20.08.2015   NUCLEAR REACTOR ENGINEERING

Plant Description

15.53. Should an electrical generating capacity of 1395 MW be desired, a plant would consist of nine reactor modules arranged in three identical 465-MW(el) power blocks, each with its own turbine generator. Thus, smaller plant sizes of 465 MW(el) and 930 MW(el) can be provided by using one or two of the standard power blocks. Steam generators, one for each module, are in a separate building. Thus, only the reactor modules themselves need be constructed to nuclear safety grade standards.

15.54. A summary of important system characteristics is given in Table 15.4. A reactor module is shown in Fig. 15.5. The core immersed in a pool configuration provides large thermal inertia. Primary sodium coolant is circulated by four electromagnetic pumps from an outer compartment of the vessel receiving cold discharge from two intermediate heat exchangers (IHXs) to a high-pressure plenum at the bottom of the core. Heated sodium leaving the core enters the surrounding pool, from which the IHXs are fed. Secondary sodium flow to the IHXs is provided by an electromagnetic pump in the steam generator facility.

General

Thermal-Hydraulic

Power

Thermal 1413 MW Electrical 465 MW

Primary Sodium

Inlet temp. 318°C (604°F)

Outlet temp. 485°C (905°F)

Flow rate 2.54 Mg/s Intermediate sodium Inlet temp. 282°C (540°F)

Outlet temp. 443°C (830°F)

Flow rate 2.27 Mg/s Peak linear heat rate 34.5 kW/m (10.5 kW/ft)

Reactor Vessel

Outer diameter 5.74 m Length 16.94 m Design pressure 0.24 MPa

Core Assembly Number

Control

Fuel 42 Internal blanket 25 Radial blanket 48 Radial shield 42 Control 6

System requirements (dollars) Burnup reactivity

swing 1.3 Temp, defect 3.6 Shutdown margin 1.0 Uncertainties 1.3 Total 6.2

Fuel

Composition, %, 27 Pu, 63 U, 10 Zr Assembly, 217 rods in hex. bundle Rod, O. D. 7.2 mm (0.283 in) Clad material, HT-9 ferritic alloy

REACTOR VESSEL AUXILIARY COOLING SYSTEM (RVACS)

 

CONTROL

— DRIVES (6)

"ROTATABLE

PLUG

„SEISMIC

ISOLATORS

 

-PRIMARY EM PUMP (4)

— SPENT FUEL STORAGE (1 Cycle) ‘ METAL FUEL (Oxide Alternative) ‘RADIAL SHIELDING

 

HIGH PRESSURE PLENUM

 
image337

Fig. 15.5. Advanced liquid-metal-cooled reactor module (General Electric Co.).

 

image338

15.55. Decay heat is normally removed by sending steam directly to the condenser. Natural circulation of secondary sodium to the steam generator is one passive backup. A second backup is by natural circulation of at­mospheric air around the containment (guard) vessel in the silo as shown in Fig. 15.5 for the reactor vessel auxiliary cooling system (RVACS).

15.56. The reactor modules, located in underground silos, rest on seis­mic isolators which decouple the systems from horizontal accelerations. Containment is provided by a guard vessel which backs up the primary vessel and an upper containment dome which backs up the head closure. During power operation, all sodium and cover gas service lines are closed with double isolation valves. Although there are no penetrations in the reactor vessel, the reactor vessel and containment vessel are sized so that if a leak should occur, the core and IHX inlets will always remain covered.