1. the FARETRA project at LNL
INFN-LNL
Istituto Nazionale di Fisica Nucleare
Laboratori Nazionali di Legnaro
SPES cyclotron-driven fast neutron irradiation facility aimed at nuclear data needs for next generation nuclear reactors:
the FARETRA project at LNL
Juan Esposito
INFN-E meeting
Presidenza INFN, Roma
July 17, 2012

2. Nuclear physics of next Gen-IV/ADS reactor systems
Significant combustion cycle improvement would result by burning not only U and Pu but even most of waste material (including long-lifetime actinides) produced by current thermal (Gen II-III) reactors: Np, Am, Cm series.
Most minor actinides have
a fission threshold (~ 1 MeV)
To burn nuclear waste
fast reactors (or ADS systems)
are needed
Gen IV fast breeder reactors fulfill a
fuel closed cycle (better use of U fuel
minimizing waste production)
About 2 orders of magnitude increase
in output power per unit mass of U
1 MeV
Typical neutron spectrum
in fast (Gen-IV/ADS) like
reactors
Neutron
cross-sections
(with threshold)
Fissile isotopes
(without threshold)
The development of Gen IV fast reactors requires cross section data for several actinides in a wide energy range, mainly in the fast region (En>100 keV).

3. New ADS /Gen-IV reactors design requirement
Design of innovative new reactor types is basically done by using:
- performant, state of the art codes
for Monte Carlo simulation
- reliable cross section libraries with
known data precision
- benchmarking
The European project ELSY

4. Database problems: imprecise data extrapolation (example)

5. Database problems: inaccuracy in data files (example)2 4 6 8 10 12 14 16 18 20 40 80
120 61
Co: N=24/2.499 MeV; 6.48/-.89: D
=1.50 keV
N=11/1.682 MeV; 6.85/-.87:
N=24/2.499 MeV ; 6.85/-.75:
TALYS_0.49
Paul (1953)
Cross (1963)
Preiss (1960)
Qaim (1977)
Bahal (1984)
Qaim (1984)
Viennot
Ribansky (1985)
Viennot (1991)
Molla (1991)
Osman (1996)
Val'ter (1962)
Levkovskiy (1969)
IRMM
cross section (mb)
neutron energy (MeV)
61Ni(n,p)61Co
Model prediction

6. New nuclear data needs: cross section measurements
Nuclear fuel (U/Pu and Th/U cycles)
Th, U, Pu, Np, Am, Cm (n,f), (n,) …
Long-lived Fission Products
99Tc, 103Rh, 135Xe, 135Cs, 149Sm (n,)
Structural and cooling material
Fe, Cr, Ni, Zr, Pb, Na, ... all
Data on a large number of isotopes are needed for design of advanced systems and for improving safety of current reactors.
NEA/WPEC-26 (ISBN )
The overall list of requirements is rather long:
capture cross sections of 235,238U, 237Np, Pu, 241,242m,243Am, 244Cm
fission cross sections of 234U, 237Np, 238, Pu, 241,242m,243Am, Cm
Topic: Fission : Improved nuclear data for advanced reactor systems.
The combination of advanced simulation systems and more precise nuclear data will allow optimising the use of and need for experimental and demonstration facilities in the design and deployment of new reactors. A concerted effort including new nuclear data measurements, dedicated benchmarks (i.e. integral experiments) and improved evaluation and modelling is needed in order to achieve the required accuracies. The project shall aim to obtain high precision nuclear data for the major actinides present in advanced reactor fuels, to reduce uncertainties in new isotopes in closed cycles with waste minimization and to better assess the uncertainties and correlations in their evaluation.
FP VII EURATOM requests

7. New nuclear data needs: cross section measurements
Thermal
region
Resolved resonance region
Unresolved resonance region
High energy
Necessary to measure cross-sections in a wide energy range, high accuracy and high resolution (resonances are important for self-absorption in fuel elements)
Cross-section measurements with Time-of-flight techniques are under way worldwide at TOF facilities, (GELINA, n_TOF, in Europe, LANSCE, Los Alamos, etc…) in order to reduce uncertainties for reactor applications.
For shorter-lived isotopes like e.g. 238Pu, 241Pu, 242mAm, 243,244Cm, etc… existing facilities however cannot provide sufficiently intense neutron beams.
In such cases, a valuable alternative experimental technique is represented by integral measurements, which exploit relatively intense neutron fluxes with suitable energy distributions (e.g. the European Project Myrrha).
FARETRA (FAst REactor simulator for TRAnsmutation studies) is a INFN-Legnaro labs (Padova, Italy) project aiming at shifting an accelerator-driven neutron source spectrum into a Gen-IV/ADS-like reactor one. FARETRA facility will make use of SPES project cyclotron

8. a d g b The SPES project strategy at LNL
Develop a Neutron Rich ISOL facility delivering Radioactive Ion Beams at 10AMeV using the LNL linear accelerator ALPI as re-accelerator .
Make use of a Direct ISOL Target based on UCx and able to reach
1013 Fission/s to produce neutron rich exotic beams.
Apply the technology and the components of the ISOL facility to develop applications in neutron production and medicine.
The SPES project strategy at LNL
Exotic nuclei
ISOL facility for
Neutron rich nuclei by U fission 1013 f/s
high purity beam
Reacceleration up to >10 MeV/u
Applications
Proton and neutron facility for applied physics
Radioisotope produduction
& Medical applications a g b d

9. The SPES Project @ LNL: a multi-user project
SPES building and coupling to the ALPI linac accelerator
Approved for construction
Dual exit Cyclotron proton driver
70MeV 0,750 mA
Applied physics area
2 ISOL production bunkers
ISOL RIB FACILITY
for nuclear physics research
ALPI superconductive linac
Applied Physics with proton beam
70 MeV 500 mA
Primary Beam: 300 mA, 40 MeV protons
Production Target: UCx 1013 fission s-1
Re-accelerator: ALPI Superconductive Linac up to 11 AMeV for A=130

10. Laboratori Nazionali di Legnaro: site area
More than m2
occupied 1/3 available 2/3
200m
SPES
infrastructure

11. SPES Facility Layout ALPI the SPES facility inside LNL ~ 50 x 60 m2
Tandem
Exp. Hall 3
~ 50 x 60 m2
Level -1: production
Level 0: laboratories
Level 1: services CB
NC RFQ

12. Cyclotron service rooms
To subcritical structure
Radioisotopes production area
Neutrons hall
Cyclotron service rooms
Neutrons halls
Beam commissioning site

13. SPES ISOL facility layout:
Level -1
Application
bunker2
Cyclotron
ISOL bunker2
Application
bunker1
RIB selection and transport
ISOL bunker1
Low energy experimental area

14. The SPES Cyclotron: main data
16/03/2017
The SPES Cyclotron: main data
Accelerated particles: H-
Variable Energy: MeV - 70 MeV
Maximum beam current accelerated >700 µA
Maximum beam current at the exit port 500 µA
Extraction system:
Stripper  H-
Beam shared on two exit ports
Performances:
exit1: 300µA H- 40MeV
exit2: 400µA H- 70MeV
Dual beam operation
Running time > 5000 h/year
Minimum Beam Loss to avoid activation (< 5%) 14

15. FARETRA FAst REactor simulator for TRAnsmutation studies
Proponenti: J. Esposito, N. Colonna, P. Boccaccio
Purpose: an accelerator-based neutron facility able to provide, in a proper irradiation chamber, a GenIV-like fast neutron spectrum to start cross sections integral measurements on actinides fission fragments and structural materials, which main nuclear information are still lacking for
Proposal: Using the SPES cyclotron proton beam (40-50 MeV) on a (Be,W o Pb) neutron converter and a proper neutron spectrum shifter system
SPES
Cyclotron
driver
Project goal: Neutron source level: Sn ~2∙1014 s-1
moderation efficiency: 10-3 ÷ cm Total neutron flux expected: Φn= ~ 1010 cm-2s-1
1 μgr 238Pu (87 y, 0.6 MBq) σ(n,f) ~ 1 b
Expected Transmutation Rate = 20 c/s

16. Preliminary modeling of FARETRA facility
Fe inner spectrum shifter
Al outer spectrum shifter
Proton beam pipe
Pb gamma shield (inner)
Poly-B neutron shield
W conical target
70 cm
CF2+Pobyboron shielded Irradiation chamber
70 cm
75 cm
Insertion / extraction rods

17. The experimental neutron spectra W(p,xn) Ep=50 MeV
The present evaporation nuclear models implemented inside the most used transport codes (MCNPX, FLUKA, GEANT) are known to underestimate the neutron yielding by a factor 2-4 in the MeV region.
In such a preliminary study the (p,xn) stage has been skipped, by directly using the experimental double differential data at 50 MeV for the neutron source production by tungsten target in the facility modeling.
T. Aoki, M. Baba, S. Yonai, N. kawata, M. Hagiwara, T. Miura, T. Nakamura, Measurement of Differential Thick-Target Neutron Yields of C, Al, Ta, W(p,xn) for 50 MeV Protons; Nuclear Science and Engineering, 146, (2004) ;

18. W(p,xn) @Ep=50 MeV EXFOR vs. MCNPX-LA150 library

19. Neutron spectrum inside irradiation chamber MCNPX calculation results (Preliminary)
Accelerator-driven Systems (ADS) and Fast Reactors (FR) in Advanced Nuclear Fuel Cycles: A comparative study
NEA-OEDC, 2002
FARETRA facility
Moderation Efficiency (10 eV -10 MeV) : ~ 5∙10-4
Integral neutron flux: Φn= ~ 1.0∙1011 cm-2s-1

20. FARETRA sub project:
Coated-optical-fiber-based, few energy group neutron prompt detector development for critical high-flux mixed neutron-gamma fields
INFN, Laboratori Nazionali di Legnaro : P. Boccaccio, J. Esposito
Universita’ e Istituto Nazionale di Fisica Nucleare, Bologna : A. Zoccoli, R. Dona’
Coated non-scintillating plastic fibers are a possible neutron detection technique.
neutrons
Clear fiber coated with neutron absorber and scintillator powder mixture
photomultiplier
Radiation Hardness
Excellent neutron/gamma rejection ratio
Fast Response
Can be conveniently employed in ADS/Reactor environment/high flux neutron facilities

21. Some nuclear reactions for thermal neutron detection
n + 3He  3H + 1H MeV
n + 6Li  4He + 3H MeV
n + 10B  7Li* + 4He7Li + 4He MeV+ gamma (0.48 MeV) (93%)  7Li + 4He MeV ( 7%)
n + 14N  14C + 1H MeV
n + 155Gd  Gd*  gamma-ray spectrum + conversion electron spectrum (~70 keV)
n + 157Gd  Gd*  gamma-ray spectrum + conversion electron spectrum (~70 keV)
n + 235U  xn + fission fragments + ~160 MeV (<x> ~ 2.5)
n + 239Pu  xn + fission fragments + ~160 MeV (<x> ~ 2.5)
197Au(4.906 eV), 115In( 1.46 eV), 181Ta(4.28 eV), 238U(6.67, eV); energy-selective detectors, narrow resonances, prompt capture gamma rays

22. Some Common Scintillating materials for Neutron Detection
Li glass (Ce)
1.75x1022
0.45 %
395 nm
~7,000
LiI (Eu)
1.83x1022
2.8 %
470
~51,000
ZnS (Ag) - LiF
1.18x1022
9.2 %
450
~160,000
Material
6Li atomic density
(cm-3)
Scintillation
efficiency
Photon
wavelength (nm)
Photons per neutron
Li6Gd(BO3)3 (Ce),
YAP
~18,000
per MeV gamma
3.3x1022
~40,000
~ 400
350 NA
ZnS(Ag)  brightest intrinsic scintillator known. It may be heterogeneously mixed with converter material (usually Li6F) in the “Stedman” recipe, to form scintillating composites, which are semitransparent
Small concentrations of ions (“wave shifters”) may be also included to shift the originally emitted light wavelength to the longer values easily sensed by photomultipliers.

23. Position-Sensitive Neutron Imaging Detector Basics
Clear Fiber
2-D tube
Coincidence tube
Neutron Beam
Wavelength-shifting fiber
Aluminum wire
Scintillator Screen

24. 6Li-ZnS-based neutron detector
The scintillator screen for such a detector is 6LiF and silver-activated ZnS powder mixture dispersed in an epoxy binder, deposited as a thin film around an optical fiber.
Neutrons hitting the screen react with 6Li to produce a triton and an alpha particle. Interaction of these charged particles in ZnS(Ag) induce scintillation at a wavelength of approximately 450 nm.
The 450 nm photons are absorbed in the wavelength-shifting fibers where they are converted to 520 nm photons emitted in modes that propagate out the ends of the fibers.
Quartz Optical fiber
Scintillator screen
n Li  4He + 3H MeV

25. SCHEMATIC LAYOUT OF PROPOSED fiber NEUTRON DETECTOR
QUARTZ FIBER
to PMT
Epoxy binder
ZnS (grain)
n-capture material (grain)

26. Neutron Fiber Detector R&D
Quartz Fibers tests in intense neutron flux environments, as in fission reactors, exhibited good radiation resistance, up to a fast neutron fluence of 1×1023 n/m2 (Fusion Eng. Des. 51 (2000) 179)
Besides 6Li (thermal neutron detection) and fissionable isotopes (fast neutron detection) other isotopes are under investigation, exploiting charged-particle decay of composite nuclei following neutron capture to deduce (through suitable calibration) incident neutron energy.
En (MeV)

27. The 6Li-ZnS neutron detector prototype developed
Hamamatsu PMT
PMT light shield
PMT housing
Optical fiber connection capg
flange

28. The 6Li-ZnS neutron detector prototypes assembled ready for tests at LNL
Two detectors assembled: gamma tests already performed and passed to assess gamma rejection : OK
Test with neutron sources at CN Van der Graaff accelerator: waiting for a parasitic run (En ~ 1 MeV)