Ionizing Radiation - Introduction

Update 27 November 2023

Live nuclear weapons (unexploded – for VA clarification)1 in the custody of DOD during the Cold War period contained weapons-grade plutonium and/or uranium. They emitted four types of ionizing radiation: Alpha, Beta, Gamma, and Neutron. “Ionizing activity can alter molecules within the cells of our body2 and damage DNA. Note: Neutron radiation was largely unknown to Nuclear Weapons Technicians throughout our time in service, and for decades later.


Penetrating Power of Various Types of Radiation



Electromagnetic (EM) Spectrum

Chart : Department of Energy, EHSS Info Brief December 2017

Electromagnetic radiation is energy that travels as particles or waves, spreading out as it goes.
Radiation can be considered in two categories, non-ionizing and ionizing. As depicted in the chart, radiowaves, microwaves and infrared are non-ionizing. Ionizing radiation can break molecular bonds, causing serious damage to cells. Ionizing radiation, with its shorter wavelengths, damages structures inside cells, such as DNA and proteins, and can cause mutations to occur. These mutations can result in numerous problems for cells, including cancer and other diseases or other illnesses. Mutated DNA can be passed to offspring through the reproductive process potentially leading to genetic disorders, congenital defects, and/or cancer.


Alpha Particles

Alpha particles have the least penetrating power and can be stopped by a sheet of paper or human skin. However, they can be inhaled, swallowed, or enter the body through a cut. In those situations, Alpha particles are extremely dangerous, can damage sensitive living tissue, and cause severe damage to cells and DNA. The radiation weighting factor (biological damage) is 20 times greater than gamma and beta. 3

Note: Nuclear Weapons Technicians rubbed off (by hand, generally with gloves) radioactive core material that separated ("spalled")from the surface of the nuclear weapon core as a function of the normal radioactive decay process. Much of the "spalling" material consisted of Alpha particles that subsequently became airborne or otherwise contaminated clothing. Significant portions of those radioactive particles ended up on the uniforms of the Technicians, easiily transported to their barracks, homes, and family members.

Beta Particles

Beta particles are lighter than alpha particles and permeate more deeply, penetrating skin and traveling several feet in air, but are stopped by a fraction of an inch of metal or plastic.

Gamma and Neutron Radiation

Gamma and neutron radiation is continuously emitted through warhead exterior cases and endangers personnel during maintenance, disassembly, internal limited-life component exchange, handing, modification, transport, and storage. Gamma rays “require a layer of dense material, such as lead, for shielding”. 4 They are a radiation hazard for the entire body” and “can cause ionizations that damage tissue and DNA”. 5

Neutrons are high-speed nuclear particles that have an exceptional ability to penetrate other materials. 6 Neutron radiation also causes other items to become radioactive, including hardware and other materials inside or near the nuclear weapon. The radiation weighting factor [Wr] of ionizing neutron radiation is 5-20 times greater than gamma and beta, depending on neutron energy.7 Shielding neutron radiation requires thick layers of materials rich in hydrogen, such as water or concrete.8

The emissions of the four types of nuclear radiation continue through a natural process of radioactive decay. The materials used in nuclear weapons generally range in half-life periods from 24,000 years to over 700 million years.9


Additional Information on Alpha Particles — Generally unknown to Cold War veteran Nuclear Weapons Technicians

"Plutonium predominantly emits alpha particles—a type of radiation that is easily stopped with a short range—and also neutrons, beta particles, and gamma rays. The alpha radiation makes it a serious internal hazard, made worse by its immobility in the body where it can remain for decades—as much as 80% of any amount absorbed will remain 50 years later. Just a few micrograms distributed through the lungs, liver, or bones can statistically increase the likelihood of cancer. This has contributed to its reputation as one of the most toxic substances known— the Department of Energy’s limit of occupational concentration in air is about a million times lower than for lead. Nonetheless, there are organic toxins that are many factors more deadly—plutonium absorption is mainly dangerous in the long term. Consequently, this aspect of plutonium can be managed with careful monitoring." 10

________________________________________

Footnotes:

[1] A VA claim/appeal response included incorrect comments stating unexploded nuclear weapons were not radiation risks because they were “sealed and shielded”. https://www.va.gov/vetapp20/Files7/20048516.txt
[2] https://www.cdc.gov/nceh/radiation/ionizing_radiation.html. Reviewed 7-16-23.
[3] Centers for Disease Control and Prevention (CDCP) (2015): European Nuclear Society, “Learning from Fukushima: Nuclear power in East Asia, 2017.” https://press-files.anu.edu.au/downloads/press/n3873/pdf/ch08.pdf.
[4] DOD Nuclear Matters Handbook 2020 (revised), Ch 11, p. 134.
[5] EPA.gov/radiation/radiation-basics. Reviewed 7-16-23.
[6] Nuclear Regulatory Commission. https://www.nrc.gov/about-nrc/radiation/health=effects/radiation-basics.html. Reviewed 10-27-23.
[7] Ibid. CDC (2015). Table 8-1, Radiation weighting factor. Note: https://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1004.html. Includes “Quality Factor” of 10 for “Neutrons of unknown energy”
[8] Ibid. DOD Nuclear Matters Handbook
[9] Nuclear Weapons Technology 101 for Policy Wonks, B. Goodwin, Lawrence Livermore National Lab, 2021.
[10] Los Alamos National Laboratory, “A History of Plutonium”, by Owen Summerscales, September 21, 2022. https://discover.lanl.gov/publications/actinide-research-quarterly/first-quarter-2022/shining-light-on-a-dark-element/.  Retrieved 11-21-23.