## Dose rate into a nuclear reactor coolant

Cyril R
Posts: 5037
Joined: Jul 14, 2008 3:12 pm

### Dose rate into a nuclear reactor coolant

Just checking the math here.

Assume 3400 MWt PWR, core flow 67 million kg/h primary flow rate. Assuming 4% of the thermal load generated by absorption of neutrons and gammas in the water. This makes an ionizing radiation heating of 136 MWt, 489600 MJ/h. 7300 Gray/h.

That's a yearly dose of some 64,000,000 Gray/year. Yes, MILLION grays per year.

Is this roughly correct?

Cyril R
Posts: 5037
Joined: Jul 14, 2008 3:12 pm

### Re: Dose rate into a nuclear reactor coolant

I guess my question is, OR do you use the total core coolant inventory only (not the flow rate) since this is the same water that gets circulated many times over?

fab
Posts: 256
Joined: Oct 28, 2013 12:24 am

### Re: Dose rate into a nuclear reactor coolant

I guess that 7300 Grays is the dose received by the water which passes only one time in the core. Since the water passes many times in the core we must divided the energy received by the water in one hour by the total inventory of water of the primary circuit ( some water remains in the pressurizer but we can neglect this effect if we want an order of magnitude).

The datas I have is that the volume of primary water for a 3817 MWth 4 loops PWR at full power in steady state is 399 m^3 of liquid water and 25 m^3 of steam (I guess that it is saturated steam in the pressurizer, I don't take it into consideration).

With an approximation of liquid water at 700 kg/m^3 , we have an estimation of roughly 250 tons of water in the primary circuit of your 3400 MWth PWR.

If we assume 4 % of the thermal load generated in the water, that gives us a dose of roughly 2 000 000 Gray/h or 17.5 billions grays per year.

Sorry for the eventual mistakes.

PS : the fraction of power generated in the coolant seems to be 2.6 % in this document ( see page 22 of the PDF ) :

Cyril R
Posts: 5037
Joined: Jul 14, 2008 3:12 pm

### Re: Dose rate into a nuclear reactor coolant

Thanks a lot fab. So we are looking at ballpark figures of 11 billion gray per year.

This simple exercise really makes me appreciate a nuclear coolant.

Kirk Sorensen
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Joined: Nov 30, 2006 3:30 pm
Location: Alabama
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### Re: Dose rate into a nuclear reactor coolant

So how many neutrons does a PWR spend turning protium into deuterium?

Cyril R
Posts: 5037
Joined: Jul 14, 2008 3:12 pm

### Re: Dose rate into a nuclear reactor coolant

Kirk Sorensen wrote:So how many neutrons does a PWR spend turning protium into deuterium?
Good question! I don't know really. Most of the literature just talks about non-fuel captures, which includes boron in the coolant and zircalloy clad. Its got to be over 5% though.