TUNDER Design of a conceptual D2O moderated MSR

[Johan]

Title: M/S Thunder - Design and analysis of a conceptual thorium fueled heavy water moderated molten salt reactor
Author: Johan Simu
Availability: Downloadable, from http://nuclearpoweryesplease.org/pub/thunder%2013-12.pdf

This is my master of science thesis. It is a basic reactor physics studie of a new kind of reactor: A heavy water moderated molten salt reactor.

Abstract

In this thesis the basic design of a conceptual molten salt reactor, THUNDER, is introduced. THUNDER is a heavy water moderated molten salt reactor, running on a closed thorium fuel cycle. The design is loosely based on the CANDU reactor with individual fuel channels and unpressurized, cold moderator. The purpose of THUNDER is to combine the attractive properties associated with:

• The superior neutron economy of having heavy water as moderator
• The low production of long lived minor actinides in radioactive waste and the ability to obtain breeding in a thermal neutron spectrum, wich are attractive features of the thorium fuel cycle
• The unique safety characteristics of molten salt reactors along with the ability for online fuel reprocessing

The fundamental physical characteristics of the THUNDER reactor is examined with regards to basic reactor parameters like, fuel channel radius, fuel channel pitch, reprocessing time and fuel composition. Particular attention is given to how these parameters affect temperature feedbacks, rectivity and conversion of fertile material. Furthermore heavy water moderation is compared to the standard case of using graphite as moderator and an unmoderated design, with regards to safety characteristics and efficiency of fertil to fissile conversion.

The results of the study are encouraging but not conclusive. By selecting an optimal set of design parameters it seems feasible to achieve a critical reactor with acceptable safety characteristics, and that a self breeding equilibrium state can be obtained, in wich the reactor is fuelled only with fertile thorium. THUNDER is shown to have a slight advantage over graphite through a higher conversion ratio, but it is not clear if THUNDER has any significant overall advantage over graphite moderated molten salt reactors.

[Joffan]

Thanks Johan, very interesting. This concept looks worthy of a lot more study. Is there any reason you chose graphite for the salt tubes?

p26, You have Table 7 mislabelled as Table 6. MURE looks like it will become a vey useful piece of software, once all the issues are ironed out.

[Johan]

Thanks Joffan!

The choice of graphite was because of the need for a material that is compatible with the salt and can handle high temperatures without loosing its strenght. My choice of fuel salt, LiF-(HN)F4 is what forces me to use graphite since the melting temperature is so high. The regular material in MSR's, hastalloy, isnt heat resistant enough. Its kind of a arbitrary pic though, one could choose a more conventional salt with lower melting temp and hastalloy tubes instead, I suspect the graphite might be cheaper and its a bit better from a neutron point of view since it absorbs less neutrons. But its also weaker so its a tradeoff.

Thanks for the heads up on the table numbering