Post Fukushima & Safety Upgrades

Post Fukushima & Safety Upgrades

EdF - Mobile Cooling Systems for AGR

Background

In response to the Fukushima event in Japan in 2011, EdF Energy carried out an assessment of its UK nuclear power stations and its ability to respond to extreme weather events. It was identified during this process that there was a need for back-up equipment to provide additional provisions to support emergency response.

Our Solution

Ansaldo Nuclear Ltd was appointed to design, manufacture, assemble, test and provide support for the back-up system capable of assisting quick recovery of the nuclear power plant during and after potentially devastating events, like natural disasters. 

We designed a diesel driven, self-contained packaged unit, capable of extracting 500kWth of heat from 15 liters per second of spent fuel storage pond cooling water. This back-up unit can maintain the levels and temperature of the pond cooling water, giving enough time for the engineering teams to reactivate the on-site system or remove the spent fuel rods, avoiding potential safety and environmental risks.

The developed Ansaldo Nuclear Ltd JER pond water package cooler contains all the necessary equipment and systems required to be set in place, started and function autonomously for extended periods of time, with the option available to run from external bulk fuel sources if necessary.

All the equipment is housed and/or stored ready for transport on a fabricated skid unit, which in turn is mounted onto an off-road truck, ready for deployment if necessary.

This equipment includes:

  • Diesel driven generator complete with:
    • fuel supply systems and fuel storage tank; 
    • an exhaust system complete with spark arrestor;
    • a control panel and main circuit breaker.
  • A pond water to sea water heat exchanger rated for 500kW cooling duty at the maximum rated ambient environmental and fluid temperature conditions;
  • A pond water to air heat exchanger rated for 500kW cooling duty;
  • Valves, instrumentation and ancillary equipment;
  • Pipe work system made of stainless steel for the pond water and sea water chemical composition and conditions;
  • A PLC control system and other electrical systems necessary for the function of the system;
  • Four floatation compensated pumps for extracting water from the pond;
  • One boost pumps to overcome the internal pressure losses associated with the system components and returning water to the pond;
  • Interface equipment such as electrical power and control cables, lay-flat hoses and couplers.

Chernobyl: Design and Supply of the IAMS

ANSALDO NUCLEARE is the leader of a Joint Venture Partnership which includes also: Thales Alenia Space Italy, CESI, and Atom Remont Service.

The IAMS will be installed inside the Shelter Object and within the exclusion zone surrounding the ChNPP, where the site is contaminated and access to the areas is restricted.

IAMS is composed of four lower-level systems, receiving information directly from sensors, and one upper-level system, performing functions of a centralized information system linked to the lower-level systems and the external systems (these latter not included in the scope of this contract).
The five IAMS Systems are:

  • Stationary Radiation Monitoring System (SRMS)
  • Nuclear Safety Monitoring System (NSMS)
  • Structure Monitoring System (SSMS), 
  • Seismic Monitoring System (SMS) and 
  • Integrated Monitoring System (IMS).

Each lower-level system is developed as a distributed system consisting of measuring sensors connected to several Data Acquisition Units (DAU) which are linked to a Data Collection Unit (DCU). The link of all DAU, but SMS, to DCU is obtained by a ring of fiber optic cable, while the data from SMS DAU to their DCU is obtained by radio links, since each SMS DAU is housed in a small building (also included in the scope of this contract) located all around ChNPP at a distance of 15-20 Km.

Each DCU is linked to the upper level IMS.

The four DCU and main part of IMS (servers) are contained in 4 cabinets:

  • IMS basically includes also 3 workstations, 11 monitors and 3 printers.
  • NSMS contains 6 DAU and 19 gamma/neutron Detection Units.
  • SRMS contains 18 DAU and 58 gamma, alpha, beta sensors.
  • SSMS contains 8 DAU and 42 sensors (strain gages, seismometers, inclinometers, linear displacement)
  • SMS contains 5 DAU and 5 accelerometers

IAMS basic objectives are the following: Improvement of radiation, nuclear and environmental safety; Improvement of emergency preparedness.

IAMS basic functions are the following: Collection and storage of data on parameters of the Shelter status and the ChNPP local area required for consequent safety analysis in order to timely identify negative tendencies, which may result in degradation of the Shelter safety level; Display of visual and/or auditable data characterizing the Shelter monitored status.

The scope of supply includes detailed design, procurement, safety reports and support for Ukraine Safety Authority licensing documentation, delivery, installation, set-up, training of personnel and commissioning of the whole system.

Cernavoda: Engineering Services for CCW System

Background

The Cernavoda NPP consists of five 700 MWe CANDU-6 Units, sited on the Danube river, 150 km East of Bucharest.

Since 1990, ANSALDO Nucleare, in joint venture with the Canadian company AECL, managed the realization and the initial operation of the Unit 1, connected to the grid in July 1996. This Unit provides, since then, about 8 % of the Country's electrical power requirement, with a remarkable average load factor of 87%.

Our Solution

Ansaldo Nucleare is providing assistance services to the Operation and Maintenance of the Unit 1, through its own qualified staff.

Realization of Cernavoda NPP Unit 2 was completed in 2007 and started full power electricity production in October 2007. Since then ANSALDO Nucleare is providing assistance services to Operation and Maintenance also for unit 2.

Service Activities provided by ANN can be grouped in two categories:

  • Spare Parts Supply and Maintenance Assistance for Equipment Overhauling
  • Engineering Activities and Technical Assistance to Operation

     ANN Service activities for Cernavoda NPP unit 1 and 2 include the following tasks:
    - Support Home Office Engineering
    - Procurement Services
    - Support to Site Activities

    Some examples of the technical support provided by ANSALDO NUCLEARE service staff are described in the following:
  • Spare Parts Supply and Maintenance Assistance for Equipment Overhauling
  • Supply of Spare Parts for BOP Control Valves (2007-today)
  • Equipment Overhauling and Supply of Spare Parts for BOP Condenser and Feedwater Pumps (2002-today)
  • Expansion Joints In-service Inspection and Replacement (2005)
  • Replacement of Pneumatic Control Circuits of Boilers Level Control Valves (2013-2014)

Cernavoda Post Fukushima Stress Test

Ansaldo Nucleare was involved in the Stress Tests on the two operating CANDU Units of Nuclear Power Site of Cernavoda (Romania) on which Ansaldo Nucleare has been the responsible part of the Balance of Plant and Electric Power Generation from the design phase to the commissioning phase. The "Stress Tests" developed by ENSREG (European Nuclear Safety Regulators Group) are defined as targeted reassessments of the safety margins of nuclear power plants, against the occurrence of external events challenging the plant safety functions and potentially leading to a severe accident.

Ansaldo Nucleare carried out the Stress Tests in cooperation with the Plants Licensee SNN (Societatea Nationala Nuclearelectrica) and the CANDU Tecnology Owner AECL (Atomic Energy of Canada Limited). Ansaldo Nucleare had an on-site involvement with a multidisciplinary expertise task force covering all the aspects relevant to the plant safety margins, in plant design review and extended walk down inspections in the plant. Ansaldo Nucleare has played a role as technical leader in the plant safety margin assessment for external flooding initiating event, evaluation of potential flooding events caused by a beyond design basis earthquake and, as technical reviewer, in the earthquake design basis evaluation and margin assessment for loss of electrical power, loss of ultimate heat sink and severe accident management evaluation.

The stress tests resulted in reports outlining the reassessment of the safety margin provided by the plant design and of the configuration against beyond design events and the identification of the enhancements and protective measures capable of increasing the robustness of the NPP at the occurrence of those events.