Education at Lviv Polytechnic

The safety analysis of forced pressure reduction for the hermetic protection system of power unit No. 4 at the Rivne Nuclear Power Plant

Students Name: Krupko Yevhenii Yuriiovych

Qualification Level: magister

Speciality: Nuclear Рower Еngineering

Institute: Institute of Power Engineering and Control Systems

Mode of Study: full

Academic Year: 2020-2021 н.р.

Language of Defence: ukrainian

Abstract: Krupko E.Y. (performer), Galyanchuk I.R. (supervisor). The safety analysis of forced pressure reduction for the hermetic protection system of power unit No. 4 at the Rivne Nuclear Power Plant. Master’s thesis. – Lviv Polytechnic National University, Lviv, 2020. One of the fundamental principles of NPP safety is the implementation of a strategy of deep tier protection [1]. An important element of deep protection is a system of airtight fencing (SAF). SAF is the last physical barrier to the spread of radioactive substances from the reactor core destroyed as a result of a severe accident. One of the main goals of the implementation of the system of forced pressure relief from containment (SFPR), according to the project of FRAMATOME, is to prevent the destruction of SAF during a severe accident by increasing the pressure in the area of the accident above the design limit [2]. The design of SFPR provides, after completion of cycles of dumping of the environment from a zone of localization of accident, a return to a zone of localization of accident of the radioactive substances kept by the system. The main part of the aerosols coming from the accident localization zone is fixed in the scrubber solution. Upon completion of the SFPR, the filtered radioactive substances will remain within the last barrier of deep-layer protection. As shown by the results of the calculated modeling of severe accidents with prolonged de-energization of power units [3], as well as the study of the development and consequences of a severe accident on March 11, 2011. in Japan at the Fukushima nuclear power plant, during severe accidents with a complete power outage, the reactor collapses, generates large amounts of water vapor and hydrogen, increases the temperature and pressure in the containment and the pressure may rise above the design limit for containment. As a result, the destruction of contamination is possible. After a serious accident on March 11, 2011. In Japan, at the Fukushima nuclear power plant in the nuclear industry of all countries, interest in systems of forced filtering of the steam-gas mixture from contamination has grown. The introduction of SFPR, which includes steam and gas filters, allows in case of severe accidents to increase the reliability of safety functions of the SAF in full compliance with the general safety regulations for Ukrainian NPPs in terms of requirements for implementing a strategy of deep protection for NPP units [4]. The master’s qualification work is devoted to the study of the efficiency and safety of the system of forced pressure relief from the system of hermetic protection. The first section of the work considers the main technical data and characteristics of the SFPR, the composition of the system, its main functions, and operation of the system. The second section provides general information about the Scrubber Venturi gas cleaning unit - one of the main elements of the system. The principle of operation and the mechanism of aerosol retention in the scrubber are described. In the third section the calculation-analytical substantiation of sufficiency and efficiency of SFPR is carried out, the reliability of elements of the system is proved. An assessment of the impact of the modification on safety by the requirements of norms and rules. In the fourth section the estimation of radiation influence of modification on the environment in the conditions of a severe accident are carried out. The section of the economic part listed the technical and economic indicators of the unit, determined the cost of electricity and profitability of the unit. In the section on automation the design of the system of automatic regulation of the level of cleaning liquid and pressure in SFPR is carried out, the short description of the technological scheme is given, the choice of system of regulation and technical means of automation is made, the functional scheme of automation is made and described. The results of the study showed that the introduction of a system of forced pressure relief improves the implementation of one of the fundamental principles of safety - the implementation of a strategy of deep protection, by increasing the reliability of the last safety barrier (containment) at design and severe accidents. The object of research – purification of the vapor-gas mixture by a system of forced pressure relief. Scope of research – safety, and efficiency of the system of forced pressure relief. The goal of research: to increase the reliability of the last safety barrier (containment) at the stage of beyond design and severe accidents, by introducing a system of forced pressure relief; determining the efficiency and safety of the system of forced pressure relief from the system of the airtight enclosure. Keywords: hermetic protection system, containment, forced pressure relief system, Venturi scrubber, vapor-gas mixture, beyond design basis accident, severe accident. References: 1. Osnovnye pravila obespecheniya radiacionnoj bezopasnosti Ukrainy. OSPU-2005. MOZ Ukrainy. 2005g. 2. Eckardt B.A., Betz, R.O., Greger, Dr.G.U., Werner, K.; Siemens KWU (now Framatome); Process for Retention of Iodine and Aerosols during Containment Venting; Report BMFT 1500 760/3 (Translation); 1990. 3. Filtered Containment Venting System; Independent Data Compilation, Addendum to the JAVA Report “Process for Retention of Iodine and Aerosols during Containment Venting”; D02-ARV-01-097-193; Rev. A; 2016-06-20; AREVA. 4. NP 306.2.141-2008. Obshchie polozheniya bezopasnosti atomnyh stancij.