[Neutron] PhD position for water neutron moderator studies and 2 work placements at ILL

[Emmanuel FARHI]

The ILL, Grenoble, France is recruiting two 5-6 months work placements 
and a PhD student (3 years) to work on neutron moderators in 
collaboration with IRSN, Saclay/Paris, France.

1- work placement: Neutron coherent scattering study of liquid hydrogen. 
Increase of thermal neutron cross sections accuracy - ref. 15/CS-1. 6 
monthsILL
2- work placement: Light and heavy water thermal cross sections for 
neutron transport codes, up to 350C and 150 bar - ref. 15/BPC_1. 6 
months ILL
3- PhD: Experimental and Theoretical Studies of Light Water Effective 
Thermal Scattering Kernel. 3 years IRSN/ILL, as a continuation of ref. 
15/BPC_1

The details of the positions follows.
-------------------------------------

WORK PLACEMENT 1: Neutron coherent scattering study of liquid hydrogen. 
Increase of thermal neutron cross sections accuracy - ref. ILL/15/CS-1
(ILL Science Division / Scientific Computing group, France)

Hydrogen-based (H2, D2) neutron moderators are used to produce cold 
neutrons which feed many neutron scattering experiments. This is the 
reason why neutron production facilities need to get the highest 
available level of accuracy for neutron cross-section data in such 
materials. Modelling accurately such neutron sources is crucial for 
their refurbishment or merely for safety considerations. Furthermore, 
recent investments of the European Community addressed to the general 
amendment of the poor accuracy of existing nuclear databases, also 
regarded cryogenic liquids.

This internship will thus be dedicated to a neutron inelastic scattering 
experiment carried out on liquid hydrogen and the treatment and analysis 
of the recorded data. Such measurements are particularly challenging 
because of the experimental conditions and because of the high level of 
accuracy required. The teachings will be shared by scientists from the 
ILL and from the University of Florence (Italy). Furthermore, the 
internship is part of the NAUSICAA project 
(https://www.ill.eu/?id=15488) which has just been launched and takes 
part of an international collaboration, under the auspices of the OECD/NEA.

Duration: 5 months maximum
Level: 5th year university studies in physics
Supervisor: E. Farhi farhi(at)ill.fr and Y. Calzavara calzavara(at)ill.fr

---

WORK PLACEMENT 2: Light and heavy water thermal cross sections for 
neutron transport codes, up to 350C and 150 bar - ref. ILL/15/BPC_1
(ILL Projects and Techniques Division, France)

Water is a major component of the nuclear facilities, including research 
reactors, spallations sources and power plants. In these facilities, 
water acts both as a coolant and a neutron moderator (to slow down 
neutron emitted at very high energy). The resulting neutrons, labelled 
as 'thermal', are used to probe matter in neutron scattering 
instruments, to extract structural and dynamical information. This is 
the reason why neutron production facilities absolutely need to get the 
highest available level of accuracy for neutron cross-section data. 
Moreover, modelling such neutron sources is crucial for their 
refurbishment or merely for safety considerations. Last, recent 
investments of the European Community addressed to the general amendment 
of the poor accuracy of existing nuclear databases, including common 
liquids.

The neutron cross-section data can be obtained from e.g. neutron 
scattering experiments, and from molecular dynamics simulations. The 
neutron scattering experiments will be performed at the ILL, on 
time-of-flight spectrometers, which will directly provide structural and 
dynamic properties of water. As the measurement range is finite, we plan 
to extend the determination of these properties using molecular dynamics 
simulations, with codes such as NAMD. This study will consider both 
light (H2O) and heavy (D2O) water, from normal conditions up to T=350 oC 
and P=150 bar. Last, the data sets must be combined and treated to 
extract the dynamic structure factor 
<http://en.wikipedia.org/wiki/Dynamic_structure_factor> (see also 
Ashcroft and Mermin, Solid State Physics, Appendix N) and compute the 
neutron scattering cross-sections.

This internship sits within this ambitious task. The internship is part 
of the international NAUSICAA collaboration 
<https://www.ill.eu/?id=15488> which has just been launched, under the 
auspices of the OECD/NEA. A six months' research activity is appropriate 
for the performance and analysis of the measurements, and for learning 
and practising with available calculation tools. The teaching will be 
shared by scientists from the ILL, with collaborations in Italy, Germany 
and Canada. In this project we shall use the IN4 and IN5 spectrometers, 
the iFit and LAMP data treatment software, the NAMD and nMoldyn 
molecular dynamics simulation codes, and the McStas neutron ray-tracing 
simulation package.

Duration: 6 months maximum
Level: 5 th year university studies in physics
Supervisors : E. Farhi farhi(at)ill.fr and Y. Calzavara calzavara(at)ill.fr

---

PhD POSITION: Experimental and Theoretical Studies of Light Water 
Effective Thermal Scattering Kernel (IRSN-Saclay and ILL, France)

Neutronic calculations of nuclear reactor core in operation in France 
are based on two major essential principles, namely, the use of computer 
codes to model and solve the neutron transport equation and the 
underlying nuclear data describing the neutron interaction with the 
reactor material components. The past 30 years have seen an overwhelming 
improvement in the methodologies used for reactor calculations leading 
to significant reduction in the reactor uncertainty results. However, 
nuclear data libraries have not yet achieved the level of self-assurance 
needed for reactor applications and consequently there are still needs 
for improvements of nuclear data and their uncertainties.
Neutron slowing down and thermalization by water are very important for 
pressurized water reactors (PWR) core calculations. A good knowledge of 
nuclear data and uncertainties for these processes are required to 
address the uncertainty in the system multiplication factors. Although 
progress has been reached for improving nuclear data evaluation for 
fission, capture, and elastic cross sections very little has been done 
for double-differential neutron scattering cross sections in the energy 
region where the incident neutron energies are comparable to the 
molecular energy. The proposed thesis consists of performing nuclear 
data measurements of light water thermal scattering cross section 
corresponding to conditions of a PWR operation, i.e., high-temperature, 
high-pressure, etc. The measurements will be performed at the Lau 
Langevin Institute (ILL) located in Grenoble using the thermal neutron 
time-of-flight (TOF) spectrometer IN4 and the cold neutron multi-chopper 
TOF spectrometer IN5. Subsequently the measured data will be analyzed 
and evaluated using molecular dynamics technique to extract the 
double-differential cross section and the scattering Kernel S(a,b). The 
evaluation of the experimental data will provide the grounds to obtain 
the uncertainties associated with the experimental conditions in 
connection with the measurements, namely, the systematic and the 
statistical uncertainties. While existing nuclear data libraries contain 
S(a,b) evaluation for water for certain reactor operational condition it 
should be noted that no uncertainty information exists based on actual 
experimental data. The results of the proposed work will improve 
calculation of PWR effective multiplication factor and will provide a 
better understanding of its uncertainties.

This PhD project can advantageously follow the work placement ref. 
ILL/15/BPC_1 above.

Candidate Profile:
Applicants are expected to be familiar with the nuclear physics dealing 
with thermal neutron scattering. In addition, familiarization with 
experimental techniques used for nuclear data measurements is needed. In 
particular some knowledge of the technique commonly used in molecular 
dynamic application will be of extreme value for the success of the 
work. Familiarization with format of the nuclear data library and 
processing codes used to process the library are deemed needed.

Duration: 3 years (Paris IRSN, CEA/Saclay and ILL)
Contact: E. Farhi farhi(at)ill.fr and Y. Calzavara calzavara(at)ill.fr

-- 
Emmanuel FARHI,www.ill.eu/computing/people/emmanuel-farhi \|/ ____ \|/
CS-Group ILL4/221, Institut Laue-Langevin (ILL) Grenoble  ~@-/ oO \-@~
71 av des Martyrs,CS 20156,38042 Grenoble Cedex 9,France  /_( \__/ )_\
Work :Tel (33/0) 4 76 20 71 35. Fax (33/0) 4 76 48 39 06     \__U_/