Operation SANDSTONE

Note: For information related to claims, call the Department of Veterans Affairs (VA) at 800-827-1000 or 

the Department of Justice (DOJ) at 800-729-7327. For all other information, call the Nuclear Test 

Personnel Review (NTPR) Program at 800-462-3683.

Operation SANDSTONE was a three-detonation nuclear test series held at Enewetak Atoll, the Atomic Energy 

Commission’s (AEC) Pacific Proving Ground (PPG), in Spring 1948. Located in the Central Pacific Ocean, the 

PPG consisted principally of Enewetak and Bikini Atolls in the northwestern Marshall Islands.

Summary of Operation SANDSTONE Nuclear Weapons Testsa

Shot Local Date Location Yield (kiloton)b

X-RAY Apr 15 200-foot (61-meter) tower on Enjebi Island 37

YOKE May 1 200-foot (61-meter) tower on Aomon Island 49

ZEBRA May 15 200-foot (61-meter) tower on Runit Island 18

a Source: United States Nuclear Tests, July 1945 through September 1992, DOE/NV-209 (Rev. 15), Dec 2000.

b One kiloton equals the approximate energy release of one thousand tons of TNT.

Historical Background

SANDSTONE was the second test series to be held in the Marshall Islands, but it differed from the first series 

(CROSSROADS in 1946) in that it was primarily an AEC scientific test series with the armed forces serving in 

a supporting role. Its purpose was to proof-test improved-design weapons, whereas the purpose of 

CROSSROADS was to test nuclear weapons effects on ships.

The weapons were tested at Enewetak by a joint military and civilian organization designated Joint Task 

Force 7 (JTF 7). This was a military organization in form, but contained military, civil service, and contractor 

personnel of the Department of Defense (DOD) and the AEC. The commander of this force was the appointed 

representative of the AEC and reported to both the Joint Chiefs of Staff and the Commander-in-Chief, Pacific. 

Peak DOD numerical strength at SANDSTONE was approximately 19,700 personnel.

Numerous technical projects were carried out in conjunction with each of the three detonations. These 

projects measured the yield and efficiency of the devices and attempted to gauge military effects of the 

explosions. DOD personnel participated in this test operation as individuals involved in AEC weapon design 

and development, as units performing separate projects, and as units performing various support roles.
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Radiation Protection Standards

An extensive radiological safety program with the following objectives was instituted:

1. Keeping personnel radiation exposure at the lowest possible level consistent with medical knowledge of 

radiation effects and the importance of the test series.

2. Avoiding inadvertent contamination of populated islands and transient shipping.

This program established an organization to provide radiological safety expertise and services to commanders 

of the separate components of the task force, who were responsible for personnel safety within their 

commands. Personnel were trained in radiological safety. Standards governing permissible exposure were 

established. The standards were 0.1 roentgen (R) per 24-hour period and a maximum exposure of 3 R for 

specifically approved missions. Film badges were issued to persons likely to be exposed to radiation, as well 

as a representative group of the task force. An extensive weather forecasting group was established to predict 

wind directions and areas of potential fallout. Personnel were evacuated from danger areas before each 

detonation. Reentry to radioactive areas was restricted to personnel required to retrieve important data, and 

their radiation exposures were monitored.

Radiation Doses at Operation SANDSTONE

Most of the inhabited islands and support ships in the area did not receive appreciable fallout from the three 

SANDSTONE shots. The reconstructed dose from fallout for most persons who were resident on Enewetak or 

Kwajalein or were shipboard for the entire operation is less than 1.0 rem∗

. Kwajalein Atoll received the 

principal amount of fallout among these on May 3, 2 days after Shot YOKE.

The only personnel who received more than the fallout on the residence islands were those working where 

exposures were expected to occur, such as handling cloud samples, recovering instruments from the forward 

islands, and monitoring areas of high radiation.

Eight DOD personnel received doses in excess of the 3 rem limit. The Army’s highest dose was 6.1 rem 

accrued by an individual supporting scientific projects, and the Navy’s highest dose was 4.7 rem accrued by a 

radiation monitor with the Joint Radiological Safety Group. The average of the badge doses for JTF 7 

personnel at SANDSTONE was less than 0.2 rem, and approximately 65 percent had a dose of zero rem.

 ∗

A rem is a radiation protection unit of measure that quantifies the risk of biological effects resulting from exposure to 

ionizing radiation. Ionizing radiation is any radiation (gamma, x-ray, beta, neutron, or alpha) capable of displacing 

electrons from atoms or molecules, thereby producing ions. According to the National Council on Radiation Protection 

and Measurements (NCRP, Report No. 160, Table 1.1), the general U.S. population receives about 0.62 rem per year 

from natural background radiation sources (radon, cosmic rays, and rocks) and man-made radiation sources (medical 

diagnostic x-rays and consumer products).
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The totals of reconstructed and film badge doses for SANDSTONE participants are depicted Figure 1.

Figure 1. Doses accrued by SANDSTONE personnel

For more information on reconstructed doses, see the report “Analysis of Radiation Exposure for Naval 

Personnel at Operation SANDSTONE” (DNA-TR-83-13). Also see the report “Operation SANDSTONE 1948” 

(DNA 6033F). These reports are available online at 

http://www.dtra.mil/DTRA-Mission/Reference-Documents/NTPR-info/.

September 2021