The CNRS Research Program on the Thorium cycle ... - Pacen - IN2P3
The CNRS Research Program on the Thorium cycle ... - Pacen - IN2P3
The CNRS Research Program on the Thorium cycle ... - Pacen - IN2P3
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<strong>Thorium</strong> Cycle – Molten Salt Reactors June 2008<br />
Fig.4. Reprocessing capacity requirement for a TMSR-NM system operated in <strong>the</strong> Th-U <strong>cycle</strong>. <str<strong>on</strong>g>The</str<strong>on</strong>g><br />
ordinate gives <strong>the</strong> weight of heavy nuclei reprocessed per day while <strong>the</strong> abscissa corresp<strong>on</strong>ds to <strong>the</strong><br />
initial fissile ( 233 U) inventory. Heavy nuclei proporti<strong>on</strong>s in <strong>the</strong> MSR fuel are indicated (x % HN as in<br />
Table 1). <str<strong>on</strong>g>The</str<strong>on</strong>g> black line separates breeding and n<strong>on</strong>-breeding z<strong>on</strong>es. In <strong>the</strong> breeding z<strong>on</strong>e, <strong>the</strong> red<br />
and green lines indicate <strong>the</strong> reprocessing requirements which allow <strong>the</strong> generati<strong>on</strong> of <strong>the</strong> 233 U needed<br />
for a new TMSR-NM reactor with <strong>the</strong> same inventory over 100y and 50y respectively.<br />
III.D.2 Transuranic Elements<br />
<str<strong>on</strong>g>The</str<strong>on</strong>g> TMSR-NM presented in secti<strong>on</strong> III.a can also be started with an initial actinide load c<strong>on</strong>sisting<br />
in thorium and in a mix of TRU elements (Pu, Np, Am and Cm) as <strong>the</strong>y exist in <strong>the</strong> used fuel of <strong>the</strong><br />
water moderated reactors presently operated with ei<strong>the</strong>r natural or slightly enriched uranium. For<br />
instance, <strong>the</strong> simulati<strong>on</strong> discussed below assumes a TMSR-NM started with <strong>the</strong> TRU c<strong>on</strong>tents of a<br />
PWR UOX fuel for 60GWd/T GEN-III reactor after five years of storage [Pu 87.5% ( 238 Pu 2.7%, 239 Pu<br />
45.9%, 240 Pu 21.5%, 241 Pu 10.7%, 242 Pu 6.7%), Np 6.3% , Am 5.3%, Cm 0.9%].<br />
For a typical TMSR-NM c<strong>on</strong>figurati<strong>on</strong> with 22.5% of HN in <strong>the</strong> salt, an amount of 8400 kg of fissile<br />
elements is needed initially, corresp<strong>on</strong>ding to approximately 4% of Plut<strong>on</strong>ium (See Table 1). This is<br />
very similar to <strong>the</strong> amount of fissile matter needed to start a SFR.<br />
HN<br />
233<br />
U-started TMSR- TRU-started TMSRproporti<strong>on</strong><br />
NM<br />
NM<br />
Th<br />
233<br />
U Th<br />
239 241<br />
Pu+ Pu<br />
7.5% 19760 2550 13850 4887<br />
10% 24050 3105 17560 5524<br />
12.5% 27790 3575 20890 6022<br />
15% 33060 4140 25380 6786<br />
17.5% 37230 4650 29150 7297<br />
20% 42380 5170 33640 7968<br />
22.5% 46100 5580 37040 8378<br />
25% 48640 5820 39320 8668<br />
27.5% 52190 6180 42570 9037<br />
Table 1. Initial inventories (kilograms) of Th and fissile matter for 233 U-started TMSR-NMs and for<br />
TRU-started TMSR-NMs. For <strong>the</strong> TRU-started TMSR-NM <strong>the</strong> table <strong>on</strong>ly gives <strong>the</strong> mass of fissile Pu<br />
isotopes ( 239 Pu+ 241 Pu). <str<strong>on</strong>g>The</str<strong>on</strong>g> weight of <strong>the</strong> o<strong>the</strong>r Pu isotopes and <strong>the</strong> minor actinides (Np, Am, Cm) in<br />
<strong>the</strong> initial fuel can be determined from <strong>the</strong> percentages given in <strong>the</strong> text. <str<strong>on</strong>g>The</str<strong>on</strong>g> HN c<strong>on</strong>centrati<strong>on</strong>s (left<br />
column) are those which label <strong>the</strong> points <strong>on</strong> <strong>the</strong> curves displayed in Figure 4.<br />
III.E Deterministic Safety<br />
<str<strong>on</strong>g>The</str<strong>on</strong>g> total feedback coefficient at equilibrium is displayed in Fig. 5 as a functi<strong>on</strong> of <strong>the</strong> HN<br />
proporti<strong>on</strong> for both a 233 U and TRU started TMSR-NM (see Table 1). Fig.5 also shows <strong>the</strong> c<strong>on</strong>tributi<strong>on</strong>s<br />
of <strong>the</strong> salt heating and salt density to <strong>the</strong> feedback coefficient for <strong>the</strong> 233 U case. <str<strong>on</strong>g>The</str<strong>on</strong>g> safety coefficients<br />
remain negative for all HN proporti<strong>on</strong>s, including <strong>the</strong> density coefficient which can be viewed as a void<br />
coefficient. <str<strong>on</strong>g>The</str<strong>on</strong>g> total feedback coefficient, which ranges from -10 pcm/K to -5 pcm/K, ensures a good<br />
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