Sunday, February 24, 2008

WASH-1222 with Comments: Part 3

Introduction: In the first section of my exploration of WASH-1222, I pointed to what might be considered errors in logic or reasoning, in which argument went from true assumptions to false conclusions. But in the WASH-1222 discussion of the actual state of Molten Salt Reactor technology, we clearly encounter repeated a dishonest statements of facts. I will presently demonstrate the depth of this dishonesty.


The breeding reactions of the thorium cycle are:

232Th +n --> 233Th --> 233 Pa --> 233U

Because of the number of neutrons produced perneutron absorbed and the small fast-fission bonus associated with 233U and 232Th in the thermal spectrum, a breeding ratio only slightly greater than unity is achievable. In order to realize breeding with the thorium cycle it is necessary to remove the bred 233Pa and the various nuclear poisons produced by the fission process from the high-flux region as quickly as possible. The Molten-Salt Breeder Reactor concept permits rapid removal of 233Pa and the nuclear poisons (e.g. 135Xe and the rare earth elements). The reactor is a fluid-fueled system containing UF4 and ThF4 dissolved in LiF - BeF2. The molten fuel salt flows through a graphite moderator where the nuclear reactions take place. A side stream is continuously processed to remove the Pa and rare earth elements, thereby permitting the achievement of a calculated breeding ratio of about 1.06.

The MSBR is attractive because of the following:
  1. Use of a fluid fuel and on-site processing would eliminate the problems of solid fuel fabrication and the handling and shipping and reprocessing of spent fuel elements which are associated with all other reactor types under active consideration. 

  2. MSBR operation on the thorium-uranium fuel cycle would help conserve uranium and thorium resources by utilizing thorium reserves with high efficiency. 

  3. The MSBR is projected to have attractive fuel cycle costs. The major uncertainty in the fuel cycle cost is associated with the continuous fuel processing plant which has not been developed.
  4. The safety issues associated with the MSBR are generally different from those of solid fuel reactors. Thus, there might be safety advantages for the MSBR when considering major accidents. An accurate assessment of MSBR safety is not possible today because of the early state of development. 

  5. Like other advanced reactor systems such as the LMFBR and HTGR, the MSBR would employ modem steam technology for power generation with high thermal efficiencies. This would reduce the amount of waste heat to be discharged to the environment.
[Statement 4 is particularly agregous because safety is on of the towering strengths of the MSR. By 1972 safety issues involving the MSR had been well thought out, and solutions identified. The characteristic features of the MSR, its molten core, and salt fluid, conferred enormous safety advantages on the MSR concept. Statement 4. simply overlooks what was known about the safety advantages of MSR technology in 1972.

To give an idea of the extent to which Statement 4 subverts the truth I will compare it with Eric H. Ottewitte sometime latter listing of the safety advantages of the MSR:

1 .Already being a molten fuel, further "meltdown" cannot occur
2 .Fluid fuel has inherently a strong negative temperature coefficient of reactivity due to expansion, greatly inhibiting boiling
3 .Elimination of pressurized and pressure-evolving components inside the containment
4 .Elimination of the possibility of gas and vapor evolution, especially the release of free hydrogen and attendant fire hazard
5 .Reduced risk of radioactivity release outside the containment due to
a .reduced risk of failure of the containment, and
b .two orders of magnitude reduction in the FP decay heat source relative to
conventional solid-fuel reactors, due to continuous on-site chemical processing
6 .Reduced FP inventory improves the capability for emergency heat removal by natural
convection, thereby greatly reducing the designated evacuation area
7 .Fluidity facilitates removal from the reactor to ever-safe containers
8 .High heat capacity of fuel restricts temperature rise on loss of normal cooling
9 .Low salt vapor pressure minimizes the effect of any temperature rise

Ottewitte's list would have been based on knowledge that the writers of WASH-1222 in 1972.The list should not be regarded as comprehensive. Thus WASH-1222 appears to be deliberately minimizing the numerous and well established safety advantages of the MSR.
- CB]

Selected conceptual design data for a large MSBR, based primarily on design studies performed at ORNL, are given in Table I.

There are, however, problem areas associated with the MSBR which must be overcome before the potential of the concept could be attained. These include development of continuous fuel processing, reactor and processing structural materials, tritium control methods, reactor equipment and systems, maintenance techniques, safety technology, and MSBR codes and standards. Each of these problem areas will now be evaluated in some detail, using as a reference point the technology which was demonstrated by the Molten Salt Reactor Experiment (MSRE) during its design, construction and operation at Oak Ridge and the conceptual design parameters presented in Table I and in Appendix A. A conceptual flowsheet for this system is shown in Figure 1.

[I will comment on the problems alluded too in this paragraph as WASH-1222 discusses them in greater detail. - CB]

1 comment:

DaveMart said...

There is a lot of misinformation about at the moment, Charles.
I was pleased with this post of mine at TOD, which argued:
'My conclusion then is that nuclear is not only two to three times cheaper now that the proposed off-shore build, but that as the years go by the cost difference is likely to widen greatly.'



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