AIR LEAKAGE STAKES: EXAMPLE IN NUCLEAR POWERPLANT
The Role of the Compressed Air Distribution Circuit (SAR)
Circuit SAR is made to distribute compressed air in regulation to valves with pneumatic control. This type of valve can be found on many levels into a nuclear powerplant: steam processing and distribution circuits, cooling circuit, chemistry, sampling, etc...
Many supplied gears are Important For Safety. This circuit ensures their availability and manoeuvrability. Circuit SAR is also partially Important For Safety.
Stakes for a Nuclear Powerplant
Air Leakages are not easily audible in the noisy primary pumps environment. By the network extent and the significant valves quantity on this circuit, air leakages volume can be consequent. And thus budget can be consequent.
But stakes go further. Within the Engine Building, circuit SAR supplies sampling, volumetric and chemical control, boron (isotope capturing neutrons) and water adding, cooling circuits and so on... as many major elements which must absolutely be available.
With a too important leak-flow within the Engine Building, the nuclear energy policy does not authorize to restart. Outage and unproductive days are expansive; so tracking and sealing off leaks is an important matter.
Workers qualified to this research know the difficulty to reach some sections. MMC’s high technology equipment is the most adapted to this configuration. This ultrasounds sensitive tool with its parabola and its laser aiming is terribly effective.
It is possible to quantify air leakages. On this basis, we can easily determine which leaks to seal first and which not. With this information, you can avoid to send teams in highly dosing environment to repair insignificant leaks; interesting into the ALARA step.
Recently, MMC made air leakage testing in a french nuclear powerplant. This operation had well quickly driven to reduce the leak-flow indeed below the acceptable criterion of 180 Nm³ per day.
A unit was having a leak-flow exceeding 400 Nm³ per day. Our teams allowed to effectively reducing the outage duration while bringing back the leak-flow to 120 Nm³ per day. More than a substantial economy for the power station, it was a great result to EDF which commits itself each day provide to the consumer.
Availability, reactivity and effectiveness of our teams were the key driving to this success.