Xiaosong Li

Technische Universität München, Chemistry, Faculty Member

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In situ measurement of neutron temperature for the extended k0 NAA at FRM II

Journal of Radioanalytical and Nuclear Chemistry

The neutron temperature at different irradiation positions in the research reactor FRM II was mea... more The neutron temperature at different irradiation positions in the research reactor FRM II was measured using thermometer labels together with lutetium standards. This was the first time to measure the local temperature at the irradiation positions with this combination. The simplified Westcott formalism was used to calculate the neutron temperature using Lu and g(Tn) factors from different data sources. The results showed agreement between neutron temperature according to the Lu method and the temperature showed on the labels. They can be used as a reliable alternative to determine the neutron temperature instead of using Lu standards in the extended k0 NAA.

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Rapid determination of uranium and plutonium content in mixtures through measurement of the intensity–time curve of delayed neutrons

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

The delayed neutron emission of fissile isotopes after irradiation can be described by the six-gr... more The delayed neutron emission of fissile isotopes after irradiation can be described by the six-groups theory. Due to the different half-lives and yields of the fission fragments, the intensity-time curve of delayed neutrons has an individual shape for different fissile isotopes. According to this characteristic, a new rapid analysis method has been developed to determine the concentration of different isotopes in a mixture, such as 235 U and 239 Pu, without any chemical separation. The intensity-time curve of delayed neutrons is measured by using the multichannel scanning (MCS) method with five 3 He-detectors installed on a fast transfer system at the research reactor Munich (FRM). This method was validated by about 200 measurements with different isotope contents even below the microgram region.

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What happened to the moon? A lunar history mission using neutrons

2011 2nd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications, 2011

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Spurennachweis von Uran und Plutonium mittels Messung spaltungsinduzierter verzögerter Neutronen sowie NAA an einer schnellen Rohrpostanlage am FRM /

Zugl.: München, Techn. Universiẗat, Diss., 2001.

An automated fast transfer system at the research reactor Munich

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2004

ABSTRACT An automated fast sample transfer system for the determination of measurements of short-... more ABSTRACT An automated fast sample transfer system for the determination of measurements of short-lived isotopes has been constructed at the Research Reactor Munich FRM. Instrumental neutron activation analysis and analysis of fissile materials by delayed neutron counting are performed on this transfer device. A LabVIEWTM program on a PC with WindowsNT operating system controls the whole pneumatic system via a PCI-1200 interface and four signal conditioning SCXI-modules of National Instruments. Infrared sensors are used to monitor key points in the transfer system. The sample capsule can be automatically removed from the “rabbit” in a special switch prior to spectrum collection. γ-Spectra are acquired by a HPGe detector with the Loss-Free-Counting method of Westphal. The delayed neutrons are measured by five 3He-detectors and a multichannel scaler. The transfer time is about . The system and its mode of operation for routine work will be described.

Applications of k 0 NAA at FRM II with high f values

Journal of Radioanalytical and Nuclear Chemistry, 2014

The research reactor FRM II offers different irradiation facilities with highly thermalized neutr... more The research reactor FRM II offers different irradiation facilities with highly thermalized neutron flux. 3 facilities for the k 0 neutron activation analysis (k 0 NAA) will be introduced shortly. The influence of flux parameter a on the concentration calculation of samples irradiated in a neutron field with very high ratio of thermal to epithermal neutron flux f [ 1,000 are here investigated. Even for the most k 0 isotopes with big Q 0 values, the uncertainty of a concentration calculation without a correction is \3 %, when the f value larger than 3,000. The uncertainty is about 5 % for the isotope 96 Zr in this case. The k 0 library of the computer program MULTINAA is updated. A standard reference material IAEA/soil-7 was analyzed to verify the k 0 NAA at FRM II.

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The program “MULTINAA” for various standardization methods in neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry, 1997

A computer program MULTINAA was developed to facilitate the evaluation of NAA data. It is written... more A computer program MULTINAA was developed to facilitate the evaluation of NAA data. It is written for the VAX/VMS system and operates in the Canberra/ND Genie spectroscopy software environment. MULTINAA can be applied to relative, k0-, monostandard (modified) and absolute methods, including the fast neutron threshold reaction. For each calculation, the available standardizations can be used individually or mixed. In all the standardization modes MULTINAA fetches the data directly from the y-ray spectra and libraries, thus reducing the manual work to a minimum. MULTINAA is flexible to meet various situations in NAA practical work. The required neutron flux parameters for all the non-relative methods are supplied by an accompanying program MULTIFLUX.

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Silicon doping system at the research reactor FRM II

Applied Radiation and Isotopes, 2009

Silicon doping has being carried out at FRM II since 2 years. During the commissioning of our new... more Silicon doping has being carried out at FRM II since 2 years. During the commissioning of our new reactor, a simple test rig was used to determine the neutron flux profile at the irradiation position and optimise a nickel absorber liner, which is equipped at the irradiation position for vertical smoothing of the neutron flux profile. MCNP-code was used during the design of the liner. The final automatic doping system is designed to allow the irradiation of cylindrical silicon single crystals 500 mm high and up to 200 mm in diameter. Silicon ingots are additionally rotated continuously about their own cylinder axis during irradiation. The neutron flux density is measured online by using self-powered-neutron (SPN) detectors. The necessary doping homogeneity of 75% is achieved. The doping procedure and doping quality of ingots with high target resistivity are also discussed.

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Evaluation of neutron sources for ISAGE—in-situ-NAA for a future lunar mission

Applied Radiation and Isotopes, 2011

For a future Moon landing, a concept for an in-situ NAA involving age determination using the 40A... more For a future Moon landing, a concept for an in-situ NAA involving age determination using the 40Ar–39Ar method is developed. A neutron source 252Cf is chosen for sample irradiation on the Moon. A special sample-in-source irradiation geometry is designed to provide a homogeneous distribution of neutron flux at the irradiation position. Using reflector, the neutron flux is likely to increase

Determination of Characteristic Trace Elements in a Middle Age Bronze Door of the Augsburg Cathedral by Using Neutron Activation Analysis (NAA)

Neutron activation analysis (NAA) was used to analyze samples from an old bronze door of the Augs... more Neutron activation analysis (NAA) was used to analyze samples from an old bronze door of the Augsburg Cathedral, in order to establish a reliable screening method for a total of 35 different reliefs and more than 100 other bronze components on this object, manufactured in the 11th century. Based on the fingerprint method, two bronze heads could be confirmed as copies of their neighboring counterparts. This result is an important indication for an early, local, and probably »careful« preservation in the past.

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DETERMINATION OF CHARACTERISTIC TRACE ELEMENTS IN A MIDDLE AGE BRONZE DOOR OF THE AUGSBURG CATHEDRAL BY USING NEUTRON ACTIVATION ANALYSIS (NAA

Neutron activation analysis (NAA) was used to analyze samples from an old bronze door of the Augs... more Neutron activation analysis (NAA) was used to analyze samples from an old bronze door of the Augsburg Cathe- dral, in order to establish a reliable screening method for a total of 35 different reliefs and more than 100 other bronze components on this object, manufactured in the 11th century. Based on the fingerprint method using NAA, two bronze heads could be confirmed as copies of their neighboring counterparts. This result is an important indication for an early, local, and probably »careful« preservation in the past.

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