The Answer to Climate Change Is Renewable Energy, Not Nuclear Power

[PamW]

33. Vessel lifetime

kristopher,

What determines the lifetime of a reactor? The lifetime is determined by the life of the reactor vessel. ALL the other parts of the reactor are removable / replaceable. For example, if there is a problem, the control rod drives can be replaced or repair. The only thing that can't be replaced readily is the vessel, itself.

Do you think a reactor vessel "wears"? There's no moving parts. It's just a big tank.

Do you have any air tanks or water tanks in your house? How about saucepans and dutch ovens for boiling water.

How long do you think they last? Do they only last 40 years? What's the "wear" mechanism that wears them out?

With a nuclear reactor vessel; like the saucepans; there ISN'T any; except one; neutron embrittlement.

The vessel is exposed to fast neutrons that can knock atoms from their proper place in the crystal lattice. Because a misplaced atom can impede elastic strain as a metal is subjected to stress; the metal becomes embrittled.

In the early days of nuclear power, it was HYPOTHESIZED that such embrittlement might lead to a limited lifetime of the reactor vessel. However, this has been a very active area of material research.

University researchers have been irradiating reactor metal in university research reactors for years to determine the degree to which neutrons induce embrittlement. The answer is that this effect is a LOT LESS SEVERE than originally expected.

In any case; embrittlement can be "treated". The effects of embrittlement are reversible by annealing, which means heating the material so that atoms have the energy to return to their proper places in the crystal lattice.

Neutron embrittlement is something that is monitored by the NRC when a reactor comes up for license renewal. If the operator can show that the amount of embrittlement measured on the vessel is well below limits, and that the original 40 years of operation didn't approach the limit; then projecting forward another 20 years, the limits will also not be reached; then the reactor can be re-licensed. If it would exceed the limits; then it would need to be annealed. NONE of the reactors that the NRC has re-licensed have needed to be annealed.

It was amusing to see an advertisement for the Nuclear Energy Institute come up next to kristopher's original post.

PamW