The Updated Version of Chinese Evaluated Nuclear Data Library (CENDL-3.1)

Journal of the Korean Physical Society, Vol. 59, No. 2, August 2011, pp. 1052 1056 The Updated Version of Chinese Evaluated Nuclear Data Library (CENDL-3.1) Z. G. Ge, Z. X. Zhao and H. H. Xia China Nuclear Data Committee, Beijing 102413, China and China Nuclear Data Center, China Institute of Atomic Energy, Beijing 102413, China Y. X. Zhuang, T. J. Liu, J. S. Zhang and H. C. Wu China Nuclear Data Center, China Institute of Atomic Energy, Beijing 102413, China (Received 26 April 2010) The updated Chinese Evaluated Nuclear Data Library CENDL-3.1 is an important achievement based on the nuclear data evaluation works in recent years, at China Nuclear Data Center (CNDC) in cooperation with China Nuclear Data Coordination Network (CNDCN). CENDL-3.1 contains the evaluated data for reactions with incident neutrons on 240 nuclides (from 1 H to 249 Cf) in energy region of 10 5 ev 20 MeV. All data obtained according to the evaluations of experimental data and the predictions of the nuclear reaction model calculations. For most important nuclei of this library, the benchmark testing and validations have been performed, the comparisons with other nuclear data libraries (ENDF/B, JENDL, BROND, JEF, et al.) have been done. The testing version of CENDL-3.1 is CENDL-3.0, which has been provided for China domestic users. Follow the using back feed of CENDL-3.0, a lot of improvement has been done. The CENDL3.1 is provided for all users by ENDF format and is released to the world in the end of 2009. The overview, evaluation methodology and some important results of new evaluations, benchmark testing and validations for this library will be introduced in this contribution. PACS numbers: 25.40.-h, 24.10.-i Keywords: Nuclear data library, Evaluation, Benchmark, Nuclear model, ENDF DOI: 10.3938/jkps.59.1052 I. INTRODUCTION OF CENDL-3.1 CENDL-3.1 is a general purpose evaluated nuclear data library, which contains the fruits of the nuclear data evaluation and measurement works in recent years in China. CENDL-3.1 contains the evaluated data files for reactions with incident neutrons on 240 nuclides (see Table 1), among them, 206 nuclides are newly evaluated, 10 nuclides are revised based on CENDL-2.1 [1], and 24 nuclides are taken from CENDL-2.1. During the evaluation processes, the newest experimental information including new measurements made by Chinese scientists in China domestically, are collected, evaluated carefully and corrected by using the new standard cross sections and decay data et al.. One can see that the anmount of nuclei CENDL- 3.1 included is increased by almost three times compared with the previous version of CENDL(CENDL-2, CENDL-2.1). Table 1 shows the detailed nuclei including in the CENDL-3.1 and Fig. 1 shows the number of CENDL-3.1 content compared with CENDL previous. E-mail: gezg@ciae.ac.cn Fig. 1. (Color online) The No. of nuclei CENDL-3.1 contained. II. THE EVALUTATION ACTIVITES OF CENDL-3.1 All the member of China Nuclear Data Coordination Network (CNDCN) is involved in the evaluations for the CENDL-3.1 in the past years. CNDC developed a series methods and techniques to perform the new evaluations, which including the nuclear reaction model code, covariance data evaluation system and systematics et al., and some new foundation research achievements are used in -1052-

The Updated Version of Chinese Evaluated Nuclear Data Library (CENDL-3.1) Z. G. Ge et al. -1053- Table 1. The nuclides of CENDL-3.1. Nucl. Light Elements Structural Materials Fission Products & Medium Elements Actinides Content of Nuclei 1 3 H, 3,4 He, 6,7 Li, 9 Be, 10,11 B, 12 C, 14 N, 16 O, 19 F 23 Na, 24 26 Mg, 27 Al, 28 30 Si, 31 P, 0 S, 0 Cl, 0 K, 0 Ca, 46 50 Ti, 0 V, 50,52 54 Cr, 55 Mn, 54,56 58 Fe,59 Co, 58,60 62,64 Ni,0,63,65 Cu, 0 Zn, 0 Ge, 90 92,94,96 Zr, 92,94 98,100 Mo,0,107,109 Ag, 0 Cd, 0 Sn, 174,176 180 Hf, 181 Ta, 0 W, 197 Au, 0 Hg, 0 Tl, 204,206 208 Pb, 209 Bi 69,71 Ga, 70 78 Ge, 75,77,79 As, 83 86 Kr, 85,87 Rb, 88 90 Sr, 89,91 Y, 93,95 Zr 93,95 Nb, 99 Tc, 99 105 Ru, 103,105 Rh, 105,108 Pd, 113 Cd, 113,115 In, 112,114 120,122,124 Sn, 121,123,125 Sb, 130 Te, 127,129,135 I 123,124,129,131,132,134 136 Xe, 133 135,137 Cs, 130,132,134 138 Ba, 139 La 136,138,140 142,144 141 Ce, Pr, 142 148,150 Nd, 147,148,148m,149 Pm 144,147 152,154 151,153 155 Sm, Eu, 152,154 158,160 Gd, 164 Dy 232 232 241 236 239 Th, U, Np, 236 246 Pu, 240 244,242m Am, 249 Bk, 249 Cf the developments 1. The Model Code Calculations and Related Experimental Data Evaluation A. UNF Code System The UNF code system [2] is used as the key system for the model calculations in the new evaluations of CENDL-3.1. This system is developed by CNDC. The code system contains the spherical optical model, Hauser-Feshbach model [3] and the unified HauserFeshbach and exciton model [4] et al.. The UNF code system, which can be used to calculate for neutron introduced reactions with light, structural and actinide nuclei. The full sets of neutron data, i.e., cross sections of all reactions, energy and angular distribution of secondary neutrons and differential cross sections, etc. were provided in ENDF format [5]. Fig. 2. (Color online) The double differential cross sections (MF-6) of n+9 Be comparison with exp. data. B. Light elements evaluation Based on the updated experimental information and the model calculations with UNF code system, new- evaluations or re-valuations for 10 nuclei were performed. UNF code system has the ability to perform the double differential cross sections (MF-6) analysis for the 1p shell light nuclei [6]. As an example, Figs. 2 and 3 show the comparison of the calculated double differential cross sections for n+9 Be [7] and n+16 O reaction [8] and experimental data measured by M. Baba, et al. [5]. One can see from Figs. 2 and 3, the calculated results are very good in agreement with the measurement. The MF-6 files of n+9 Be, 10,11 B, 12 C, 14 N and 16 O in CENDL-3.1 are all obtained by this code system. C. Structural material and FP The UNF code system was also used for structural material and medium nuclides calculations in the new evaluations in CENDL-3.1. The full neutron data set Fig. 3. The double differential cross sections (MF-6) of n+16 O comparison with exp. data. (MF1-6, MF12-15 and MF31-35 and γ-production data including for some nuclei) are provided in ENDF format. For fission products nuclei the MF-1 to MF-5 are evaluated and provided only. The evaluated data of 101

-1054- Journal of the Korean Physical Society, Vol. 59, No. 2, August 2011 Fig. 4. (Color online) 48 Ti (n, tot) comparison with exp. Fig. 5. (Color online) 90 Zr (n, tot) comparison with exp. data other data files. fission products nuclides are sent to join in the international comparison of FP and coordinated by WPEC Subgroup 21, and some of them are selected as the data file of ENDF/B-VII [10]. Compared to previous CENDL, the main improvement of CENDL-3.1 for the structured materials is that in addition to the data of natural elements, the data of their isotopes are also included, and the data consistent between the natural elements and their isotopes are made. As the examples, the evaluated total cross sections of n+ 48 Ti [11] and n+ 90 Zr are showed in Fig. 4 and 5, and the evaluations of CENDL-3.1 are good enough in agreement with the exp. data. D. Fission Nuclides The nuclear reactor design, operation and relevent nuclear fuel treatment and other application fields need the accurate neutron data file for fissile materials nuclei. In other words, the evaluated data files for the main ac- Fig. 6. (Color online) 234 U (n, f) comparison with exp. tinides (U and Pu isotopes) are the most important part in a evaluated neutron data library. For the new evaluations of fission nuclei in CENDL- 3.1, all experimental data available were collected and corrected by using the standard data in ENDF/B- VI [12]. The model calculations were performed with the UNF code system based on the preliminary evaluated experimental data mentioned before. A data file is obtained by combining the preliminary evaluated experimental data and the model calcuated results. Then a series benchmark tests were performed for this data file. After all feedback from the preliminary evaluation, model calculation and benchmark testing, re-evaluation for the related data was performed. After many times of this circle, a final evaluated file is obtained. Total 32 actinides are evaluated or re-evaluated in CENDL-3.1. Important nuclides, such as 235 U and 238 U, were evaluated in the way mentioned above MF-1 6, 12 15 are included for important actinides (i.e., U, Pu isotopes), and MF-1 5 for others. As the examples, Fig. 6 to Fig. 8 show the new evaluations for 234 U (n, f), 237 Np (n, 2n) reactions and the Pu isotopes results of CENDL-3.1 compared with ENDF/B-VII. From the results showed in Figs. 6 to 8, one can see that in certain cases, the files of CENDL-3.1 are better and more reasonable than other libraries compared with experimental data. 2. Benchmark Testing of CENDL-3.1 A. The benchmark testing and validation system in CNDC A system named ENDITS for benchmark testing of nuclear data library has been development at CNDC. The benchmarks of system is consists of criticality benchmarks from ICSBEP, shielding benchmarks based on IAEA specifications for the FNS (Fusion Neutronics Source) experiments [13] and OKTAVIAN experiments [15] in Japan, and the integral capture cross section measurements. The criticality benchmarks were used to test

The Updated Version of Chinese Evaluated Nuclear Data Library (CENDL-3.1) Z. G. Ge et al. -1055- Fig. 9. (Color online) Validation of evaluations for CENDL using ENDITS system. Fig. 7. (Color online) 237 Np (n, 2n) comparison with exp. Fig. 10. (Color online) Time of flight spectrum for the LLNL pulsed shpere benchmark, 0.7 mfp-thick Oxygen sphere. Fig. 8. (Color online) The Pu isotopes results of CENDL3.1 compared with ENDF/B-VII. evaluations of actinides, structure materials and light nuclides under thermal, intermediate and fast spectrum. The shielding benchmarks are used to test nuclei for fusion spectrum. The integral capture cross section measurements are used to validate capture cross sections of fission products. As shown in Fig. 9, the three parts are used to test the different nuclei region and quantity of CENDL-3.1. B. The benchmark testing/validation for CENDL-3.1 In order to test the reliability of the data from CENDL-3.1, integral tests for some light medium-heavy nuclides and actinides have been performed with. The calculations and analysis of benchmarks are done with Monte Carlo code MCNP [16]. The data processing is carried out by using the internationally used nuclear data processing code system NJOY99 [17]. During the validation, some results are compared with ENDF/BVII, JENDL-3.3 [18] and JEFF-31 [19] libraries to identify the source of the discrepancies with the experimental results. Actually, many data files of CENDL-3.1 were re- evaluated and improved after the benchmark testing. Figure 10 shows the comparison of the calculated and experimental time of flight leakage from LLNL 0.7 mfpthick Oxygen pulsed sphere [20]. The result for CENDL3.1 was significant improved by validation work compared with CENDL-3.1. Figure 11 shows another improvement obtained with the efforts from both benchmark testing and evaluation. The serious keff bias in calculating eigenvalue for copper reflected fast criticality benchmarks using CENDL-2.1 or other library is smeared The C/E values calculated using CENDL-3.1 show quite good prediction of the keff values for these benchmarks. III. CONCLUSION CENDL-3.1 is finished and released in the end of 2009 and available for all users [21]. Nuclides and data files of CENDL-3.1 are increased and extended a lot compared with CENDL-2.1. All evaluations performed based on the new experimental data and new model calculations carefully. The evaluated data of the most important nuclides in CENDL-3.1 are validated by the benchmark testing. CENDL-3.1 is notably improved compared with

-1056- Journal of the Korean Physical Society, Vol. 59, No. 2, August 2011 Fig. 11. (Color online) Comparison of C/E value of eigenvalue for copper-reflected metal fast system. CENDL previous version. Some of them are better than other evaluated libraries according to the comparisons with updated experimental data and the results of the benchmark testing. ACKNOWLEDGMENTS The authors would like to thank all members of CNDCN to share the evaluation task of CENDL-3.1, and to make their great contributions. The authors also would like to make acknowledgments for IAEA/NDS, NEA-DB and other nuclear data centres for their useful advices and kindly help during evaluation process of CENDL-3.1. REFERENCES [2] J. S. Zhang, Nucl. Sci. Eng. 142, 207 (2002). [3] W. Hauser, H. Feshbach, Phys. Rev. 87, 366 (1952). [4] J. S. Zhang, Nucl. Sci. Eng. 114, 55 (1993). [5] M. Herman, BNL-NCS-44945-05-Rev., Brookhaven National Laboratory, 2005. [6] J. S. ZHANG, Commun. Theor. Phys. 39, 433 (2003). [7] J. F. Duan, J. S. Zhang, H. C. Wu et al., Phys. Rev. C: Nucl. Phys. 80,064612 (2009). [8] J. F. Duan, Y. L. Yan, J. M. Wang et al., Commun. Theor. Phys. 44, 701 (2005). [9] M. Baba et al., Conf. on Nuclear Data for Basic and Applied Science (Santa Fe, USA, 1985), p. 223. [10] M. B. Chadwick, P. Oblozinsky, M. Herman et al., Nucl. Data Sheets 107, 2931 (2006). [11] R. R. Xu, H. C. WU, Z. G. Ge et al., Nucl Sci. Eng. 160, 334 (2008). [12] V. McLane and M.O.CSEWG., BNL-NCS-17541, Brookhaven National Laboratory Report, 1996. [13] Fusion Evaluated Nuclear Data Library CDROM, IAEA-NDS-CD-6. [14] Y. Oyama and H. Maekawa, JAERI-M 94-014, Japan Atomic Energy Research Institute, 1994. [15] Chihiro Ichihara, Katsuhei Kobayashi and Shu A. Hayashi et al., JAERI-M 94-014, Japan Atomic Energy Research Institute, 1994. [16] J. D. Court, R. C. Brockhoff and J. S. Hendricks, LA- 12885, Los Alamos National Laboratory, 1994. [17] R. E. MacFarlane and D. W. Muir, LA-12740-M, Los Alamos National Laboratory, 2000. [18] K. Shibata, T. Kawano, T. Nakagawa et al., J. Nucl. Sci. Technol. 11, 1125 (2002). [19] A. Koning, R. Forrest, M. Kellett et al., JEFF Report 21, Nuclear Energy Agency, 2006. [20] C. Wong, J. D. Anderson, P. Brown et al., UCRL-51144, Lawrence Livermore National Laboratory, 1971. [21] http://www-nds.iaea.org/exfor/endf.htm. [1] Chinese Nuclear Data Center IAEA-NDS-61(Rev. 3), International Atomic Energy Agency, 1996.