Sandia LabNews

Testing, testing leads to safe nuclear weapons arsenal

Testing, testing leads to safe nuclear weapons arsenal

Editor’s note: This is part of a series of Lab News articles covering Sandia’s Nuclear Weapons Surveillance Program.

When realtors talk about the value of a piece of property, they always emphasize "location, location, location."

When members of the nuclear weapons community talk about the safety, security, and reliability of the nuclear weapons arsenal, they refer to "testing, testing, testing."

And in this era where weapons testing by underground explosions of nuclear devices is banned, non-nuclear testing remains one of the few ways available to determine if weapons will work when they are supposed to and not work when they are not supposed to.

That is where Departments 2955 and 2956 come in. They build system test equipment (STE) to conduct non-nuclear testing that determines if nuclear weapons are safe, secure, and reliable.

"Our product consists of the complete design and implementation of test systems, including electrical hardware, mechanical hardware, software, and documentation," says Oscar Hernandez, Manager of Test Equipment Design Dept. 2955. "Our efforts support the mission of the Stockpile Surveillance Program by providing the design, development, and maintenance of test systems used in evaluating stockpiled weapons."

Every year 11 weapons are randomly pulled for testing from each of the nine enduring stockpile systems, making for about 100 weapons tested annually. Eight of the 11 weapons systems are typically sent to Sandia’s Weapons Evaluation Test Laboratory (WETL) at the US National Nuclear Security Administration (NNSA) Pantex Plant near Amarillo, Texas, where they undergo more than 700 tests on "testers" built by the two departments (Lab News, Jan. 24). The tests are conducted by 18 Sandia engineers and technicians who work at the WETL facility.

The current 40-year-old WETL structure houses about $90 million in testing equipment and is the only US facility that conducts systems-level tests on nuclear weapon non-nuclear subsystems and components. Earlier this year ground was broken for a new 30,000-square-foot, $22 million WETL facility that will replace the old building when it is completed in 2004. In addition, the weapons program is setting aside $30 million over the next several years for Sandia engineers to build a new generation of modernized testers.

Nuclear weapons disassembly

The sampled weapons, which are turned over to the NNSA by the military, go through a disassembly and inspection (D&I) process by BWXT personnel at the Pantex plant. The Sandia-designed subsystems and components are then reassembled into a "testbed" that is transported to the WETL for testing. Testbeds are designed so they replicate the configuration of the weapon to the extent possible without nuclear systems. Non-nuclear subsystems and components are kept intact in the testbed so testers can determine how they function together as a complete system.

"We’re looking for defects and anomalies," Oscar says.

He gives the example of an electrical subsystem that might consist of several components. Contact corrosion may have occurred that causes the subsystem to not function properly. If the subsystem is totally dismantled, the corrosion may be scraped off and go away. As a result, the reassembled subsystem would work and the problem would be missed.

Many of the testers at WETL are old, some dating back 30 years. Consequently, they do not take advantage of modern technologies, such as fast computers, that can provide a richer suite of information about weapons needed by weapon engineers to gauge their functionality.

One tester instead of three

"Our mission is to design, develop, and deliver the next generation of STE," says Roger Lizut, Manager of the newly formed New Systems Testers Dept. 2956, which was broken off from Dept. 2955. "The new STE will provide improvement in two ways — efficiency and effectiveness. The efficiency is achieved by combining the functionality of similar weapons into an integrated STE. For example, the first new STE will test the W76-0, W76-1, and the W88. By having one tester instead of three, we reduce total cost for operation and maintenance. Effectiveness is realized by incorporating an expanded suite of tests that will provide data to better understand the current, and possibly, future, state of health of the weapon system."

Building new testers starts with a "requirement-gathering phase."

"Engineers from throughout the Labs with different interests — systems engineers, component designers, nuclear safety, quality, human factors, independent surveillance assessment — get together and make up a wish-list of what the tester could do," Oscar says. "Coordinated by a systems evaluation engineer, we then distill that list down to essential requirements that are achievable."

Working from a set of B-series drawings (test requirements) and component specifications, engineers from Departments 2955 and 2956 design testers that will be able to meet the test requirements.

Toward the end of the process they use actual components to make sure the tester works.

Prior to completion of the testers, WETL technicians are brought in to train on the STEs and to work with the design staff in the final debugging and development of operations procedures. After they are checked out, the systems are shipped to the WETL.

Roger notes that the two departments’ work is critical.

"Our work in maintaining current testers and implementing new generation testers is important to the Stockpile Stewardship Program," says Roger.