Systemic signalling, plants

Warning system signals for system shutdown, plant evacuation, and emergency services response. 

The production and release of organic molecules by the root systems of plants have been extensively studied under a wide range of soil conditions (nutrient and water availability, pre.sence of pollutants, etc.,. see Chaps. 2 and 3). Furthermore it has been clearly demonstrated that soil microorganisms are able to produce molecules that can affect the physiology and architecture of roots (3) evidence has been also provided that molecular signals between plants and microorganisms are exchanged (see Chap. 7). 

Ueda H, Matsuda K (2011) VOC-mediated within-plant communications and nonvolatile systemic signals upregulate pyrethrin biosynthesis in wounded seedlings of Chrysanthemum cinerariaefolium. J Plant Interact 6 89-91... 

Signaling Systems of Plants Have Some of the Same Components Used by Microbes and Mammals... 

Toll-like Signaling Activates an Ancient Defense System in Plants and Animals... 

Remember that the BPCS operates with signals that are relatively dynamic. This makes BPCS failures generally detectable by plant personnel. Example diagnostic methods include flat line outputs, quality indicators, pre-alarms, deviation alarms, and out of range signals. While a BPCS operates under relatively dynamic conditions, safety instrumented system signals are static Boolean variables. Since the SIS only takes action when a potentially dangerous condition is detected, it can be very hard for operations and maintenance persormel to detect certain failure modes of a SIS. 

The results of the analysis show that the overtemperature AT reactor protection system signal provides adequate protection against the reactor coolant system depressurisation events. The calculated DNBR remains above the design limit. The long-term plant response due to a stuck-open ADS valve or pressuriser safety valve, which cannot be isolated, is bounded by the small-break LOCA analysis. 

The letdown flow outside containment isolation valve is a normally closed, fail closed, air-operated globe valve that isolates letdown to the liquid radwaste system. This valve automatically opens and closes on a plant control system signal from the pressuriser level control system or a containment isolation signal from the protection and safety monitoring system. Ibis valve operates in the same fashion as the letdown flow inside containment isolation valve. The letdown flow outside containment isolation valve eloses more quickly than inside containment letdown flow isolation valve to limit seat wear of inside containment isolation valve. This valve operator has a flow restricting orifice in the air line, so it opens more slowly than inside containment letdown flow isolation valve. In addition, during brief periods of shutdown, when the reactor coolant system is water solid, this valve throttles to maintain the reactor coolant system pressure. Manual control is also provided in the main control room and at the remote shutdown workstation. 

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