scope:

SCOPE AND GENERAL REQUIREMENTS

ASPECTS OF CONSTRUCTION COVERED BY THESE RULES

Subsection NE establishes rules for material, design, fabrication, examination, inspection, testing, and preparation of reports for metal containment vessels.

RULES FOR CLASS MC CONTAINMENT VESSELS

(a) Class MC containment vessels shall be constructed in accordance with the rules of this Subsection, except as provided in NCA-2134(c). Only containment vessels and their appurtenances shall be classified as Class MC. Piping, pumps, and valves which are part of the containment system (NE-1130) or which penetrate or are attached to the containment vessel shall be classified as Class 1 or Class 2 by the Design Specification and meet the requirements of the applicable Subsection. Figure NE-1120-1 shows some typical penetrations with different Class designations.

(b) Subsection NE does not contain rules to cover all details of construction of Class MC containment vessels. The Certificate Holder shall provide details of construction which will be consistent with those provided by the rules of this Subsection. These details of construction shall be subject to the approval of the Owner or his designee, and acceptance by the Inspector.

BOUNDARIES OF JURISDICTION

The containment system includes (a) through (c) as follows:

(a) the containment vessel;

(b) all penetration assemblies or appurtenances attached to the containment vessel;

(c) all piping, pumps, and valves attached to the containment vessel, or to penetration assemblies out to and including any valves required to isolate the system and provide a pressure boundary for the containment function. Classification of such items shall be given in the Design Specifications (NCA-3250 and NE-1120). 

Boundaries of the Containment Vessel

The Design Specification shall define the boundary of a containment vessel to which piping or another component is attached. Figure NE-1132-1 shows typical jurisdictional boundaries. The boundary shall not be closer to the containment vessel than:

(a) the first circumferential joint in welded connections (the connecting weld shall be considered part of the piping);

(b) the face of the first flange in bolted connections (the bolts shall be considered part of the piping);

(c) the first threaded joint in screwed connections.

Boundary Between Containment Vessel and Attachments

Attachments

(a) An attachment is an element in contact with or connected to the inside or outside of the pressure retaining portion of a containment vessel.

(b) Attachments may have either a pressure retaining function or a nonpressure retaining function.

(1) Attachments with a pressure retaining function include items such as:

(a) pressure boundary stiffeners;

(b) vessel opening reinforcement.

(2) Attachments with nonpressure retaining function include items such as:

(a) thermal sleeves and turning vanes;

(b) vessel saddles, support and shear lugs, brackets, skirts, and other items within the containment vessel support load path.

(c) Attachments may also have either a structural or nonstructural function.

(1) Attachments with a structural function (structural attachments):

(a) perform a pressure retaining function;

(b) are in the containment vessel support load path.

(2) Attachments with a nonstructural function (nonstructural attachments):

(a) do not perform a pressure retaining function;

(b) are not in the containment vessel support load path;

(c) may be permanent or temporary.

Nonstructural attachments include items such as nameplates, insulation supports, and locating and lifting lugs.

Jurisdictional Boundary. The jurisdictional boundary between the containment vessel and an attachment defined in the Design Specification shall not be any closer to the pressure retaining portion of the vessel than as defined in (a) through (g) below. Figures NE- 1132.2-1, NE-1132.2-2, and NE-1132.2-3 are provided as an aid in defining the boundary and construction requirements of this Subsection.

(a) Attachments cast or forged with the containment vessel and weld buildup on the vessel surface shall be considered part of the containment vessel.

(b) Attachments, welds, and fasteners having a pressure retaining function shall be considered part of the containment vessel.

(c) Except as provided in (d) and (e) below, the boundary between the containment vessel and an attachment not having a pressure retaining function shall be at the surface of the vessel.

(d) The first connecting weld of a nonpressure-retaining structural attachment to the containment vessel shall be considered part of the vessel unless the weld is more than 2t from the pressure retaining portion of the vessel, where t is the nominal thickness of the pressure retaining material. Beyond 2t from the pressure retaining portion of the vessel, the first weld shall be considered part of the attachment.

(e) The first connecting weld of a welded nonstructural attachment to the containment vessel shall be considered part of the attachment. At or within 2t from the pressure retaining portion of the component the first connecting weld shall conform to NE-4430.

(f) Mechanical fasteners used to connect a nonpressureretaining attachment to the containment vessel shall be considered part of the attachment.

(g) The boundary may be located further from the pressure retaining portion of the containment vessel than as defined in (a) through (f) above when specified in the Design Specification.