By Mary Manning (contact)

Wed, Oct 29, 2008 (4 p.m.)

Treating radioactive wastes lingering from the Cold War era when the United States experimented with nuclear weapons at the Nevada Test Site is in its final chapter, the National Nuclear Security Administration said today.

Since completing 48 shipments involving 1,860 55-gallon drums of what's known as "transuranic," or TRU, wastes from the Test Site, 65 miles northwest of Las Vegas, to the Waste Isolation Pilot Plant near Carlsbad, N.M. In November 2005, Nevada is preparing another 58 oversized boxes for disposal.

Transuranic wastes contain man-made radioactive elements heavier than uranium, such as plutonium, so the "trans" refers to radioactive elements beyond uranium.

The Waste Isolation Pilot Plant has been accepting most wastes containing plutonium from across the country, a legacy of the Cold War efforts in national laboratories. From the 1950s until the 1990s the labs and the Nevada Test Site were crucial players in the Cold War between the United States and the former Soviet Union.

Most of the transuranic wastes at the Nevada Test Site came from Lawrence Livermore National Laboratory in northern California and were stored at Area 5.

Ensuring worker safety as these wastes were prepared to go to WIPP involved supplying and training workers with protective clothing and supplying oxygen, said Gary Pyles, acting TRU waste sub-project director.

The workers have been working two six-hour shifts per day, six days a week.

A third of the remaining wastes contain transuranic waste, while two-thirds of the waste was determined to be low-level and mixed low-level (chemical and low radioactive) wastes.

The rest of the wastes should be shipped off the Test Site by Dec. 31, the National Nuclear Security Administration said.