Date of Approval 2017/6/26
Approver Takenao Shinohara
Date of Report 2017/6/26

Experimental Report
Project No.

Name of Instrument scientist

2016A0272

Takenao Shinohara
Title of experiment

Name of Instrument/ BL No.

Neutron Transmission Spectroscopic Imaging for Analysis ofFreezing Process of Lead Bismuth Eutectic

RADEN/BL-22
Date of Experiment

Name of principal investigator

2016/6/3 5, 2017/1/19 21

Yasushi Saito
Affiliation
Kyoto University

Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
Name of sample(s) and chemical formula, or compositions including physical form.
Sample : Lead-bismuth eutectic alloy (PbBi)

Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

Experiments
The pulsed neutron imaging experiments wereperformed at BL22. A test section was installed in a frontof the detector. In the present experiments, a GEM
detector (nGEM, Bee Beans Technologies Co., Ltd.) wasapplied

toget

two-dimensional

distributions

oftime-of-flight (TOF) information. The spatial resolution ofthis detector is 0.8 mm/pixel and the imaging area is 100 ×100 mm2.
A schematic diagram of the test section for thesolidification experiments is illustrated in Fig. 1. In order
to simulate one-dimensional solidification process,Fig.1 Experimental setup

Experimental method and results (continued)
a rectangular vessel was used. The LBE sample was encapsulated in the vessel and sealed. The walls of the test
section have 1 mm thickness and were made of stainless steel which has similar thermal conductivity with theLBE. The size of the confined LBE was 80 mm in width, 80 mm in height and 10 mm in thickness. In order todecrease the influence of the convection of the liquid phase, the heating section was placed on top vessel and thecooling one was placed at the bottom. The heating and cooling sections were made of aluminum. In the heatingsection, two cartridge heaters were inserted and the power was controlled by a temperature controlling unit. TheLBE vessel and the heating section were covered by thermal insulator to prevent the heat loss. Two heat sinks
with fans were used in the cooling section. Five thermocouples were inserted from the side walls of the vessel, as
shown in Fig. 1, and the axial temperature profiles in the LBE region were measured with a sampling frequencyof 1 Hz during the experiments. Also, the temperatures at the upper and lower walls were recorded.
Results
By heating the test section from upper side, thecondition that the LBE sample in upper half is liquid state

0.7

and that in lower half is solid state could be produced.

0.6

Then, the neutron transmission spectra in the upper and0.5

lower area were compared. The estimated spectra areshown in Fig. 2. In the lower area, there is a large edge at

0.40.3characteristic edge could not be observed in the liquid area.
Therefore, the Bragg edge at 5.4 Å was used to recognize
the solid and liquid phases. Fig. 3 shows the Bragg edge
images in the cooling process of the LBE. The jumps of theupper area
lower area

0.2
3.5

4.0

4.5

5.0

5.5

6.0

6.5

Wavelength [Å]Fig.2 Neutron transmission spectra in the upperand lower area of the test sectionedge at 5.4 Å in the spectra which is averaged for 30
minutes were estimated at each pixel, and the images were made by using the amplitude of the jump. The solidand liquid phases can be identified by the image contrast and the interface is roughly visualized at the middle ofthe test section, as shown in Fig.3(a). During the solidification process, the solid part grows upward with timeand finally the solid-liquid interface reaches to upside wall. From these results, Bragg edge imaging technique
was successfully applied to study the LBE crystal structure. Further quantitative evaluation of the solidification
process should be performed in future.

abcdT [-]
0.3

0-0.3

Fig. 3 Bragg edge images in LBE solidification process; (a) t = 0~0.5 hours, (b) t = 1~1.5 hours,(c) t = 2~2.5 hours, (d) t = 3~3.5 hours