Friday, 15 October 2010

Oldbury visit part two

Continuing on with some more on the recent tour of Oldbury nuclear power station that I recently participated in. If you missed part one please take a look here.

The next part of the power station I want to discuss I find particularly interesting. The reactor pressure vessel. It is actually constructed of pre-stressed concrete. I believe this was the first reactor to be constructed in this way. The approach seems to have been very successful as Oldbury's sister reactor Wylfa was also constructed using this method as were the later AGR (Advanced Gas Cooled Reactor) designs.

In the image below you can see one of the areas known as a stressing gallery. What you can see here are the ends of the steel pre-stressing "tendons" as they emerge from within the concrete of the reactor pressure vessel.

Upper stressing gallery  (Photo Credit: Magnox North Ltd)

What the photograph does not show is how hot it was here! It felt to be at least 35 degrees C. A member of staff mentioned that it had been as warm as 47 degrees in recent days in this area. It's not surprising considering this is as close as somebody can get without actually being IN the reactor core.  

It may be helpful to refer to the cutaway drawing of  the similar Wylfa reactors. The cutaway and 104 others can be found at the New Mexico Digital Collection. Even if you don't take a look at the cutaways now I urge you to bookmark it for later as they really are an excellent way to get a good feel for the layout of various reactors.

Next up on the tour was the spent fuel pond. Once fuel elements have completed their stay in the reactor they require many months of cooling as the continued decay of fission products produces heat. Used fuel elements are removed from the reactor core and transferred down into the fuel storage pond. This is done via various chutes which deliver the fuel elements to the fuel pond area of the facility.

Fuel storage pond  (Photo Credit: Magnox North Ltd) 
Following a storage period in the fuel ponds the fuel elements are loaded into specialized fuel transport flasks and sent off site for disposal/storage. These flasks are rather large and are very well shielded.

Fuel transport flask  (Photo Credit: Magnox North Ltd) 

The final area of the tour was a gas recirculator hall. The Magnox type reactor (as are the newer AGRs) are cooled with Carbon Dioxide gas. Large fan like circulators are used to maintain an adequate flow of coolant gas throughout the core. Unfortunately I cannot locate any images of the circulators or the drive motors. I will attempt to locate some more information on the gas circulators. Needless to say this area was also fairly warm but was very noisy due to the circulator motors.

It's worth remembering that these reactors were operating before humankind set foot on the Moon. Thinking of the lifespan of these reactors in those terms really puts in perspective the kind of things that have already been accomplished with nuclear power.

Lookout for details of my visit to the Imperial College London CONSORT research reactor facility and a look at a very interesting future reactor concept in future posts.