As the nation’s nuclear stockpile moves further from the nuclear test base due to aging, remanufactured components and Life Extension Programs (LEPs), the need for predictive weapon calculations is becoming increasingly urgent. Crossroads, the third Advanced Technology (AT) system in the Advanced Simulation and Computing (ASC) Program, will be critical to the success of the National Nuclear Security Administration (NNSA) Stockpile Stewardship Program (SSP) and the current and planned LEP activities. The primary users of ASC platforms are designers, analysts and computational scientists.

In 2022, the first AT system, Trinity, will be nearing the end of its useful lifetime. Crossroads is a Trinity replacement, a tri-lab computing resource for existing simulation codes and a larger resource for ever-increasing computing requirements to support the weapons program. Crossroads will provide a large portion of the AT system resources for the NNSA ASC tri-lab simulation community—Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL)—during the fiscal year 2022 (FY22) through FY27 timeframe.

In addition to meeting NNSA Defense Programs’ mission needs, the architecture of Crossroads will keep ASC moving forward by allowing applications to fully explore and exploit upcoming technologies. These new technologies include processors, memory, input/output (I/O), interconnect, power efficiency and reliability. Some of the largest and most demanding capability-class jobs will be able to run on Crossroads. These capabilities are required for supporting stockpile stewardship certification and assessments to ensure that the Nation’s nuclear stockpile is safe, secure and reliable.

Crossroads will establish a validated predictive capability for key physical phenomena, quantifying and aggregating uncertainties in simulation tools and providing mission-responsive computational environments. Simulation fidelity improvements include the following:

Physics fidelity—replacing calibrations with physics models to improve confidence of extrapolation away from the nuclear test base
Numerical fidelity—significant finding investigations (SFIs) are sensitive to fine-scale three-dimensional (3D) features, requiring much finer resolution

Geometric fidelity—neglected features need to be included; many are inherently 3D
Crossroads will continue to push the cutting edge of what is possible on current systems with its 3D simulations capabilities. By 2022, the goal of running high-resolution 3D simulations with full physics and geometric features will be attainable. Ultimately, Crossroads will accelerate industry’s research and development (R&D) technology roadmap for the ASC program’s future exascale-class computational needs.

The Alliance for Computing at Extreme Scale (ACES) is a collaboration between LANL and SNL.

Press Releases


March 2020: Contract awarded

September 2020: Technology announced

Spring 2022:  First delivery

Summer 2022: Delivery complete

Fall 2022: Transition to production


In the News