NUCLEAR DATA MEASURING AND EVALUATION AT LOW AND MEDIUM ENERGIES

1. Neutron nuclear data at 14 MeV
2. Nuclear data reaching
3. Measuring of cross-sections of heavy nuclei fission under impact of neutrons with energy about 200 MeV

1. Neutron nuclear data at 14 MeV

Systematic measuring of cross-sections of nuclear reactions caused by neutrons with energies of 13.4 - 14.9 MeV is realized at Radium Institute since 1994. Cross-sections of more than two hundred reactions for the nuclei with mass numbers from 23 to 241 were measured for this period, and more than one thousand and three hundred new experimental values of sections were reached too. The data we have reached are best presented in publications [1-3]. The data obtained are also included into EXFOR files.

The results of measurements carried out before 1999 are collected in publication [17]. This work presents the detailed description of experimental technique and contains 852 values of cross-sections for 116 reactions. The results collected in [17] have contributed to sizeable progress in determination of cross-sections for such reactions as ²⁷Al(n,2n)²⁶Al, ⁵⁸Ni(n,p)^58mCo, ⁹³Nb(n,2n)^92mNb, ¹⁰⁹Ag(n,2n)^108mAg, ¹³⁸Ba(n,n'p)¹³⁷Cs, ¹⁵¹Eu(n,2n)^150gEu, ¹⁵³Eu(n,2n)^152m2+gEu, ¹⁸²W(n,n'α)^178m2Hf, ²⁴¹Am(n,2n)²⁴⁰Am, ²⁴¹Am(n,3n)²³⁹Am and other.

The publication [18] presents activation cross-sections obtained in experiments at Radium Institute in 1999 - 2001. The technique of experiment has received further development in this work. The spectra registered by Ge-detector have first allowed to separation and analysis of β-particle contribution. Sensitivity of several measurements reached 10^-7 bn. Among the most interesting outcomes of the work [18] there are measurements of cross-sections for the following reactions: ⁵⁰V(n,α)⁴⁷Sc, ⁵⁰V(n,n'α)⁴⁶Sc, ⁵¹V(n,n'α)⁴⁷Sc, ⁹³Nb(n,α)^90gY, ¹⁰⁶Cd(n,2n)¹⁰⁵Cd, ¹⁰⁶Cd(n,np)¹⁰⁵Ag, ⁹⁹Tc(n,n'α)⁹⁵Nb, ⁹⁹Tc(n,α)⁹⁶Nb, ⁹⁹Tc(n,p)⁹⁹Mo, ¹⁰³Rh(n,n'α)^99mTc, ¹⁰³Rh(n,p)¹⁰³Ru , and some other. The work [18] presents in total 228 new cross-section values for 50 reactions.

The work presented in publication [19] was carried out in 2001-2003. It was resulted in reaching 201 new experimental cross-section values for 38 reactions. The data for 16 reactions that is about 42% of those studied in the work [3] have not been earlier presented in EXFOR file or have been measured only once. Reaching of cross-section values measured for ¹⁸²W(n,p)^182m2Ta, ¹⁸³W(n,α)^180mHf, ¹⁹⁰Os(n,p)^190mRe, ¹⁹¹Ir(n,α)¹⁸⁸Re, ¹⁹³Ir(n,α)^190mRe, ¹⁹⁴Pt(n,p)^194mIr, ¹⁹⁶Pt(n,p)^196mIr, ¹⁹⁷Au(n,α)^194mIr and ¹⁹⁷Au(n,p)^197mPt . reactions can be attributed to the most valuable findings of the work [19]. Sizeable discrepancy is detected for these reactions between the data obtained in experiments and evaluations, at that a ratio of cross-section values measured in experiments to those from evaluations varies from 0.03 to 5.2. The reached results are stimulatory to the further development of works aimed at improvement of nuclear data libraries.

The works on measuring cross-sections of nuclear reactions caused by fast neutrons are being realized through the support by ISTC, IAEA, and UKAEA.

2. Nuclear data reaching

• Kalinin Valeriy Anatolievich
  Telephone: (812) 297-57-22 (ДПВ.3); fax: (812) 297-61-81; Email:
• c.p.-m.s. Yakovlev Vladimir Anatolievich
  Telephone: (812) 297-57-22 (ДПВ.3); fax: (812) 297-61-81;E-mail:

They conduct researches in the following directions:

• Measuring of isotopic yields at heavy nucleus fission by light particles charged with energies about 20 MeV.
• Physical measurements of ²³⁷Np, ^233,235,238U and ²³⁹Pu actinoid nucleus fission cross-sections in 2-20 MeV neutron energy range by the method of time correlated concomitant particles.
• Neutron field metrology and physical calibrations of neutron detectors on the basis of the same method.
• Nuclear data evaluations, in particular, evaluation of ²³⁷Np fission cross-section within the range of neutron energies about 0.2-20 MeV.

3. Measuring of cross-sections of heavy nuclei fission under impact of neutrons with energy about 200 MeV

With the purpose to improve nuclear databases for transmutation technologies they realize experimental and theoretical studies of heavy nucleus fission reactions.

Experiments are realized on synchrocyclotron (PINP, Gatchina) on fast neutron flux of 1-GeV energy. The available installation allows to measuring cross-sections of heavy nucleus fission caused by fast neutrons within energy range of 0.5-200 MeV in 1-MeV intervals.

The are completed two ISTC Projects, in the run of which we have measured neutron fission cross-sections for ²³⁸U and ²³³U, ²³²Th, ²³⁹Pu, ²⁴⁰Pu, ²⁴³Am, Pb, Bi, W with respect to ²³⁵U.

The Laboratory has plans to modernize the installation:

• expand energy range accessible for measurements to both lower and higher energies;
• measure fission cross-section for the standard, ²³⁵U, with respect to cross-section on hydrogen.

Theoretical investigations are aimed at studying of such a variable of the forced fission reaction, as a pulse transferred to a target's nucleus. The Laboratory elaborates a technique to derive values of this parameter from experimental data on angular distribution of fission fragments. We hunt a method to test nuclear models on the basis of data obtained in such experiment.