Page 172 - Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

144 Thermal Hydraulics Aspects of Liquid Metal Cooled Nuclear Reactors

Fig. 3.4.9 In-loop cleaning of LEad CORrosion (LECOR) Pb loop facility at ENEA
Brasimone with CH 3 COOH/H 2 O 2 mixture. The liquid (blue line) enters from the expansion
vessel, exits from the draining line, and is sent again to the expansion vessel by an
external pump.

applying specific filling procedures according to the configuration. In this case,
diluted solutions of CH 3 COOH/H 2 O 2 or HNO 3 are recommended as well to avoid
too much heat generation and gas formation, preventing the release of the cleaning
mixture outside the facility. If the facility is a loop, circulation of the acidic aqueous
solution is recommended for good cleaning results, and it can be performed by using
an external pump, as shown in Fig. 3.4.9. After cleaning, the facility is washed with
water to remove residual acid traces.

3.4.11 Summary

A fully generic operational procedure cannot be written for all liquid-metal facilities,
simply due to the unique characteristics and experimental requirements of each facil-
ity. These notes, however, serve as a guideline for liquid-metal facility operation and
identify some of the necessary precautions required when operating such a facility.
The fact that liquid-metal coolants can solidify within the system requires precaution-
ary measures to prevent solidification and possible damage to sensitive components.
The high density of HLM means that HLM facilities experience significantly higher
system loads than conventional systems. Supporting of components, piping flexibility
analysis, bearing loads, and high inertial forces are design and operational factors to be
considered. Rapid changes in HLM velocity should be avoided, and so, careful tran-
sient operational sequences involving valve closure and the start-up and shutdown of
pumps are therefore important. Systematic oxygen control is recommended to