Re: H-3 production (follow up to C-14 production)

[JGinniver@AOL.COM]

In a message dated 30/8/04 5:07:50 pm, ben.morgan@pgnmail.com writes:





> American National Standard ANSI/ANS-18.1-1999, "radioactive source term

> for normal operation of light water reactors", shows the tritium

> concentration in reactor coolant as 1.0E-02 uCi/g for BWRs and 1.0 uCi/g

> for PWRs.

> 

> Unlike BWRs, PWRs use boric acid in the coolant as a form of reactivity

> control. This produces tritium from B10(n,2a)T and B10(n,a)Li7(n,na)T

> reactions.

> 

> The pH of the PWR coolant is controlled by the addition of LiOH which

> contains primarily Li7. This produces tritium by the Li7(n,na)T

> reaction.

> 

> NOTE: There are also B11 and Li6 reactions that produce T but these are

> negligible contributors.

> 

> 



Ben,

a study was carried out during the design phase of the UKs sole PWR at 

Sizewell in Suffolk which indicated that Li6 reactions are much more significant 

than those for Li7.



The B10 reaction was estimated to contribute about 57% of the tritium present 

in the coolant, Ternary Fission about 22%, Li6 about 21% and H2 about 0.4%.   

 



The estimates were based on the plant using enriched LiOH where the Li7 

concentration is enriched to 99.9%, rather than using natural LiOH where the Li6 

concentration would be 7.4%



In the literature I have available, there is very little information on the 

contribution of Li7 to the level of tritium present in the coolant, other than 

it is negligable.



In answer to the original issue of the possible levels of C14 present in the 

graphite core of the Chornobyl reactor, estimates of the level in a single UK 

AGR (which contains approximately 1500 tonnes of graphite) after 30 calendar 

years of operation is between 50 and 80 GBq.   These values were based on mean 

value of 15 ppm Nitrogen in samples taken of the graphite in two UK AGRs, and 

the natural level of approximately 1.1% of C13 in the graphite. 



Regards,

     Julian