# Dismantlement of Nuclear Power Plant (Canada)

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1. Feb 29, 2016

### Cyril St-Amand

Hi everyone this is my first time posting here,

First of all, excuse my english because here in Mtl we speak French mostly.

My team and I are working on an university project in Montreal (Qc) Canada (Polytechnique) regarding the recycling of radioactive material waste. We are working on the dismantlement of a Canadian nuclear facility (situated between Ontario and the province of Quebec, it's a fictive project, but the most realistic plant studied is the ''GENTILLY'' one) .

The first part of the project in due for this coming Wed nesday and we need to figure out a few things we couldn't find online. It regards the acceptable exposure rates / protection from gamma rays, some physics conversion we could not figure out and the concrete or carbon steel concrete for the confinement on the radioactive scorie (radioactive Ceasium).

1. How do we go about convertir Becquerels to mSv then to eV ? Is that even possible? Any pist of solution from your part? Here are the references we have used to far:

Références :

2. We need to figure out and come up with some NUMBERS for the confinement of the radioactive scorie (slag in english?). We thought about using the CSA norms N287 (N287.2 is unavailable at our university):

Références :

3. We are pouring the molten iron into a concrete tank, and we need to figure out how much concrete (standards, norms or fomulaes) needs to be used as an absorber to contain the radio active slag.

4. We are using two ovens to melt the radioactive iron. We need to figure out a way to transport the molten iron from oven01 to oven02 (potentially through concrete pipes, but we cannot figure out the thickness recquired to ensure staff safety).

5. We need norms and standards (Canadian or American) for staff exposure to radioactive substance in the facility altoget her.

Références :

http://www.nuclearconnect.org/know-nuclear/science/protecting

6. We know that we will have to use robotic arms and proper PPE (personal protection equipment) to deal with all this radioactive waste. Are there any formulaes that can help us with the radioactive emission linked with thickness of protective absorbent concrete pipes, equipments ?

Thanks a lot for any reference, formulaes or solutions from your part. Please if you are a phD student working on similar thesis, or an industrial, we need concrete and clear sources as our project in for a real mining company in Quebec, Canada.

Cyril St-Amand
4th year chemical engineering student at École Polytechnique de Montréal

2016-02-29

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2. Feb 29, 2016

### etudiant

Hi Cyril,
No nuclear expert, but the old civil defense documents produced by the Canadian Armed Services would give you good numbers for thickness of cement or shielding to protect from hazardous radiation. Do note it was all given as thickness to reduce the dose by half, so you then cumulate multiple layers to get the reduction you need.
There is no simple conversion of becquerels to dose, because the former only measures number of disintegrations per minute. You must specify the atom involved to know what radioactive emission are produced and how hazardous they are. Only then can a dose be determined.
Note that concrete is expensive and inflexible as shielding material. Water works pretty well and is cheap, try to use it as much as possible.
Melting contaminated iron has its own challenges, as the contaminants often get mobilized that way, so there are filtering problems. Why do it?
Have you considered cutting up the pieces instead? Abrasive slurries under high pressure can cut the very thick metal involved reasonably effectively.

3. Mar 1, 2016

### nikkkom

Melting of radioactive metal scrap seems to be pointless, it only releases more volatile compounds (paint, rust, grease, etc). The resulting ingots are economically useless, as they are still radioactive (even if slightly), and no one would want to use that for anything - it's not like this planet suffers from the lack of metal product vendors.

Consider shredding/compacting scrap.

4. Mar 1, 2016

### eXorikos

It actually isn't. It is withheld as a method to decrease the waste volume. Most radioactive elements will either have gaseous release or will accumulate in the slug. You can cope with both. The result is a metal which is ready for normal release and a part which is disposed of a radioactuve waste.

5. Mar 1, 2016

### etudiant

This melt process is not inexpensive and also leaves a somewhat contaminated smelting facility. Am consequently not persuaded that such an effort to 'decrease the waste volume' and have 'metal ready for normal release' is good policy.

6. Mar 2, 2016

### eXorikos

Operators are convinced and consider this a good way to recycle the RPV. For the other primary components surface treatment (chemical and physical) is considered sufficient for free release.

7. Mar 2, 2016

### etudiant

Afaik, no RPV has ever been recycled.
The RPV weight is around 500 tons and stainless steel sells for $2000/ton or less, so the scrap metal value is around$1mm.
Recycling that does not sound like an economic proposition to me.

8. Mar 2, 2016

### nikkkom

I find it hard to believe, as RPV has non-negligible levels of neutron activation. You can't get rid of radioactive isotopes of iron / nickel by melting, they will remain in the melt. Why would you use ("recycle") such metal when there is plenty of non-radioactive metal on the market?

9. Mar 2, 2016

### eXorikos

I have worked on the planning of the dismantling of 2 NPPs. There are at least 2 facilities that would do this. One in Finland and one in the USA.

Also, you have to account for the volume of high radiactive waste that you no longer have to store. This is by far the largest factor to take into account.

10. Mar 2, 2016

### Staff: Mentor

I can't believe that you are searching for such answers online instead of employing radiological safety and health professionals. This must be a joke.

11. Mar 3, 2016

### Zacarias Nason

I can only think you may have missed it in the original post, but if I understood correctly this is for what I'm guessing is a university project for a fictitious reactor. They wouldn't employ anybody to complete a school project.

12. Mar 3, 2016

### Staff: Mentor

Yes. Let me point it out:

13. Mar 3, 2016

### Staff: Mentor

I did miss the word fictive in the OP. Apologies.

14. Mar 5, 2016

### Astronuc

Staff Emeritus
From the first citation - "One gray corresponds to one joule of radiation energy absorbed by one kilogram of matter."

One can convert convert activity (becquerels, Sieverts or grays) to energy by taking the activity for various decays, multiplying the mean energy per decay, and integrating over time (confinement time), otherwise decay rate times energy per decay yields power or energy per unit time.

Iron or steel is generally not melted in an oven, but rather in a furnace, which is typically an induction or electric arc furnace (EAF), or occasionally in a basic oxygen furnace (BOF). Molten steel is usually collected in a steel vessel which is lined with refractory ceramic/concrete lining, e.g., a tundish or ladle. It might be worthwhile to find a foundry program at the university and ask a faculty member about steel foundry operations.

https://en.wikipedia.org/wiki/Steelmaking
https://en.wikipedia.org/wiki/HIsarna_steelmaking_process

Update:
ONE-PIECE REACTOR REMOVAL AND DISPOSAL
http://www.wmsym.org/archives/2001/10a/10a-16.pdf

The last page has a picture of the shielded vessel in preparation for being transported to the graveyard on the Hanford site.

The reactor contained approximately 155 curies of internal surface contamination and 2.01 million curies of activated metal at the time of disposal. The RPV activity is 4 orders of magnitude higher than the internal surface activity. One could make an estimate of the volume of the RPV and calculate the activity per unit volume, then determine how much steel would have to be used to dilute the activity to acceptable low levels.

Last edited: Mar 5, 2016