Upper plenum

FIG. 17-60 Reverse-pulse fabric filter (a) filter cylinders (b) wire retainers (c) collars id.) tube sheet (e) venturi nozzle (/) nozzle or orifice (g) solenoid valve (h) timer (j) air manifold (k) collector bousing (l) inlet (m) hopper (n) air lock in) upper plenum. (Mikmpul Division, U.S. Filter Corp. )... 

Figure 3 shows the nodalisation of the HTTR-IS system model. The reactor consists of the internal flow path (P2), permanent reflector blocks (HS25), upper plenum (B4), reactor pressure vessel (RPV) (HS30), vessel cooling system, reactor core bypass flow (P10), lower plenum (B12) and reactor core. The... 

Fig. 18 Schematic of the primary coolant circuit of a BWR having external pumps. The regions are identified as follows (1) core channels, (2) core bypass, (3) upper plenum, (4) mixing plenum, (5) upper downcomer,...

CC Core channel CB Core bypass UP Upper plenum MP Mixing plenum UD Upper downcomer LD Lower downcomer RS Recirculation system JP Jet pump BLP Bottom lower plenum TLP Top lower plenum. . . . . ... 

CC Core channel CB Core bypass UP Upper plenum MP Mixing plenum... 

Sodium temperature (at outlet of the core) Sodium temperature (bounding the mam vessel) Sodium temperature (upper plenum)... 

HIGH RELIABILITY SIEELPRESSURE VESSELS ANO VESSEL SUPPOHT UPPER PLENUM THERMAL PROTECTION STRUCTURE PRESSURE VESSEL RELIEF... 

Reactor Internals o Permanent Reflector o Core Lateral Restraint o Core Support Floor Structure o Upper Plenum Thermal Protection Structure... 

Upper Plenum Thermal Protection Structures Failure Modes and Effects... 

Approximately 89 percent of the circulator helium flow passes through the upper plenum and traverses the active core through the coolant channels in the fuel elements. The remaining 11 percent bypasses the core in the coolant channels in the gaps between columns in the core and reflector and the control rod channels. The primary coolant, which passes through fuel... 

Guide Tubes The guide tubes for the control rods extend from the gamma shield downward through the top head of the reactor vessel and the upper plenum to interface with the plenum elements on top of the core. 

A seal member surrounds the upper end of each of the lower guide tubes. This member is supported by a bellows attached to the upper end of the lower guide tube and is intended to restrict flow between the upper core plenum and the relatively stagnant helium layer in the region between the upper plenum structure and the top head of the reactor vessel while permitting misalignment of these two large structures. 

A large diameter bellows permits limited misalignment of a seal member which engages the upper plenum structure and restricts the flow of hot helium to the relatively stagnant helium layer between the upper plenum structure and the pressure vessel. 

The Reactor Internals Subsystem (RISS) consists of the core lateral restraint (CLR), permanent side reflector (PSR), graphite core support structure (GCSS), metallic core support structure (MCSS), upper plenum thermal protection structure (UPTPS), and the hot duct. Figure 4.4-1 illustrates the location of the components of the RISS within the Reactor System. 

The core lateral restraint and the permanent reflector surround the core the graphite core support structure and metallic core support structure are located below the core the upper plenum thermal protection structure is located above the core and the hot duct is located within the cross duct between the reactor vessel and the steam generator vessel. 

As discussed in Section 4.1.2.2, the radionuclide control function which is performed by the upper plenum thermal protection structure is to limit chemical attack on the fuel by limiting fuel oxidation. This structure functions to provide protection to the upper vessel assuring primary coolant boundary reliability and restricting the possibility of air ingress to the core. 

The core lateral restraint, the permanent side reflector, the graphite core support structure, the metallic core support structure, and the upper plenum thermal protection structure are "safety related". The hot duct is not "safety related". 

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