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Table 3. Target-volume-averaged direct fission and<br />

disappearance reaction rates in the various targets irradiated in BR2 and MYRRHA<br />

Target Nuclide Reaction rates in BR2 Reaction rates in MYRRHA<br />

NpO 2 -MgAl 2 O 4 -Al<br />

Am 2 O 3 -MgAl 2 O 4 -Al<br />

Tc-metal<br />

NaI<br />

237 Np<br />

241 Am<br />

243 Am<br />

99 Tc<br />

129 I<br />

direct fiss.<br />

(s -1 )<br />

disapp.<br />

(s -1 )<br />

direct fiss.<br />

/disapp.<br />

direct fiss.<br />

(s -1 )<br />

disapp.<br />

(s -1 )<br />

direct fiss.<br />

/disapp.<br />

5.50 10 -10<br />

9.09 10 -10<br />

4.75 10 -10 3.99 10 -8<br />

7.05 10 -8<br />

2.87 10 -8 0.014<br />

0.013<br />

0.017<br />

1.29 10 -9<br />

1.09 10 -9<br />

8.67 10 -10 3.88 10 -9<br />

3.89 10 -9<br />

3.27 10 -9 0.33<br />

0.28<br />

0.27<br />

3.93 10 -9<br />

8.95 10 -10<br />

5.86 10 -9 4.90 10 -10<br />

Table 4 indicates the resulting percent MA and LLFP disappearance, by fissions and total, after<br />

an irradiation period of 200 effective full power days (EFPD). The isotopes 241 Am and 243 Am are<br />

considered separately. The fissions indicated are the “direct” fissions of 237 Np, 241 Am and 243 Am and<br />

do not include the “secondary” fissions, viz those of the actinides formed by (Q UHDFWLRQVGXULQJWKH<br />

irradiation, possibly followed by natural decay. In the case of irradiations in BR2, these “secondary”<br />

fissions are very important: see further, Table 6.<br />

Table 4. Percentage disappearance (through direct fissions and total)<br />

of the MAs and the LLFPs irradiated in BR2 and MYRRHA during 200 EFPD<br />

Target Nuclide Disappearance in BR2 Disappearance in MYRRHA<br />

NpO 2 -MgAl 2 O 4 -Al<br />

237 Np<br />

% direct<br />

fissions<br />

0.69<br />

%<br />

total<br />

49.79<br />

direct<br />

fiss./total<br />

0.014<br />

% direct<br />

fissions<br />

2.16<br />

%<br />

total<br />

6.49<br />

direct<br />

fiss./total<br />

0.33<br />

Am 2 O 3 -MgAl 2 O 4 -Al<br />

Tc-metal<br />

NaI<br />

241 Am<br />

243 Am<br />

99 Tc<br />

129 I<br />

0.91<br />

0.65<br />

70.42<br />

39.10<br />

8.99<br />

9.63<br />

0.013<br />

0.017<br />

1.82<br />

1.46<br />

6.50<br />

5.49<br />

1.53<br />

0.84<br />

0.28<br />

0.27<br />

5. Discussion<br />

5.1 Comparison with data published previously for BR2 and MYRRHA<br />

In [14], presented in 1992 at the Second Information Exchange Meeting on Actinide and Fission<br />

Product Separation and Transmutation, the MA and LLFP transmutation rates in BR2 were calculated<br />

for a large variety of targets as to their dimensions and material concentrations. Compared to the<br />

calculations discussed in the present paper, entirely different codes and different cross-section<br />

libraries were used. Nevertheless, for the 1992 target dimensions and MA and LLFP concentrations<br />

corresponding to those studied in the present paper, the comparison of the calculated transmutation<br />

rates indicates, for the MAs, an excellent agreement (within 5%), and for 99 Tc and 129 I, an agreement<br />

within about 10%. The deductions made in [14] as to the total amounts of MAs and LLFPs that could<br />

801

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