Reactor protection system

The Reactor Protection System encloses all electrical and mechanical devices and circuitry involved in generating the initiation signals associated with protective functions that are carry out by the Safety Actuation Systems. 

The following criteria is normally taken into account during the design of the Reactor Protection System  

The objective of the reactor protection system is to trigger the safety actuation systems 

To achieve these functions, appropriate Safety System Settings (SSS) shall be defined to limit safety variables. Typical safety variables are shown in Table II. Safety variables, which are monitored by the reactor protection system, are typically grouped in different types of channels as shovra below. 

TABLE H TYPICAL SAFETY VARIABLES IN RESEARCH REACTORS 

The requirements for the reactor protection system are discussed in paras 626-634 of Safety Series No.35-Sl. The reactor protection system, including all its components, shall be described in detail. A schematic diagram shall show how the parameters for initiating protective actions are derived from monitored process variables, such as neutron flux, temperatures and flow, and how these parameters are logically combined. 

The adequacy of the protection system to shut down the reactor in a safe manner (e.g. by providing redundancy) and to bring the reactor into a safe condition shall be described. A reliability analysis of the protection system should also be presented. 

The means for detecting failures within the reactor protection system shall be described. 

This section shall describe the methods used to prevent adverse environmental conditions (temperature, humidity, high voltage, electromagnetic fields, etc.) from influencing the reactor protection system, and methods to protect against tampering. 

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Render reactor lubcrilical Reactor protection system Render reactor subcritical Reactor protection system Standby liquid control sy.stein... 

Erdmann, R. C. et al., 1976, ATWS A Reappraisal Part If Evaluation of Societal Risks Due to Reactor Protection System Failure Vol IIBWR Risk Analysis EPRINP-265,. ugust. 

Kdly, J. E. et al 1976, ATWS, A Reappraisal Part II, Evaluation of Societal Risks due to Reactor Protection System Failure Vol.3 PWR Risk Analysis, EPRINP 265, August. 

Integrated control system This includes various safety, monitoring, and control systems, including a reactor protection system. 

The determination of rate change of the logarithm of the neutron level, as in the source range, is accomplished by the differentiator. The differentiator measures reactor period or startup rate. Startup rate in the intermediate range is more stable because the neutron level signal is subject to less sudden large variations. For this reason, intermediate-range startup rate is often used as an input to the reactor protection system. 

A signal to the reactor protection system at a selected value (normally 10% reactor power) to disable the high startup rate reactor trip... 

Two core make-up tanks provide berated make-up water whenever die normal make-up system is unavailable. The tanks are located above die reactor coolant system loop piping and kept at system pressure by steam lines from die pressurizer. These tanks function at any system pressure, using only gravity as a motive force. If the reactor protection system detects a need for make-up water, core make-up tanks discharge and... 

The two first events are associated with the reactor start-up tests. However, the two last ones, although they initiated an emergency shut-down thank to the "fail-safe" design of the reactor protection system, present the problem of its reliability. 

Scalability SPINLINE 3 fits various sizes of I C systems. It can be used for highly distributed architectures such as a reactor protection system, distributed processing for acquisition, function processing and vote. 

NUREG/CR-6101, Software Reliability and Safety in Nuclear Reactor Protection Systems, Nov. 1993... 

There are five safety systems in Lungmen DCIS. They are Reactor Protection System (RPS), Neutron Monitor System (NMS), Process Radiation Monitoring System (PRMS), Containment Monitoring System (CMS), and Engineered Safety Features (ESF). The software development for all these safety systems follows the BTP-14 requirements. Along with the development, the IV V activities are performed. Of the safety systems, RPS, NMS, PRMS and CMS are designed by GE NUMAC, and ESF is sub-contracted by GE to Eaton Corporation. 

General Description of NPP Temelin Primary Reactor Protection System (PRPS)... 

The safety system consists of 4 divisions and the 2 out of 4 logic is employed. As for consideration for common mode failures, some hard-wired back-up countermeasures were installed based on the defense-indepth concepts. Figure 2 and 3 show the configuration of RPS (Reactor Protection System) and LSF (Lngineering Safety Features), respectively. 

Digital Reactor Protection System (DRPS) which is a replacement of the existing HO-1 and SOB... 

Common requirements for the reactor protection system, engineered safety features actuation system and emergency load sequencer on one side, and for the reactor limitation system on the other side have been set forth in the following areas ... 

Third core heat removal system is a passive heat removal system (PHRS). The heat is removed from the monoblock to the water storage tank located around the monoblock vessel. This system ensures the reactor core cooling in case of postulated maximal accident with all secondary equipment failed, reactor protection system failure and total de-energizing of the NPP. 

Since the number of LOR and scram during high power operations was very high, an exercise was carried out to optimize the trip parameters. As a first step, high winding temperature trips of sodium pump drive system motors (88 No) were deleted and control panels of these systems were housed in an air conditional atmosphere. These steps have vastly improved performance of the drive system. As second step the trip parameters of reactor protection system were reviewed and the following modifications were carried out to improve the reliability of the system without compromising the safety. 

All the above modification improved the reliability of reactor protection system and spurious trips reduced. 

The specific scenario of a spurious start of HPIS needs particular attention. In such case, the three trains would start injecting because of modifications in the new reactor protection system. Due to the flow from the three HPIS pumps, the level will increase in the pressurizer. 

Gravity driven injection system of borated water at high pressure makes up the Second Shutdown System. It actuates automatically when the Reactor Protection System detects the failure of the First Shutdown System or in case of LOCA. The system consists of tanks connected to the reactor vessel by two piping lines which valves are opened automatically when the system is triggered. Then one of the pipes -from the steam dome to the upper part of the tank- equalizes pressures, and the other -from a position below the reactor water level to the lower part of the tank- discharges the borated water into the primary system by gravity. 

PM EQA The Reactor Protection System (RPS) initiated a reactor scram as aresult of the turbine trip. All MSIVs closed due to the loss of RPS power). 

Figure 1 provides a schematic view of typical TS for Safety-Related Equipment (SRE) of a NPP, which consists of several sections (both LCO and SR are shown in detail) as presented in Martorell et al. (2004). Herein, for sake of clarity in the presentation it will be considered the case of the RPS (Reactor Protection System) of a Pressurized Water Reactor (PWR). 

A case of application is presented devoted to the analysis of a STI change of the Reactor Protection System of a NPP. The results obtained for the base case shows the CDF impact of the proposed change is small as it stands in Region 111, close to Region II, which means the change will be considered regardless of whether there is a calculation of the total CDF, which in addition is well away of 10 . In addition, even the 95% percentile stands below the boundary value. 

Analysis should verify the effectiveness of the reactor protection systems. 

Anticipated transients without scram are the most significant group of BDBAs. These include failures of the reactor protection system in addition to the following anticipated operational occurrences ... 

Chapter 15 lists the assumptions used in the turbine trip e analysis. These assumptions are chosen so that they tend to maximize the required pressure relieving capacity of the primary and secondary valves. The analysis demonstrates that sufficient relieving capacity has been provided so that when acting in conjunction with the reactor protective system the safety valves will prevent the pressure from exceeding 110% of the design pressure. 

Overpressurization of the Reactor Coolant System (RCS) and steam generators is precluded by means of primary safety valves, secondary safety valves and the Reactor Protection System (RPS). Pressure relief capacity for the steam generators and RCS is conservatively sized to satisfy the overpressure requirements of the ASME Boiler and Pressure Vessel Code, Section III. The safety valves in conjunction with the RPS, are designed to provide overpressure protection for a loss-of-load incident with a delayed reactor trip. 

The System 80+ Standard Design, steam generators, and reactor coolant system are protected from overpressurization in accordance with the guidelines set forth in the ASME Boiler and Pressure Vessel Code, Section III. Peak reactor coolant system and secondary system pressures are limited to 110% of design pressures during a worst case loss load event. Overpressure protection is afforded by primary safety valves, secondary safety valves, and the Reactor Protection System. 

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