# Energy Department grants $226m to NuScale Power Tags: 1. Dec 13, 2013 ### Greg Bernhardt ### Staff: Admin Energy Department to Give$226 Million to Support Nuclear Reactor Design
http://www.nytimes.com/2013/12/13/b...lion-to-new-nuclear-reactor-design.html?_r=1&

2. Dec 14, 2013

### middlephysics

3. Dec 28, 2013

### OmCheeto

4. Dec 28, 2013

### gmax137

5. Dec 29, 2013

### caldweab

The water in a BWR is contaminated, I'm sure it has something to do with that. BWR also has lower operating efficiency than a PWR

6. Dec 29, 2013

### Astronuc

Staff Emeritus
Primary water in any LWR is contaminated with tramp uranium, particularly if a fuel rod becomes breached, but mainly from corrosion products which settle on the fuel during operation and become activated. BWRs are not necessarily less [thermodynamically] efficient than PWRs. Efficiency is unit specific, with some units more efficient than others. The design of the steam turbine blades and seals can significantly affect plant efficiency, and improvements in turbine efficiency have added between 1 and 2% to the net efficiency of some plants.

One issue for SMR designers is the control elements and external hardware, i.e., control rod drive mechanisms. Traditionally, BWR control elements are hydraulically inserted from below the core, which means the drive mechanisms are external to the RV. The upper structure has liquid/vapor separators and steam dryers. PWR control rod drives sit above the RV and the control elements are inserted by gravity.

Also, certain organizations may have expertise in PWR fuel/core designs rather than traditional BWR designs. BWR fuel must be channeled.

Last edited: Dec 29, 2013
7. Dec 29, 2013

### middlephysics

If the NRC would magically allow for any small (modular) reactor would you push for a gas, molton salt, liquid metal reactor or which type if any? Also does modular imply small?

8. Dec 29, 2013

### OmCheeto

I believe "modular", in this case, implies something prefabricated, and easily transported.

"small" implies small.

bolding mine

Astro will have to answer your first question, as it involves magic.

9. Dec 30, 2013

### caldweab

I know the water in the primary loop of a PWR is contaminated but a BWR only has one circuit and therefore that radioactive water or steam contaminates the turbine and other parts of the reactor system. I forgot about the control mechanisms part of it.

10. Jan 28, 2014

### mheslep

Thanks for that reference.

It seems to me the SMR cost containment is heavily dependent on the NRC's policy on security measures. That is, if the current requirements for redundant security infrastructure, the near SWAT team security personnel, the population evacuation plans, etc that apply to the large plants are also levied as-is on SMR then SMR is dead on arrival. It appears SMR advocates make a sound case that the design is more robust and the chance of various accidents are reduced in comparison to large light water PWRs, but I don't see how that helps SMR in the event of a malicious attack.

11. Jan 31, 2014

### QuantumPion

Smaller reactors have much lower source term. The potential for large scale release is not as much of an issue. E.g. university research reactors don't require the same level of security. These would be of an intermediate size.

That being said I think if they are going to make a SMR it should be a physically meltdown proof, power excursion-proof design.

12. Feb 2, 2014

### mheslep

Source term? The SMR is smaller, I think that means a large intentional release would impact, say, a country sized area as opposed ten of them? Any idea what's happened to university reactors since 911? I know there are far fewer than twenty years ago, but they might be do to the lack of new plant construction in the US.

I'm pursuing the security issue because the concept of SMRs, if it is to scale up, entails thousands of tens of thousands of SMRs around the US and new concept of their use. They can't then all be cited in remote, population sparse locations. That distribution would require a greater focus on either i) security, or ii) a very benign design.

Agreed.

13. Feb 3, 2014

### QuantumPion

No. Even Chernobyl, a very large, high burnup reactor, in the absolute worst case scenario with actual core debris scattered throughout the environment, only seriously affected the immediate area of Pripyat.

14. Feb 3, 2014

### mheslep

Arg, yes, I know. I meant to say county-sized not country.

15. Feb 4, 2014

### nikkkom

Chernobyl's fuel, by todays standards, wasn't high burn-up. IIRC it was below 20 GWd/tU.