Condensate pump trip

A fairly detailed chronology of the TMI-2 accident is provided in Table 2.4-1. The reader may find it useful to refer to this chronology and the associated Figures frequently. For the most part, times in the following discussion are measure in hours (h), minutes (min), and seconds (s) from turbine trip, which occurred 1 s after the condensate pump trip. Where clock times are specified, they are denoted with an a.m. or p.m. suffix, as in 4 00 36 a.m. 

Loss of offsite power Condensate pump trip... 

Since the function of the AFS is to keep the main coolant flow rate in the event of the unavailability of the RCPs, its actuation signals should be released by detecting an abnormality in the RCPs or a decrease in the main coolant flow rate. Reactor coolant pump trip and main coolant flow rate low are taken as the AFS signals. Loss of offsite power, condensate pump trip, turbine control valves quickly closed, main stop valves closure, and MSIV closure are also taken as the AFS signals because these abnormalities cause a trip of the RCPs. 

Loss of supply of coolant to the deaerator would also cause a trip of the RCPs because the inlet pressure of the RCPs decreases with the water level in the deaerator. This abnormality is represented by the loss of offsite power transient where the motor-driven condensate pumps stop. Since there is a large amount of water in the deaerator, the RCPs are expected not to stop for some period after the trip of the condensate pumps. The capacity of the deaerator has not yet been determined. If it is 140 m, which corresponds with the typical design of 1,000 MWe class FPPs, the water level in the deaerator would decrease by only 7% in 10 s after the trip of the condensate pumps. In the safety analysis, it is conservatively assumed that the trip of the RCPs occurs 10 s after the condensate pump trip [5]. This transient is less severe than a total loss of reactor coolant flow accident because a reactor scram is possible before the trip of the RCPs. In the safety analysis, the reactor scram by the signal of loss of offsite power, condensate pump trip, or turbine control valves quickly closed is credited. 

This is the typical transient where both RCPs trip. However, its sequence is different from a total loss of reactor coolant flow accident as described in Sect. 6.4. In the loss of offsite power, the motor-driven condensate pumps are assumed to trip instantaneously. The turbine control valves are quickly closed due to a turbine trip. The turbine bypass valves open immediately after that. A scram signal and AFS signal are released by detecting the loss of offsite power or turbine control valves quickly closed or condensate pump trip. Both RCPs are assumed to trip at 10 s... 

Trip of one feedwater pump (or condensate pump) 24. Feedwater low flow... 

Resin blockage caused trip of the condensate pump and main feedwater pumps,... 

TRIPPING OF COOLING WATER SUPPLY PUMP TO CONDENSER VkiLL TRIP DRIVE MOTOR OF OOMRESSOR. 

Anticipated operational occurrences are off-normal events, usually plant transients, which can be coped with by the plant protection systems and normal plant systems but which could have the potential to damage the reactor if some additional malfunction should happen. Their typical frequency of occurrence may be more than 10 year Some of the anticipated occurrences (PIEs - postulated initiating events) are due to the increase of reactor heat removal (as might occur for an inadvertent opening of a steam relief valve, malfunctions in control systems, etc.). Some are due to the decrease of reactor heat removal (such as for feed-water pumps tripping, loss of condenser vacuum and control systems malfunctions). Some are due to a decrease in reactor coolant system flow rate, as in the case of a trip of one or more coolant pumps. Some are connected with reactivity and power distribution anomalies, such as for an inadvertent control rod withdrawal or unwanted boron dilution due to a malfunction of the volume control system for a PWR. Events entailing the increase or decrease of the reactor coolant inventory may also happen, due to malfunctions of the volume control system or small leaks. Finally, releases of radioactive substances from components may occur. 

Anticipated operational occurrences. Anticipated operational occurrences mean those conditions of normal operation which are expected to occur one or more times during the life of the nuclear power unit and include but are not limited to loss of power to all recirculation pumps, tripping of the turbine generator set, isolation of the main condenser, and loss of all offsite power. 

Increase in reactor heat removal inadvertent opening of steam relief valves secondary pressure control malfunctions leading to an increase in steam flow rate feedwater system malfunctions leading to an increase in the heat removal rate. —Decrease in reactor heat removal feedwater pump trips reduction in the steam flow rate for various reasons (control malfunctions, main steam valve closure, turbine trip, loss of external load, loss of power, loss of condenser vacuum). 

The condenser is cooled by the circulating water system which typically incorporates three electrically driven pumps loss of one pump will call for a power reduction, but will not yield a turbine trip in the short term. The condensate is pumped forward to the dearator (or the feedwater tank) through low pressure heaters and a condensate cleanup system with ion exchange filters by means of three 50% condensate pumps. The drmnage from the heaters is pumped forward through the cleanup system by means of a dedicated low pressure drain pump. 

At 9 50 p.m. the B pump tripped out and could not be restarted. If neither of the two condensate pumps could be started within 30 minutes then the platform would have to be shut down—an expensive decision—so the decision was made to put pump A back into service. 

Number of main condensate pumps required for full power - the number of condensate pumps that are normally in operation at the rated turbine power. It is usual for some of the condensate pumps available to be on standby in case an operating pump trips. The value should be entered in the same form as for the total number of condensate pumps. 

Under normal circumstances, compressed air is used to "fluff spent resins, which are then transferred in demineralized water through a transfer line between the tanks. But a resin block developed in the transfer line driving water back through the isolation valve between the demineralizer and the condensate pumps. As a result, water entered an instrument air line through a check valve that had frozen open. This apparently caused the polisher inlet and/or outlet isolation valves to drift toward the closed position. The accident began when all the isolation valves on the condensate polishers closed. This in turn caused one of the two operating condensate pumps and both of the condensate booster pumps to trip initiating the TMI-2 accident at 4 00 36 a.m. on Wednesday, March 28, 1979. 

Condensate pump lA and condensate booster pumps trip. 

On the day of the incident, a pump that supplied hot lean oil to a large heat exchanger on the absorber column tripped. A chart recorder that should have indicated the upset was out of ink. The temperature in the exchanger dropped because of cold condensate flowing through the tubes. After several hours, two supervisors discovered the problem and restored hot lean oil flow to the exchanger to warm it up. This act was car-... 

Confirm working of all safety devices, safety interconnections, overload trip settings, working of effluent treatment plant (along with availability of chemicals for treatment) DG sets, cooling systems for reactors and condensers lire fighting pumps, gas detectors, etc. Clean (flush) all the pipelines and ducts. Check all other equipments required for the particular plant. All instmments and process controllers shall be calibrated and tested. 

The turbine exhaust flows to a condenser which has three shells, located under the low pressure turbine exhaust hoods. The condenser also accepts the exhaust flow from the feed pump turbines and, on startup, hot standby and turbine trip, flow from the main steam and bypass system. 

For those events where offsite ac power is lost, an appropriate time delay between turbine trip and the postulated loss of offsite ac power is assumed in the analyses. A time delay of 3 seconds is used. This time delay is based on the inherent stability of the offeite power grid (see subsection 8.2 of Reference 5.6). Following the time delay, the effect of the loss of offsite ac power on plant auxiliary equipment (such as reactor coolant pumps, main feedwater pumps, condenser, startup feedwater pumps, and RCCAs) is considered in the analyses. 

There is a capability to isolate each primary loop from the reactor using two gate valves on the suction and pressure pipelines of the circuit. On the pressure pipeline of each loop downstream of the PSP a flap-type check valve is provided eliminating coolant backflow in the event of a PSP trip in one loop when the other PSPs are operative. The secondary sodium circuits comprise EHX heat transfer tubes, pipelines, secondary sodium pumps and steam generators. Due to utilization of the reactor energy for fresh water production the steam-water system has some specific features. Steam from the SG is supplied to turbines of two types a condensing turbine (K-100-45) and a back-pressure turbine (K-50-45). Exhaust steam flows from the back-pressure turbine and from intermediate bleeds of K-100-45 turbine are supplied to the water desalination facilities. At a heat output of 750 MW the reactor produces ... 

Operators tried to restart condensate booster pump 2B but it tripped. 

About 13 hours after turbine trip, the auxiliary boiler was brought back into operation. Steam for the turbine seals was now available and it was possible to hold a vacuum on the condenser. Two condenser vacuum pumps were started. It was the operator s belief that the main condenser would... 

At 1 59 a,m the No. 1 AFW pump suction transferred spuriously from the condensate storage tank to the service water system (malfunction number 10). This action was not significant, but it had occurred before and had not been corrected. Similarly, a source range nuclear instrument became inoperable after the reactor trip (malfunction number 11) and the operators initiated emergency boration pursuant to procedures. (Note One channel had been inoperable prior to the event.) The source range instrumentation had malfunctioned previously and apparently had not been properly repaired. Also, the control room ventilation system tripped into its emergency recirculation mode (malfunction number 12), which had also occurred prior to this event. 

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