Page 155 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Operational aspects of 3.4

experimental liquid metal
facilities

G. Kennedy, I. Di Piazza, S. Bassini
SCK CEN, Mol, Belgium

Generally, the operation of liquid-metal facilities and the associated components
should not be vastly different from conventional systems operation. However, as
introduced in the beginning of this chapter, the relatively high temperatures and prop-
erties of liquid metals present some unique operational and safety aspects. This section
therefore intends to inform new and current users of liquid-metal facilities about some
typical but unique aspects of liquid-metal facility operation, previously experienced
on existing facilities. Following good operational practices is important for the safety
of personnel; protection of experimental infrastructure investments; and producing
high-quality, representative, and repeatable experimental data.
While not necessarily specific to liquid-metal facilities, it is customary in many
system engineering processes to develop a functional performance specification
(FPS). Such a functional specification is not intended to describe the details of the
system implementation, but rather describes how the system should function during
normal operation and during off-design scenarios. The FPS also defines the proposed
interaction between the user and the software system and in turn defines or forms part
of the operational procedures.
Defining so-called system states and modes is a commonly used method to describe
the functionality of a system. Fig. 3.4.1 illustrates a very simplified mode and state
flowchart that could be applied to a liquid-metal facility. With reference to the exam-
ple state flow diagram in Fig. 3.4.1, the typical generic states are identified and tab-
ulated in Table 3.4.1.
Using a state and mode approach, as shown in Fig. 3.4.1, allows the functional
requirements to be uniquely defined for each state. For these states to exist indepen-
dently, there must also be transitions (sequences) between these states. For example,
filling, draining, purging (gas conditioning), coolant circulation start-up and shut-
down, emergency shutdown (e.g., in case of a leak), heating, and cooling are typical
transition sequences that could be applicable in experimental liquid-metal facilities.
This system approach also allows the system owners or designers to define the require-
ments for a transition sequence to be triggered, that is, transition set-point triggers and
interlocks. Depending on the system complexity and the choice of hardware/software
(e.g., manual valves as opposed to actuated valves), these triggers can be manual or
automated or a combination of both. Manual triggers will require user input in the
programmable logic controller (PLC). Automated triggers will be initiated by feed-
back from instrumentation with appropriate set points.

Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors. https://doi.org/10.1016/B978-0-08-101980-1.00014-4
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