Comparison between the measured and calculated reactivity in measuring the effectiveness of the emergency protection at
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arison between the Measured and Calculated Reactivity in Measuring the Effectiveness of the Emergency Protection at the Stage of Physical Startup of Unit No. 3 at the Kalinin Nuclear Power Plant O. Yu. Kavun, A. I. Popykin, R. A. Shevchenko*, and S. A. Shevchenko Scientific and Engineering Center for Nuclear and Radiation Safety, ul. Malaya Krasnosel’skaya 2/8, str. 5, Moscow, 107140 Russia Received October 11, 2010
Abstract—This paper presents comparisons between the effectiveness of the emergency protection under both sta tionary and nonstationary formulations calculated with the use of the RADUGA7.5 package [1] and experimen tal data obtained in measuring the “weight” of the emergency protection in the process of physical startup of the VVER1000 reactor of unit no. 3 of the Kalinin NPP. On the basis of the results obtained, recommendations are given on comparing the measured and calculated reactivity and parameters determined by using its value. Keywords: VVER, Kalinin NPP, reactivity, ionization chamber, experiment, measurement, simulation, cal culation, comparison, RADUGA7.5 package. DOI: 10.1134/S1063778812130030
INTRODUCTION Reactivity effects and coefficients are among the basic physical characteristics of a nuclear reactor. They, as well as other values associated with the con cept of reactivity and determined by means of calcula tions and measurements (the effectiveness of the emergency protection, the subcriticality, etc.), are used as design and operational limits. Their permissi ble values should be justified in the design of the reac tor facility of the NPP (item 2.2.1, NP08207 [2]). At present, in accordance with the requirements speci fied in normative documents, the values of some of these parameters obtained by calculation should be supported by measurements carried out at a minimum controllable power level (item 3.1.1, NP08207 [2]) prior to the use of each new fuel charge. There exist certain difficulties in comparing mea sured and calculated values of the reactivity, on one hand, and values obtained by the use of it, on the other hand, especially when measuring the reactivity at states of high subcriticality. To verify stationary pro grams, including the verification of the reactivity cal culated from these programs, measurements are used that have been carried out on critical assemblies and at reactor facilities now in operation for which the reac tivity is determined from the current in an ionization chamber measured by means of a reactivity meter dur ing the transition process. However, sometimes this is * Email: [email protected]
contrary to the logic of stationary calculations, since in this case the value of the reactivity calculated by means of a stationary program is the difference between the effective (reciprocal) multiplication fac tors in two steady states. But when measurements are carried out, in most cases, the temporal dependence of parameters to be measured in the system under consideration is deter mined by delayed neutrons, and, if the system is f
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