A Novel Technique for Raman Analysis of Highly Radioactive Samples Using Any Standard Micro-Raman Spectrometer

The overall goal of this technical development is to allow the measurement of samples needing confinement towards atmosphere, such as radioactive samples with the full capabilities of a standard micro-Raman spectrometer instrument. This method can answer key questions in the study of spectrolic properties of other loose material like nuclear components. The main advantage of this technique is to allow you to use the full capabilities of your Raman instrument on some parts needing confinement.

Demonstrating the preparation of the sample order Will be Andreas Hesselschwerdt, a technician from our workshop. Mark Sierig, working at the glove box will demonstrate the sample loading into the sample order. Sarah Nourry, doing instrumental per total will demonstrate the installation of the sample in the Raman microscope and its measurement.

To begin, collect all of the parts composing the standard capsule. To ensure that the installed window is optically clean, wear clean gloves and unpack the window from its original packaging. Place it in the groove on the Acrylglas capsule.

Glue the window on the capsule body by using the glue applicator to evenly apply a small amount of epoxy resin directly on the outer part of the groove fitting the window. Carefully check through the window to see if the glue is evenly applied between the window and the Acrylglas. After 24 hours curing, any extra glue can be turned away.

To fix the bag on the capsule, first insert the capsule, windows first, from the wide side of the funnel shaped bag into the narrow part of the funnel shaped bag. End up at the point where the cylinder can not slide further because of the jut. If necessary, adjust the bag position so that the cylinder sticks out of the funnel shaped bag by about 1.5 centimeters.

Place the tightening O ring over the bag in the groove of the cylinder. Tape the bag with flexible electrical tape onto the cylinder to leave about eight millimeters of the cylinder's upper part uncovered. This part will be used to fix the cylinder in the Raman microscope.

After preparing for tightness testing as described in the text protocol, move a portable hydrogen gas detector all around the capsule and the bag, taking special care around the area where the window is glued. To prepare the plunger, install the sliding O ring in the plunger groove. Then install the pin stub mount on the plunger.

Stick the double sided adhesive tab on the pin stub mount, keeping the protective layer on the surface towards the outside. If the sample is powder or has parts smaller than one millimeter, install the exterior circlip, preventing the interaction of the sample with the window in the last groove of the plunger. Next, screw the pole screw into the other side of the plunger.

Install the sample holder and the plunger in the confinement system according to the local procedure. First, remove the protective layer from the double sided adhesive tab. Place the sample on the adhesive tab.

If the sample is a single piece, press a little bit on the sample with tweezers of a chemical spoon. Next insert the plunger in the capsule. Push it in until it can not go any further in, while taking care to keep the capsule in a vertical position.

Once the sample is in the sample holder, separate the sample holder from glove box confinement according to the local procedure. Following sample holder separation from the confinement system, fix a metal ring slide with a blocking screw on the tape free upper part of the capsule. Then, tighten the side screw to block it.

Insert the capsule from either the top or the bottom of the microscope stage. Mount the metal ring slide on the stage slide holder and secure it with the slide holder springs. Check if the bag below the stage can freely move within any needed X, Y, and Z movements of the stage.

Finally, perform the Raman spectrometer measurement as described in the text protocol. Shown here is the Raman spectra of Neptunium Oxide, measured with different laser excitation energies. The spectra show the typical Raman features of Fluorite structure.

Mainly T2g, 1LO, and 2LO modes. Together with the asymmetric mode at 431 reciprocal centimeters. The stokes and anti-stokes parts of the Raman spectrum of Neptunium Oxide is shown as different laser powers.

The ratio of intensity between the stoke and the anti-stokes of the T2g mode provides direct estimation of the surface temperature. The evolution of the sample surface temperature as a function of laser power is portrayed in this figure. Presented here is the intensity behavior with temperature of the mode at 431 reciprocal centimeters.

The decrease in intensity with temperature is a fingerprint of the electronic origin of this mode. Shown here is the optical image of the Chernobyl lave sample showing the location of the three areas measured by micro-Raman spectroscopy. Typical Raman spectra corresponding to the measured area on the Chernobyl lava sample are shown.

Spectra one and two correspond to crystal and silica doped with Uranium and Zirconium, while spectrum three shows the presence of an amorphous silica phase. After watching this video, you should have a good understanding on how to measure all your samples needing a tight confinement with the full capabilities of your micro-Raman spectrometer. The present technique has paved the way for researchers to investigate vibrational and electronic properties of nuclear materials by taking advantage of all the features offered by Raman spectroscopy.

This approach was mainly developed for the safe investigation of alpha meters. However it can also be applied while measuring Raman spectra to stimulate the interaction between any kind of sample in a specific environment. Like vacuum, or a high pressure gas.

Don't forget that this technical development implies a confinement of radioactive materials and is subject to radio protection regulations.