Number 30 June, 2000

We are taking a break from the usual NUtrino content to bring you some radiation news from around the world.

Warheads!

Ever wonder what happens to nuclear warheads when they are removed from the stockpile? All of them go back to their birthplace, the DOE Pantex Plant in Amarillo,Texas, where they are disassembled. The plant can disassemble up to 2,000 warheads per year, consistent with strategic weapon reduction agreements.

Back in the 1960's the U.S. manufactured and stockpiled a warhead called the W48. The W48 was the Artillery Fired Atomic Projectile; it was retired from the arsenal in 1992. This kiloton-yield weapon was fired from a 155 mm howitzer and was intended to support battlefield operations. The W48 was 31 inches long, 6.1 inches in diameter and weighed 120 pounds. It was a relatively simple device; the major components consisted of the plutonium core and high explosive charges. Disassembly was a two-step procedure. First, external hardware was removed while the weapon was manipulated behind high density polyethylene shields that minimized neutron exposure to workers. Next, the projectile was taken to a massive Cell facility for dismantlement of the plutonium "pit" and the high explosives. The Cell facility is designed to minimize blast effects and contain radioactive particulates should the explosive charge accidentally detonate. The roof of the cell is covered by 15 feet of gravel that would lift up and collapse down, burying the contents. An accidental detonation has never occurred.

The high explosive was dissolved off of the plutonium pit, followed by a good scrubbing of the pit by hand. Workers wore lead-lined gloves and lead aprons for this procedure. When the pit was "clean" it was packaged in a safe-geometry container for storage.

This information was taken from "Dismantlement of the U.S. W48 Nuclear Warheads," L.D. Vickers and B.W. Wehring, in Operational Radiation Safety, a supplement to Health Physics, vol. 76, No.5, May, 1999. This publication is on file in the Office for Research Safety.

Speaking of neutrons.

Last year's criticality accident in Japan killed one worker and seriously injured several others. Speculation is that the system may not have gone critical had not the fatally injured worker pressed his body close to the uranium tank, causing excess neutrons to be reflected back into it. Poor work practices and operational controls were to blame.

Mortality among TMI residents not related to radioactivity
according to new study

A study of the mortality records of 32,135 members of the population living near the Three Mile Island nuclear plant at the time of the 1979 accident says "the mortality surveillance of this cohort does not provide consistent evidence that radioactivity released during the TMI accident has a significant impact on the mortality experience of this cohort to date." The study was conducted by researchers at the University of Pittsburgh and published in Environmental Health Perspectives, Volume 108, Number 6, June 2000. Click here for the abstract.