What components are in what class?

[leaning]

Hello!

This seems like an easy question, but even in digging through the B&PV Code, I can't find any good words:

Div 1 (Subsection NB) applies to Class 1 components, Subsection NC applies to Class 2 components, and Subsection ND applies to Class 3 components.

Ok, I got that. But what components are considered Class 1 (and 2 and 3)?

Is there a list or criteria somewhere? What I want is to be able to input a component and then something spit out "That is Class 2", etc.


???

I appreciate the help!

Lost

 

[Duwe6]

Class 1 components are in the Reactor Primary System, as in the items that circulate the reactor water. In a PWR, these are all in the reactor building, closed loop flow from reactor to steam generator to pump and back to reactor.

On a teakettle - BWR - the primary system extends through the turbine, as the steam is made by boiling water in the reactor proper. I'm not sure where the Class 1 boundary is in a BWR.

Class 2 items are those that have been designated as essential for the safe shutdown of the plant.

Class 3 are items that are essential for operating the nuclear end of the plant. Thus the turbine in a PWR is not Class 3.

This is the "Cliff Notes" version. Anything more accurate depends on the specific design of the specific plant, and what the design engineers and NRC deemed appropriate. Meaning you gotta see the approved spec's or current drawing. Nothing else is acceptable for nuke work.

People thought we were building power plants. Actually we were building the biggest Swiss Watches on the planet. Tolerances are simple -- if it is not essentially perfect, cut it out and start over.

 

[leaning]

Duwe6,

Thanks for that! And here is the answer from ASME themselves which mirrors what you said:

The following was taken from

http://www.edilex.fi/stuklex/en/lainsaadanto/saannosto/YVL2-1

which should address your question:

Systems classification

Safety Class 1

a. Reactor fuel.
b. Primary circuit components whose rupture would result in a leakage of such magnitude that it could not be compensated for by the make-up water systems of the nuclear power plant. In conformity with this principle, the following primary circuit components remain outside Safety Class 1:
o small-diameter pipes (inner diameter not more than 20 mm)
o components connected to the reactor coolant system through a passive flow-limiting device and which, if ruptured, do not cause a leak larger than that caused by the rupture of a 20 mm pipe, as well as
o components which, in the event of their failure, can be isolated from the reactor coolant system by two successive, automatically closing valves whose closing time is short enough to allow for normal reactor shutdown and cooldown.

Safety Class 2

a. Primary circuit components not assigned to Safety Class 1.
b. Systems and components required for a reactor trip.
c. Emergency core cooling systems intended for loss-of-coolant accidents.
d. The boron supply system required to shut down the reactor or to maintain it in a sub-critical condition during a postulated accident.
e. A decay heat removal system for circulating the water of the reactor coolant system.
f. At a PWR plant, the part of the make-up water system which is bounded by make-up water pumps and the primary circuit.
g. The following parts of the steam and feed water systems
o at a PWR plant, the part inside the reactor containment that is bounded by the outermost isolation valves
o at a PWR plant, the part of the emergency feed water system of the steam generators that is bounded by the emergency feed water pumps and steam generators, and
o at a BWR plant, those parts of the steam system outside the reactor containment that are bounded by the isolation valves and the subsequent shut-off valves.
h. The reactor containment and related systems required to ensure containment integrity in a postulated accident. Such systems may be for example:
o the containment spray system
o other systems intended for the reduction of pressure and temperature within the containment
o systems to prevent the formation of an explosive mixture of gases
o personnel and material locks, penetrations and other equivalent structures, and
o isolation valves of the reactor containment other than those included in the primary circuit, and parts of the piping penetrating the containment that are bounded by the valves.
i. Supporting structures of the primary circuit
j. Structures, such as emergency restraints and missile barriers, which protect components in Safety Class 1.
k. Internals of the reactor pressure vessel that support the reactor core and are important for its coolability.
l. Storage racks for fresh and spent fuel.
m. A protective instrumentation and automation system for starting a reactor trip, reactor emergency cooling, isolation of reactor containment or other safety function necessary in a postulated accident.
n. Electrical components and distribution systems necessary for the accomplishment of safety functions of systems in Safety Class 1 and 2.
o. Electrical power supply equipment ensuring electricity supply to Safety Class 2 components upon loss of both offsite power and power supplied by the main generators.


Safety Class 3

a. The boron supply system bounded by the borated water storage tank in so far as the system or parts thereof are not classified to a higher safety class.
b. At a PWR plant, those parts of the reactor volume control system that are not assigned to a higher safety class.
c. At a PWR plant, those parts of the emergency feed water system that are not assigned to Safety Class 2.
d. Systems needed for the cooling and pressure relief of the primary circuit, if they are not classified to a higher safety class.
e. Cooling systems, including their cooling water channels and tunnels, essential for the removal of
o reactor decay heat
o decay heat from spent fuel stored outside the reactor
o heat generated by Safety Class 2 components
o heat generated by the above-mentioned systems themselves
into the ultimate heat sink, and which do not belong to a higher safety class.
f. Parts of the sealing water, pressurised air, lubricating, fuel, etc systems necessary for the start-up or operation of systems in Safety Classes 2 and 3.
g. Systems for treating liquids or gases containing radioactive substances the failure of which could, compared to normal conditions, result in a significant dose increase to a plant employee or a member of the public.
o Examples of such systems are:
o reactor cooling water cleanup system
o sampling systems of the primary circuit
o treatment and storage systems for liquid wastes, and
o radioactive gas treatment systems.
h. Ventilation systems that reduce the radiation exposure of employees or the releases of radioactive materials into the environment. Below are examples of the functions of these systems:
o maintaining of pressure differences in the reactor building and filtering of its exhaust air (including the containment with its surrounding spaces)
o ventilation of those rooms in the auxiliary building where radioactive contamination could occur
o ventilation of the spent fuel storage
o ventilation of quarters containing radioactive waste
o ventilation of laboratories where considerable amounts of radioactive materials are handled, and
o securing of working conditions in the control room and other rooms requiring continued stay during accidents, in case the air on-site contains radioactive or other hazardous materials.
i. Air cooling and heating systems in rooms containing components classified to Safety Classes 1, 2 and 3; the systems are needed to maintain the temperature required for ensuring reliable functioning of the equipment, taking into account extreme outdoor air temperatures and the waste heat released in these rooms.
j. Those reactor pressure vessel internals not assigned to Safety Class 2.
k. Nuclear fuel handling and inspection systems whose malfunction could endanger fuel integrity.
l. The following hoisting and transfer equipment:
o those parts of the control rod drives that are not assigned to Safety Class 1 or 2
o the reactor building main crane
o equipment needed for the lifting and transfer of nuclear fuel.
m. Storages of spent fuel and liquid wastes, including pools and tanks.
n. Buildings and structures designed to
o protect or support equipment in Safety Classes 2 or 3 and the failure of which could endanger the integrity of the equipment
o protect workers to assure their ability to maintain functions important to safety in accident conditions.
o. Concrete structures inside the reactor containment other than those assigned to Safety Class 2.
p. Instrumentation and automation systems and components required for the following functions and not classified to a higher safety class:
o reactor power limitation systems
o control of reactor main parameters (power, pressure, coolant volume)
o monitoring and control of safety functions during accidents
o monitoring and control of reactor power peaking
o monitoring and control of safe plant shutdown from the main and standby control rooms
o monitoring of reactor criticality during fuel loading
o monitoring of primary circuit leaks
o monitoring of hydrogen and oxygen concentrations inside the containment
o monitoring of primary circuit water chemistry
o on-site radiation monitoring during accidents
o monitoring of radioactive releases
o monitoring for radiation in rooms.
q. Electrical components and electric power distribution systems required to accomplish the safety functions of Safety Class 3 systems.
r. Systems designed to ensure the integrity of the reactor containment or to limit releases especially in a severe accident. Examples thereof are:
o systems limiting the containment pressure
o systems intended for the control and filtering of releases out of the containment
o air circulating and filtering systems that clean the containment air space
o systems that prevent the formation of an explosive gas mixture
o systems intended for the monitoring of the condition of the reactor and the containment, and
o systems and components required for cooling a molten core and for ensuring the integrity of containment penetrations and other openings.



Thanks, all!

Respectfully,
Leaning