Need help on research

[RoyID]

Hello all,

I'm currently working on a research involving the choice of valves in industrial processes. In the available documentation I can find valve specs are mainly concerning cost-efficiency, function and safety. However, I haven't faced any notes on abrasion and wear resistance. Does this mean that in nuclear technology there are no processes requiring abrasion-resistant valves i.e. there are no flows containing particles, dusts etc?
I find this quite hard to believe, is there anyone who can confirm this or explain what is the correct situation?

This would be of great help to push my research in the right directions, so thanks a lot in advance.

Roy

[tr]

In general, nuclear plants mainly pump around water that the plant has spent a lot of money cleaning up.  As such, there is not a lot of what could be called abrasive liquid.  On the other hand, we pump a LOT of water around.  As such, flow erosion and cavitation damage are real concerns.  The main area of damage is usually the piping, rather than the valves themselves.  All plants have flow accelerated corrosion (FAC) programs where all susceptible components get inspected on a periodic basis, and replaced as necessary.  There have been fatalities within the industry due to FAC related piping failures.  I believe the majority of the fatalities were due to the high temperature of the released liquid/steam.

As a start to your research, I suggest searching for the following on Google:

nuclear plant pipe rupture accidents

[Adam Grundleger]

I doubt you'll find much relevant info on the power generation end, but try contacting somebody at the NEF (National Enrichment Facility) in New Mexico.  I believe they should be starting production this year.  It's a new facility so lots of the sort of information you're looking for is probably still available. 

Keep in mind that component selection is not solely affected by engineering concerns or economics; the code of construction and accepted ten-year-plan restrict the selection of components greatly. 

[RoyID]

tr: Thanks for the info. This makes a lot clear. Have you got any idea what kind of shut-off valves are commonly used?

Adam: Thanks for the advise, I will certainly try to contact them!

[RoyID]

One more question. I know that I'm a stranger in nuclear energy, but just want this confirmerd. As far as I learned, all nuclear energy is captured as the reaction in vast rods of uranium heats water which causes a movement creating power?
This would mean that the metallurgical process creating uranium which can be used in reactors stands completely free from the actual phases within the reactor?

[Already Gone]

Not exactly.

The fuel, assembled in the rods or pins (actually they are tubes full of fuel pellets) is capable of producing a nuclear reaction and sustaining it to produce thermal energy (heat) which is converted to electrical energy the same way it is in coal or steam fired units.

The nuclear reaction is simply the splitting of a large atom into smaller ones by allowing free neutrons to collide with the nucleus.  The smaller fragments are themselves atoms that may or may not be radioactive or fissionable materials. 

The sustainability of the continued nuclear reaction depends on the amount of Uranium (or other nuclear fuel) contained in the pellets, the geometry in which they are arranged, the pressure and temperature of the medium surrounding them (called a moderator) and the presence of neutron absorbers (poisons) or control rods (which also absorb neutrons).

Over the course of a fuel cycle.  Some reactors are designed to convert the Uranium to Plutonium or other nuclear fuel isotopes, which then can be removed to fuel other reactors or bombs.  These are known as "Breeder" reactors.  Other reactors are loaded with a fuel mix that will do pretty much the same, but the product is not removed - just used to continue to fuel the same reactor.  This is called a "converter" reactor.

The commercial power plant reactors in the US, and the ones used to propel Navy ships, are simple reactors that are not intended or designed to "breed" plutonium or bomb-grade material.

[RoyID]

Thanks for the explanation, gave me better idea of how things work. However, returning to the base of my question, I think that in the nuclear power plants no abrasive pellets can get into the water circulating systems. This would exclude the necessity to use arbasion-preventing(and thus more expensive) valves. Am I correct?

[Marlin]

Thanks for the explanation, gave me better idea of how things work. However, returning to the base of my question, I think that in the nuclear power plants no abrasive pellets can get into the water circulating systems. This would exclude the necessity to use arbasion-preventing(and thus more expensive) valves. Am I correct?

Any contaminant in the water (moderator/coolant) may be activated (made radioactive) by the intense neutron flux in the reactor core. Water purity is kept very high in the coolant systems. In the waste systems there are some valves that may be in the category you are looking for where expended resins and debris from cleanup systems are processed. Typical valves here can be diaphragm valves, ball valves, and other components that are abrasive sensitive.

[RoyID]

You guys sure know how to explain things in an understandable way

What kind of valves are utilized in the 'normal' pumping round circuit of a boiler? It seems to me that the pressure must be very high, making it quite a severe service as well.

[Marlin]

You guys sure know how to explain things in an understandable way

What kind of valves are utilized in the 'normal' pumping round circuit of a boiler? It seems to me that the pressure must be very high, making it quite a severe service as well.

Try these links:

http://www.nucleartourist.com/

http://www.nei.org/

http://www.cranenuclear.com/valves/valves.php

http://www.velan.com/products/pdfs/vel-nukpro-web.pdf