Experiment to validate EAF activation data: Activation on CuCrZr in NPI d-be neutron field

Transcription

1 Nuclear Physics Institute Řež Report NPI ASCR Řež EXP(EFDA)-03/00 Experiment to validate EAF activation data: Activation on CuCrZr in NPI d-be neutron field P. Bém, V. Burjan, M. Götz, M. Honusek, J. Hep ++), U. Fischer +), V. Kroha, U. v. Möllendorff +), J. Novák, S. P.Simakov +) and E. Šimečková Nuclear Physics Institute, Řež, +) Forschungszentrum Karlsruhe, D-7601 Karlsruhe, ++) SKODA Nuclear Machinery plc., Plzeň 1

2 Content An activation of CuCrZr alloy (the material for a heat sink in the first wall of ITER) was investigated to provide integral experimental data for benchmarking the nuclear data base of EASY. Originally, this experiment was planned at FZK before the ending of Karlsruhe cyclotron operation. The CuCrZr-alloy samples were activated in neutron field provided by the NPI cyclotron-based fast neutron source. To simulate the neutron spectral characteristics of Karlsruhe source, the source reaction d(17mev)+be(thick target) was utilized. The induced gamma-emitting radioactivity was then determined repeatedly, after different cooling time intervals, by gamma ray spectrometry using a high-purity germanium detectors. Part of measured activities was compared with preliminary calculations carried out at SKODA NM employing the Fispact-003 code with EASY-003 library [Forest: FISPACT-003 User manual. UKAEA FUS 85]. Final C/E results will be done after the neutron spectrum and flux density at the position of irradiated samples for the NPI d-be neutron source will be determined correctly utilizing the combination of experimental and calculation methods.

3 Neutron flux and spectrum of d-be source White-spectrum neutrons with mean energy of 7 MeV extending up to 18 MeV is produced by the stripping reaction Be(d,xn) at 18MeV deuteron energy Arrangement of producing target is similar to d(19mev)-be source of FZK cyclotron spectral flux at the position of irradiated sample was taken from Karsruhe data: total flux 1.7x10 10 n/s/cm at 1µA [as determined by U. v. Möllendorff et al., 1999] Neutron Energy [MeV] Flux[x10 9 n/cm /s/mev] at 10 µa 3,0,5,0 1,5 1,0 0,5 0,0 Initial Guess Spectrum

4 Be-target and CuCrZr sample Compared to 13 mm at FZK, in present experiment the investigated sample is located at 16 mm distance from the front surface of Be disk (9 mm thickness enough to stop 18 MeV deuterons). Up to kw beam power could be utilized due to intensive cooling, but only up to 8µA of deuteron beam is delivered to the target at present. Aluminum activation foils are located at front and back surface of the sample, all having 10 mm square dimension. Main components of sample consist of Cu: , Cr: 0.75, and Zr: 0.163%. Main admixtures are Fe: 0.009, Al: 0.006, and W: 0.006%.

5 Irradiation of samples Two samples were activated at neutron flux density of about 8x10 10 n/s/cm for 0., 1. and 8.9 hours. Run N o Sample / Weight (mg) Dim. (mm) x (mm) Activation time T A (s) Beam charge (µc) Neutron fluence ( n/cm ) R05 R06 R07 N5 / 87.1 N / 88.3 N5 / x10 10x10 10x E+03.1 E E+05 Neutron fluence was determine from deuteron current (beam charge in 100s intervals). Relatively stable time-profile of irradiation was achieved for long-time irradiation E+1.15 E E Bean Current (µa) 3 Bean Current (µa) Bean Current (µa) Time (min) Time (min) Time (min) 5

6 Gamma spectrometry and results Gamma spectrometry of the activated samples was performed at different cooling times, ranging from minutes to 150 days. The activated samples were investigated by two calibrated HPGe detectors of 3 and 50% efficiency and of FWHM 1.8 kev at 1.3 MeV. Evaluation of spectra was performed by the NPI/DEIMOS code. The resulting specific activities in Becquerels per kilogram of sample material at different cooling times are given in following Figures and data recalculated to the end of irradiation are given in following tables. The uncertainty includes statistical uncertainty and the uncertainty of the efficiency calibration (including the geometry factor). In summary, the 1 activation products were reliably determined from irradiation of CuCrZr samples in the d-be neutron field. 6

7 Run 07, Long irradiation Activities at different cooling times Activity (Bq/kg) Activity (Bq/kg) Na Co Ni Cooling time (h) Cr Co60 Cu6 Activity (Bq/kg) Here and in the further list, the curves and tabulated data correspond to the decay calculated for relevant reaction products from weighted averaging of experimental data Zr95 Mn Zr Cooling time (h) Cooling time (h) 7

8 Run 07, Long irradiation, Activities to the end of irradiation Isotope Reaction T 1/ Ac[Bq/kg] Err [%] Na 7 Al(n,α) Na 3 Na(n,γ) Na 1.96 h Cr 51 5 Cr(n,n) 51 Cr 7.7 d Mn Mn(n,γ) 56 Mn.58 h Co Cu(n,α) 60 Co 5.7 y Co 61 Cu(n,n α) 61 Co 1. h Cu 6 Cu(n,n) 6 Cu 63 Cu(n,γ) 6 Cu 1.7 h Ni Zr 89 Cu(n,p) Ni 90 Zr(n,n) 89 Zr.5 h 78. h Zr 95 9 Zr(n,γ) 95 Zr 6.0 d Zr(n,n) 95 Zr

9 Run 06, Middle irradiation Activities at different cooling times Observed strong radiation accompanying the β + emitters 89 Zr, 6 Cu and 6 Cu, that could present an important source of radiation hazard, have led to difficulties in present analysis of spectra. 9

10 Run 06, Middle irradiation, Activities to the end of irradiation Isotope Reaction T 1/ Ac[Bq/kg] Err [%] Na 7 Al(n,α) Na 3 Na(n,γ) Na 1.96 h Cr 51 5 Cr(n,n) 51 Cr 7.7 d Mn Mn(n,γ) 56 Mn.58 h Co 61 Cu(n,n α) 61 Co 1. h Co 6m Cu(n,α) 6m Co 13.9 m Cu 6 Cu(n,n) 6 Cu 63 Cu(n,γ) 6 Cu 1.7 h Ni Zr 89 Cu(n,p) Ni 90 Zr(n,n) 89 Zr.5 h 78. h Zr 95 9 Zr(n,γ) 95 Zr 96 Zr(n,n) 95 Zr 6.0 d

11 Run 05, Short irradiation Activities at different cooling times Compared to results obtained for CuCrZr at Dresden (1 MeV dt-source), the additional product of Cu 66 (5.1 m) was determined. Further observed transition was ascribed to the V 5 (3.7 m) as resulting from (n,p) reaction on Cr Activity (Bq/kg) Co61 Co6m Cu Cooling time (min) Activity (Bq/kg) Cu Cu66 V , Cooling time (min) 11

12 Run 05, Short irradiation, Activities to the end of irradiation Isotope Reaction T 1/ Ac[Bq/kg] Err [%] Co 61 Cu(n,n α) 61 Co 1. h Co 6m Cu(n,α) 6m Co 13.9 m Cu 6 Cu(n,n) 6 Cu 1.7 h Cu(n,γ) 6 Cu Cu 6 63 Cu(n,n) 6 Cu 9.7 m Cu 66 Cu(n,γ) 66 Cu 5.1 m V 5 5 Cr(n,p) 5 V 3.7 m

13 C/E analysis Middle irradiation Neutron flux [10 10 n/cm /s] Bean Current (ma) Time (min) For a preliminary benchmark analysis of resulting data (middle irradiation time) the Fispact-003 code (EASY-003 library) [R. Forest: UKEA FUS 85] was utilized. The figure shows the time profile of the source strength during the irradiation as recorded by the beam-current integrator and as represented in the calculations. Neutron spectrum and overall flux density at the position of irradiated samples were taken from Karsruhe d-be source. 13

14 C/E analysis Middle irradiation Activity (Bq/kg) 10 9 Na Co Ni The comparison of calculation with measured activities indicates very good agreement for Cr 51, and Zr 89 radio-nuclides and an overestimation for other ones. Overall mean value C/E = 1.3 could result from slightly non-correct evaluation of the neutron fluency , Cooling time (d) This statements are also illustrated by the comparison of present results with data of other authors, presented in the following table. Activity (Bq/kg) 10 9 Cr51 Co6m Cu Activity (Bq/kg) 10 6 Zr95 Mn56 Zr ,01 0, Cooling time (d) 0,01 0, Cooling time (d) 1

15 C/E analysis Middle irradiation Nuclide T 1/ (1)FZK dbe LiSO EAF99 ()FZK dbe Eu97 EAF99 (3)FZK dbe DF JENDL NPI dbe CuCrZr EAF03 ()TUD dt CuCrZr EAF99 () dt CuCrZr EAF01 Na 0.6 d 0.83(0,) (5,0) Cr d <1.8(5,35) 0.86(15,) (3,5) 1.16(5,11) 1.16(5,11) Mn h 1.18(10,0) Co y 1.1(10,9) 1.1(10,9) Co h 0.6(,0) 1.73(9,0) 1.73(9,0) Co 6m 13.9 m.1(5,0) 0.6(11,6) 1.53(11,6) Ni.50 h (,15) 1.(7,10) 1.19(7,10) Cu m 1.09(11,5) 1.09(11,5) Cu h 1.3(,9) 1.13(35,5) 1.13(35,5) Zr d (3,19) 1.1(10,51) 1.1(10,51) Zr d 1.(1.5) (1) UvM et al,. EFF-DOC-77 () UvM et al,. EFF-DOC-770 (3) UvM et al,. FUSION TECHNOLOGY 36(1999)1 () R.Eichin et al., EFF-DOC

16 Conclusions The activation of CuCrZr sample was investigated in the neutron field simulating the low-energy part of fusion neutron peak. The quantitative results with experimental uncertainties and relevant parameters of the experiment are given as a basis for next benchmark calculation. Preliminary results of C/E analysis carried out by the Fispact (EAF 003) on a part of measured data indicate the need for further investigation of spectral and fluence characteristics of the NPI d-be neutron source and some discrepancies in the activation cross-section data as well. 16