# Measurement of Oxygen Concentration in Sodium with Plug Indicator FR-22

Determining oxygen concentration in sodium using plug indicators is crucial for experimental facilities and nuclear reactors. This involves lowering sodium temperature slowly until sodium oxide crystallization begins, indicating saturation temperature (TS). Several solubility equations exist for calculating oxygen concentration in sodium, with considerations for impurities. Researchers have established a correlation between compensation temperature and the logarithm of molecular mass for soluble substances, aiding in the analysis of impurities in liquid metals. The results allow for the development of a universal solubility equation applicable to various facilities and propose a calibration method for plug indicators during installation.

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**ON MEASUREMENT OF OXYGEN**CONCENTRATION IN SODIUM WITH PLUG INDICATOR FR-22 / IAEA, VIENA Loginov Nikolai Ivanovich, Vereshchagina Tatyana Nikolaevna General Scientist, General Scientist**Introduction**Plug indicators (PI) of impurities in sodium are used at experimental facilities and at nuclear reactors to determine saturation temperature TS of sodium with oxygen. To determine TS, sodium temperature at PI is lowered slowly, and a flow rate of sodium and measured continuously. When the temperature crystallization of sodium oxide begins, and flow rate of sodium decrease. The temperature at that moment is called plugging temperature and considered as saturation temperature TS. Using Ts, oxygen concentration in sodium can be determined by a solubility equation, for example Noden s one : lgC(ppm) = 6,2571 + 2444,5/TS(K). it s temperature are falls down to TS, 2**Solubility equations of oxygen in sodium**General solubility equation is: lgC = A + B/T, [ C ]=ppm, [ T ]=K The oxygen solubility impurities in sodium, such as H, Fe, Cr, Si. List of impurities and their different at different facilities and can change during operation. Therefore more than 20 solubility equations with different coefficients A and B are existing. Normal concentration of oxygen in sodium of nuclear reactors corresponds to TS=150 (103/ = 2,4). At this point these equations differ more than 10 times. But almost all of them (except for 2) divergence at 103/ =1.79. Root mean square deviation from average value of 19 equations is 4%, and lgC=1.957 4%. depends on other quantity are have a minimum This the consequence of Meier-Neldel s compensation law. is not random result. This is 3**Results of analyses**Authors of [1] have discovered a correlation between the compensation temperature * and logarithm of molecular mass M of a soluble substances: 103/ * = n lg M This correlation was validated by many examples with different solvents and soluble substances, presented in the table. The compensation temperature 103/ =1.79 (558 , 285 ), for sodium indeed corresponds to Na2O (M=62; lg M=1.792). Therefore, the point (103/ =1.79; LgC=1.957) is valid for all 19 equations. 103/ * Solvent Soluble element LgM Soluble element 0 1.146 1.204 Lg M Soluble substance 1.502 1.542 1.475 Soluble substans in melt (LiH)4 Li3N Li2O (NaH)2 C Na2O Si Na3,75Pb Na2Ag KH Note n H N O 1.50 1.54 1.475 1 1 1 Li 300- 550 H C O Si Pb Ag H O 1.68 1.08 1.79 1.45 2.47 2.19 1.6 1.174 0 1.079 1.204 1.447 2.316 2.033 0 0.204 1.681 - 1.792 - 2.4675 2.187 1.603 2.3478 1 1 1 1 1 1 1 0.5 PbO Na 300- 550 NaK Pb [1] MOROZOV V. A., MOROZOV A. V. On the Condition of Impurities in Liquid Metals // Izvestiya Vysshikh Uchebnykh Zavedeniy. Yadernaya Energetika, 2007, No.1, pp. 159-166. 4**Conclusion**The results allows to obtain solubility equation which is valid for any particular facility, and to propose the calibration method of a plug indicator directly at it s installation. The method is the next: 1. To determine oxygen concentration 1 by means of a sampler-distiller existing usually at the experimental or the reactor facility. 2. To determine plugging temperature 1by means of the plug indicator. 3. To create the solubility equation using two points: (103/ 1; lgC1) and (103/ = 1.792; LgC = 1.957). 4. This method can be used periodically during facility operation. 5**Thank you for**attention Loginov Nikolai Ivanovich General researcher Tel.: +7 (484) 399 85 55, Mob. tel: +7 (910) 709 56 60 E-mail: loginov@ippe.ru 19-22.04.2022