1. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 1 EVALUATION OF 236 U NUCLEAR DECAY DATA Aurelian Luca “Horia Hulubei” National Institute of Physics and Nuclear Engineering (IFIN-HH), Radioisotope Production Dept., Radionuclide Metrology Laboratory, Magurele, Romania

2. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 2 Introduction The evaluation of 236 U nuclear decay data was performed in the frame of the IAEA Research contract no. 13341/2005 (“Improved decay data for important actinides”), within the IAEA CRP “Updated Decay Data Library for Actinides”, according to the DDEP procedures. 236 U: alpha-gamma radiations emitter, with weak spontaneous fission (9.4  10 -8 % branch) and very weak cluster decay – Ne and Mg emission (~10 -13 probability relative to alpha decay, according to Tretyakova et al., 1994).

3. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 3 References (selection) K.F. Flynn, A.H. Jaffey, W.C. Bentley and A.M. Essling, “Precision Measurement of Half-Life and Specific Activity of 236 U”, J. Inorg. Nucl. Chem. 34, 1121-1129, 1972 A. Rytz, “New Catalogue of Recommended Alpha Energy and Intensity Values”, At. Data Nucl. Data Tables 23, 507-533, 1979. W.B. Ewbank, Y.A. Ellis and M.R. Schmorak, “Spontaneous Fission Activities”, Nuclear Data Sheets 26, 1-3, 1979. M.R. Schmorak, “Nuclear Data Sheets for A=232, 236”, Nuclear Data Sheets 36, 367-427, 1982 and Nuclear Data Sheets 63, 139-215, 1991 S.N. Belenky, M.D. Skorokhvatov and A.V. Etenko, “Measurement of the Characteristics of Spontaneous Fission of 238 U and 236 U”, Sov. At. Energy 55, 528-531, 1983. “Decay Data of the Transactinium Nuclides”, Technical Reports Series no. 261, IAEA, Vienna, 1986, A. Lorenz, p. 157,163, 168. R.J. Gehrke, J.D. Baker and C.L. Riddle, “Feeding of the 232 Th levels from the decay of 236 U”, Appl. Radiat. Isot. 56, 567-568, 2002. G. Audi, A.H. Wapstra and C. Thibault, "The Ame2003 atomic mass evaluation (II)", Nuclear Physics A729, 337-676, 2003. E. Browne, “Nuclear Data Sheets for A=232”, Nuclear Data Sheets 107, 2579, 2006

4. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 4 236 U Nuclear Decay Scheme (Isotope Explorer v.2.23/1999)

5. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 5 Evaluation Tools (software) SAISINUC 2000, version 2006-fevrier, 2/16/2006 [Laboratoire National “Henri Becquerel”(LNHB), CEA, BNM, France] Lweight4 for Excel (C. Dulieu, LNHB), based on LWeight (D. MacMahon, E. Browne) ICC2005 (LNHB, CEA, BNM, France) BrIcc v.2.0 (T. Kibedi et al., 2005) EMISSION v.3.03, 2001 (PTB, Germany) Nuclear Science References (NSR) database, NNDC/BNL, USA (http://www.nndc.bnl.gov/nsr/)http://www.nndc.bnl.gov/nsr/

6. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 6 Half-life Evaluation Crt. No. Half-life and uncertainty (/10 7 years) ReferenceEvaluated value (/10 7 years) 1.2.46(14)Jaffey et al., 1951 2.2.391(57)Fleming et al., 19522.371(37) 3.2.3415(39)Flynn et al., 1972

7. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 7 Spontaneous Fission Half-life Evaluation Crt. No. S.F. Half-life & uncertainty (/10 16 years) ReferenceEvaluated value (/10 16 years) 1.2.0(16)Jaffey and Hirsch (1949) 2.2.7(3)Conde and Holmberg (1971) 2.56(17) 3.2.43(13)von Gunten et al. (1981) 4.2.7(4)Belenky et al. (1983)

8. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 8 Alpha Emissions, Normalization, Other Details The spin, parity and energy levels, alpha and gamma-ray transitions energies, alpha intensities, are adopted from the recent evaluation of E. Browne (2006); the relative  - ray emission intensities are from the measured values of Gehrke et al., 2002. The alpha energy, intensity and their uncertainty values are: 4168 keV [0.000 001 42 (48)], 4332 (8) keV [0.001 49 (22)], 4445 (5) keV [0.261 (40)]; the resulting intensity of the main emission [4494 (3) keV] is 0.738 (40). Normalization for the 232 Th ground state:

9. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 9 Gamma-ray Emission Intensities

10. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 10 Internal Conversion Coefficients (ICC) The most important case: 49.46 keV gamma-ray transitions

11. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 11 Internal Conversion Coefficients (ICC) cont. The weak conversion case: 171.15 keV gamma-ray transitions

12. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 12 X-rays Energy and Intensity Values

13. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 13 CONCLUSIONS The evaluation of 236 U nuclear decay data was performed in the frame of the IAEA Research Project no.13341/2005, according to the DDEP procedures and by using several evaluation tools. The normalization condition applied to the 232 Th ground state, lead to the absolute intensity value of the main gamma-ray emission of 49.46 keV. An excellent agreement was obtained in computing the ICC values with the BrIcc v.2.0a and ICC2005 (with hole hypothesis) software. The X-rays intensity values are in good agreement with the values from TOI, but have higher uncertainties; a future comparison with experimental values would be very useful.

14. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 14 Acknowledgements  Thanks are due to: IAEA and Dr. Mark A. Kellett (Project Officer) Dr. Marie-Martine Be Dr. Valery P. Chechev Dr. Filip G. Kondev Dr. Edgardo Browne U.S. Department of Energy (for using Isotope Explorer)

15. DDEP-2008 Workshop, 2008, May 12-14, Bucharest, Romania 15 THANK YOU !