1. Introduction
In the process of nuclear/thermonuclear (N/TN) explosion, new nuclides are formed due to multiple neutron capture as in stellar nucleosynthesis [1]. The difference of stellar impulse nucleosynthesis from the process of nuclei formation in N/TN explosion [26] is primarily in the time parameters of the process. The explosive N/TNprocess has small duration time (t
Studies of the formation of transuranium nuclei in this process were carried out in the USA in 1952 – 1964 in thermonuclear tests. Transuranium isotopes (up to
In Figure 1 shows the normalized experimental data on Y(A) yields for three explosions Mike" [3], "Barbel" [6] and "Par" [4]. The decreasing dependence of Y(A) is fitted as follows:
The standard r.m.s. deviations of this approximation are: δ
2. Method of calculation
In the modeling the prprocess of nuclear/thermonuclear explosions, were made serious simplification due to the fact that neutron capture and decay of the nuclides are separated in time. So the system of equations for the time dependence of the concentrations N(A; Z; t) of nuclei with the mass number A and the charge Z has the form:
where
The timedependent part of the system of equations (2) was solved using the adiabatic binary model (ABM) [10] where numerical simulation is performed by dividing duration of prprocess by small nanosecond time steps with calculations of isotope yields in succession for each step. The initial conditions are also determined by the isotope composition of the target and are determined by the yield of the preceding isotopes in the previous time step. In view of the binary, twostage character of the TN explosion: the nuclear explosion (the first stage with the fission reaction) and the second stage associated with thermonuclear reaction, two neutron fluxes and two sets of initial concentrations were used in the calculations.
3. Results
In all calculations of this work, a unified approach was used within the framework of the adiabatic binary model (ABM)  it was assumed that there was an admixture of
Table 1


"Mike"  "Par"  "Barbel"  
A 
Y(A)

Y(A)

A 
Y(A)

Y(A)

A 
Y(A)

Y(A)

239  1.00  1.00  245  1.00  1.00  244  1.00  1.00 
240 
3.63

6.48

246 
8.50

4.93

245 
1.61

2.21

241 
3.90

1.34

247 
1.10

1.39

246 
1.13

7.38

242 
1.91

4.11

248 
5.10

5.15

247 
1.35

1.63

243 
2.10

5.25

249 
9.00

1.35

248 
5.22

4.36

244 
1.18

1.03

250 
4.10

3.79

249 
9.57

1.20

245 
1.24

1.06

251 
1.30

9.69

250 
2.57

2.65

246 
4.78

1.70

252 
2.20

2.13

251  – 
8.59

247 
3.90

2.91

253 
1.10

5.31

252 
2.30

1.58

248 
1.20

5.61

254 
1.20

9.58

253 
9.57

4.82

249 
1.10

1.83

255 
4.30

2.32

254 
7.83

7.87

250  – 
3.33

256 
2.60

3.54

255 
3.96

2.14

251  – 
1.04

257 
5.60

8.07

256  – 
3.08

252 
1.03

1.58

257 
5.65

7.24


253 
4.0

4.05


254 
4.2

5.44


255 
5.7

1.20


δ %  56 (1a)  91  87 (1c)  39  60 (1b)  29 
To illustrate the degree of agreement between calculations and experiments "Mike", "Par" and "Barbel", the calculated yields (normalized to experimental data) are presented on Figures 24, where calculations of other authors are given for comparison. The fitting of the experiments (1) (see Figure 1) is also presented in the normalized form.
Yields calculations for "Mike" experiment were performed earlier more than once and the best ones are shown in Figure 2. The accuracy of these calculations is small, so for [11] r.m.s. δ
The most successful for nucleosynthesis was "Par" experiment [4], where nuclides with all mass numbers up to A = 257 were detected. The ABM model allowed to reduce significantly the deviations from the experiment (up to 33%) and to provide a discrepancy for each isotope better than in two times for neutron fluxes of 5.31
However, in the next experiment, "Barbel" [6], which was supposed to confirm the results of "Par" (and oriented to obtaining transuraniums), where were not detected isotopes with A
4. Conclusion
The process of heavy elements production under the intensive pulsed neutron fluxes (up to 10
The calculations include the processes of delayed fission (DF) and the emission of delayed neutrons (DN), which determine the "losing factor" – the total loss of isotopes concentration in the isobaric chains. The DN and DF probabilities were calculated in the microscopic theory of finite Fermi systems [8]. Thus, it was possible to describe the evenodd anomaly in the distribution of concentrations N(A) in the mass number region A = 251 – 257. It is shown qualitatively also that the oddeven anomaly may be explained mainly by DF and DN processes in very neutronrich uranium isotopes.
Acknowledgements
We are grateful to E.P. Velikhov, L.B. Bezrukov, S.S. Gershtein, B.K. Lubsandorzhiev, I.V. Panov, E.E. Saperstein, V.N. Tikhonov, I.I. Tkachev and S.V. Tolokonnikov for stimulating discussions and assistance in the work. The work is supported by the Russian RFBR grants 160200228, 180200670 and RSF project 161210161.