Test Site Rad-Safe Organization. The exposures recorded by the Rad-Safe film badges are reported as returned by the unit at the test site. The aircrews from the delivery and alternate delivery aircraft were flown to LASL within 5 hours after the time of detonation for counting in the whole-body counter operated by the H-4 group of LASL. By measuring the induced gamma radiation from NaILLEGIBLE in the body, this operation gives a measure of the neutron exposure. A background level for the radiation emitted by each crew member had been established by a count taken 5 weeks prior to shot day. This background level does not change appreciably over a period of several months. At the time of the postshot counting, each individual was also scanned by a crystal scintillation counter. The spectral analysis from this operation made certain ILLEGIBLE ILLEGIBLE increase in gamma radiation emitted by the body was from NaILLEGIBLE and not from ILLEGIBLE-product contamination, either external or internal. Details of the construction, duration, and use of the Los Alamos human counter can be found in Reference 6. 2.3 DESCRIPTION OF REQUIRED DATA The data required for the purpose of this project consisted of the total gamma and neutron exposure as measured by the instruments and devices described in the previous section. For both gamma and neutron measurements, the reliability and accuracy of the data depend on the magnitude of the exposure. Film measurements of gamma radiation are normally considered to be accurate to ñ 20 percent. The chemical dosimeters furnished by Project 39.5 are accurate to ñ 20 percent for gamma exposures above 5 r. They are not sufficiently sensitive to measure exposures below this value. The threshold for neutron measurements using chemical dosimeters is about 10 rep. Above this level they are reliable to ñ 20 percent. Fission-foil detectors for fast neutrons have a lower limit, which is dependent on the amount of exposure and the time between exposure and evaluation. For the present case, this lower limit was about 5 rep. The thermal-neutron threshold detectors will measure a thermal-neutron exposure of 10ILLEGIBLE neutrons/cmILLEGIBLE. Above these lower limits, the detectors are accurate to ñ 20 percent, but they are not usable below these limits. Neutron-dose measurements made in the human counter at LASL are presently considered accurate to within a factor of two. This level of confidence may be improved by more-extensive calibration of the counter, but this will not be completed for several ILLEGIBLE. This method of measurement has the unique capability of detecting fast-neutron ILLEGIBLE of the order of magnitude of 0.1 rep and can be considered to be the best method ILLEGIBLE available for the evaluation of small neutron exposures. Since all of the instruments were amenable to postshot evaluation and interpretation, no special methods or devices were used to record, reduce, or correlate the data. 11 The location of the burst and the position of each aircraft relative to the burst had to be known with as great a degree of accuracy as possible. The point of burst was obtained from Program 9 and is considered to be correct to ñ100 feet in space. The aircraft were controlled and positioned by MSQ-1A radar. Their positions at the time of detonation were obtained through Project 5.5. The aircraft-position values were determined graphically from the chart presentation are are correct to within ñ100 yards. More accurate values will be available from Boeing data-box records and will be incorporated in the final report. 12 Chapter 3 RESULTS and DISCUSSION The radiation measurements are recorded in Table 3.1. No values are shown for the chemical dosimeters or neutron detectors, since in every case the exposure was below a threshold value for these instruments. Even though no precise measurements of the ILLEGIBLE were obtainable from these devices, they served to establish an upper limit of 5 r ILLEGIBLE gamma exposure and 5 rep for neutron exposure. Because of the limited amount of calibration work for neutron exposures that has been ILLEGIBLE with the Los Alamos human counter, the exact counting rates are of little significance to this report. Only generalized statements may be made concerning the neutron ILLEGIBLE received. If more extensive calibration is completed before the preparation of the ILLEGIBLE report for this project, the exact counting rates and more precise dose measurements will be included. A total neutron exposure of approximately 3 rep for the crew of the delivery aircraft is indicated. This is the dose which corresponds to the whole-body ILLEGIBLE of 12 times the background level. The crew of the alternate delivery aircraft ILLEGIBLE approximately 1-1/2 times the background level. This indicates a neutron dose of ILLEGIBLE rep. No differentiation between the exposure of the two crew members was ILLEGIBLE in either instance. These measurements were made at about H + 5 hours. The ILLEGIBLE were corrected for decay of NaILLEGIBLE activity before the neutron dose was calculated. A secondary objective of this project was to observe the shielding afforded by different parts of the airframe. From the values shown in Table 3.1, it can be seen that the gamma exposures of the wingtips were essentially the same. This is to be expected, as much as the wing tips are of identical configuration. The orientation of the aircraft with respect to the point of burst is of no significance, since it was as a distance of several mean free paths from the burst. At this distance the geometry for the radiation essentially non-directional (4 ILLEGIBLE). The gamma dose in the rear cockpit is only one third ILLEGIBLE of the wingtips. This difference is ILLEGIBLE to the shielding provided by the airframe. The pilot in each aircraft received a gamma radiation dose about 30 percent greater than that of the radar observed in the rear cockpit. This can be accounted for by the greater amount of shielding from prompt radiation given to the rear cockpit by the jet engines. It is interesting to note this is the exact opposite of the situation that arises when the aircraft becomes contaminated with fission products by flight through the radioactive cloud. In the latter situation, the radar observer receives the greater exposure, because the jet engine is the primary source of residual radiation. Table 3.2 shows a comparison of the measured gamma and neutron doses compared with predicted values for the same distances from a 2-kt device. The aircraft and the burst point were all at an altitude of approximately 19,000 feet ILLEGIBLE. The measured gamma doses were less than the predicted doses for the distances of concern. This difference can be attributed, in part, to the facts that shielding by the airframe was not ILLEGIBLE in the comparison of the predicted doses ILLEGIBLE Field measurements of neutron exposures of this magnitude ILLEGIBLE techniques available to this project are somewhat uncertain. This uncertainty is at ILLEGIBLE as great as the difference between the predicted and measured values. A more-detailed analysis of predicted and actual doses will appear in the report of project 2.5 (ILLEGIBLE-1414). 13 Table 3.1 Summary of Gamma Doses Closest Dose Measured Dose Measured Approach Location of By Rad-Safe By ILLEGIBLE AIRCRAFT To Burst Instruments Film Badge NBS Film Badge (Yards) (mr) (mr) Delivery 2,400 Rear Cockpit 1,100 930 Left Wingtip 3,400 ILLEGIBLE Right Wingtip 3,730 ILLEGIBLE Tail Section 3,370 ILLEGIBLE Pilot 1,330* ILLEGIBLE Radar Observer 1,110* ILLEGIBLE Alternate 3,000 Rear Cockpit ILLEGIBLE ILLEGIBLE0 Delivery Left Wingtip ILLEGIBLE ILLEGIBLE Right Wingtip ILLEGIBLE ILLEGIBLE Tail Section ILLEGIBLE ILLEGIBLE Pilot ILLEGIBLE* ILLEGIBLE Radar Observer ILLEGIBLE* ILLEGIBLE Blast 2,000 Rear Cockpit 1,580 1,180 Effects Right Wingtip ILLEGIBLE ILLEGIBLE Nose Section ILLEGIBLE ILLEGIBLE Tail Section 3,420 ILLEGIBLE Pilot ILLEGIBLE* ILLEGIBLE Radar Observer ILLEGIBLE* ILLEGIBLE *These values are the average of two film badges. One was issued through the normal Rad-Safe channels. The second was attached to the case of the ILLEGIBLE film badge and was issued through this project. However, both were processed and interpreted by the Rad- Safe unit. Table 3.1 - Comparison of ILLEGIBLE and Measured Doses* Aircraft Crew Distance From Predicted Dose Measured Dose Member Burst Point ILLEGIBLE Gamma ILLEGIBLE Gamma (yards) (rep) (r) (rep) (r) Delivery Pilot 1,400 -1 1.1 -3 1.1 Delivery BO 1,400 -1 1.1 -3 1.1 Alternate Pilot 3,000 <1 0.3 ILL ILL Alternate BO 3,000 <1 ILL ILL ILL Blast Effects Pilot 1,000 -1 ILL ILL ILL Blast Effects BO 1,000 -1 ILL ILL ILL *Predicted doses based on a device yield of ILLEGIBLE ILLEGIBLE and a ILLEGIBLE delivery at 12,000 ILLEGIBLE ILLEGIBLE. +These values are the average of two film badges. One was issued through the normal Nevada Test Site Rad-Safe channels. The second was attached to the case of the ILLEGIBLE film badge and was issued through this project. However, both were processed and interpreted by the Nevada Test Site Rad-Safe unit. 14 CONCLUSIONS The MB-1 rocket can be delivered in an operational situation at an attitude of 19,000 ILLEGIBLE MSL with a radiation dose to the aircrew within acceptable limits. For the three distances from the burst that are considered in this report, the theoretical predictions of the gamma-radiation exposure to be received by the aircrew are on the conservative side. The predicted neutron doses agree with the measured doses within the uncertainty of these measurements. The difference in the case of the gamma dose is contributed to the shielding provided by the airframe. Although no definite statements can be made concerning altitudes other than 19,000 feet MSL, it is felt that theoretical predictions made for other altitudes would hold equally well. 15 REFERENCES 1. York, E.N.; "Initial Nuclear Radiation from Low Yield Fission Weapons"; AFSWC-TN-56-14, November 1956, Air Force Special Weapons Center, Kirtland AFB, New Mexico; Secret Restricted Data. 2. Cook. T.B. and others; TM 60-56-51, January 1956, Sandia Corporation, Sandia Base, Albuquerque, New Mexico; Secret Restricted Data. 3. Blaylock John A.; "A Study of Sulfur Neutrons from Fission Weapons"; AFSWC-TN-56-13, May 1956, Air Force Special Weapons Center, Kirtland AFB, New Mexico; Secret Restricted Data. 4. Rigotti, D.L., and others; "Neutron Flux Measurements of Selected Nuclear Devices"; Project 2.3, Operation Plumbbob, ITR- 1412, August 1957, Chemical Warfare Laboratory, Edgewood, Maryland; Secret Restricted Data. 5. Sigoloff, S., and others; "Radiation Dosimetry for Human Exposures"; Project 39.5, Operation Plumbbob, ITR-1504, August 1957, Oak Ridge National Laboratories, Oak Ridge, Tennessee; Secret Restricted Data. 6. Anderson, E.C., and others; "The Los Alamos Human Counter"; Nucleonics, January 1956, Page 26; McGraw Hill Publishing Company, Inc., New York, New York; Unclassified. 16