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1 II. Physikalisches Institut, Universität Gießen 11. Januar 2012
Instituts-Seminar II. Physikalisches Institut, Universität Gießen 11. Januar 2012 Beta-delayed neutron emission evaluation for reactor physics and astrophysics Dr. B. Pfeiffer II. Physik. Institut, Justus-Liebig-Universität, Gießen GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt Do we need a new evaluation? Can it be done under the auspices of the IAEA? Instituts-Seminar II. Phys. Gießen

2 GSI contributions to data bases
At GSI, many installations are studying nuclear structure. The measured quantities are of interest for different fields ranging from basic science to technical applications. A (personally biased) example are the ground-state masses of atoms. In 2008, European nuclear physics institutions instigated an effort to intensify their participation in the international task of establishing ``Reference Data Libraries for Nuclear Applications'' ``Reference Data Libraries for Nuclear Applications -- ENSDF''; Report of Technical Meeting of IAEA Nuclear Data Section INDC(NDS)-0543, November 2008, Vienna At FRS, decay properties of neutron-rich nuclei are studied. The half-lives can be measured following the β-decays. For nuclei far from stability, quite complicated decay chains can result. An alternative technique observes the β-delayed neutron activity with, in general, less complex decay chains. Browsing the literature, we could not find a recent evaluation of this decay mode. In addition, all evaluations up till now were restricted to fission products. Instituts-Seminar II. Phys. Gießen

3 Discovery of fission Already in the first year after the discovery of fission (O. Hahn, F. Straßmann, Die Naturwissenschaften 27, 11 (1939)), it was observed that the fission products have an asymmetric mass distribution („Kamelhöckerkurve“); more than 1 prompt neutron is emitted per fission event (H. Halban, F. Joliot, L. Kowarski, F. Perrin: J. de phys. et rad. 10, 428 (1939); and Nature 143, 470, 680, 939 (1939); L. Szilard, W. Zinn, Phys.Rev. 55, 799 (1939)), opening the way to chain reactions; delayed neutrons are emitted for 1 ½ min (R.B. Roberts, R.C. Meyer, P. Wang, Phys.Rev. 55, 510 (1939; R.B. Roberts, L.R. Hofstad, R.C. Meyer, P. Wang, Phys.Rev. 55, 664 (1939)), neutrons allowing to control the chain reactions in a nuclear reactor; thermal neutrons fission 235U (A.O. Nier, E.T. Booth, J.R. Dunning, A.V. Grosse, Phys.Rev. 57, 546 (1940)). 3 Instituts-Seminar II. Phys. Gießen

4 Ewald’s double-focusing spectrograph
A.O. Nier had used a mass spectrometer to separate the Uranium isotopes and irradiated them with neutrons. At the same time, Ewald had joined the group of Mattauch at the Kaiser-Wilhelm-Inst. I could not find a contribution of the Mattauch group to the study of the fission process. Heinz Ewald Heinz Ewald designed a double-focusing mass spectrograph at the Kaiser-Wilhelm- Institut in the years 1942 – It accompanied him in all his career and ended at the II. Physikalisches Institut in Gießen. There I saw it as a young student in a dark cellar. Now it is displayed more openly. Instituts-Seminar II. Phys. Gießen

5 Proposal of Ewald for an isotope separator 1942
Prof. Ewald was involved with the Uranverein. I could find only one mention. Recently, R. Karlsch put forward the hypothesis that the German scientists had made substantial progress on the way to the atomic bomb. In Ewald/Hintenberger is shown a proposal for an isotope separator by Ewald 1942 (see Fig. right). In M. Walker „German National Socialism and the Quest for Nuclear Power “ is reported, that M. von Ardenne picked-up the idea and constructed a proto-type in his laboratory. Prof. Schmidt-Rohr presumes that Ardenne built also a fullfledged separator with the „Forschungsanstalt der Deutschen Reichspost“ in a circular bunker near Bad Saarow south of Berlin, as this bunker corresponds to the one constructed for a cyclotron at Miersdorf. Instituts-Seminar II. Phys. Gießen

6 Beta-delayed particle emission
A necessary condition for β-delayed particle emission is that the Q-value is superior to the binding energy of the last particle, either a neutron or a proton. With increasing distance to the valley of stability, Q-values increase and separation energies decrease. So, in general, the nuclides undergoing delayed emission are situated away from stability and have quite low half-lives. Historically, such nuclides could nearly exclusively be obtained as products of neutron-induced fission. Interestingly, the most intense source for neutrons are nuclear reactors. And for the control of a reactor, β-delayed neutrons are playing an essential role. Therefore, β-delayed neutrons were studied intensively. 6 6 Instituts-Seminar II. Phys. Gießen

7 New developments But although many groups in many countries dedicated much effort in the study of delayed emitters among fission products, there exist elements for which not a single Pn value has been reported (see Fig. on next slide). They are mainly situated in the region of symmetric fission with low yields and/or are refractory elements not suited for ion sources. New developments The data on delayed neutrons collected for reactor applications are now applied in totally different fields (partly by the same scientists), as e.g. calculations of the nucleosynthesis in explosive stellar environments‡. Due to the extremely high neutron fluxes, the properties of very neutron-rich isotopes must be obtained. With the advent of radioactive beam facilities, short-lived neutron- (and proton-) rich nuclides can now be produced for all elements. The past compilations/evaluations comprised mainly fission products, the new developments necessitate also new evaluations. ‡ very recent article: B. Pritychenko; rXiv: Stellar Nucleosynthesis Nuclear Data Mining Instituts-Seminar II. Phys. Gießen

8 Overview NUBASE11 8 8 Instituts-Seminar II. Phys. Gießen

9 Chain-reaction assemblies
For atomic bombs, reactor and decay heat applications, data on the several hundred individual precursors are not imperitavely needed. „Aggregate“ or group data are sufficient and have been measured partly with daring and perilous installations as the fast reactors of the GODIVA type. The first drop-installation „The Dragon“ had already been built by O.R. Frisch end of 1944 at Los Alamos. The time-dependance of delayed-neutrons after short irradiations with fast neutrons had been studied, p.e. F. de Hoffmann et al., Delayed Neutrons from U-235 After Short Irradiation Phys.Rev. 74, 1330 (1948) . LADY GODIVA D.Loaiza et al., Measurement of Absolute Delayed Neutron Yield and Group Constants in the Fast Fission of U-235 and NP-237 Nucl.Sci.Eng. 128, 270 (1998) John Collier (ca. 1898) 9

10 The Keepin Groups For reactor applications, the decay-curve of the delayed neutrons can be approximated – according to Keepin – with a sum of 6 exponential functions, which depend on a few nuclides with high fission yields. Table 2. Parameters of the delayed-neutron groups for three fissile nuclei i Possible precursor nuclei Mean energy (MeV) Average half-life of the precursor nuclei (s) Delayed-neutron fraction (%) 235U 239Pu 233U 1 87Br, 142Cs 0.25 55.72 54.28 55.0 0.021 0.0072 0.0226 2 137I, 88Br 0.56 22.72 23.04 20.57 0.140 0.0626 0.0786 3 138I, 89Br, (93,94)Rb 0.43 6.22 5.60 5.00 0.126 0.0444 0.0658 4 139I, (93,94)Kr 143Xe, (90,92)Br 0.62 2.3 2.13 0.252 0.0685 0.0730 5 140I, 145Cs 0.42 0.61 0.618 0.615 0.074 0.018 0.0135 6 (Br, Rb, As etc) - 0.23 0.257 0.277 0.027 0.0093 0.0087 Total 0.64 0.21 0.26 1957Ke67 Phys.Rev. 107, 1044 (1957) G.R.Keepin, T.F.Wimett, R.K.Zeigler Delayed Neutrons from Fissionable Isotopes of Uranium, Plutonium, and Thorium 10 10 10 Instituts-Seminar II. Phys. Gießen

11 TRIGA-reactor Mainz For reactor technology, time dependent neutron
spectra of the Keepin groups are sought for. Such measurements had also been performed at the TRIGA reactor in Mainz. This pulsed reactor had been chosen by Strassmann as it can produce short-lived fission products. (see, e.g. 1984STZT     Inst.fur Kernchemie, Univ.Mainz, Jahresbericht 1983, p.79 (1984) B.Steinmuller, H.Gabelmann, K.-L.Kratz Das Gruppenspektrum β-Verzogerter Neutronen der 22-s-Komponente aus der Spaltung von 235U mit Thermischen Neutronen NUCLEAR REACTIONS 235U(n, F), E=thermal; measured fission fragment β-delayed neutron emission probability. K.-L. Kratz, B. Steinmüller, H. Gabelmann, Jahrestagung Kerntechnik, Aachen 1986 The Mainz results have been taken into account in Los Alamos. But what about the many (civilian) data bases? 11 Instituts-Seminar II. Phys. Gießen

12 Frederic de Hoffmann, who had worked on delayed neutrons at Los Alamos
Ankauf des Mainzer TRIGA-Reaktors Frederic de Hoffmann, who had worked on delayed neutrons at Los Alamos Phys.Rev. 72, 567 (1947); Phys.Rev. 74, 1330 (1948) later founded in California General Atomic. One of their products is the TRIGA research reactor. Günter Herrmann Fritz Straßmann „Atomminister“ Siegfried Balke Frederic de Hoffmann

13 At the on-line separator at the
high-flux reactor in Grenoble, nuclear structure was studied by the II. Phys. Inst. in close internatonal collaboration. One of the main research topics was the β-delayed neutron emission of short- lived fission products. The Mainz-group continued their work, especially with the neutron spectrometers. Instituts-Seminar II. Phys. Gießen

14 decay heat calculations, weapons safeguard.
Data on β-delayed neutrons are of vital interest for reactor technology, decay heat calculations, weapons safeguard. Therefore, since a long time, the UN agency for atomic energy IAEA (founded in 1957) is engaged in collecting, evaluating and disseminating information relevant to nuclear energy. Examples are conferences and consultants meetings: Eisenhower at UNO 8. Dezember 1953 G. Rudstam, in Proceedings, 2nd IAEA Advisory Group Meeting on Fission Product Nuclear Data, Petten, The Netherlands (Sept. 5-9, 1977), Vol. II, p. 567 G. Rudstam, in Proceedings, Consultants Meeting on Delayed Neutron Properties, Vienna, Austria (Mar , 1979), IAEA Report INDC NDS-107/G + Special (1979), p. 69 K.-L. Kratz, ibid., p.103 14 Instituts-Seminar II. Phys. Gießen

15 Compilations / evaluations for β-decay properties
Data on β-decay properties are sought for in many applications. In all laboratories one finds a Nuclear Wallet Card. There exist a multitude of compilations for special properties as well as more general overviews, as the long series of „Table of the Isotopes“. The internationally accepted standard evaluation of decay properties are the Nuclear Data Sheets based on the ENSDF, the „Evaluated Nuclear Structure Data File“ (partly quite outdated; no very light nuclei). Neutron data can be found in reaction data bases as EXFOR (Experimental Nuclear Reaction Data) and in special data bases as JEFF Decay Data Library (of the OECD), ENDF/B-VII-1 (in December, with values from Pfeiffer et al.(2002)). I suppose that especially for delayed neutrons there must exist evaluations collected for the exclusive internal use of research laboratories or enterprises engaged in the development of nuclear reactors (and weapons). Instituts-Seminar II. Phys. Gießen

16 The NUBASE Evaluation of Nuclear and Decay Properties
Since 1997, the Atomic Mass Evaluation has been supplemented by data on decay properties of the ground-state and long-lived isomers as half-lives, spin and parities, delayed emission probabilities. NUBASE: G. Audi et al., Nucl. Phys. A624, 1 (1997) G. Audi et al., Nucl. Phys. A729, 3 (2003) The main source for the data is ENSDF, but the relevant literature is scanned independently and some data points included in NUBASE are not applied in the Nuclear Data Sheets. On the web, there are now available intermediate versions of the mass tables and the NUBASE evaluation: It is highly recommented to apply the mass values from the 2011 intermediate release. Now with collaboration from Gießen/Darmstadt 16 16 16 Instituts-Seminar II. Phys. Gießen

17 Recent attempts on dedicated compilations / evaluations (I)
Proc. Int. Conf. Delayed Neutron Properties, Birmingham, England, D.R. Weaver, Ed., (1987) 1989BrZI: Thesis, Texas A-M Univ. (1989); LA T (1989) M.C.Brady Evaluation and Application of Delayed Neutron Precursor Data COMPILATION 79,80,81Ga,85As,87,88,89,90,91,92Br,92,93,94,95,96,97, 98Rb,129,130In,134,135Sb, 136Te,137,138,139,140,141I,141,142,143,144, 145,146,147Cs; compiled,evaluated beta-delayed neutron spectra, precursor data. 1989Br25: Nucl.Sci.Eng. 103, 129 (1989) M.C.Brady, T.R.England Delayed Neutron Data and Group Parameters for 43 Fissioning Systems COMPILATION 227,229,232Th,231Pa,232,233,234,235,236,237,238U,237, 238Np, 238,239,240,241,242Pu,241,242m,243Am,242,245Cm,249,251,252Cf, 254Es,255Fm; compiled,evaluated delayed neutron six-group parameters. „Mikey“ Brady Karl-Ludwig Kratz had been consultant at Los Alamos working with Tall England. He made neutron spectra from Mainz, Grenoble, Geneva available for this group. STATUS OF DELAYED NEUTRON DATA – 1990, J. Blachot et al. NEACRP-L-323, NEANDC-299"U“; OECD Nuclear Energy Agency Instituts-Seminar II. Phys. Gießen

18 Recent attempts on dedicated compilations / evaluations (II)
From 1990 to 2000, the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD) run a Working Party on International Nuclear Data Evaluation Co-operation (WPEC). The Subgroup-6 Delayed Neutron Data published a summary report in 2002: Report NEA/WPEC-6: and A. D’Angelo, Prog.Nucl.Energy 41, 5 (2002) Remark: Our evaluation 2002Pf04 appeared in the same volume of Prog.Nucl.Energy and is cited in these reports. 18 Instituts-Seminar II. Phys. Gießen

19 Recent attempts on dedicated compilations / evaluations (III)
1993Ru01 G.Rudstam, K.Aleklett, L.Sihver, At.Data Nucl.Data Tables 53, 1 (1993) Delayed- Neutron Branching Ratios of Precursors in the Fission Product Region COMPILATION A=75-150; compiled beta--decay T-1/2,neutron emission probability; deduced average delayed-neutron branching ratios. RADIOACTIVITY 80,81,83,79,82Ga,84Ge,84,85,86,87As,88,89,91,87Se,100, 99,98mY, 100,98Sr,99,98,97,96,95,94,93,92Rb, 91,90,89,88,87Br,129m, 129,130m,131,128m,128,132In,150,149,148,147La,149,148,147,146Ba, 148, 147,146,145,144,143,142,141Cs,139,138,137I,137,136Te,136,135,134Sb, 134,133Sn(beta-n) (Dedicated experiment at Studsvik and evaluation to be entered in JEFF and ENDF.) 2002Pf04 B.Pfeiffer, K.Kratz, P.Möller, Prog.Nucl.Energy 41, 39 (2002) Status of delayed-Neutron Precursor Data: Half-Lives and Neutron Emission Probabilities COMPILATION Z=27-63; compiled,analyzed beta-decay T-1/2,neutron emission probabilities, model predictions. 19 19 Instituts-Seminar II. Phys. Gießen

20 Compilation or evaluation? (I)
With the comments, I would call this an evaluation. 20 20 Instituts-Seminar II. Phys. Gießen

21 Compilation or evaluation? (II)
2002Pf04: B.Pfeiffer, K.Kratz, P.Möller, Prog.Nucl.Energy 41, 39 (2002) Status of delayed-Neutron Precursor Data: Half-Lives and Neutron Emission Probabilities COMPILATION Z=27-63 The primary reason for presenting T1/2 and Pn of fission products was a comparison with the values calculated with different assumptions in order to have an idea which model might be best suited for extrapolations to unknown nuclides. Unfortunately, the editors even cancelled the list of references for the experimental values, and there is no hint at all left to the limited evaluation performed. 21 21 Instituts-Seminar II. Phys. Gießen

22 Consultant’s meeting The astrophysics as well as the reactor technology and the nuclear structure communities (partly in „Personalunion“) would like to establish a new evaluation encompassing not only the fission product region but also the low- and high-Z precursors. Regarding the long history of evaluations under the auspices of the IAEA, the nuclear data section was addressed. In order to prepare a report for an eventual (near) future IAEA CRP (co-ordinated research project) a consultants meeting took place at Vienna in October 2011. Daniel Cano-Ott was participating via video-conference. Instituts-Seminar II. Phys. Gießen

23 In preparation ! Report for IAEA
INDC(NDS)-0599 Distr. …. INDC International Nuclear Data Committee Summary Report of Consultants’ Meeting Beta delayed neutron emission evaluation IAEA Headquarters, Vienna, Austria 10 – 12 October 2011 Prepared by Daniel Abriola IAEA Nuclear Data Section Vienna, Austria Balraj Singh McMaster University Hamilton, Ontario, Canada Iris Dillmann Justus-Liebig-Universität Giessen, Germany In preparation ! Will be published on Instituts-Seminar II. Phys. Gießen

24 Some remarks on pitfalls for future evaluators
In summer, Balraj Singh visited us for a preparatory meeting. He had extracted all the data on T1/2 and Pn contained in the ENSDF as a starting point for an evaluation. But quite a lot of the isobaric chains have not been updated since several years and the masses below 40 had not been evaluated by Brookhaven. Many measurements have been performed long ago. The input parameters applied might have changed meanwhile. Can one recalibrate the old data? During the meeting in Vienna, we wanted to give an overview of methods to measure Pn values and try to describe advantages and drawbacks of them. Partly we had already problems to find out how the described methods worked [„Ion counting“ was measuring the beam current!]. What if future researchers want to start-up the work again in case that atomic energy has to be used in future? Rudstam et al., ADNDT 53,1 (1993) Instituts-Seminar II. Phys. Gießen

25 A message from a former consultant on delayed neutrons
As a trained nuclear chemist, Karl-Ludwig was personally involved in the measure-ments of delayed-neutron emission propabilities and the spectroscopy of delayed neutrons. He told me that the evaluators keep in mind that the very early experiments on delayed neutrons were based on chemistry: Typically, uranium samples were irradiated in a reactor and then chemically separated. Then the number of delayed neutrons were determined for the different isotopes. In general, there was no direct measurement of the β-decays preceding the neutrons. The delayed neutron emission probabilities Pn were derived from systematics of nuclear-charge distributions of the fission fragments. Unfortunately, the earliest systematics did not take into account the odd-even effect in the distributions. If one wants to use the older evaluations, one must be careful. A.C. Wahl et al., Phys. Rev. 126, 112 (1962) A.C. Wahl, At. Data Nucl. Data Tables 39, 1(1988) K.-L. Kratz, Review of delayed neutron energy spectra in Proceedings, Consultants Meeting on Delayed Neutron Properties, Vienna, Austria (Mar , 1979), IAEA Report INDC NDS-107/G + Special (1979), p. 103 25 Instituts-Seminar II. Phys. Gießen

26 Neutron emitter at the stability line: 17N
17N is the first non-fission emitter discovered It decays to the stable 17O with few excited states. This enables the spectroscopy of the delayed neutron branches. J.H. Kelley et al., Nucl. Phys. A564, 1 (1993) Note added in proof: Not evaluated by NDS! For the Pn value of 95.1(7)%, only one reference is cited in NDS: 1976AL02 Is this an adequate standard? 1976OH05 26 Instituts-Seminar II. Phys. Gießen

27 Determination of Pn values with absolute γ-intensities
ENSDF [%] 3,52(34) 68.0(67) 7,4(15) 20,2(20) 61,0(71) 94,2(9) 22,6(12) 15,8(7) 49(3) 1982KR11 71,9(34) 26,3 25.0(25) ≈46 3,91(16)*0,90(5) 1000(55)*0,068(3) 976(53)*0,0076(11) 1000(50)*0,0202(10) 100.00(5)*0,61(4) 100*0,942(9) 100*0,226(12) 100*0,158(7) 100*0,49(3) 100,00(5)*0,780(20) 94,0(30)*0,765(12) 1000*0,0263 1000*0,0250(25) 20*≈2,30 1982KR11 27 Instituts-Seminar II. Phys. Gießen

28 Differences between ENSDF and NUBASE-2011
As an example, the T1/2 of 150La is given in NUBASE as 510(30) ms, in ENSDF as 860(50) ms: Whereas NUBASE refers to E. derMateosian and J. K. Tuli$CIT=NDS 75, 827 (1995); CUT=1-MAR-1995 0.86 S 5 %B-=100$%B-N=2.7 3 (1993RU01) T$from n counting (1993Ru01). Others: …….. 1995Ok02 Z.Phys. A351, 243 (1995) K.Okano, A.Taniguchi, S.Yamada, T.Sharshar, M.Shibata, K.Yamauchi: “Identification of Beta-Decay of 150La” The article was submitted end of January, so it appeared just after the cut-off date. No update of NDS since 1995! 28 28 28 Instituts-Seminar II. Phys. Gießen

29 Need for theoretical models
Not all delayed-neutron precursors are available for experimental studies. Missing data have to be derived from systematics and / or calculations. The necessity to develop reliable mathematical schemes is quite obvious for applications in astrophysics. Most of the nuclides involved in explosive nucleosynthesis scenarios as the r-process are not accessible for experimentation, so reliable extrapolations and calculations have to be developed. But also new applications in reactor technology and decay heat calculations depend on calculated data to complement experimental data, in particular neutron spectra for individuel precursors. Instituts-Seminar II. Phys. Gießen

30 Empirical formulas for Pn values
In the fission product region, there is in general a high level density above Sn . Therefore one may derive „simple“ expressions to describe the Pn values, as S. Amiel and H. Feldstein, Phys.Lett. 31B, 59 (1970) or K.-L. Kratz and G.Herrmann, Z. Phys.263, 435 (1973) The results are comparibel to sophisticated calculations and are used in some data bases (as the new version of ENDF). Updated parameters in 2002PF04 30 Instituts-Seminar II. Phys. Gießen

31 QRPA-calculations (I)
More „sophisticated“ calculations of β-decay are based on the shell model. Single-particle energies are determined for a given nuclear potential, in this case a Folded-Yukawa-potential, the parameters of which were adjusted to experimental decay-schemes. The ground-state deformations were taken from the fit to nuclear masses. The influence of the nuclear structure to the β-decay is displayed as the strength function. The observed β- intensities are obtained by multiplaying with the Fermi function. From this, the half-lives and Pn values are calculated. calc. exp. T1/ ms 378 ms Pn % % Peter Möller assumes that the Gamow- Teller strength is the dominant decay mode for most nuclei, so not taking into account e.g. the first-forbidden strength. 31 Instituts-Seminar II. Phys. Gießen

32 QRPA-calculations (II)
Peter Möller has performed these calculations for nearly all possible isotopes. In his approach he obtains wave functions, from which he can calculate not only masses but in a consistent way separation energies, spin, parities and β-decay properties as half-lives and emission probabilities: 1997Mo25 At.Data Nucl.Data Tables 66, 131 (1997) P.Moller, J.R.Nix, K.-L.Kratz Nuclear Properties for Astrophysical and Radioactive-Ion-Beam Applications NUCLEAR STRUCTURE Z=8-136; A=16-339; calculated,compiled total binding energy,one-,two-neutron,proton separation energies,pairing gaps, odd-nucleon parity,spin projection. These data are used for many applications, as the Nuclear Data Sheets. But there are some problems, especially in calculating T1/2 and Pn. The procedure takes only the Gamow-Teller selection rules into account. This can lead to huge errors, if e.g. the Gamow-Teller decays feed into high-lying levels and first-forbidden ones near the ground state. The calculated single-particle energies depend on the parameters of the nuclear potential. There are cases that strong β-branches feed excited states close to the Sn value. Tiny changes in the parameters can shift the excited states, so that the calculated Pn values may be „undetermined“, shifting from 100% to 0%. The article 2002PF04 wanted to look for ways to overcome these deficencies. 32 Instituts-Seminar II. Phys. Gießen

33 Sn Qβ Warning: This is an unrealistic case for showing
a drastic effect! Mother and daughter are deformed in the ground state. Pn=81%; T1/2=350 ms Pn=9%; T1/2=378 ms exp. In this model calculation, the main β-decay feeds an excited state just above Sn , so Pn = 100%. With very small changes in the parameters of the nuclear potential and/or the atomic masses, one can obtain Pn = 0%. In this case still close to stability, at least Qβ (9229(20) keV) and Sn (4352(9) keV) are well known. Sn To account for uncertainties in level and separation energies , we therefore folded all transitions with a Gaussian. Instituts-Seminar II. Phys. Gießen

34 Qβ S3n S1n S2n Although there is in general a good
reproduction of half-lives and Pn-values, there are some striking discrepancies between model predictions and experi- ments. One such case is the very neu- tron-rich 134In. The model predicts that the β-decay predominantly feeds a level at about 8 MeV well above the two-neutron seperation energy, leading to the surpr- isingly high P2n=84 %, whereas the experimental value is P1n=7%; P2n=84%; P3n=0.02% S3n S1n S2n Data base: T1/2=140(4) ms ;P1n=65 % P1n=13%; P2n=81%; P3n=0.02% If this result would be confirmed, there must be problems with the model: Ought the shell model parameters be readjusted? - Are the nuclei close to 132Sn deformed? P. Hoff et al., PRL 77, 1020 (1996) Instituts-Seminar II. Phys. Gießen

35 Need for neutron spectra
For applications as reactor technology and decay heat calculations, the energy spectra of the delayed neutrons are essential input parameters, so many studies have been undertaken. An overview may be found in As examples for this talk, I have chosen spectra taken at the on-line isotope separator OSTIS: 1982Kr11 K.-L.Kratz, A.Schroder, H.Ohm, M.Zendel, H.Gabelmann, W.Ziegert, P.Peuser, G.Jung, B.Pfeiffer, K.D.Wunsch, H.Wollnik, C.Ristori, J.Crancon Beta-Delayed Neutron Emission from Rb to Excited States in the Residual Sr Isotopes Z.Phys. A306, 239 (1982) 1983Kr11 K.-L.Kratz, H.Ohm, A.Schroder, H.Gabelmann, W.Ziegert, B.Pfeiffer, G.Jung, E.Monnand, J.A.Pinston, F.Schussler, G.I.Crawford, S.G.Prussin, Oliveira The Beta-Decay of 95Rb and 97Rb Z.Phys. A312, 43 (1983) Instituts-Seminar II. Phys. Gießen

36 Neutron spectra for 95Rb precursor (I)
(from 1983KR11) Due to long beam times available at research reactors, we could even perform n-γ-coincidence measurements. And what could we have done with nowadays electronics and data handling systems! Instituts-Seminar II. Phys. Gießen

37 Neutron spectra for 95Rb precursor (II)
(from 1982KR11) (from 1983KR11) The measured energy spectra had been compared to theoretical calculations, applying the latest optical model trans- mission coefficients. It would be interesting to see, if the new CGM-calculations of Los Alamos can deliver better results. Instituts-Seminar II. Phys. Gießen

38 Calculation of delayed-neutron spectra
The neutron and γ decay code CGM (Cascading Gamma and Multiplicity) In the EXFOR data base, there are only 36 experimental delayed-neutron spectra. With the CGM code, 271 spectra were calculated to be used e.g. in decay heat studies. (They will be applied for ENDF/B-VII-1.) T. Kawano, P. Möller, W.B. Wilson, Phys. Rev. C78, (2008) Instituts-Seminar II. Phys. Gießen

39 Call for old data Administrators of data banks at the
consultants‘ meeting asked for old neutron spectra which might be digitized and entered into the data bases. It was questionable if the formats of the data files allow to enter spectra. They were not foreseen in ENSDF, but perhaps with some tricks? The JEFF files contain less than 50 „spectra“ of individual precursors in the form of lists of neutron lines. Instituts-Seminar II. Phys. Gießen

40 By courtesy of Mark A. Kellett, contribution to Consultants‘ Meeting
Instituts-Seminar II. Phys. Gießen

41 Original spectra In JEFF, the few spectra are stored as discrete neutron lines only. They will try to digitize from old publications. 3He-spectrometer TOF 1982KR11 1983KR11 Instituts-Seminar II. Phys. Gießen

42 Example from ENDF/B-VII.1 (December 2011)
By courtesy of Alejandro Sonzogni, contribution to Consultants‘ Meeting Instituts-Seminar II. Phys. Gießen

43 Beta-delayed charged particle emission and fission
For NUBASE, the following article was applied. Are there more recent ones? 1989HaZC: Particle Emission from Nuclei, Vol.3, p.99, CRC Press, Florida (1989) J.C.Hardy, E.Hagberg Beta-Delayed Proton and Alpha Emission Beta-delayed p-emission is interesting for astrophysics, but certainly not for nuclear reactors, so one will need a separate evaluation. Beta-delayed α-emission can even „compete“ with neutron emission. In the β-decay of 17N, there is a branching of 2.5(4)*10-5 . For very heavy nuclei, also β-delayed fission and β-delayed n-emission followed by fission has been observed. 2005Pa06 Nucl.Phys. A747, 633 (2005) I.V.Panov, E.Kolbe, B.Pfeiffer, T.Rauscher, K.-L.Kratz, F.-K.Thielemann Calculations of fission rates for r-process nucleosynthesis NUCLEAR STRUCTURE A= ; calculated neutron-induced and beta-delayed fission rates,related features. Astrophysical implications discussed. 43 Instituts-Seminar II. Phys. Gießen

44 Beta- and EC-delayed fission
Studies of ßDF in the lead region are foreseen for SUPER-FRS. Courtsey Valentina Liberati Instituts-Seminar II. Phys. Gießen

45 Résumé collected, evaluated and applied worldwide.
Beta-delayed neutron emission evaluation for reactor physics and astrophysics Contrary to the development in Germany, nuclear data continues to be collected, evaluated and applied worldwide. For the planning of reactors of the IVth generation based on fast fission, decay heat, accelerator driven systems data on β-delayed neutron emission are needed. The existing and especially the future radioactive beam facilities will produce neutron-rich isotopes all over the nuclidic chart. The measurements of T1/2 and Pn values are challenging due to a high background of beam generated high-energy neutrons, but nevertheless many new values will be obtained. Can neutron spectra be measured at these facilities? Up till now, no evaluation for precursors outside the fission range has been published (at least to my knowledge). These data will hopefully be applied to develop advanced theoretical models for masses and decay properties. Instituts-Seminar II. Phys. Gießen

46 Instituts-Seminar II. Phys. Gießen 11.1.12
Topics Nuclear reaction data Nuclear structure and decay data Delayed neutrons Fission yields Atomic masses Experimental facilities and detection techniques Nuclear data measurements and analysis Nuclear theories, models and data evaluation Uncertainty quantification and covariances Evaluated nuclear data libraries Nuclear data processing Nuclear data adjustment Validation of evaluated data Integral experiments Cross section and decay standards, Data dissemination and international collaboration Nuclear Fission (75th anniversary) Nuclear data for reactors Nuclear decay heat Dosimetry and shielding Safeguards and security Criticality safety Homeland security and safety Accelerator related applications Fusion technology Space, cosmic-rays, radiation effects on electronics Astrophysics and cosmology Medical and environmental applications Instituts-Seminar II. Phys. Gießen

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