Fact Sheet
Bureau of Arms Control, Verification, and Compliance
December 13, 2012


Key Point: The use of data from surveillance of our nuclear weapons enables us to predict how the weapons will perform over time without nuclear explosive testing. This capability has improved significantly over the past decade and provides us with the capability to ensure an effective nuclear stockpile.

Surveillance information is critical for the predictive models used in the annual nuclear weapon assessment process. These tools and the detailed quantitative modeling they support serve as key elements of the capability to maintain a safe, secure and effective U.S. nuclear weapons stockpile without underground nuclear explosive testing

The National Nuclear Security Administration (NNSA) annual assessment process has evolved significantly since the end of underground nuclear explosive testing to ensure an effective nuclear weapons stockpile. The current approach aims to achieve a comprehensive, science-based understanding of nuclear weapon systems. Surveillance tools and models play critical roles in providing information essential to assessing weapon safety, security, and performance changes that would impact military effectiveness without performing underground nuclear explosive tests.

These surveillance tools aid in the understanding of two conditions of weapons systems: the “as-built” and “as-aged” conditions. The “as-built” condition reflects the frequency and severity of original design or manufacturing defects. The “as-aged” condition reflects the evolution of age-related changes in materials, components, and subsystems that can alter performance. Over the last few years, several advances in this area have contributed to a better understanding of the condition of our existing nuclear weapons and the ways in which the current condition could affect safety, reliability or performance.

Through the weapons surveillance program, we have in-depth knowledge of the core plutonium components housed within weapons, also referred as “pits,” by using technologies such as non‑destructive laser gas sampling and high-resolution pit computed tomography (commonly referred to as a Pit CT). System tests also assess the functionality of all major non-nuclear components.

As an example, Pit CT enables the evaluation of the nuclear weapon’s “pit” to assess aging issues that were previously not detectable. Data collected from these and other advanced diagnostic tools help to ensure that predictive models reflect both the “as-built” condition and age-related changes. With this information, models can be used to assess changes in performance relative to the design baseline.