RESULTS OF AUTOMATIC SYSTEM IMPLEMENTATION FOR COFRENTES POWER PLANT DETECTION SYSTEM LPRM INSPECTION EXECUTION

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1 2011 International Nuclear Atlantic Conference - INAC 2011 Belo Horizonte,MG, Brazil, October 24-28, 2011 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: RESULTS OF AUTOMATIC SYSTEM IMPLEMENTATION FOR COFRENTES POWER PLANT DETECTION SYSTEM LPRM INSPECTION EXECUTION M.Palomo 1, M.Urrea 2, M.Curiel 3 and A.Arnaldos 4 1 Departamento de Ingeniería Química y Nuclear, Universidad Politécnica de Valencia, Camino de Vera s/n, Valencia, 46022, , mpalomo@iqn.upv.es 2 C.N.Cofrentes Iberdrola Generación S.A., Carretera Almansa Requena s/n 4662, Cofrentes, Valencia, matias.urrea@iberdrola.es 3 LAINSA, Grupo Dominguis, Sorolla Center, local 10, Avda. de las Cortes Valencianas, nº 58, Valencia, 46015, , m.curiel@lainsa.com 4 TITANIA Servicios Teconológicos, Grupo Dominguis, Sorolla Center, local 10, Avda. de las Cortes Valencianas, nº 58, Valencia, 46015, , a.arnaldos@titaniast.com ABSTRACT During this presentation we are going to introduce the results of Cofrentes Nuclear Power Plant automatization of the Detection System LPRM (Local Power Range Monitor) Inspection Procedure. An LPRM s Test System has been developed and it consists in a software application and Data acquisition hardware that performs automatically the complete detection system process: - Refueling, Storage and Operation Inspection: o Ramp voltage generation o Measured voltage Plateaux evaluation o Qualification report emission - Historical Analysis to scan burn evolution. The inspections differentiations are developed by the different specifications that it has to fulfil: - Operation Inspection: it is made to check the fission bolt wearing, the detection system functioning and to analyse malfunctioning. From technical specifications and curves analyses it can be determined each LPRM s substitution. - Storage Inspection: it is made to check the correct functioning and isolation losses before being installed in the core during refueling. - Refueling Inspection: it s checked that storage LPRM s installation is correct and that they are ready for new fuel cycle. The software application LPRM s Test has been developed by National Instruments LabVIEWTM, and it performs the following actions:

2 - Protocol IEEE-488 (GPIB) control of the source KEITHLEY 237. This source generates the ramp voltage and measure voltage. - Information acquisition of storage, process and source, identifying LPRM and realization conditions of the same. - Data analysis and conditions report. - Historical comparative analysis. 1. INTRODUCTION This paper presents the LPRM TESTING application that has been designed to conduct Inspection of LPRM Detectors at the reactor core of Cofrentes Nuclear Power Plant (CNC) and of LPRM detectors in storage that are to be fitted during refueling. Once the LPRM detectors have been fitted, they are spread axially and radially at the core and they are fitted with a fission camera that detects the fissions in each position and that, after converting them to physical magnitude, provide the core s power distribution. Preliminary inspection of LPRMs is conducted during normal plant operations, in order to check the level of depletion of the fission cameras, check the functioning of the detectors and analyse any malfunctions. Based on this analysis, and mindful of CNC s technical specifications, we can determine the LPRMs that need to be replaced during refueling. The next inspection focuses on the LPRMs that are in storage and that are to be installed in the core during refueling. The purpose of this inspection is to check that they are functioning correctly and that they are not losing any insulation before they are fitted. Finally, once the LPRMs have been installed and the plant is in shut-down mode, we check that they have been properly installed and that the detectors are ready for the new fuel cycle. The LPRM TESTING application has been designed to carry out these three inspections in the field and to produce the relevant reports. We have also developed a module that allows one to monitor CNC s available testing histories to which we add the new tests. 2. DESCRIPTION OF EQUIPMENT USED To conduct the inspections, the following pieces of equipment are required: - KEITHLEY model 237 Source Measure Unit [1] - Laptop computer. - PCMCIA-GPIB card for obtaining signals and monitoring the power source. - Card-equipment communication cable. - Connection cables to the LPRMs in storage and booths MΩ resistance. 3. TECHNICAL SPECIFICATIONS FOR INSPECTING LPRM DETECTORS As described, three inspections are made of the LPRMs. Each of them has the following technical specifications as defined by CNC:

3 - Fitted detector Plant in operation (Plateaux) - New detector in storage - Fitted detector 3.1. Fitted Detector Plateaux This test is conducted on the fitted detectors with the Plant in normal operational mode, in order to determine which LPRMs should be replaced during refueling. Using the LPRM TESTING application, the power source is programmed to supply voltage to the LPRMs. To carry out the PLATEAUX, the power source generates a voltage from 0 to 300 Vdc with an increase of 1.5 Vdc per second. For each new voltage figure, 20 intensity readings are taken, discarding the first 5, that will generate a delay of 250 µsec, which is the voltage stabilization period. We obtain the next 15 power readings at intervals of approximately 50 µsec and they will produce an average with which to calculate the Intensity to the 100V power that extrapolated at 125% of Power will determine whether the detector has to be replaced or not. From each voltage figure until the ramp is completed at 300 Vdc, the system stores 15 readings of generated power and 15 readings of absorbed intensity and they will be charted on a laptop screen. The detector test is completed when 300 Vdc has been reached New Detector in Storage This test is conducted on detectors in Storage. The LPRM TESTING Application is programmed to supply voltage to the LPRMs. To conduct the test, the power source generates a voltage from 0 to 550 Vdc with increases of 5 volts every 5 seconds. For each new voltage figure, a variable number of figures will be taken that will depend on the time set between samples, which by default will be every 0,050 msec, giving 100 intensity readings. One third of the data will be discarded to counteract the condensing effect of the cable. The next two-thirds of the power readings are obtained and averaged out to calculate the representative figure for each voltage and thereby obtain the detector s response and determine its condition in storage. For each power reading, until the ramp is completed at 550 Vdc, the system stores two-thirds of the power readings generated and the absorbed intensity figures and shows them on two charts on the laptop screen. The detector test is completed when maximum intensity of 0.1 µa or 550 Vdc have been reached.

4 3.3. Fitted Detectors This test is conducted on detectors that have been installed, prior to starting plant operations, to check that all the LPRMs are working properly before they are put into operation. To this end, the LPRM TESTING Application is used to programme the power source to supply voltage to the LPRMs. To conduct the test, the power source generates a voltage from 0 to 550 Vdc with increases of 5 volts every 5 seconds. For each new voltage figure, a variable number of figures will be taken that will depend on the time set between samples, which by default will be every 0,050 msec, giving 100 intensity readings. One third of the data will be discarded to counteract the condensing effect of the cable. The next two-thirds of the power readings are obtained and averaged out to calculate the representative figure for each voltage and thereby obtain the detector s response and determine its condition in storage. For each power reading, until the ramp is completed at 550 Vdc, the system stores two-thirds of the power readings generated and the absorbed intensity figures and shows them on two charts on the laptop screen. The detector test is complete when: - The system detects a sudden increase in the power stream with the voltage applied, signifying that the detector s avalanche point has been reached. - When maximum voltage of 3 µa has been obtained. - If 450 Vdc have been applied to the detector. 4. DESCRIPTION OF THE FUNCTIONING OF THE LRPM TESTING APPLICATION Once the programme has been run, the main screen appears. This screen shows the modules that can be selected and which correspond to the inspection tests we have described and to the readings history comparison. Figure 1. Main screen of the LPRM Testing application

5 4.1. Fitted Detectors Plateaux If this option is selected, the following screen appears: Figure 2. Configuration of Plateaux for fitted detectors The data required for starting the test are: - Correctly select the APRM and the LPRM - Select the initials of the technicians who will be conducting the test. - Write the Gap Voltage in %. - Select the Data Recording Directory. Once these data have been correctly entered, the figures will be accepted and the test will begin, with the following window appearing on screen:

6 Figure 3. Test start screen The test is then run automatically, following the system described in section 3.1. Fitted detector plateaux. Figure 4. Results of the Fitted detector plateaux test showing that it is functioning correctly

7 Once the programme has finished testing, a screen will appear with the following test data: - Intensity obtained at 100Vdc. - Intensity at 125% of power, taking into account the Gap Voltage entered in the first screen of this test. Once the test is complete, the following options appear: - Print out the results report on the printer that has been installed as the default printer - Record data and exit the PLATEAUX configuration menu (Figure 2) - Exit the PLATEAUX configuration menu without recording the data (Figure 2) 4.2. New Detector in Storage If this option is selected, the following screen appears: Figure 5. Testing detector in storage menu screen The data required for starting the test are: - Write in the detector s Serial Number. - Correctly select the APRM and the LPRM - Select the initials of the technicians who will be conducting the test. - Select the Data Recording Directory. Once the data have been entered correctly and the Test Run Sequence configured, which is completed with CNC s technical specification, the test can be conducted and screens similar to those in figures 3 and 4 will appear.

8 Figure 6. Results of the detector in storage test, functioning correctly Figure 7. Results of the detector in storage test, functioning incorrectly As with the previous example, once the test has been completed, the following options appear: - Print out the results report on the printer that has been installed as the default printer

9 - Record data and exit the New Detectors in Storage configuration menu (Figure 5) - Exit the New Detectors in Storage configuration menu without recording the data (Figure 5) 4.3. Fitted Detector If this option is selected, the following screen appears: Figure 8. Fitted detector test menu screen The data required for starting the test are: - Correctly select the APRM and the LPRM - Select the initials of the technicians who will be conducting the test. - Select the Data Recording Directory. The options available and the way the test is run are similar to the examples described previously.

10 Figure 9. Results of the new fitted detector test, functioning incorrectly 4.4. Comparing Reading Histories If the option of comparing histories is selected, the following screen appears: Figure 10. Select Histories Screen The various tests are organized into files and once one has selected the test to be viewed, one has to select the file in which the data have been saved. Once the LPRM has been selected, a list is presented with the dates and readings of Intensity at 125% of Power, if one is reviewing the Plateaux Histories.

11 Figure 11. Viewing the History Curves Once this option has been selected, one can: - Print the screen in greater detail - Change the LPRM - Exit the View option and return to the main menu. 5. CONCLUSIONS Implementing this kind of system for automating and updating work procedures in nuclear power plants is beneficial from several points of view. Firstly, the test run time is reduced, allowing Plant technicians to use their time more effectively, and secondly, it provides more information on the system and on the tests that have been conducted. The LPRM TESTING application has been developed to automatically execute the LPRM detector inspection procedure at the Cofrentes Nuclear Power Station and the following objectives have been achieved: - Reduction and efficient use of time in the field and in the office - Standardization of tests procedures. - Provide the technicians with more information on the functioning of the LPRMs by giving the history of the tests conducted. - Make maximum use of the performance capacities of equipment. REFERENCES 1. High Voltage Source Measurement Unit. Model 237. Operators Manual. Keithley Instruments (1991).