Uranium enrichment and reprocessing - oh yea!

Fasten your seatbelts. Below is more than you ever wanted to know about the process of uranium enrichment and reprocessing. Though the U.S. doesn't currently reprocess spent nuclear fuel, there is a movement to begin doing so. It's coinciding with the growing potential of nuclear as a renewable energy source, and the Department of Energy is all for it. It's also pinned to the Yukka Mt. dilemma, which is the long-term geologic repository for radioactive waste from nuclear reactors that's still....not.....open. Over 100 reactors in the U.S. are storing their nuclear waste on-site, waiting for Yukka to open its underground doors to unwanted nuclear fission materials. Except that the nuclear waste is full of more fissionable energy and can be recycled (reprocessed) to convert into electricity. France, Russia and Germany reprocess spent nuclear waste into new fuel. 

Nuclear enrichment is increasing the concentration of the fissile U-235 in uranium supply. Uranium ore is .72% U-235 and roughly 99% U-238 (does not fission). Fuel rods for nuclear reactors is made from uranium enriched to about 4% U-235.  There are two significant processes - gaseous diffusion and gas centrifuge.

Diffusion was developed during the Manhattan Project in the 1940s. It converts uranium into UF6 -uranium hexafluoride - gas. Gaseous UF6 is fed into 100s of porous membrane barriers and the lighter U-235 molecules penetrate microscopic holes in the barriers, whereas heavier U-238 molecules are left behind. This creates a more concentrated stream of U-235, which is further enriched in the next stage, and a depleted stream of mainly U-238, which is re-harvested for more U-235.

Gas centrifuge uses many tall rotating cylinders that are interconnected in cascade formations. Simple, eh? Gaseous UF6 is fed down into the rotor, which is surrounded by evacuated casing, and spinned at a tremendously fast speed. Faster than your mind is even processing this. The centrifugal force causes the gas to move towards the wall of the rotor. The heavier U-238 molecules move closer to the wall, leaving lighter U-235 molecules in the center. The U-235 stream is withdrawn and fed into a higher stage. Centrifuge enrichment requires many cascade stages, but has a short equilibrium time and enriches faster. The plants are less cumbersome to develop but also to detect. Iran is using centrifuge technology and we have no idea how far along the enrichment process they are, do we? 

The political and moral question is this: how do you encourage the development of nuclear energy, which requires uranium enriched to 4%, and prevent the construction of nuclear warheads, which use uranium enriched to 90%? 

There's no time to discuss reprocessing today, but we'll get to that. Before the U.S. does. Maybe. 

Boulder City Council meeting, Oct. 2, 2007

Burke Lake Not to be Restored by Spring

Oct. 3, 2007

Boulder County Courthouse

 

Burke Lake has long been an amenity to residents of Frasier Meadows retirement community in south Boulder. Not many parks in Boulder come with lakes to stroll around.

 

Community members have bleakly watched it dry out and scum over for the past five years, and now they’re fighting to get their lake back.

 

 “It’s a green, scummy mess,” said Ray Joyce, a retiree who served Boulder’s city council from 1966-1970 and Northern Colorado’s Water Conservancy District for 26 years.

 

“The only thing the residents want is to have the lake restored to the way it used to be,” Joyce said.

 

Joyce and his wife Dotty have lived at Frasier Meadows for seven years. The man-made lake once sparkled as the jewel of Admiral Arleigh Burke Memorial Park; now it’s hardly visible from the walking path. Joyce officially asked the city’s Parks and Recreation Department yesterday to dip into emergency money now and restore the lake so the community can have something to enjoy this spring.

 

In a unanimous vote Tuesday, Boulder City Council decided to put the lake’s repair on hold until spring, when they knew what it would cost. Though all councilmembers voiced concern at the state of Burke Lake, Mayor Mark Ruzzin repeatedly said they needed a more complete analysis of the methods and cost of the restoration.

 

During more than 1 hour of debate over the fate of Burke Lake, Councilman Ken Wilson pressed his colleagues for more urgent leadership and funding. He said the lake would only be more “mosquito-infested” and swamp like if they waited six months. The money would come out of parks and recreation’s budget, and Wilson recommended an approved budget line to secure the lake as a priority.

 

“If they need to reduce some other budget lines to do that, fine,” Wilson said.

 

Those who live near the lake would’ve trumpeted this idea. At a neighborhood meeting with the city’s parks officials last week, Joyce and about 180 other neighbors showed up to prove how much this meant to them. Joyce said the meeting was attended by all ages, as Burke Park borders Frasier Meadows and Horizon elementary school.

 

Councilwoman Crystal Gray recently visited Frasier Meadows and spoke to residents who worried that they may not live to see the lake be restored. She has seen it growing steadily worse and marshier.

 

“I look at this as a ticking time bomb,” Gray said.

 

But there was no consensus that Burke Lake was a top priority in a litany of problems feeding on parks and recreation money, including replacement of playgrounds, park shelters, and drainage in Chataqua Park.

 

“We are behind the eight ball in terms of our repair and maintenance,” said Deputy Mayor Suzy Ageton.  “We have to make choices.”

 

The councilmembers made the choice to stick with original priorities now, but to return to the Burke Lake issue with a plan of attack. City Manager Frank Bruno was asked to identify costs and impacts of a work program that would restore the lake this spring.  There was no dissent.

 

Councilman Richard Polk said, “It’s a manmade lake. It used to be beautiful, it’s not beautiful now. We’d like it to be beautiful again.”