In addition to the above changes, several further modifications have been implemented at RBMK plants. These measures consist of:. One more was under construction in Russia Kursk 5 , but it is now cancelled. There are three distinct generations of RBMK reactors having significant differences with respect to their safety design features:. In , Rosatom said it was considering operating lifetime extensions and uprating of its operating RBMK reactors. Following significant design modifications made after the Chernobyl accident, as well as extensive refurbishment including replacement of fuel channels, a year operating lifetime is seen as realistic for the MWe-class units.
In the Table below, the 'operating until' dates are the scheduled shutdown for these plants, with year lifetime extensions in some cases. Russia's long-term plans had earlier included the possibility of replacing the Leningrad units, at the end of their extended service life, by new MKER units. These are a modification of the RBMK design. The main differences are in the spacing of the graphite lattice in the core and the incorporation of passive safety systems.
Operational dates are subject to licence extension — see information paper on Nuclear Power in Russia. The design had several shortcomings, and was the design involved in the Chernobyl disaster. Major modifications have been made to RBMK reactors still operating. Pressure tubes Within the reactor each fuel assembly is positioned in its own vertical pressure tube or channel about 7 m long. Refuelling When fuel channels are isolated, the fuel assemblies can be lifted into and out of the reactor, allowing fuel replenishment while the reactor is in operation.
Graphite moderator A series of graphite blocks surround, and hence separate, the pressure tubes. Control rods Boron carbide control rods absorb neutrons to control the rate of fission.
Coolant Two separate water coolant loops each with four pumps circulate water through the pressure tubes to remove most of the heat from fission. Steam separator Each of the two loops has two steam drums, or separators, where steam from the heated coolant is fed to the turbine to produce electricity in the generator each loop has a turbogenerator associated with it.
Containment There is no secure containment in the sense accepted in the West. Positive void coefficient The term 'positive void coefficient' is often associated with RBMK reactors. Operating reactivity margin Although the definition is not precise, the operating reactivity margin ORM is essentially the number of 'equivalent' control rods of nominal worth remaining in the reactor core.
All operating RBMK reactors in the former Soviet Union had the following changes implemented to improve operating safety: Reduction of the void coefficient of reactivity. Improvement of the response efficiency of the emergency protection system.
Introduction of calculation programs to provide an indication of the value of the operating reactivity margin ORM, i. Prevention of the emergency safety systems from being bypassed while the reactor is operating.
In order to ensure adequate subcooling at the core inlet, the avoidance of modes of operation that cause a reduction in the departure from nucleate boiling DNB ratio of the coolant at the reactor inlet. Measures to reduce the void coefficient of reactivity were carried out by: The installation of additional fixed absorbers in the core to inhibit operation at low power.
Increasing the ORM from rods in steady state operational mode to The efficiency and speed of the emergency protection system was improved by implementing three independent retrofitting operations: Retrofitting of control rods with a design that does not give rise to water columns at the bottom of the channels. Scram shut down rod insertion time cut from 18 to 12 seconds.
The installation of a fast-acting emergency protection FAEP system. These measures consist of: Replacement of the fuel channels at all units except Smolensk 3. Replacement of the group distribution headers and addition of check valves. In June , The Hon. Mr Justice Haddon-Cave addressed delegates at Piper 25 a conference to mark the 25th anniversary of Piper Alpha offshore disaster in the North Sea, in which workers died. Piper Presentation Transcript.
Malcolm Brinded also discusses leadership and how good safety performance and good business performance go hand in hand:. This make 4 key points:. Aerossurance attended the excellent Edinburgh event. They defined these as:. Safety Intelligence the various sources of quantitative information an organisation may use to identify and assess various threats. Safety Wisdom the judgement and decision-making of those in senior positions who must decide what to do to remain safe, and how they also use quantitative and qualitative information to support those decisions.
He illustrates that presentation with two charts that show the differences in perception of safety at Metro-North :. When it comes to recommending your organisation to others:. The difficulty is that once a culture is set and norms are established, it can be hard to change the status quo.
Changing a culture of fear and blame can therefore be difficult. Leadership plays a vital role in driving forward such changes…. In the last few years our understanding of culture and how we take on cultural attributes has shifted away from the idea that culture is a homogeneous solid entity to the understanding that:. Organisations need to be confident that they are hearing all the safety concerns and observations of their workforce.
In these, originally the nuclear chain reaction and power output would increase if cooling water were lost or turned to steam, in contrast to most Western designs. It was this effect which caused the uncontrolled power surge that led to the destruction of Chernobyl All of the RBMK reactors have now been modified by changes in the control rods, adding neutron absorbers and consequently increasing the fuel enrichment from 1.
Automatic shut-down mechanisms now operate faster, and other safety mechanisms have been improved. Automated inspection equipment has also been installed. A repetition of the Chernobyl accident is now virtually impossible, according to a German nuclear safety agency report. Since over 1, nuclear engineers from the former Soviet Union have visited Western nuclear power plants and there have been many reciprocal visits. Over 50 twinning arrangements between East and West nuclear plants have been put in place.
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