Originally embedded within the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, as we speak the Operation and Maintenance of Nuclear Power Plants customary for inservice testing of pumps, valves, and sure dynamic restraints (snubbers) stands by itself. Among different issues, the inservice testing program detects and displays valve security perform readiness and degradation for present nuclear vegetation and new builds.
The American Society of Mechanical Engineers (ASME) is without doubt one of the oldest standards-developing organizations within the U.S. However, its work extends properly past the states. It has places of work in Beijing, China; Brussels, Belgium; and New Delhi, India. Its said mission is: “To serve numerous international communities by advancing, disseminating and making use of engineering information for enhancing the standard of life; and speaking the joy of engineering.”
ASME offers particular operations and upkeep (OM) codes to carry out preservice and inservice inspections and testing for lots of the elements utilized in present and new nuclear reactor designs. Between the 1960s and 1980s, lots of the inservice testing (IST) necessities had been embedded within the ASME Boiler and Pressure Vessel Code, Section XI, which primarily handled standardized weld/element inservice inspection (ISI) examinations as a substitute of element useful testing.
The ASME OM Standard Committee was chartered to develop ASME’s Operation and Maintenance of Nuclear Power Plants customary (OM Code), separating the “pump and valve” necessities from Section XI to enhance effectivity when creating and refining IST necessities and acceptance standards. The OM Code necessities apply to:
■ Pumps and valves which might be required to carry out a particular perform in shutting down a reactor to the protected shutdown situation, in sustaining the protected shutdown situation, or in mitigating the results of an accident.
■ Pressure aid gadgets that shield techniques or parts of techniques that carry out a number of of the three capabilities recognized above.
■ Dynamic restraints (snubbers) utilized in techniques that carry out a number of of the three capabilities recognized above (Figure 1).
|1. Snubbers. Mechanical and hydraulic snubbers are designed to guard piping from extra shock or sway attributable to seismic and different transient forces. During regular operation, snubbers permit motion, akin to thermal enlargement or contraction. However, when an impulse occasion happens, the snubber turns into activated and acts as a restraint machine. Courtesy: Creative Commons/Sylvlba|
The function of IST is to detect and monitor for degradation in elements designated as ASME Class 1, 2, or three techniques and elements. Class 1 (Quality Group A) contains techniques and elements containing reactor coolant and forming the reactor coolant stress boundary. Items akin to reactor security valves, reactor coolant stress boundary isolation valves, and power-operated aid block valves match into the Class 1 class. Class 2 (Quality Group B) objects are non-Quality-Group-A techniques and elements vital to security, akin to emergency core cooling, reactor shutdown, and residual warmth removing techniques. Class three (Quality Group C) techniques and elements are vital to security, however not designated Class 1 or 2. Some examples embody diesel generator help techniques, and repair water and element cooling water pumps.
IST offers affordable assurance that safety-related elements will carry out their security perform when activated. The course of allows utilities to systematically establish issues and take motion to restore or change safety-related elements, if they’re degraded. IST just isn’t supposed to find out element operability. Rather, Technical Specification (TS) surveillance testing is meant to confirm that elements and techniques are operable and have been for the reason that final TS take a look at. IST is meant to offer confidence that the element will stay operable till the following TS take a look at.
The OM Code is break up into three divisions. Division 1,…