MOTEL facility

The MOTEL (MOdular TEst Loop) test facility is a model of an SMR with resemblance to the design of the NuScale type SMR. MOTEL is designed applying the principle of the strong modularity. The major components of the facility are exchangeable for a functionally similar but in the internal design a different component. An essential feature of the MOTEL design is that the heater element is exchangeable.

The MOTEL facility includes primary side parts and a helical coil type steam generator for primary to secondary side heat transfer inside a compact pressure vessel. The primary system of MOTEL operates passively by natural circulation. MOTEL is scaled at approximately 1:2 in height, referring to publicly available dimensions of an integrated naturally circulating PWR. The total height and outside diameter of the MOTEL pressure vessel are approximately 7.4 m and 711 mm, respectively. Design pressure is 4 MPa and design temperature 250 °C. Electrical heating power is 1 MW, with an upgrade in the works for tripling the power supply.

The core heater rod bundle design is generic and does not directly represent the fuel design of any existing reactor type. The core element of MOTEL consists of 132 electrically heated heater rods, 145 dummy rods and 16 measurement rods (measurement probes). The heater rods are arranged in a rectangular grid with respect to each other, while a few of the heater rods in the grid are replaced by the measurement rods. The dummy rods are placed in between this grid.

An essential feature in the MOTEL design is the helical coil steam generator construction. A specific characteristic of this type of steam generator is that the secondary side flow and boiling takes place inside the steam generator tubes, whereas the primary side water flows outside the tubes, through the shell side of the steam generator tube bundles. The pressurizer is located at the top part of the pressure vessel. The pressurizer has two heating elements to adjust the primary pressure inside the test facility.

Characteristic	MOTEL test facility
Reference system	None – architecture similar to NuScale and MASLWR
Height scale (riser & downcomer pipelines, heat exchanger) (approximate)	1:2
Maximum pressure, reactor vessel	4 MPa
Maximum heating power	990 kW
Maximum temperature, reactor vessel	250 °C
Height of the vessel	7.4 m
Height of core	1.83 m
Height of the helical coil steam generator	1.3 m
Elevation difference from core midplane to steam generator midplane	3.23 m
Core outer diameter	0.6 m
Downcomer annulus gap (riser / core)	98 mm / 36 mm
Main material of components	stainless steel
Insulation material	mineral wool, aluminum cover plate