to support the Nuclear Test Program. This effort, often referred to simply as “radchem,” included developing techniques and methods to determine the performance of nuclear devices by measuring radioisotopes produced first in aboveground tests and then, after the passage of the Limited Test Ban Treaty 1963, in underground tests. This effort required the development of ways to collect device debris and new methods for chemically separating reaction products from collected debris. Also required was the development of new and more precise ways of quantifying the radioactive isotopes whether they decayed by alpha or beta particle emission or the emission of gamma-rays and x-rays. Because of the varied decay paths of radioisotopes, their spectra are complicated and identification of radioisotopes required monitoring the change in the decay spectra as a function of time. Since both the energy and half-life were needed to verify and quantify radioactive reaction products, this drove the need for automation and the ability to handle and archive large amounts of data. Since not all reaction products are amenable to measurement by radiation detection (for example, some isotopes have long half lives or are nonradioactive), mass spectrometry techniques were also developed and utilized to enable the measurement of changes in isotopic ratios of elements and, as a result, nuclear reactions occurring during device detonation.1 Thus, the “radchem” effort—in support of the Nuclear Test Program—led to advances in many areas, such as separations science, radiation detection, mass spectrometry, and instrument automation (including data acquisition systems and small-scale stand alone computers). These advances also involved pushing existing and emerging techniques to lower detection limits and higher energy resolution to maximize the information that could be derived from the analysis of device debris. These capabilities further enabled nuclear and radiochemists to devise and carry out experiments to obtain more accurate and a wider variety of fundamental nuclear data such as cross sections, decay schemes, and half-lives needed to interpret the post-test radiochemical data.
Following the cessation of nuclear testing in 1992, a science-based approach for annual certification of nuclear warheads with aging, replaced, or modified nuclear components was adopted by the DOE’s Defense Program. The ability to certify performance of the U.S. nuclear stockpile in the absence of nuclear testing is embodied in what is now called the Stockpile Stewardship Program (SSP). The fundamental concept of the SSP is to:
1 Mass spectrometry also played an important role in fissile material production, especially with characterizing the feed, product, and tails streams from uranium enrichment and in analyzing irradiated uranium for plutonium production.