US DOE Environmental Measurements Laboratory (retired).
Divison of Cancer Epidemiology, National Cancer Institute.
Health Phys. 2020 Oct;119(4):504-516. doi: 10.1097/HP.0000000000001146.
The Trinity test device contained about 6 kg of plutonium as its fission source, resulting in a fission yield of 21 kT. However, only about 15% of the Pu actually underwent fission. The remaining unfissioned plutonium eventually was vaporized in the fireball and after cooling, was deposited downwind from the test site along with the various fission and activation products produced in the explosion. Using data from radiochemical analyses of soil samples collected postshot (most many years later), supplemented by model estimates of plutonium deposition density estimated from reported exposure rates at 12 h postshot, we have estimated the total activity and geographical distribution of the deposition density of this unfissioned plutonium in New Mexico. A majority (about 80%) of the unfissioned plutonium was deposited within the state of New Mexico, most in a relatively small area about 30-100 km downwind (the Chupadera Mesa area). For most of the state, the deposition density was a small fraction of the subsequent deposition density of Pu from Nevada Test Site tests (1951-1958) and later from global fallout from the large US and Russian thermonuclear tests (1952-1962). The fraction of the total unfissioned Pu that was deposited in New Mexico from Trinity was greater than the fraction of fission products deposited. Due to plutonium being highly refractory, a greater fraction of the Pu was incorporated into large particles that fell out closer to the test site as opposed to more volatile fission products (such as Cs and I) that tend to deposit on the surface of smaller particles that travel farther before depositing. The plutonium deposited as a result of the Trinity test was unlikely to have resulted in significant health risks to the downwind population.
三位一体测试装置的裂变源含有约 6 公斤钚，裂变产额为 21 千吨。然而，实际上只有约 15%的钚发生了裂变。其余未裂变的钚最终在火球中蒸发，冷却后，与爆炸中产生的各种裂变和活化产物一起，沿着下风方向沉积在试验场下风方向。利用爆后（大多是多年后）收集的土壤样本的放射性化学分析数据，并结合从爆后 12 小时报告的照射率估计的钚沉积密度的模型估算，我们估算了新墨西哥州未裂变钚的总活度和沉积密度的地理分布。未裂变的钚大部分（约 80%）沉积在新墨西哥州内，大部分在一个相对较小的下风区域，约 30-100 公里（Chupadera Mesa 地区）。对于该州的大部分地区，沉积密度只是来自内华达州试验场试验（1951-1958 年）和后来来自美国和俄罗斯大型热核试验的全球沉降物（1952-1962 年）的 Pu 沉降密度的一小部分。从三位一体试验中沉积在新墨西哥州的未裂变 Pu 占总 Pu 的比例大于沉积的裂变产物的比例。由于钚具有很强的难熔性，更多的 Pu 被纳入靠近试验场的大颗粒中，而不是更易挥发的裂变产物（如 Cs 和 I），它们倾向于沉积在较小颗粒的表面，然后再沉积。由于三位一体试验而沉积的钚不太可能对下风地区的人口造成重大健康风险。
