Switchgears breaker status information of NEK Process Information System
Sipro prepared design modification package for providing status information of 22 breakers of safety related and non-safety related 6,3 kV switchgears, and status of 31 breakers of safety related and non-safety related 400 V switchgears of Nuclear Power Plant Krško. The modification provided new 150 signals to Process Information System (PIS) for information and presentation on PIS mimics of breaker status of power distribution system.
The wiring changes have been designed so that proper separation criteria are provided between safety (1E) and non-safety (non-1E) wiring either by distance or by additional wire wrapping and braiding.
Project Manager: Božidar Linke, B.Sc.E.E.
Reactor Vessel Clossure Head (RVCH) replacement and upgrade with Simplified Head Assembly (SHA)
Project is to prevent possible degradation of the material of the Krško NPP reactor head in a manner that is in the nuclear industry known as Pressurized Water Stress Cracking Corosion (PWSCC) phenomenon. Because the original reactor head for the Krško NPP is made using the sensitive material to PWSCC (Alloy 600 material and welds 82/182), the Krško NPP took a proactive approach and decided to replace the head in advance.
The design of the new head uses modern materials based on Alloy 690 and 52/152 quality welds. At the same time modification upgrades the SHA, which will allow for simplified handling. Change is reflected in increased safety and benefit of saving time in future outages. The main contractor of the project is Westinghouse, USA. Local consortium Sipro / IBE has developed design documentation for incorporating the change to the existing plant systems, and for the licensing in accordance with 10CFR50.59 regulations. Reactor vessel head is a nuclear safety related component ASME Code III Class 1. It is forging composed of flange and the dome in one piece. Head is equipped with 33 sets of CRDM, 3 pcs of CETNA, RVHVS and ICCMS piping, DMIMS sensors, removable ductwork for CRDM cooling, CRDM missile shield, cables and connectors, connector panel, ifting cable bridge, lifting seismic tie-rods, thermal insulation and radiation protection. The scope provides a stress calculations per ASME Code, fracture mechanics analysis, analysis of seismic and LOCA accidents, seismic qualification of equipment for the OBE and SSE seismic events, NUREG-0612 analysis, code reconcilations with the original ASME design code 1971 Edition with 1972 Addenda, etc. Modification is implemented in the outage 2012.
Picture 1: Main components of RVCH and SHA
Picture 2: RVCH and SHA in the operating position (3D model by Westinghouse)
Picture 3: New reactor vessel head ready for lifting to Reactor building
Picture 4: Container with original reactor vessel head for permanent and safe disposal in NE Krško
Project Manager: Mladen Debeljak, B.Sc.M.E
RTDBE – RTD Bypass Elimination
Nuclear Power Plant Krško in Slovenia is 2-loops Westinghouse design PWR (pressurized water reactor) plant. Its primary coolant system is provided with temperature measurements based on high quality resistance temperature detectors (RTDs). Temperature information feed into Westinghouse ACS 7300 racks in the control room for monitoring, reactor control and protection.
Sipro participated with Westinghouse in redesign of the original narrow range temperature measurement system for NPP Krško and thus contributing to plants continuous update and development. Short history overview shows that early PWR designs were based on assumption that the hot leg temperature is uniform across the pipe, so that temperature was measured directly in loop piping at only one location.
Temperature streaming effects were identified in late 1960s caused by incomplete mixing of the coolant leaving regions of the reactor core at different temperatures, so the location of measurement became important. The RTD bypass system was then designed as a good solution for effects from temperature streaming, but operating experience has now shown new problems.
Two of the problems should be highlighted: (1) failures of equipment causing primary leakage and are large contributor to unscheduled plant downtime costs, and (2) RTD bypass becomes location with high radiation level causing very high exposures for maintenance people.
Westinghouse has been contracted to modify the system. Their vision was to remove the entire bypass piping system and insert the temperature detectors directly into the coolant loop. Thus removing all of the operating, maintenance issues and the crud deposits associated with the piping. Also by increasing the number of RTD detectors and improving the protection and control logic, the 7300 protection and control system was to gain redundancy, operating margins and stability.
Although the 7300 is of 70's vintage it is safety certified and reliable analogue computer solution used in many NPPs and Westinghouse still provides support. The design change as provided has not been implemented by Westinghouse on any of two loop plants so far, so that Krško become top-design reference in this category of PWRs. Sipro was tasked with doing detailed site walk downs and recording of as found status of systems, structures and components (mechanical, piping, civil, structural, cabling etc.).
Our engineers inspected sites in the reactor building, auxiliary buildings and main control room, where the 7300 system is located. Major project milestones before the implementation of the change were the delivery of project documentation needed for installation, testing and licensing. Design descriptions, Analyses and calculations, Bill of material, Parts lists, Component lists, Installation and Test instructions and more than 600 detailed technical drawings have been included.
Picture: RTD-bypass elimination cabling design for NPP Krško
Sipro designed detailed cable routing from the new temperature detectors in the field to the Main Control Room. An example of this is shown on the picture of conduit layouts around the reactor primary coolant loop No. 1. The cabling solution considered all required nuclear standards and technical requirements in regards to various aspects of safety, including plant specific seismic design criteria.
During the outage and while installation works took place, our engineers were engaged during implementation of changes in the plant and supported all project partners to resolve any last minute issue, as well as final commissioning and preparation of final plant documentation and project closeout. The new measurement system with RTD-bypass eliminated is now in use and plant is at 100 % power.
Project Manager: Mladen Debeljak, B.Sc.M.E.
CZ Chillers Replacement
Based on the demands of Nuclear power plant Krško, we established project documentation for replacing chillers in CZ system, which are intended for supplying cooling water for HVAC system (Heating, Ventilation and Air-Conditioning System) in the main control room.
The project is the answer to the demands of Montreal protocol 1987, which dealing with the protection of the ozone layer demands the replacement of freon chillers with the advanced ecological media. For this reason air chillers were chosen, which also solves the problem regarding the accumulation of dirt in previous chilling system, as it used water from the River Sava.
Picture: 3D Piping Layout - inside the building
The manufacturer of the chosen chillers is AAF/McQuay and is labeled ALS »E« XE 196.2 ST 134. A chilling unit has a refrigerating power of 200 tons or 700 kW. Three units shall be built in. Two of them are placed on the detached safety bus-bar, the third one as a possibility of connecting to bus-bar of previous two. The project engineering consists of preparing the construction documentation for seismic foundations of the units and retaining walls, the 3D and 2D schemes of pipe-lines (performed with the use of licensed software program AutoPlant). Seismic calculations of the steel construction and modification of electricity supply by the separation of safety bus-bars, as well as automatic control and over voltage protection was within the scope of modification.
Picture: 3D Piping Layout - outdoor
Project Manager: Mladen Debeljak, B.Sc.M.E.
Work Platform
Sipro established project documentation for Nuclear power plant Krško working platforms and access ladders installation in various locations inside and outside of the radiological controlled area, as well as in the reactor building. This involves locations which were not accessible for maintenance, examinations or operation. The project outside the reactor building is labeled 530-AB-M, while the project inside the reactor building is labeled 632-AB-L.
Picture: Model of working platform
Both are classified Non-Nuclear Safety Related. Working platforms are schemed as steel load-bearing constructions with design capability 5000 N/m2. Doing that, we followed two types of regulations; the ANSI/ASME regulation was followed inside the reactor building, on other parts we followed the Euronorm regulations. All the constructions outside the reactor building are made of black steel St42-3 quallity, constructions inside reactor building are from stainless steel AISI304 grade. All constructions are manufactured as welded and bolted, and anchored to the existent concrete structures. Some of them are bolted to the existent steel structures. We calculated static and dynamic load by using license software, including seismic load.
Project Manager: Mladen Debeljak, B.Sc.M.E.
SX Sampling Panel Replacement
In association with the companies SWAN AG from Switzerland and Iskra Sistemi from Slovenia we thoroughly updated the on-line process water analysis equipment in Nuclear power plant Krško. We also integrated modernization into process information system.
Turbine Building SX sampling panel SX101RCK-001 have been replaced due to the old, outdated, obsolete equipment, corroded parts and requirement for introduction of state-of-the-art chemical analyzing instrumentation. The rack was difficult to maintain in operable condition. It was also the case with ChemNet application. The new replacement rack has housed SWAN analyzers which have been connected with digital Profibus DP network to SIMATIC AS416 SX001PLC. The PLC has been installed in separate panel with the other IT equipment - server, I/O unit, UPS, etc. The PB network have connected total of 31 chemical analyzers located at various plant places. The control system has been based on SIMATIC PCS7. One Modbus data link to PIS Level 2 F&M2 in DEH room was provided.
Picture 1: Turbine Plant Sampling Panel
As a part of upgrade the existing cooling rack SX907HCL-001 has been replaced. Electrical and IT equipment was installed in two panels, SX101PNL001 and SX101PNL002 respectively.
Additional new analyzer rack has been provided for CY108TNK-001 sodium analysis. The rack SX914RCK-001 has housed analyzer AIT4736, sample pump and sample preparation equipment. The analyzer has been connected with Profibus DP network to SX001PLC.
Picture 2: Sample Cooler Rank
The replacement of existing equipment and installation of new one has been partially performed on-line, but major activities were done in Outage R06.
Project Manager: Božidar Linke, B.Sc.E.E.
