Nuclear power pneumatic valve technical requirements

nuclear power pneumatic valve, due to its special, complicated, bad working condition, combined with the enormous quantity wide, so the demand is higher. Nuclear power pneumatic valve working conditions:
nuclear power pneumatic valves in addition to its working environment is complex, the medium temperature, pressure and radioactivity level of rigour is also very special.
nuclear power transmission medium pneumatic valve are mainly: saturated steam and condensate, radioactive steam heavy water, corrosive, radioactive irradiation, dilute sulphuric acid and alkali medium, carbon dioxide, sodium, helium, oil, vacuum and other fluid medium.
once the drift diameter pneumatic valve working conditions on the road is the most complex, in the present stage of nuclear power plant steam parameters than the thermal power plant steam parameters ( Pressure. MPa, temperature ℃) Lower, but the nuclear power plant operating conditions is much more complicated. In the liquid metal fast neutron reactor coolant device, steam parameter as the highest ( The temperature of the steam turbine before for ℃, the pressure is zero. MPa） 。 Nuclear power pneumatic valve technical requirements
according to the actual working condition of the pneumatic valve running nuclear power, nuclear power pneumatic valve its technical characteristic and the request is higher than coal-fired power pneumatic valve. The technical requirements of nuclear power pneumatic valves in addition to conventional pneumatic valve technical requirements, but also focus on medium impurity pollution, environment temperature, operating temperature, environment humidity, radioactive, dc power supply and voltage fluctuation, the earthquake and vibration stability under the condition of technical requirements, security level, and so on.
1.
a) nuclear power pneumatic valve design Strength design
nuclear power pneumatic valve design, strength calculation is necessary. In addition to the strength of the conventional calculation, finite element analysis and seismic analysis, pneumatic valve of nuclear safety level, also asked for: the limit of a thin film stress calculation, a thin film stress + the limits of the bending stress calculation, and loop rev - — Stop cycle variations in the primary and secondary stress of about the limit of the calculation, in addition to the loop rev - — Stop working outside of the primary and secondary stress change of amplitude limit calculation and fatigue analysis.
b) Structure design of the
because most medium radioactive nuclear power systems, are not allowed to have any leaks, so the structural design of packing, corrugated pipe, pneumatic pneumatic valve seat seal structure design is particularly important, The shape of the pneumatic valve body design, rules in ASME standard) 。
abroad, packing usually use multiple seal structure, Ω ring seal structure and packing layer sandwiched between saucer reed of the stuffing box seal structure. Corrugated tube combined bellows seal structure in general. For important high pressure pneumatic valve, pneumatic valve seat structure of forging. In addition, pneumatic valve and pipeline connection with butt-joint or socket welding structure.
2.
nuclear nuclear power pneumatic valve materials pneumatic valve materials must have good corrosion resistance, radiation resistance, impact resistance and resistance to intergranular corrosion. In general:
a) Pressure parts ASMEBPVC - must be used Ⅱ- D - The material requirements in table A and table B
B) Pneumatic valve stem and bearing bolt precipitation hardened steel is often used to manufacture the
c) Packing use graphite fiber, pure asbestos or expanded graphite
3. Nuclear power pneumatic valve actuator
the quality and performance of nuclear power pneumatic valve actuator is very important and key, must have the reliability of safe operation, at the same time, should be able to withstand the temperature, pressure, humidity, irradiation, earthquake damage, a maximum chemical pollution and the change of the power supply source, and must be under the situation of water loss and, still can work within the prescribed time limit, General standard for the day) 。
in addition, in addition to drive electric parts requirements with O ring sealing isolation with the external environment, drive the working condition of nuclear power should also be taken into account by its designer with high-pressure pneumatic valve fast operational problems ( General standard, pneumatic valve, CL 'the following its rapid operation time is in seconds) 。
(4) the test and inspection of nuclear power pneumatic valve
a) Nuclear power pneumatic valves require regular hydrostatic test - — On shell test, pneumatic valve strength test, seal test, pneumatic seat sealing test, packing seal test;
b) With actuator, such as electric, pneumatic shock test pneumatic valve;
c) The pneumatic valve and static pressure in all forms of operation life test;
d) The importance of the primary circuit pneumatic valve must also after cold, hot and LOCA accidents ( The loss of coolant accident) The test.
( American standards such as ASME, Japanese JEM, on the test and inspection has made the detailed description, and provides the evaluation criteria. ）