Safety injection signal

Figure 3.4.4-6 presents a flow diagram of a simplified emergency cooling injection system. It is activated by a safety injection signal (SIS) which... 

An inadvertent safety injection signal will not result in lifting the pressurizer power-operated relief or safety valves. A continuous minimum flow path which does not require... 

The receipt of the safety injection signal initiates the following emergency core cooling actions ... 

The LER data base served as the primary source of DG failure data, while a data base for DG successes was formed from nuclear plant licensees responses to a USNRC questionnaire (Generic Letter 84-15). Estimates of DG failure on demand were calculated from the LER data, DG test data, and response data from the questionnaire. The questionnaire also provided data on DG performance during complete and partial LOSP and in response to safety injection actuation signals. Trends in DG performance are profiled. The effects of testing schedules on diesel reliability are assessed. Individual failures are identified in an appendix. 

The SCS relief valves are sized, based on an inadvertent safety injection actuation signal (SIAS) with full pressurizer heaters operating from a water-solid condition. The analysis assumes simultaneous operation of four SIS pumps and one charging pump with letdown isolated. The resulting flow capacity requirement for water is 3934 gpm. The analysis in Section 5.2.2.10.2.1 assumed that either SCS relief valve relieved water at this rate. 

A second criterion based on the conclusion of NUREG-1217 is that the safety injection pressure capability should be greater than 1275 psia and emergency feedwater should be automatically initiated on a low SG water level signal. 

The characteristics in this group identify the systems used to maintain reactor core cooling if there is a loss of the normal reactor coolant. These systems usually include both active and passive systems (safety injection pumps and core flooding hydroaccumulators). Safety injection pumps should be considered as such pumps if they can be automatically started by an Engineered Safeguard Feature Actuation System (ESFAS) or a similar safety signal. 

The two modes of operation, injection and recirculation, are automatically or manually initiated by a Safety Injection Actuation Signals (SIAS) and a Recirculation Actuation Signal (RAS), respectively. 

The priority of automatic actions over manual operator actions was ensured in the original design. In the course of development of the new symptom based EOPs some operator actions were identified as significant. An example is the reduction of safety injection flow the operator cannot take this action in the wide range of pressure below 8.3 MPa and temperature above 180°C. The safety signal reset capability is to be implemented when justified. 

Traditionally, safety pharmacology screens for cardiovascular fimction have been performed in the anesthetized dog or rat. In the rat, diastolic, systolic, and mean arterial blood pressures (DAP, SAP, MAP) are recorded via direct cannulation of a major artery (e.g., femoral or carotid), and the test article is injected directly into a vein while the animal remains anesthetized. Heart rate is determined electronically from the pressure signal, and other physiological parameters may be monitored, such as body temperature, respiration rate, and ECG. Often, an escalating dose strategy is employed to determine the minimum dose necessary to see any changes in cardiovascular function. 

In spite of obvious potential use, experienee with injection of signaling molecules is aneedotal with insuffieient data to establish efficacy or safety. FDA approved indieations for use are very limited and extreme cost makes off-label use a ehallenge. Clinieal trials, as have been done for BMP 2 and BMP 7, are required to establish indications. 

The functional concept may be based on the block diagram. All signals are read in with ASIL B and use the dependencies of the system function groups (logical elements) for plausibility checks to implement the decomposition or safety mechanisms. To control the throttle valve and the pressure injection we use current read... 

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