Joint U.S. Russia Conference on Advances in Materials Science

1. Joint U.S. Russia Conference on Advances in Materials Science Исследование старения минерального маслав контакте с конструкционными материалами нейтронного генератора Study of mineral oil ageing contacted to design materials of the neutron generatorAlexey V. Sokovishin, Ph.D., (presenter) Galina N. Prokopyeva

2. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator All-Russia Research Institute of Automatics named after N.L. Dukhov (VNIIA) 22, Suschevskaya Street, Moscow, 127055, Russia E-mail sokovishin@vniia.ru

3. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator Paper represents main methodological approaches used in engineering method for estimation of mineral oil compatibility with design materials of the neutron generator. These approaches may be applicable for materials compatibility study at design of high voltage devices with liquid insulation.

4. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator Portable neutron generators (PNGs) are widely used in such fields as oil & gas and ore well-logging, activation analysis, neutron radiography, neutron radiotherapy, physical research, etc. Exploration of the extraterrestrial objects surface is the new area of the PNG implementation. Typically the neutron tube is enclosed in a metal housing, filled with a dielectric medium (gas or liquid insulator) to provide the electrical insulation of the high voltage elements of the neutron tube unit from its surroundings. In most cases electrical insulation is provided with the mineral oil. The accelerating voltage is normally between 80 and 180 kilovolts.

5. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator AINK-89 logging complex diagram. Field applicationof AINK-89 PNG ING-06

6. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator PNG/DAN for NASA Mars mission

7. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator • Factors, affecting the PNG materials: • Electrical field (partial discharges, corona, etc.); • High temperature (especially at the neutron tube target area); • Moisture; • Oxygen; • Products of oil and design materials decomposition (gases, water, peroxides, dirt and acids, furfural, etc). • Oil provides transportation of the decomposition products within the inner volume of the neutron generator.

8. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator Mineral oil For many decades the mineral oil is used for electrical insulation provision in high voltage installations, mainly, in electrical power transformers. By now a great amount of experimental information devoted to researches of the «mineral oil – transformer design materials» system aging is accumulated all around the world. In neutron generators with oil insulation, designed by VNIIA, the set of design materials in a contact with oil is significantly wider and differ from materials used in transformers. There is a considerable difference in working conditions as well. In spite of being rather old and non ‘high-tech” product, mineral oil still have good “price-quality” ratio for commercial products.

9. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator • Reasons for research: • Replacing the type or brand of the insulating liquid; • Implementation of new design materials; • Re-design of the PNG; • Changes of the PNG operating conditions; • Expanding the PNG warranty period; • Monitoring the “technologies drift”.

10. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator Compatibility of design materials in a number of cases has a decisive importance for reliability of equipment during operation. On the one hand, design materials should not evolve substances that can influence in a negative way on electric insulating properties of the oil or cause its accelerated aging. On another hand, materials themselves should not decompose being in contact with the oil as well.

11. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator • Possible approaches: • Using design materials and insulating liquids, recommended in scientific periodicals, reference books, manufacturers recommendations, etc; • Using design materials and insulating liquids, proved by practice of manufacturing PNGs and communication with the customers; • Combination of 1 and 2; • Development of methodology based on analysis of gases, dissolved in the insulating liquid. • Complex approach proposed by the authors.

12. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator The “Complex methodology’ stages: - initial information analysis; - operating conditions analysis and determination of testing conditions based on the analysis results; - determination of design materials and units list to be tested in contact with oil, division into groups; - determination of oil and materials that are in a contact with oil controlled parameters list, determination of measurement methods (generally, standard methods are used); - carrying out an accelerated ageing (on the basis of Arrhenius’ low) of oil in contact with materials of all the groups separately and simultaneously; - analysis of oil and design materials that were taken out from generator and had completely worked their life time (comparative analysis of non-standard samples considering the limited set of parameters); - oil and materials controlled parameters determination. Aperiodicities revelation. Aperiodicities broadened research (if found). Compiling of recommendations for design improvements; - revelation of differences in oil properties and design materials that were taken out from generator after life time end and underwent an accelerated aging. Interpretation of results; - a final conclusion devoted to a possibility of a new oil brand or material(s) implementation.

13. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator • Typical scope of research: • quantity of materials subjected to research is about 50; • number of groups is from 4 up to 5; • number of parameters there are determined for each material is from 3 up to 10. For the insulating liquid they might be breakdown voltage, mechanical impurities content, dielectric loss tangent, flash temperature in closed crucible, acidity index, water-soluble acids and alkalis content, specific humidity, antioxidant additive content, gas content of oil and furan derivatives content. • Usually, aging simulation duration equals a triple generator’ life time (for revelation of slowly going processes and to consider the post-warranty service). • Separate problem is correlation between standard and non-standard samples and testing methods.

14. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator The method application Above-mentioned approach trough many years finds a successful application at VNIIA. At least three types of mineral oils and about ten synthetic liquid dielectrics (including silicon and fluororganic) were subjected to research using the same methodology. For some types of equipment were proposed design changes that allowed to eliminate potential sources of failure caused by incompatibility of insulating liquids with design materials. Absence of operational failures caused by incorrect application of materials proves the accuracy of implemented approach

15. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator Conclusion Reliability provision of complicated high-voltage electrophysical equipment, in general, and neutron generators in particular, requires proper selection of liquid dielectric and compatible generator design materials. The methodology that guarantees high level of the equipment reliability and very low probability of failures caused by improper application of materials was developed.

16. Joint U.S. Russia Conference on Advances in Materials Science Study of mineral oil ageing contacted to design materials of the neutron generator Спасибо за внимание. Вопросы? Thank you for your attention. Questions?