I looked into a position there a number of years ago. Based in Albuquerque, they had at that time 5 pilots. From a few informal discussions with one guy working there it seemed like you were on call a LOT and if you didn’t already have a TS (or Q) clearance you were at a substantial disadvantage. But YMMV.

• Approximately 5-7 full-time pilots engaged in flight operations, training, flight support projects, and administrative work.
• Provide pilot services as a Pilot in Command or Co-Pilot of 737-400 (and potentially DC-9) aircraft transporting personnel and classified cargo both domestically and internationally.
• Participate in Emergency Response exercises, and perform on-call pilot/duty officer duties as directed to support mission requirements.
• Plan/Execute aviation missions through a broad spectrum of contingency operations.
• Transport explosives, weapons, armed couriers and large amounts of radiological materials.
• Plan up to 50% travel.

https://www.energy.gov/nnsa/leadersh...s/working-nnsa