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Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela,

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Presentation on theme: "Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela,"— Presentation transcript:

1 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Measurements at n_TOF of the Neutron Capture Cross Section of Minor Actinides relevant to the Nuclear Waste Transmutation: 237 Np and 240 Pu Carlos Guerrero CIEMAT - Dpt. of Energy Nuclear Innovation group

2 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Nuclear Innovation unit at CIEMAT Research interest includes the majority of activities related with the transmutation of nuclear waste: Development of tools (software) for the simulation in ADS: EVOLCODE Participation in experiments related with ADS: MUSE, YALINA, SAD,... Evaluation of different configurations for the Transmutation of Nuclear Waste: REDIMPACT,... Evaluation of different configurations for energy production: Generation IV Measurements of nuclear data relatedwith ADS: n_TOF, FAIR,...

3 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The experimental programme of n_TOF had the goal of providing more accurate capture cross section data for minor actinides. Such data are necessary in all transmutation scenarios for making the detailed engineering designs, safety evaluations and detailed performance assessment of dedicated transmutation ADS and critical reactors, i.e. with fuels highly enriched in transuranic isotopes. WP 13 of the NTOF-ND-ADS EC 5 th Framework Programme: “Neutron capture cross section measurements on Actinides”: 237 Np, 241,243 Am, 240,242 Pu and 245 Cm: 241 Am: sample arrived at CERN but no authorisation for the measurement from TIS due to its high activity. 242 Pu and 245 Cm: no samples were available in Those capture cross section measurements are difficult due to the limited availability of sample mass (mg) and their high intrinsic activities: Need of high neutron intensity beams (favourable duty cycles) Need of high performance detectors Good control of the systematic uncertainties associated to the counting procedure (DAQ). The n_TOF project INCLUDED THE CONSTRUCTION OF A NEW FACILITY! Neutron Capture Data Needs for Minor Actinides

4 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The n_TOF facility The n_TOF facility is a spallation source built in 1999 – 2000, driven by the CERN PS and coupled to a Time Of Flight (TOF) beam line of 200 m. Typical pulses of 7·10 12 protons at 20 GeV/c and a time width of 6 ns are used for producing a spallation neutron beam with a spot of 4 cm diameter and 6·10 5 n/cm 2 /pulse at a 200 m flight path. High instantaneous neutron fluence with low repetition rate at a VERY long flight path of 200 m and VERY favourable duty cycle (key point for measuring radioactive samples). Excellent energy resolution  E n /E n < for E n < 10 5 eV Highly advanced detection systems (TAC) and monitors. Innovative and pioneering Data Acquisition System based on flash ADCs. Unique features worldwide for measuring highly radioactive samples like the ones relevant to transmutation of Nuclear Waste in ADS!

5 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 n_TOF experiments Capture 151 Sm 204,206,207,208 Pb, 209 Bi 232 Th 24,25,26 Mg 90,91,92,94,96 Zr, 93 Zr 139 La 186,187,188 Os 233,234 U 237 Np, 240 Pu, 243 Am Fission 233,234,235,236,238 U 232 Th nat Pb, 209 Bi 237 Np 241,243 Am, 245 Cm Cross sections relevant in Nuclear Astrophysics s-process: branchings presolar grains Cross sections relevant for Nuclear Waste Transmutation and related Nuclear Technologies Th/U fuel cycle (capture & fission) Transmutation of MA (capture & fission) Transmutation of FP (capture) Neutrons as probes for fundamental Nuclear Physics Nuclear level density & n-nucleus interaction The n_TOF Collaboration

6 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 PROTON BEAM LINE p current monitor p- intensity pickup Entrance to the target Water cooled Pb target n beam tube shielding NEUTRON BEAM LINE shielding

7 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Bending magnet 2nd collimator shielding EXPERIMENTAL AREA n monitor Sample changer BEAM DUMP n monitor

8 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The n_TOF Data Acquisition System (I) The n_TOF DAQ consists of 54 flash ADC channels with 8 bit amplitude resolution and sampling of 500 MSample/s. The full history of EVERY detector (BaF 2 crystals and monitors) is digitised during a period of 16 ms (0.7 eV < E n < 20 GeV) and recorded permanently on tape. Very useful feature since the raw data can be always re-investigated. The system has nearly zero dead time. 7.5 TB disk space for temporary storage. Typical data rate of 2-3 TB/day on tape after compression. Pulse shape analysis is performed on the fly at the LXBATCH Linux Batch Farm at CERN (30 CPUs exclusively dedicated) and stored in highly compressed Data Summary Tapes. Quasi on-line analysis of the data with full statistics. One of the big successes of n_TOF. Many TOF facilities are following the n_TOF example and moving to digital electronics!

9 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The n_TOF Data Acquisition System (II) A specific pulse shape analysis routine has exists for every detector (Silicon Flux Monitor, C 6 D 6 detectors, PPACs…) For the BaF 2 signals: The TOF is determined by means of a simulated Constant Fraction Discrimination. Both the fast (t=0.7ns) and slow (t=620ns) scintillation components are fitted to a Maxwellian and an Exponential (with a fixed t=620ns) distributions, respectively. Excellent  /  discrimination. Pileups occurring 300 ns after the first signal can are recognised and analysed after performing the necessary baseline correction. Flash ADC principle: What you measure is what you see!

10 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Measurement of capture cross-sections:   (E)  r (E) = Number of capture reactions Number of target nucleus per unit area  Number of neutrons of energy E NnNn nTnT NrNr Needs: sample of known mass and dimensions count the number of incident neutrons of energy E count the number of reactions … but there are a number of experimental complications

11 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The TAC consists in 40 BaF 2 crystals (12 pentagonal and 28 hexagonal) with a thickness of 15 cm. It has a nearly 100% efficiency for detecting capture events. C 12 H 20 O 4 ( 6 Li) 2 Neutron Absorber 10 B loaded Carbon Fibre Capsules Neutron Beam The measurements with the n_TOF Total Absorption Calorimeter (TAC) Too massive Ti-canning !!!

12 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 TAC count rate example: 240 Pu raw data

13 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006

14 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The 243 Am(n,  ) raw data First measurement worldwide in the RRR: Mass=10 mg and activity > 80 MBq!

15 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The  (n,  ) analysis consists of two parts: 1.Procurement of the experimental Yield 2.Resonance analysis (SAMMY)

16 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 YIELD CORRECTIONS 1.1. Detection efficiency  (m ,E sum,CR): Monte Carlo simulation + dead time model 1.2. Relative number of neutrons I n (E n ) : from n_TOF fluence and SILI monitors Normalization to 197 Au reference N Au : 197 Au saturated resonance at 4.9 eV 1.4. Neutron sensitivity: neutrons scattered at the sample and captured in the TAC Other backgrounds: estimated and then analysed with SAMMY. 1. Procurement of the Yield E n : T/E calibration from 197 Au resonances below 2 keV

17 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June  det from Monte Carlo simulations Event selection Capture signals to noise (mainly neutron scattering and target activity) ratio is improved by applying conditions in deposited energy and multiplicity.

18 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Geant4 MC simulations include: Very detailed TAC geometry (validated with  -ray sources) Event reconstruction similar to that of experimental data (including instrumental energy resolution and threshold effects).  -ray cascade generator for (n,  ) processes using both experimental and theoretical data for each nucleus. Dead time effects for individual crystals have been modeled from experimental data. geometry used for the MC simulations with GEANT4

19 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Capture Cascade Generator A+1 Z We have used a cascade generator developed at IFIC (J.L. Taín) based both on experimental information about the level scheme (ENSDF) of the compound nucleus and statistical models describing the not known part of the nucleus level scheme: level density and transition probabilities for E1,M1 and E2. S n +E n Known level scheme (ENSDF): level energy, transition probabilities, conversion electron coefficients,... Statistical region: described by level density and  -ray strength functions statistical models. Transition probabilities given by: T XL = f XL  (E-E ,I,  ) XL={ E1,M1, E2}

20 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Au efficiency from Monte Carlo simulations (I) The 4.9 eV resonances of 197 Au has been used as a reference sample and as a validation of the MC method for the estimation of the  det under different conditions on E sum and m   Experimental MC simulation

21 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Au efficiency from Monte Carlo simulations (II) The MC is capable of reproducing the E sum spectrum for different multiplicities allowing to calculate very accurately the detection efficiency for the chosen analysis conditions.

22 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Dead time correction The Dead Time in each individual crystal is modeled as a function of the energy of the two consecutive signals.This effect can produce corrections in the efficiency up to 10% for the analysis condition on multiplicity and deposited energy.

23 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Np efficiency from Monte Carlo simulations (I) The 238 Np level scheme is not as well known as 198 Au one, but it is still possible to reproduce accurately the E sum spectrum for different multiplicity conditions. Experimental MC simulation Experimental MC simulation

24 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Pu efficiency from Monte Carlo simulations (I) The 241 Pu nuclear level scheme is not as well known as 198 Au one, but it is still possible to reproduce accurately the E sum spectrum for different multiplicity conditions.

25 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The detection efficiency  det of the TAC to capture cascades has been estimated for all samples by means of Monte Carlo simulation with an accuracy better than 2%.

26 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Number of incident neutrons I n (E n ) REDUNDANT MONITORING OF THE BEAM INTENSITY: The number of neutrons is given by the SILIcons monitors and the shape of the fluence is that of the n_TOF official evaluation. 200  g/cm2 on 3  m Mylar n + 6 Li  t + 

27 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June N Au from 197 Au saturated resonance at 4.9 eV Wrong fit (i.e. normalisation) if Dead Time is not properly taken into account!!

28 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June N Au from 197 Au saturated resonance at 4.9 eV

29 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Neutron sensitivity Neutron sensitivity effects are related with the non negligible probability of a neutron tobe scattered at the actinide sample and then captured in the TAC (mainly by Ba isotopes).

30 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 OTHER CORRECTIONS 4. Neutron sensitivity: minimized, although the uncertainty in the corrections needs to be estimated. 5. Other backgrounds: taking into account in the SAMMY resonance analysis Surface density of the sample: uncertainty to be estimated, precise information is on the way (Obninsk, Russia). YIELD CORRECTIONS 1.  (m ,E sum,CR): 2.I n (E n ) : 3.N Au :

31 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 SAMMY: a very powerful resonance analysis tool developed at ORNL by Nancy Larson. It performs a bayesian fit, using the R-Matrix formalism, to the experimental yield taking into account effects like: doppler broadenning, self absorption in the sample, single and multiple scattering, data correlations (user supplied DCM),etc. Output: set of resonance parameters and associated uncetainty covariance matrix. Preliminary resonance analysis up to 100 eV in the case of 237 Np and 500 eV for 240 Pu. The sample description includes the Titanium canning in order to consider the multiple scattering and self shielding effects and capture background on the experimental Yield. Known impurities in the 240 Pu sample have been included: 239 Pu and 241 Pu. Reich-Moore R-Matrix fomalism havs been used. n_TOF results have been compared to ENDF 6.8 and JENDL 3.3. Final resonance analysis is being carried out at CIEMAT, including complete covariance matrix calculations. 243 Am(n,  ) will be analysed after the previews analysis are completely finished. 2. Resonance Analysis with SAMMY

32 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 General remarks on 237 Np  (n,  ) analysis The 237 Np sample is highly pure (>99%). 238 Np has a high level density. An adequate treatment of the correlation between resonance parameters (covariances) requires to perform the analysis over broad energy ranges (ideally only one) → large CPU times. The Doppler broadening becomes an even more important effect than usually because of the proximity between resonances. The resonance analysis is estimated to be done up to  500 eV.   >>  n for most of the resonances. Therefore resonance integrals are given by  n, whiles the shapes of the resonances will be given by  .

33 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006

34 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006

35 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006

36 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Preliminary conclusions on 237 Np  (n,  ) analysis RK n_TOF are on average 3% below the RK JENDL and 6% below the RK ENDF values. RK nTOF  97% RK JENDL RK nTOF  94% RK ENDF

37 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June Pu contamination General remarks on 240 Pu  (n,  ) analysis Isolated resonances in the range below 1 keV. The 240 Pu sample more than 10% impurities of 239 Pu and 241 Pu. Resolved resonances can be seen up to  5 keV.     n in most cases and therefore the Radiative Kernel and the shape of the resonance depend equally on   and  n. n_TOF data compared to ENDF 6.8 (1986) and JENDL 3.3 (2000).

38 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 RK n_TOF = 0.6 RK JENDL & ENDF Very Preliminary

39 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006

40 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006

41 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Preliminary conclusions on 240 Pu  (n,  ) analysis The big differences in the 1.05 eV resonance with data libraries (  40%) have not been explained by any known effect. Neutron sensitivity corrections have bigger effects in the Yield than in the 237 Np case. 239 Pu impurities affect the resonances parameters. This effect needs to be analyzed for each resonance. RK n_TOF is on average 9% smaller than RK JENDL and 7% smaller than RK ENDF. RK nTOF  91% RK JENDL RK nTOF  93% RK ENDF 1.05 eV resonance

42 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The first minor actinide  (n,  ) measurements have been succesfuly performed at n_TOF. The 243 Am  (n,  ) has been measured for first time in the world. The analysis will be carried as soon as 237Np and 240Pu s(n,g) analysis is finished. The experimental Yield and the major contributions to its uncertainty have been calculated: –Detection efficiency for the chosen analysis cuts from MC simulations: m  >2 & 2

43 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The 237 Np  (n,  ) has been analyzed up to 100 eV and will possibly be analyzed up to 500 eV. This preliminary analysis allows to conclude: - n_TOF 237 Np  (n,  ) shows a better agreement with JENDL 3.3 than with ENDF 6.8 both in energy and shape. - n_TOF 237 Np resonance area, given by the RK, is lower by 3% and 6% than JENDL and ENDF respectively. The 240 Pu  (n,  ) has been analyzed up to 500 eV and will possibly be analyzed up to 5 keV. The analysis allows to conclude: - The impurities present in the sample difficult the estimation of resonance parameters for some resonances. More accurate information on the sample mass is on the way (Obninsk). - n_TOF 240 Pu s(n,g) show a similar agreement with ENDF 6.8 than with JENDL 3.3 both in energy and shape. - For both ENDF and JENDL: the RK of the 1.05 eV saturated resonance is 40% below and for the rest of the resonance is ~8% below on average.

44 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 “A Santiago se llega lloviendo, pero se deja llorando “ Thank you for your attention

45 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 ADS and Waste n_TOF-Ph2 “The Next Generation of (n,  ) Cross Section Measurements with the Total Absorption Calorimeter (TAC)” D. Cano-Ott on behalf of CEA, CIEMAT, FZK, IFIC, INFN, ITN, UP, UPC…

46 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Transmutation of Nuclear Waste The transmutation has been proposed since long time ago for reducing substantially (1/100) the long lived component of the nuclear waste radiotoxicity inventory before its geological disposal. One of the proposed scenarios for the transmutation is the use of Accelerator Driven Systems (ADS): subcritical reactors coupled to an external spallation neutron source. It was noticed early that more accurate neutron capture cross section data for ACTINIDES are necessary. The actual knowledge on minor actinide data is mainly related to the U/Pu fuel cycle and the operation of nuclear power plants. On the contrary, the fuels proposed in all transmutation scenarios are highly enriched in transuranic isotopes, which are not so well studied. More accurate neutron cross section data are necessary for making the detailed engineering designs, safety evaluations and detailed performance assessment of dedicated transmutation ADS and Fast Critical Reactors.

47 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Composition of Nuclear Fuels

48 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Capture Rates in various nuclear Fuels and Neutron Spectra

49 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The Th Fuel Cycle 232 Th has a lower mass than 238 U. Thus, its irradiation with neutrons produces mainly U isotopes and a much lower amount of transuranic actinides. 232 Th + n -> 233 Th -> 233 Pa -> 233 U, 233 U + n -> 234 U … (7 more neutrons for reaching Pu). Revision of Standards 235 U and 238 U are key isotopes in the actual nuclear energy production scheme. The fission cross section of 235 U is an adopted standard and the ratio of cross sections  fission /  capture is an important magnitude. There is an international effort in making the  capture for 238 U as a standard.

50 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 During its first 4 years (including the construction) of existence, the n_TOF facility has demonstrated that it offers excellent conditions for measuring highly radioactive isotopes available available only in small amounts ( ~1 mg): First measurement worldwide in the RRR: Mass=10 mg and activity > 80 MBq!

51 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 The n_TOF facility offers a unique combination experimental conditions: -A high instantaneous neutron intensity at a very long flight path of 185 m. -A wide energy neutron energy range is covered in one single measurement with an excellent energy resolution  E/E~10 -4 (beyond the resolved resonance region). -The n_TOF facility concentrates in one place last generation detectors, data acquisition system and data transfer infrastructures: the n_TOF BaF 2 Total Absorption Calorimeter (TAC), ultra low neutron sensitivity C 6 D 6 detectors, 50 channels of 1 Gsample/s and 8 bits flash ADCs, CERN’s Central Data Recording infrastructure –prepared for LHC– for high speed data transfer and storage and the LXBATCH computing resources. -n_TOF is a very well characterised facility –neutron flux, resolution function, beam optics, time energy relation- by means of independent reference measurements - 6 Li(n,  ), 235,238 U(n,f), 197 Au(n,  ), 56 Fe(n,  ), 32 S(n,  ) - and Monte Carlo simulation tools (application to the design of LHC shieldings, collimators and beam dumps).

52 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Besides the high quality data obtained at n_TOF, additional valuable information has been obtained during the realisation and analysis of the experiments for looking towards more ambitious and challenging measurements. They can be performed with the facility in its actual shape, just by improving the experimental devices: -Measurements with a 10 times better signal to noise ratio by lowering the neutron sensitivity of the detection setup correspondingly. -Possibility of using lower masses and therefore lower intrinsic activities. -Simultaneous measurement of the fission and capture cross sections by means of an active tagging. Other upgrades of the facility such as a the use of shorter flight path of 20 cm would allow to consider experiments with samples of  g.

53 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Actual Setup 50  m Kapton windows 400  m ISO 2919 Ti canning (400 mg!) + actinide sample air vacuum Neutron absorber Calorimeter  rays Actual setup with very thick sample cannings

54 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 C 12 H 20 O 4 ( 6 Li) 2 Neutron Absorber 10 B loaded Carbon Fibre Capsules Neutron Beam

55 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Effect of the Ti canning (neutron sensitivity)

56 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Window surrounded by neutron absorber ( 10 B or 6 Li doped polyethylene) Thin Al backing + actinide sample vacuum Neutron absorber Calorimeter Low Neutron Sensitivity Setup This solution EXISTS already!

57 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Active Canning for the simultaneous (n,  ) (n,f) measurement Neutron beam Mini Ionisation chamber Stack of with 200  g/cm 2 samples on thin backings Fission Fragments  rays Measurement of capture cross sections of fissile materials (veto) and measurement of the (n,g)/(n,f) ratio. This solution EXISTS already!

58 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 Measurements Proposed

59 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 I. Transmutation of Nuclear Waste and Advanced Nuclear Fuels 241 Am (n,  ) measurement with LNS canning. 241 Am is one of the most important neutron poisons (high capture fraction) present in the fuels proposed in the transmutation scenarios. In addition, it is highly radioactive and therefore difficult to measure. Although feasible, the measurement could not be performed during the first n_TOF phase. 243 Am (n,  ) measurement with LNS canning. Proposed as part of the IP- EUROTRANS/NUDATRA project of the European Commission 6 th Framework Programme. Build up of Cm isotopes. First measurement worldwide at n_TOF in the resolved resonance region (1/10 of the statistics scheduled). 239 Pu (n,  ) and (n,  )/(n,f) measurement with an active canning. The actual nuclear energy production is based on the 235 U/ 239 Pu fuel cycle. 239 Pu is also one of the most abundant isotopes in the fuels proposed in various transmutation scenarios. 242 Pu (n,  ) measurement with LNS canning. It is one of the points for build up of Am and Cm isotopes. Data is very scarce. 245 Cm (n,  ) and (n,  )/(n,f) measurement with an active canning. No data is available (first measurement worldwide) at all. Highly radioactive and available in low amounts.

60 Ciemat Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas C. Guerrero NUDATRA Internal Trainning Course II Santiago de Compostela, 7-10 June 2006 II. Th Fuel Cycle 232 Th (n,  ) measurement with LNS canning. It has been measured with total energy detectors at various facilities (including n_TOF) and thick samples. A measurement at n_TOF with the TAC would provide an independent data set obtained with a completely different technique. 233 U (n,  ) and (n,  )/(n,f) measurement with an active canning. (n,f) is 10 times larger than (n,  ). III. Revision of standards 235 U (n,  ) and (n,  )/(n,f) measurement with an active canning. Important in the actual nuclear energy production scheme. The 235 U(n,f) cross section is a standard and the (n,  )/(n,f) is a very important magnitude. Very abundant data, but recent evaluations and benchmarks point out the need of revising the capture cross section data. 238 U (n,  ) measurement with LNS canning. Contribution to the international effort of making its capture cross section a standard. IV. Other materials C 6 D 6. 46,47,48,49,50 Ti (n,  ) with C 6 D 6 detectors.


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