Leak monitoring system installation

The approach described in Sect. 11.1 for permanently installed electrical leak monitoring system can be used to undertake a leak detection survey as a CQA measurement on geomembranes already covered with a layer of soil (the soil-covered geomembrane system). Typically, the layer thickness has to be less than 1 metre to obtain the appropriate efficacy and spatial resolution (Laine and Darilek 1993 Laine and Miklas 1989). However, in some cases leaks might be detected even under a much greater thickness of cover (Colucci et al. 1999 Laine et al. 1997). Instead of using an electrode... 

Installation of the leak monitoring system must be integrated into the liner construction technology. The manufacturer s installation procedure must be adapted to these conditions. In the appendix of the recommendation document, the AK DKS Working Committee has published sample drafts for the additional technical contract conditions and the performance list for an invitation to tender for leak monitoring systems plus a quality assurance plan for their installation. It is first advisable to pilot the leak monitoring system in a test field of a minimum area of 1000 m, which may be part of the liner itself The structure of the test field should be iden-... 

Table 11.1. Survey of the occurrence of frequencies of faults found with electric leak monitoring systems on 94 installation sites totalled one million square meters (Nosko 1998)...

There are two possibilities firstly, in the case of a geomembrane installation by a certified installer and accompanied by extensive quality assurance, one should perform the acceptance procedure on the basis of the quality assurance reports alone, without any special check-up leak monitoring measurement. Secondly, a process of repeated measurements, using the leak monitoring system, may accompany the different stages of the building procedure. The parties involved on site have to agree the course to follow. 

It was possible to detect the sodium leakage because Monju already had sodium leak detectors and fire detectors in the secondary circuit. However it was found that these were insufficient for the operators to grasp accurately the conditions in the room at an early stage. To help the operators confirm sodium leakage more quickly and easily, the detectors will be increased in number and diversified method and an integral leakage monitoring system will be installed. 

A monitoring display panel will be installed in the main control room and information from the various sensors and TV cameras will be displayed. The new leakage monitoring system should enable the plant operators to take the necessary actions - such as a plant trip and loop drain - earlier, since they will be able better to understand the condition at the leak site without leaving in the main control room. A schematic of this system is shown in Fig.8. 

T 0 control the spread of aerosol and the combustion of sodium, the ventilation system will be shut down more quickly by signals from the newly installed integrated leakage monitoring system. At present, in the case of small and medium-scale leaks, the shut down of the ventilation system is carried out manually by the operators. Only in the case of a large sodium leak, the ventilation is shut down automatically by an interlock signal from an abnormally low level in the steam generator. At present, if a small or medium-scale leak occurs, the sodium aerosol spreads from the leak site room to all areas that are connected by the ventilation ducts until the ventilation system is shut down. 

In Fig. 1 the lay-out of electric heaters and thermal insulation on sodium piping is shown. The heaters have 100% reserve. Earthing of the main and stand-by heaters is continuously monitored. Leaking sodium creates an electric contact between the heater and the pipe wall. Simultaneous failure of both the operating and stand-by heaters is indicative of a sodium leak. Such systems have been installed at all our fast reactors. Their operation experience has shown high reliability and sensitivity of such systems. 

Install a fixed electric leak location system and monitor quarterly until the completion of waste disposal and annually thereafter. (A protocol has to be established in advance about how to proceed when a leak is indicated. This monitoring concept seems to be relevant only for single geomembrane liner, the alternative approach is the use of composite liner systems, see Chap. 9). 

Emissions are minimised by adequate operation, by selecting effective leak free equipment, by installing VCM monitoring systems and by routine inspeetion to check the integrity of all relevant seals. Detection and repair programmes are part of the health, safety and environmental management systems of the plants. These actions are also necessary to achieve the low exposure level required to protect the health of plant staff. 

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