NUCLEAR DATA REQUIREMENTS FOR DECAY HEAT CALCULATIONS DECAY

NUCLEAR DATA REQUIREMENTS FOR DECAY HEAT CALCULATIONS DECAY DATA

DECAY DATA i k , k - , k + E i , E i energy ln 2 decay constants =t ½ ( ) branching fractions for , - and + decay to nuclide Z, A mean alpha, beta and gamma releases of nuclide Slide serial no 2 © 2002 IAEA

COMPREHENSIVE DECAY DATA FILES l l fission products actinides and decay chains Half-lives Isomeric branching ratios Mean energies (can be derived from discrete decay data) Slide serial no 3 © 2002 IAEA

CONFLICT: Short-lived fission products (half-lives less than ~ 1 min) extremely difficult to characterise discrete transitions lack of credible decay data Pandemonium effect (Hardy et al, 1977) Slide serial no 4 © 2002 IAEA

Fission products and decay chains Slide serial no 5 © 2002 IAEA

Fission products and decay chains Slide serial no 6 © 2002 IAEA

Effect of missing nuclear levels: loss of -ray energy release (Ei ) Slide serial no 7 © 2002 IAEA

Distribution of experimental beta feeding in 87 Br decay and calculated average beta energy Slide serial no 8 © 2002 IAEA

- MODELLING DECAY Gross theory (Yoshida et al) beta-strength function S (E): (a) sensitive varies “gradually” with respect to mass number A, (b) to even-odd of proton number Z and neutron number N. Characterised by odd-odd, odd-even, even-odd and even-even, and by the Q value Slide serial no 9 © 2002 IAEA Can be used to calculate half life, and beta and gamma spectra.

Normalised delayed gamma-ray spectra of odd-mass nuclides near the light peak of the mass-yield curve Slide serial no 10 © 2002 IAEA

Normalised delayed gamma-ray spectra of odd-odd nuclides near the light peak of the mass-yield curve Normalised delayed gamma-ray spectra of even-even nuclides near the light peak of the mass-yield curve Slide serial no 11 © 2002 IAEA

Normalised delayed gamma-ray spectra of odd-mass nuclides near the heavy peak of the mass-yield curve Slide serial no 12 © 2002 IAEA

Normalised delayed gamma-ray spectra of odd-odd nuclides near the heavy peak of the mass-yield curve Normalised delayed gamma-ray spectra of even-even nuclides near the heavy peak of the mass-yield curve Slide serial no 13 © 2002 IAEA

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Mean beta and gamma energies released per disintegration of fission product Slide serial no 15 © 2002 IAEA

INCORPORATION OF THEORETICAL DECAY DATA (A) JNDC library, 1980 (B) JNDC Library, 1980 + theoretical decay data Compared with decay-heat measurements of Dickens et al (1980): (A) overestimates beta energy and underestimates gamma energy (B) much closer agreement between measurements and calculations Slide serial no 16 © 2002 IAEA

Beta energy emission rate after instantaneous pulse of thermal-neutron fission of 235 U Slide serial no 17 © 2002 IAEA

Photon energy emission rate after instantaneous pulse of thermal-neutron fission of 235 U Slide serial no 18 © 2002 IAEA

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YOSHIDA AND TACHIBANA (2000) Theoretical treatment of the asymptotic behavior of fission product decay heat toward very short cooling time J. Nucl. Sci. Technol, 37, 491 -497 Use of Q 00 factor: based on beta-strength functions around the ground state of the daughter nucleus; for half-lives: Q 00 adjust on basis of = 0. 25 Me. V for even-even parent odd-even properties = 1. 0 Me. V for odd-A parent Q 00 1. 0 = 1. 75 Me. V for odd-odd parent for mean beta and gamma energies: Q 00 = 0. 4 Represents the effect of - decay selection rules on the Slide serial no 20 © 2002 IAEA

Ratios of the half-lives between gross theory calculations and experimental results Slide serial no 21 © 2002 IAEA

Calculated - and -ray components of 235 U decay heat compared with experiments at very short cooling times Slide serial no 22 © 2002 IAEA

Calculated - and -ray components of 238 U decay heat compared with experiments at very short cooling times Slide serial no 23 © 2002 IAEA

Comparison of the calculated E - values and E -values by gross theory with experimental data Slide serial no 24 © 2002 IAEA

MODELLING DECAY Klapdor (1983) Hirsch et al (1992) Microscopic structural analysis of beta-strength functions: neglect of beta-strength structure is an oversimplification, even for high-level densities Analysis of S (E) for individual levels Compared with experiments of Schreckenbach et al (1981) for electron and antineutrino spectra. Developed further as pn-QRPA (proton-neutron quasiparticle random phase approximation) Slide serial no 25 © 2002 IAEA

Electron spectrum from thermal fission of 235 U (Klapdor, 1983) 1 S (E) Avignone and Greenwood (1980) 2 S (E) Kopeykin (1980) 3 S (E) Vogel et al (1981) 4 S (E) Klapdor and Metzinger (1982 b) Slide serial no 26 © 2002 IAEA

Antineutrino spectrum from thermal fission of 235 U (Klapdor and Metzinger, 1982 b) 1 S (E) Avignone and Greenwood (1980) 2 S (E) Kopeykin (1980) 3 S (E) Vogel et al (1981) 4 S (E) Klapdor and Metzinger (1982 b) Slide serial no 27 © 2002 IAEA

MODELLING DECAY Mann et al (1982) Simpler statistical model to calculate S (E) that (effectively) ignores structure, replacing summations with integral functions to determine half-lives and beta and gamma energies. Slide serial no 28 © 2002 IAEA

Half-lives of Rb nuclides (Mann et al, 1982) Slide serial no 29 © 2002 IAEA

SPECTRAL MEASUREMENTS Rudstam et al (1990) OSIRIS ISOLDE Mass separator Rapid collection, transfer and measurement Gamma-ray emissions: Na. I(Tl) and Ge(Li) detectors Beta-particle emissions: HPGe and Si(Li) detectors Slide serial no 30 © 2002 IAEA

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Beta and gamma spectra of short-lived fission product 87 Br (Rudstam et al, 1990) Slide serial no 32 © 2002 IAEA

Beta and gamma spectra of short-lived fission product 94 Rb (Rudstam et al, 1990) Slide serial no 33 © 2002 IAEA

Beta and gamma spectra of short-lived fission product 95 Rb (Rudstam et al, 1990) Slide serial no 34 © 2002 IAEA

Beta and gamma spectra of short-lived fission product 135 Sb (Rudstam et al, 1990) Slide serial no 35 © 2002 IAEA

SPECTRAL MEASUREMENTS Greenwood et al (1994, 1996 and 1997) He gas-jet transport to mass separator Rapid collection, transport and measurement TAGS - total absorption gamma-ray spectrometry: well Na. I(Tl) detector with deep-axial counting for complete summing of -ray cascades; Si detector also located in the counting well Operate in 4 - coincidence mode to determine branch to ground state of daughter Slide serial no 36 © 2002 IAEA

Comparison of measured singles spectrum for 138 g. Cs with the simulated spectrum for the evaluated decay scheme (Greenwood et al, 1994) Slide serial no 37 © 2002 IAEA

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Comparison of measured singles spectrum for 138 g. Cs with the simulated spectrum for the re-adjusted decay scheme (Greenwood et al, 1994) Slide serial no 39 © 2002 IAEA

Comparison of measured singles spectrum for 138 m. Cs with the simulated spectrum for the evaluated decay scheme (Greenwood et al, 1994) Slide serial no 40 © 2002 IAEA

138 m. Cs - emission probabilities P (Greenwood et al, 1997) Slide serial no 41 © 2002 IAEA

Comparison of measured singles spectrum for 138 m. Cs with the simulated spectrum for the re-adjusted decay scheme (Greenwood et al, 1994) Slide serial no 42 © 2002 IAEA

ENDPOINT ENERGY MEASUREMENTS Numerous: for example, Wünsch et al (1978) Przewloka et al (1992 a and 1992 b) Ikuta et al (1994) Mass separator coincidence and singles spectra Fermi-Kurie plots Slide serial no 43 © 2002 IAEA

-endpoint spectrum of 92 Rb (Przewloka et al, 1992 a) Slide serial no 44 © 2002 IAEA

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JEF-2. 2, NEA DATA BANK Fission Products: 860 evaluated nuclides 730 radioactive nuclides 130 stable nuclides Of 730 radioactive nuclides, 611 are derived from measured discrete decay data, and 199 from gross measurements (Rudstam et al, 1990) and theoretical data. Slide serial no 47 © 2002 IAEA

RECENT DEVELOPMENTS (1) Re-evaluations of discrete decay data (2) Re-evaluations /development of theoretical decay data (3) Evidence for further new short-lived radionuclides eg. , 107 m. Ag, 112 m. Rh, 113 m. Pd, 122 n. In and 146 m. La Slide serial no 48 © 2002 IAEA

Evaluation of discrete decay data – consistency of data sets requested for JEFF-3 Slide serial no 49 © 2002 IAEA

Short-lived fission products requested for JEFF-3 – US ENDF/B-VI decay data adopted or modified unless stated otherwise Slide serial no 50 © 2002 IAEA

JEFF-3 T, NEA DATA BANK New set of data libraries in preparation: thermal-neutron cross sections (April 2002); fission yields (late 2002); decay data (late 2002) see: Jacqmin et al “Status of the JEFF-3 Project” ND 2001, Int. Conf. on Nucl. Data for Science and Technology, 7 - 12 October 2001, Tsukuba, Japan Slide serial no 51 © 2002 IAEA

JEFF-3 T, NEA DATA BANK Fission yields: UKFY 3 in preparation for incorporation into JEFF-3 T (Mills, BNF plc, UK) Decay data: 3755 nuclides, including files for stable nuclides (mass, natural abundance, spin and parity) see: O. Bersillon et al “JEFF-3 T: Decay Data and Fission Yield Libraries”, ND 2001, Int. Conf. On Nucl. Data for Science and Technology, 7 – 12 October 2001, Tsukuba, Japan Slide serial no 52 © 2002 IAEA

JEFF-3 T, NEA DATA BANK Decay data: 1. NUBASE used to create complete library of 3755 nuclides G. Audi et al “The NUBASE Evaluation of Nuclear and Decay Properties”, Nucl. Phys. , A 624(1997) 1 -124. 2. Discrete decay data files extracted from UKPADD-6 and UKHEDD-2; and French files formulated from ENSDF. Slide serial no 53 © 2002 IAEA

DECAY HEAT DISCREPANCIES Yoshida et al (1997 and 1999) JNDC-FP-V 2 library: 0 - 20 sec 300 - 3000 sec (~1000 sec) Slide serial no 54 © 2002 IAEA

Gamma-ray discrepancies seen in 239 Pu decay heat after a fission burst (Yoshida et al, 1999) Slide serial no 55 © 2002 IAEA

YOSHIDA et al (1997 and 1999) Introduced an additional - decay chain of two radionuclides Energy release of 1. 5 Me. V per decay Discrepancy between 300 and 3000 sec reduced significantly (eliminated? ) in the various fissioning systems: candidates for additional energy release include 102 Tc, 104 Tc and 105 Tc Slide serial no 56 © 2002 IAEA

Removal of -ray discrepancy by including 1. 5 Me. V -ray emitter (Yoshida et al, 1999) Slide serial no 57 © 2002 IAEA

YOSHIDA et al (1997 and 1999) 108 Rh - 108 m. Rh half-lives 17 sec - 6 min - 17 sec JNDC-FP-V 2 JEF -2. 2 Change of 108 Rh ground-state half-life from 17 sec to 6 min [factor of ~20 difference] leads to significant increase of decay heat around 1000 sec (and closer agreement with experiments). Slide serial no 58 © 2002 IAEA

239 Pu -decay heat after a fission burst: 102 Tc and 108 Rh data adjusted in JEF-2. 2 (Yoshida et al, 1999) Slide serial no 59 © 2002 IAEA

DECAY DATA LIBRARIES l CD-ROM l Internet access IAEA Nuclear Data Section, Vienna http: //www-nds. iaea. org US National Nuclear Data Centre, Brookhaven http: //www. nndc. bnl. gov/ NEA Data Bank, France http: //www. nea. fr and many others Slide serial no 60 © 2002 IAEA

NUCLEAR DATA AND DECAY HEAT CALCULATIONS (1) Availability of authoritative nuclear data libraries in a standard format (2) Comprehensive checks for consistency and completeness (3) Validation (4) Measurement-based discrete data files are inadequate for decay heat calculations Slide serial no 61 © 2002 IAEA

FIXES (1) Fission yields: systematic fitting procedures (2) Decay data: lack of comprehensive discrete data - gross energy measurements and theoretical data Slide serial no 62 © 2002 IAEA

QUESTION: Are we striving for perfection when good is good enough ? Significant gaps in measured fission yields and decay data do exist, and imply we are still some way from such an enviable position. Slide serial no 63 © 2002 IAEA

DEFINITION OF AN EVALUATOR l l optimistic cynic no funding for measurement programmes Guidance notes: (1) If two measurements of a nuclear parameter produce the same result, the true evaluator can only be confident that both results are incorrect. (2) Data evaluation is the act of assembling experimental data, theory and guesswork so as to make something useful (out of indifferent beginnings). Slide serial no 64 © 2002 IAEA