NPP Safety Research Articles

Modernization of Fire Extinguishing Installations at Ukrainian NPPs

Fire safety of nuclear power plants is a relevant task, which shall be solved using the latest approaches taking into account NPP design and construction practices, including those in foreign countries.
 The paper describes results of analysis of NPP fire safety in Ukraine based on national and international assessments, identifies problems in this area and presents priority measures aimed at NPP safety improvement, in particular modernization of fire protection of safety system rooms and implementation of gas and powder fire extinguishers at Ukrainian NPPs.

Key results of commissioning activities for the emergency and scheduled cooldown system of the AES-2006 unit with the V-392M reactor plant

The paper describes the combination of safety and normal operation functions adopted in the AES-2006 design, as illustrated by a two-channel structure of active safety systems, showing the major innovative solutions and their differences from earlier designs, such as:– The use of a pump-ejector assembly in the primary circuit emergency and scheduled cooldown and spent fuel pool cooling system;– The emergency and scheduled cooldown and spent fuel pool cooling system is designed as two fully independent channels (each channels consists of two legs, each channel leg has a capacity of 100%);– The redundancy rate is 2 × 200%.Differences in the emergency and scheduled cooldown systems are considered for the V-392M и V-320 designs. Compliance with the acceptance criteria is shown based on test results, including additional tests performed in different modes during the commissioning of the Novovoronezh NPP II Unit 1 with the V-392M reactor plant. A description and a pattern are provided for the full-scale simulator tests to justify the long-term performance of the pump-ejector assembly scheduled for 2017, including an inspection of the water-jet pump nozzle inner surface condition and the water-jet pump service life tests followed by an examination for possible damage and visible defects on the nozzle surface.As a result of the innovations, the overall reliability of safety systems has been improved. The successful completion of the life tests of the pump-ejector assembly of the emergency and planned cooling system made it possible to confirm the reliability and efficiency of the water-jet unit used for the first time in the NPP safety systems.

Comparative efficacy of ways of long-term usage of start-up boilers in the scheme of nuclear power plant

There was carried out an analysis of technical characteristics of boiler houses in a number of Russian NPPs. We justified the possibility of their usage for autonomous generation of electrical energy and improvement of maneuvering properties of power complexes as a single object of regulation, as well as the possibility of increasing the total generation capacity of NPP power units during peak hours. Then the selection of the main equipment of house boiler for its autonomous work was done. There were composed basic thermal diagrams of the power complex on the basis of NPP start-up boiler (SUB) and the satellite turbine. The article also considers some options of reconstruction of SUB into the heat-recovery boiler. The developed power complexes are designed to be used on the basis of the two-loop NPP with pressurized power reactors (PWR). They can be applied with serial and projected domestic NPP units with the aim of getting more power, improving the plant capacity factor (PCF), as well as with the aim of NPP participation in the regulation of the load curve above the nominal value with partial replacement of new construction. The power complexes can be a relevant solution in the light of the energy strategy of the Russian Federation, which is aimed at, firstly, further improvement of efficiency and safety at the NPP, and, secondly, solving the problem of adequate maneuverability and ensuring the adjustment range limits in power systems with high share of nuclear power plants. Implementation of new hybrid thermal diagrams allows simultaneous increase in the safety of NPP, and usage of nuclear power plants emergency frequency control in power systems by fast load drop and rise by -4÷+2 % of the nominal value. Due to the usage of different fuels in power complexes, uranium loading in the core of reactor facilities and gas in SUB, there was proposed and formalized the criterion of “thermoeconomic index”. This criterion represents the ratio of the gross receipt from the sale of electricity to the total cost of fuel of all kinds, spent on ensuring power efficiency.

Improving Safety and Economic Feasibility of NPP by Management of Secondary Side Piping Life

Flow accelerated corrosion (FAC), which caused major accidents at Sarri-2 NPP and Mihama-3 NPP, is the main ageing mechanism of NPP secondary side piping. FAC determines the service life of piping made of carbon steel. Wear prediction using computer codes is considered a tool for life management. The paper presents analysis of computer codes of the USA, Germany and Russia and considers the advantages of computer codes for life management and repair planning. Some problems that arise from using computer codes for analyzing the results of ultrasonic thickness gauging are indicated. The paper provides the algorithm for piping life management at Japanese NPPs and proposes the ways of improving piping life management algorithm, which makes it possible to proceed to the implementation of piping repair concept according to their condition.

On the possible geological and geophysical risks and prospects of the Chernobyl Exclusion Zone

Scientific and engineering center of radiohydrogeogeological polygon studies of the National Academy of Sciences of Ukraine.Evidence and mechanisms of the potential influence of local depression (micro-geodynamic) zones on the NPP safety were considered. The depression forms were revealed within the Chernobyl NPP site, including location of the new safe confinement. Nature of zones and character of their influence is determined by fault structures and conjugated deep degassing processes, which cannot be detected and studied by conventional methods of engineering-exploration works during NPP siting. The assumption was made that significant and still unexplored risks for nuclear facilities are associated with probable escape of deep hydrogen through the bottom of depressions along sub-bottom channels. The approaches were proposed to studying the system of “depression with its sub-bottom channel” within the sites of Chernobyl NPP and other nuclear power plants. The prospects of searching for hydrogen accumulations as efficient energy resource were considered.

Проблеми безпеки АЕС, ядерного паливного циклу та диверсифікації джерел постачання ядерного палива України

Проблеми безпеки АЕС, ядерного паливного циклу та диверсифікації джерел постачання ядерного палива України

Innovative Activities of JSC 'Concern Rosenergoatom' to Ensure NPP Safety: Strategy and Plans to Implement Nuclear Knowledge Management

The Russian operating organization Concern Rosenergoatom established a program for knowledge management (KM) implementation in the organization, as part of ROSATOM State Corporation KM activities [1]. The plan includes activities both in the framework of classic knowledge management cycle: detection, preservation, retention, sharing and transfer, as well as creation of new knowledge such as training programs for new build nuclear power plants. The approach embraces key techniques overviewed in IAEA documents on KM and ROSATOM strategical focus on the commercial use of R&D results and corporate knowledge and, thus, contributes to safe, reliable and efficient operation of NPPs.

Multifunctional Backup for NPP Internal Needs

The multifunctional backup power system for the internal needs of nuclear power plants uses an added steam turbine. This approach makes it possible to increase the power capacity of NPP with water cooled reactors and at the same time maintain high safety and reliability. The reactor cools down in 72 h in the event of an accident with total blackout of NPP. The significant results of multifunctional backup are: positive economic impact, pay back of the added capital investments in the safety system, and higher technical and economic efficiency, safety, and competitiveness of NPP.

Safety Factors for Neutron Fluences in NPP Safety Assessment

In accordance with global practice and a number of existing regulations, the use of conservative approach is required for the calculations related to nuclear safety assessment of NPP. It implies the need to consider the determination of neutron fluence errors that is rather complicated. It is proposed to carry out the consideration by the way of multiplying the neutron fluences obtained with transport calculations by safety factors. The safety factor values are calculated by the developed technique based on the theory of errors, features of the neutron transport calculation code and the results obtained with the code. It is shown that the safety factor value is equal 1.18 with the confidence level of not less than 0.95 for the majority of VVER-1000 reactor places where neutron fluences are determined by MCPV code, and its maximum value is 1.25.

МИНИМИЗАЦИЯ ВЛИЯНИЯ ЧЕЛОВЕЧЕСКОГО ФАКТОРА НА НАДЕЖНОСТЬ И БЕЗАВАРИЙНОСТЬ РАБОТЫ АЭС И ДРУГИХ ОПАСНЫХ ОБЪЕКТОВ ЗА СЧЕТ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ УЧЕБНО-ТРЕНИРОВОЧНЫХ ЗАНЯТИЙ*

МИНИМИЗАЦИЯ ВЛИЯНИЯ ЧЕЛОВЕЧЕСКОГО ФАКТОРА НА НАДЕЖНОСТЬ И БЕЗАВАРИЙНОСТЬ РАБОТЫ АЭС И ДРУГИХ ОПАСНЫХ ОБЪЕКТОВ ЗА СЧЕТ ПОВЫШЕНИЯ ЭФФЕКТИВНОСТИ УЧЕБНО-ТРЕНИРОВОЧНЫХ ЗАНЯТИЙ*

The Analysis of Operational Events at Ukrainian NPPs during 2015 and the First Six Months of 2016

The events that occurred at Ukrainian NPPs in 2015 and the first six months of 2016 have been analyzed in the areas that characterize operational safety.
 The paper presents results of NPP operational events analysis carried out to identify common features and trends that indicate whether there were (or not) inconsistencies during investigation of events, and provides information on the current level of NPP safety. Negative trends have been determined for each NPP site that identify the areas to be improved and require control of the regulatory authority. Causes of negative trends are analyzed individually.
 Events with common characteristics were evaluated, with the results to be used for the development and implementation of preventive measures to avoid the reoccurrence of such events. Safety-important areas have been determined for inspections and recommendations have been provided to the operator on the improvement of the operating experience feedback system and increase in the level of operational safety.

Lithuanian foreign policy vis-à-vis Belarusian nuclear power plant in Ostrovets

Abstract The development of nuclear power in Belarus is an important issue addressed by Lithuanian foreign policy due to a mixture of geographic, political and nuclear safety concerns. Despite the pronounced relevance, the topic has received very limited academic attention. The paper attempts to fill this gap by identifying key objectives of Lithuanian foreign policy towards Ostrovets NPP and strategy for attaining them. The research is based on the analysis of high-level meetings and statements of six Lithuanian decision makers and a wide range of official documents. The paper argues that despite the apparent focus on nuclear safety of Ostrovets NPP, Lithuanian foreign policy aims to prevent its construction or at least to prolong the process. In order to do this, Lithuanian pressures Belarus via European Union and other international organizations and platforms by highlighting the nuclear safety issues of the plant, Belarusian non-compliance with Espoo and Aarhus conventions and presenting it as matter of international concern.

On Geological and Geophysical Safety of the New Safe Confinement for ChNPP-4

The paper considers evidences and mechanisms of potential impact of local depression (microgeodynamic) zones on NPP safety. The depression forms were revealed within the Chornobyl NPP site, including location of the new safe confinement. Nature of zones and character of their influence is determined by fault structures and conjugated deep degassing processes, which cannot be detected and studied by traditional methods of engineering and exploration works during NPP siting. The assumption was made that significant and still unexplored risks for nuclear facilities are related to probable release of deep hydrogen through the bottom of depressions along sub-bottom channels. The approaches were proposed to studying the system of “depression with its sub-bottom channel” within the sites of Chornobyl NPP and other nuclear power plants.

원전 상태 감시 및 조기 경보용 빅데이터 시범 플랫폼의 설계를 위한 시스템 엔지니어링 방법론 적용 연구

1) Institute for Advanced Engineering (IAE)2) MNDAbstract : With the era of big data, the big data has been expected to have a large impact in the NPP safety areas. Although high interests of the big data for the NPP safe ty, only a limited researches concerning this issue are revealed. Especially, researches on the logical/physi cal structure and systematic design methods for the big data platform for the NPP safety were not dealt with. I n this research, we design a new big data pilot platform for the NPP safety especially focusing on health moni toring and early warning services. For this, we propose a tailored design process based on SE approaches to man age inherent high complexities of the platform design. The proposed design process is consist of seve ral steps from elicitate stakeholders to integration test via define operational concept and scenarios, and system requirements, design a conceptual functional architecture, select alternative physical modules fo r the derived functions and assess the applicability of the alternative modules, design a conceptual physical architecture, implement an d integrate the * 교신저자 : Jae-Min Cha, jmcha@iae.re.kr* This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0) which pe rmits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Codes for NPP severe accident simulation: development, validation and applications

The software tools that describe various safety aspects of NPP with VVER reactor have been developed at the Nuclear Safety Institute of the Russian Academy of Sciences (IBRAE RAN). Functionally, the codes can be divided into two groups: the calculation codes that describe separate elements of NPP equipment and/or a group of processes and integrated software systems that allow solving the tasks of the NPP safety assessment in coupled formulation. In particular, IBRAE RAN in cooperation with the nuclear industry organizations has developed the integrated software package SOCRAT designed to analyze the behavior of NPP with VVER at various stages of beyond-design-basis accidents, including the stages of reactor core degradation and long-term melt retention in a core catcher. The general information about development, validation and applications of SOCRAT code is presented and discussed in the paper.

Preliminary Study on Mass Flow Rate in Passive Cooling Experimental Simulation During Transient Using NC-Queen Apparatus

The research related to thermal management has been significantly inreased, especially for NPP safety. The use of passive cooling systems both during the accident and operation become reliable in the advanced reactor safety systems. Therefore it should be enhanced through experimental studies to investigate heat transfer phenomenon of the heat decay in transient cooling condition . An i nvestigation has been performed through experimen t using an NC-Queen apparatus constructed with rectangular loop. Piping were consisting of tubes of SS316L with diameter, length, and width of 3/4 inch, 2.7 m, and 0.5 m respectively. The height between heater and cooler was 1.4 m. The experiment used initial water temperature at 70 o C, 80 o C, and 90 o C in heater area. Transient temperature was used as experimental data to calculate water mass flow rate. The results showed that the temperature in heater area and cooler area were decreasing of about 90.6% and 95.7% at initial temperatur of 80 o C, and of about 71.1% and 59.4% at initial temperature of 70 o C. Those results were at higher initial temperature of 90 o C compared with the initial temperature of 90 o C. The average of water mass flow rate increased 81.03% from initial temperatur of 70 o C. It was shown that the average s of removed heat in every second from water due to heat loss and cooler , were 3.51 watts, 5.06 watts and 6.85 watts respectively. T he initial condition of heat stored in the water was quite different , but to the cooler heat removal capacity and heat loss was almost the same . Received: 10 November 2014; Revised: 23 December 2014: 24 December 2014

Radiation intensification of the reactor pressure vessels recovery by low temperature heat treatment (wet annealing)

As a main barrier against radioactivity outlet reactor pressure vessel (RPV) is a key component in terms of NPP safety. Therefore present-day demands in RPV reliability enhance have to be met by all possible actions for RPV in-service embrittlement mitigation. Annealing treatment is known to be the effective measure to restore the RPV metal properties deteriorated by neutron irradiation.There are two approaches to annealing. The first one is so-called «dry» high temperature (∼475°C) annealing. It allows obtaining practically complete recovery, but requires the removal of the reactor core and internals. External heat source (furnace) is required to carry out RPV heat treatment.The alternative approach is to anneal RPV at a maximum coolant temperature which can be obtained using the reactor core or primary circuit pumps while operating within the RPV design limits. This low temperature «wet» annealing, although it cannot be expected to produce complete recovery, is more attractive from the practical point of view especially in cases when the removal of the internals is impossible.

核电厂中主要弱β释放体的放射性量及控制方法研究

随着核电厂中对正常满功率运行时裂变产物和腐蚀产物控制水平的不断提高，主要的弱β释放体(如氚和C-14)对公众的辐射影响变得日益重要。GB 6249-2011中对流出物中氚和C-14的单机组和厂址排放总量规定了控制值，也对内陆厂址排放口下游1 km处受纳水体中氚浓度进行了限制。本文根据核电厂中氚和C-14的主要产生途径，采用理论方法对其产生量进行分析，并从其产生途径和设计的角度，提出了切实可行的对释放到环境中的氚和C-14进行控制的方法和措施，以用于优化电厂设计，为环境影响评价和安全分析提供审评的依据。 As the control technology of fission and corrosion products develops during the full power operation in the nuclear power plant, the impact from the main β emitters (like tritium and Carbon-14) to people becomes increasingly important. Certain limits of the tritium and carbon-14 concentration in the effluences for both single unit and site are established in GB6249-2011, also, it includes the tritium concentration restriction in the 1 km downstream water from the discharge canal for inland sites. Based on the main generation pathway, a theoretical method is applied to analyze the tritium and carbon-14 generations in this paper, and some tritium and carbon-14 release control recommended measures are provided from both the generating pathway and design aspects. Also, these measures could be used for the NPP design optimization, safety analysis and environment assessment.

Multi-criteria decision making in formation of balanced portfolio of npp safety improvement projects

Multi-criteria decision making in formation of balanced portfolio of npp safety improvement projects

Conceptual studies of construction and safety enhancement of ocean SMART mounted on GBS

From the Fukushima accident, protection of NPPs from any imaginable natural disasters became very important. In this study, the authors suggest a new concept of ocean nuclear power plant (ONPP) by using SMART as a reference reactor, which is the most recent Small Modular Reactor (SMR) developed by Korea, to demonstrate that the proposed concept can improve the safety of NPP from earthquake and tsunami. The proposed concept utilizes Gravity Based Structure (GBS), which is a widely spread construction technique of offshore plants. Because, floating type or submerged type NPPs can be easily affected by severe ocean environments such as tsunamis and storms, additional safety features have to be added to the existing land based plant. In contrast, the newly proposed GBS-type ONPP does not require going through significant design modifications due to inherent characteristics of the construction method. The authors have demonstrated this concept can be applied to the large nuclear power plant in the previous work and will expand this concept for SMRs in this paper. The authors discuss the new concept by presenting design parameters, design requirements, and the new total general arrangement. Furthermore, due to the unique configuration of ONPP SMART, innovative passive safety features can be added to the existing SMART design. The performance of proposed concept to resist earthquake as well as newly added passive safety feature will be discussed by presenting simplified analysis results.