NNSA DC Overflights

News reports are circulating that the National Nuclear Security Administration (NNSA) is doing radiation monitoring flights around the Washington, DC area over the next couple of weeks.

http://nnsa.energy.gov/mediaroom/pressreleases/dcflyover122612

These flights will be using NNSA helicopters equipped with sensors designed to monitor normal background levels of radiation. The NNSA’s Remote Sensing Laboratory (RSL) out of Joint Base Andrews will be performing the assessment for local law enforcement of D.C. area.

As far as active frequencies, the NNSA has assignments all over the federal spectrum, so searching might reveal something new. However, I'm not sure how much radio chatter there will be during these flights. You might catch the helicopter on some of the VHF low-altitude VFR aircraft frequencies, possibly using the ENERGY call sign.