Andrey Afanasiev, Victor Makarov, Leonid Lyakishev, Ivan Matvienko, Michail Puchkov, Dmitry Ivanov

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1 SEISMIC AND HYDRODYNAMIC TESTS OF FA DUMMY AND SHEM-3 RCCA DRIVE FOR AES-2006 PROJECT IN A LARGE-SCALE TESTING FACILITY Andrey Afanasiev, Victor Makarov, Leonid Lyakishev, Ivan Matvienko, Michail Puchkov, Dmitry Ivanov Joint Stock Company"Experimental and Design Organization "GIDROPRESS", State Atomic Energy Corporation "Rosatom", Podolsk, , Moscow Region, Ordzhonikidze Str., 21, Russia. makarov@grpress.podolsk.ru Introduction The technical and economic indices of VVER reactor safety are largely defined by FA strength and stability under operational loads both under normal operating conditions and under anticipated operational occurrences, in particular, under OBE and SSE. The main requirements imposed on the reactor reactivity channels at NOC and SSE are as follows: - a possibility of a free drop of RCCA absorber rods in FA guide channels for reactor scram; - keeping component integrity; - a possibility of core unloading. The strength and stability of a FA with ShEM-3 RCCA drive is justified in experimental studies and analytical calculations. The results of experimental studies with full-scale dummies at testing facilities are the input data for computer code adjustment. Seismic tests of ShEM-3 RCCA drive were performed at OKB Gidropress seismic test facility in 2004 for the Bushehr NPP. The ShEM-3 RCCA drive was installed in a column on two supports, fastened to the test facility metalworks. The column vessel had two nozzles for water inlet and two nozzles for water outlet. The system of vibration loading for the FA with ShEM-3 RCCA drive comprised four vibrodynamic shakers. One shaker was placed at the bottom of the column to create a vertical dynamic input on AFA fuel assembly with RCCA drive and three shakers that created horizontal impacts were placed in the test facility metalworks at three different elevation marks in one vertical plane: at the level of reactor top head, at the level of nozzle-to-drive housing flange and at the level of PPI flange. Seismic input on reactivity control channel was simulated by applying a seismic signal to each of the shakers the signal being obtained by combining two harmonic signals (11 and 28,9 Hz). IAEA experts who reviewed the justification of strength and stability of a FA with ShEM-3 RCCA drive for the Bushehr NPP made comments to the methods of experimental studies, mainly to the above methods of dynamic impacts. The comments on the methods of dynamic impacts covered: - entire spectrum of seismic loads is to be simulated, not particular harmonics; - FA and drive horizontal vibration shall be two-component. Since the design of the test facility did not make it possible to get rid of the above deficiencies, a new largescale test facility for FA seismic and vibration tests was commissioned at the end of 2008 to perform experimental studies to justify AES-2006 fuel assembly. The new test facility allows seismic testing of FA assembled with ShEM- 3 RCCA drive to an improved methods that consider IAEA expert comments. Along with the seismic and vibration tests of AES-2006 FA assembled with ShEM-3 RCCA drive already implemented at the facility, similar tests of other designs of FAs will be carried out. Brief description of test facility for seismic stability tests of FA assembled with ShEM-3 RCCA drive Test facility for FA seismic and vibration studies is a multi-purpose test facility intended for experimental studies of dynamics and strength of AES-2006 and VVER-1000 FAs with ShEM-3 RCCA drive under the conditions of NOC, NOC+OBE and NOC+SSE to justify FA vibration strength of for VVER reactor safety. The facility contains the following main systems: - hydraulic system; - ShEM-3 RCCA drive with control rods and control system; - FA and drive vibration loading system; - vibration test measurement and control system; - process instrumentation; - framework. Hydraulic system is designed to create coolant flow through FA at a flowrate close to operating. The main hydraulic parameters of the test facility are: - coolant: water; - coolant temperature: up to 55 C;

3 - coolant flowrate through the column: up to 1200 mp P/h; - hydraulic circuit pressure: up to 1 MPa. Figure 1 provides the diagram of FA seismic and vibration test facility.

The system comprises six electrodynamic shakers installed in pairs at the angle of 90 at three elevation marks: at the level of top and bottom column flanges and at the level of drive support.

2 3 - coolant flowrate through the column: up to 1200 mp P/h; - hydraulic circuit pressure: up to 1 MPa. Figure 1 provides the diagram of FA seismic and vibration test facility. The system of vibration loading (Figure 1) is designed to induce FA and drive vibration with amplitudes and at frequencies typical of the conditions of NOC, OBE and SSE. The system comprises six electrodynamic shakers installed in pairs at the angle of 90 at three elevation marks: at the level of top and bottom column flanges and at the level of drive support. Привод СУЗ ShEM-3M RCCA drive ШЭМ-3М Вибратор Shaker Чехол Drive привода housing Опора колонки Column support Проставка Insertion Опорная металлоконструкция Support metalwork Колонка Column Figure 1 FA seismic and vibration test facility

In the bottom and top flanges the facility column is provided with the inlet and outlet nozzles of lateral circulation of coolant.

3 FA dummy is installed into the facility column that simulates standard conditions of FA fastening. The column (Figure 2) is a hexahedral prism with width across the flats dimensions (263±3) mm, which provides a possibility for not less than ±10 mm displacement of the middle part of FA. In the bottom and top flanges the facility column is provided with the inlet and outlet nozzles of lateral circulation of coolant. Instrumentation nozzle for dynamic pressure sensors, coolant velocity sensors etc. Laser vibrometer beam Windows FA dummy Figure 2 Column of the FA seismic and vibration test facility (viewed from the bottom) There are 18 transparent observation windows on the opposite facets of the column (9 windows on each one) to measure the vibration response of the fuel assembly and fuel rods with laser vibration meters. Instrumentation nozzles house dynamic pressure sensors, coolant velocity sensors etc. along the column axis. Objective, methods, scope and testing modes The purpose of seismic tests of FA and ShEM-3 drive with RCCA was a study of the correlation of the time and drop velocity versus such controlled factors as coolant pressure differential across the FA, time of scram signal since the beginning of the earthquake and a justification of seismic stability for ShEM-3 drive with RCCA for Novovoronezh NPP-2 site. A specific feature of the completed seismic tests is the methods of a real-time simulation of the calculated seismograms of FA and drive support accelerations. The shakers are controlled and monitored parameters (accelerations, shaker reaction force, fuel rod vibration rate, FA vibration response) are measured by a system that comprises Scadas III system unit, 36 measurement channels and a PC with dedicated computer software of LMS Test.Lab and Cada-X Time Waveform Replication (Belgium). With account for the actual frequency response functions of the facility design and mutual effect of the shakers given system makes it possible to reproduce the assigned time behavior of vibrations (accelerograms) in the assigned points of the structure. Thus, in the course of the tests at three elevation levels (column top and bottom supports, RCCA drive support) in two perpendicular directions calculated seismic loads were simultaneously simulated. The calculated accelerograms were obtained for Novovoronezh NPP-2 power unit. Figure 3 shows an example of calculated dependence of FA top support acceleration in Y-axis direction versus time (target accelerogram for MSK- 64 scale magnitude 7 earthquake). The duration of dynamic loading was 20 s.

4 t/s Figure 3 Correlation of FA top nozzle overloading coefficient in the direction of Y-axis versus time. Coolant temperature was the main difference between the in-pile conditions and the conditions in the facility. To estimate water temperature as one of the factors that influence the course of RCCA drop, RCCA drop was tested at WWER-1000 hot run-in test facility in the cold and hot conditions of its operation with the same pressure differential across the FA. The water properties in the cold conditions contribute to the drop time, on the average, 0,3 s. Thus, in the cold water tests such factors as Archimedes force and viscous friction contribute to RCCA friction force in comparison with hot water due to higher density and viscosity of coolant, i.e. the tests are conservative. Coolant flowrate in the test facility was assigned to provide pressure differential across FA (176±5) kpa. Pressure differential across the FA, equal to 176 kpa, corresponds to the top calculated value of pressure differential across the core of reactor plant V-392M. The experiment matrix is shown in Table 1. A number of drops were made with a delay of (1-11) seconds after the beginning of seismic impact simulation to consider the effect of the time of scram signal generation. Table 1. Experiment matrix Site NV NPP-2 Earthquake magnitude SSE, magnitude 7 No seismic loading Drop height, m 3,80 3,62 3,80 Pressure differential across FA, kpa Number of drops

5 Experimental results Figure 4 shows an example of a dependence of FA top support acceleration in X-axis direction versus time (target accelerogram) calculated for Novovoronezh NPP-2 power unit and the dependence of accelelration versus time, obtained in the experiment. The difference in the plots of the measured acceleration (shown in red) and the target seismogram (shown in blue) do not exceed 10 % F Time Measurement resp:4_meas_filt F Time Target resp:4 (3) B Time Magnet resp:7current Acceleration, m/sp (m/s2) Real Fixing magnet current, rel. unitsp Amplitude V s Time, s F Time Measurement resp:4_meas_filt 3.00 F Time Target resp:4 (3) Acceleration, m/sp (m/s2) Real Amplitude Time, s Figure 4 Acceleration of FA top support versus time

6 Figure 5 shows the spectrum of FA top support accelerations. In the frequency range up to 400 Hz, in acceleration spectra in the six points of load application a strong harmonic with the frequency of 148,6 Hz is observed, which is close to the circulation pump blade frequency. The fact that the harmonic with the frequency of 148,6 Hz is the pump blade frequency is supported by the decrease of the frequency of this harmonic during the coastdown following the pump trip F Spectrum unfiltresp:3:+y g Vibration acceleration Amplitude amplitude, g Figure 5 Spectrum of FA top support accelerations In the course of the tests the scram signal was sent with a delay from 2 to 10 s with a 2-second step after the beginning of seismogram representation with an error of ±1 s. The tests resulted in defining the total time of RCCA rods drop that is equal to the time interval for rod passage between the upper and lower limit switches, and for some conditions also the time for rod to pass certain areas. All-in-all, there were 15 drops of RCCA rods under different testing conditions and modes. Table 2 shows the effect of earthquake on the RCCA rod drop time. Table 2 The effect of earthquake on RCCA rod drop time Pressure differential, kpa Drop height, m Frequency, Hz Drop time, s No seismic loading SSE, magnitude 7 3,8 1,977 2,925 3,8 1,981 2,459 3,8 1,985 2,726 3,8-2,873 3,8-3,101 3,8-2,799 3,8-2,494 3,8-2,937 3,8-2,901 Average 1,981 2,802 It is seen in the Table that an earthquake increases the RCCA rod drop time, on the average, by 0,82 s. The factor of time between the seismogram start-up and scram signal, in the range of 2-10 s does not make considerable effect on the RCCA rod drop time. It is concluded from Figure 6 that provides the dependence of RCCA rod drop time versus delay time.

7 RCCA rod drop time, s Scram signal delay, s Figure 6 - Dependence of RCCA rod drop time versus scram signal delay time The results of tests to define the natural frequencies, shapes, and damping factors of FAs are shown in Table 4. The tests were performed in the air, in stagnant water and in coolant flow. In the tests in coolant flow the natural oscillations were studied at exciting broadband vibrations (white noise) and at harmonic support vibrations with 2 frequency sweep and at constant amplitude of 0,02 m/sp P. Table 3 Characteristics of natural oscillations the air, in stagnant water and coolant flow Frequency, Hz Damping coefficient, % of critical Shape Stagnant Flowrate, Stagnant Flowrate, Air 3 Air 3 water 300 mp P/h water 300 mp P/h Bending mode 1 5,3 4,3 4,0 1,1 4,7 12,2 Bending mode 2 10,8 9,6 9,2 2,2 3,6 10,9 Bending mode 3 17,5 14,9-1,1 2,9 - Bending mode 4 23,1 20,1-0,7 2,9 - It concluded from a comparison of FA modal characteristics in the air, in stagnant water and in coolant flow that in stagnant water the frequencies of natural oscillations are decreased by % and the damping coefficients 3 increase three times, on the average. In coolant flow with the flowrate through the FA of 300 mp P/h in comparison with stagnant water the natural frequencies further decrease by 0,3-0,4 Hz and the damping factors increase three times, on the average.

8 Conclusions 1. A programme and methods of seismic and hydrodynamic tests of AES-2006 FA with ShEM-3 RCCA drive was developed. 2. Seismic tests were performed for ShEM-3 RCCA drive and AES-2006 FA for seismic stability in a simulated magnitude 7 earthquake calculated for the sites of NVNPP drops of RCCA rods were performed at pressure differential across the FA of 176 kpa, equal to the maximum calculated value of pressure differential across the core of reactor plant V-392M. 2. In the drops with SSE simulation (pressure differential 176 MPa) the RCCA rod drop time was from 2,46 s to 3,10 s (on the average, 2,80 s), which does not exceed the design requirement of 4,0 s for the maximum drop time. SSE simulation (magnitude 7) on FA supports and ShEM-3 RCCA drive support leads to an increase in the average RCCA rod drop time by 0,82 s. 3. Vibration response of FA to the applied seismic impact was determined. FA displacement amplitude was found to be less than the amplitude of support displacement 1,3 3 times. 4. The tests performed have shown that the seismic stability of ShEM-3 RCCA drive and AES-2006 FA is ensured. 5. A study of AES-2006 FA dummy natural oscillations in stagnant water and in coolant flow were performed. 6. Frequencies, shapes and damping coefficients of natural oscillations were determined. The frequencies of natural and forces oscillations of FA as a single structure decease to 23% (for bending mode 1) at transition from air to stagnant water and to 7,5% (in comparison with the stagnant water) as coolant flowrate through the FA increases. The natural oscillation damping factors increase 4,3 times (for bending mode 1) at transition from air to stagnant water and 2,6 times (in comparison with stagnant water) at coolant flowrate increase through the FA. At coolant 3 flowrate through the FA of about 500 mp P/h the damping factors of particular vibration modes are by an order higher than those in the air.

Seismic Non-linear analysis of Polar Crane Alexander Schukin, Maxim Vayndrakh

Seismic Non-linear analysis of Polar Crane Alexander Schukin, Maxim Vayndrakh CKTI Vibroseism, Saint Petersburg, Russia ABSTRACT One of the requirements for Safe Design of NPP is that structures, systems,