Rosatom implements 4 maintenance strategies: scheduled or time-based, condition-based maintenance, risk-centered maintenance, and run-to-failure.

Risk-centered maintenance or predictive maintenance assessing the risks is based on following algorithm:

1) Develop the list of critical equipment, the failure of which will causes to the NPP operation malfunction in order to NP-004 (Norms and Rules of the Regulator) or to the power decrease. In this case, the results of the probabilistic safety analysis and the results of the deterministic analysis are used.

2) Conduct continuous monitoring of changes in the technical condition of the equipment from the list to determine two criteria:

A) the probability of failure-free operation for a given operating time (for example, 20,000 hours),

B) or operating time at a given probability of failure-free operation (for example, P = 0.9995).

3) Determine the time of a potential failure occurrence so that it is sufficient for maintenance (cleaning, lubrication, oil or filter replacement, etc.). It is necessary for the equipment is being able to operate until the scheduled shutdown for repairs. Here, a procedure for changing the scope of repair work and assessing the duration (impact on the critical path) and changing the cost of repairs should be implemented.

4) If it is obvious that the equipment will not be able to operate until the NPP scheduled shutdown, then the NPP carries out the works

a) to change the planned dates for shutdown (shift to the left). Here, the NPP assesses the cost of “unburned” nuclear fuel and the fines from the system operator of the energy market,

b) to repair of equipment with the need for a short-term unscheduled shutdown of the power unit. Here, the NPP assesses the fines and the cost of an emergency shutdown of the power unit due to equipment failure.

5) Analyze the trends and fill in the report based on operating and repair experience, changing the equipment maintenance programme.

Important:

1) availability of reliable operating and repair statistic data

2) initial reliability of the equipment from the manufacturer, correct installation, correct operation in normal modes (without overloads),

3) reliable diagnostic tools, certified diagnostic methods and trained personnel to obtain reliable data,

4) distribution of responsibility between the equipment owner, diagnostic service and repair service for the equipment operability and technical condition,

5) availability of a fund of spare parts, components, equipment units for prompt replacement in order to minimize equipment downtime. Rosatom has created a repair exchange stock (for all plants), an insurance and operational stock (for each plant). The stocks’ set is reviewed by a group of experts annually taking into account the operating and repair experience and the procurement procedures.

At the moment, the predictive maintenance support software is at the pilot stage. Therefore it is too early to talk about the actual economic efficiency. The planned calculation showed that the technical and economic efficiency is present. Rosatom have a calculation technique for this purpose.

Hope I could clarify some items.

The cost savings for Predictive Maintenance come from less uplanned downtime of equiepment. The idea is we can detect an impending failure of an item, such as through noise moitoring of bearings. As an example, if you can determine an impending failure is going to happen in the near future, then you have some time window to fix the issue. In the mechanical example of a bearing, perhaps there is a contaminant in the oil. Changing out the oil is a lot easier job than replacing a bearning. Most person;s automobiles monitor the state of the oil in the care and determine how much 'Oil life" is left, verus doing an oil change every 3000 miles.

Such predictive maintenance can reduce overtime costs of fixing a failure versus preventing a failture. "You can pay me now, or pay me later".