Stuckert, J.

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KIT – University of the State of Baden-Württemberg andNational Large-scale Research Center of the Helmholtz AssociationInstitute for Applied Materials;  Program NUKLEARwww.kit.eduOverview of LOCA tests performed at KIT during last 30 yearsJ. StuckertQWS19, Karlsruhe 20132 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheOut-of-pile KfK single tube isothermal tests TUBA between 600°C and 1200°C: investigation of creep rupture timeP. Hofmann, S. Raff.    KfK 3168, Juli 1981scheme of TUBA rig (TUbe Burst Apparatus)60 testssamples: as received Zry-4 tubes (without pellets) with length of 60 mm;pressure-less heating to work T in He;filling of sample with Ar during 1 sto overpressures 2…200 bar;one TC at sample bottom;axial T difference between sample middle and sample end-plugs (pre-test): 25 K;azimuthal ∆T:   < 3 K;strain measurement on cross projection with video camera. He3 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheSingle tube isothermal TUBA tests:  dependence of burst strainand rod bending on temperature800°C23 bar80% strain950°C16 bar80% strainmax burst strain vs. temperaure650°C100 bar80% strain1050°C5 bar70% strain1) two minimums of the burst strain:at 900°C (α+β region) and 1050°C (β region);2) significant rod bending at temperaturesbefore phase transition (α region);absence of rod bending at temperatures duringand after phase transition;3) axial contraction in α region due toanisotropy.4 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheSingle tube isothermal TUBA tests: criterion of creep rupture time(dependence of burst time on temperature and pressure)Zry-4 samplesafter burstat 850°C Zry-4 samplesafter burstat 900°C *burst strain expressed as a percentage*pressure pihoop stress, σHSOstress rupture lifepressure strain pressure strain5 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheKfK single rod transient tests FABIOLAL. Schmidt, H. Lehning, K. Müller, D. Piel, H. Schleger.    KfK 3250, Juni 1982X-ray picture of FABIOLA rig> 100 testssamples: as received Zry-4 tubeswith length of 200 mm, filled with Al2O3 or UO2 pellets (no influence of pellet material was detected);filling of sample with He during 1 sto overpressures 40…125 bar at 600°C;transient heating in steam with rates 2…11 K/s until clad burst;temperature measurements: 3 pyrometers along axial direction (75 mm interval),    3 thermocouples at burst position (only few samples; 120° interval);axial T gradient between sample middle and sample end-plugs:    0.2 K/mm;azimuthal ∆T:    15 K;strain measurement on longitudinal projection with X-ray  camera. pressure tubesteam 1 m/sshroud(heated)6 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheSingle rod transient tests FABIOLA: dependence of burst time and burst strain on pressure68 bar122 barburst at 766°C (α‐region)burst at 866°C (α+β‐region)strain 39%  strain 52%7 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheOut-of-pile single rod transient tests FABIOLA: dependence of burst strain on temperatureα+β‐region: 810…980°Cminimum of burst strain lies in α+β-region at 900°C - similar to isotherm tests8 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheFR2 in-pile single rod tests with electrical heatingM. Prüßmann, E. H. Karb, L. Sepold.    KfK 3255, September 19828 reference tests with rod simulators inside FR2 reactor channel(reactor out of order)samples: as received Zry-4 tubesfilled with Al2O3;Internal Inconel heater 50 W/cm;filling of sample with He during to overpressures 20…110 bar at 370°C;transient heat up with rate 12 K/s until desired T of 820…1000°C;temperature measurements: 6 surface TC along axial direction;axial ∆T between sample middle and sample end-plugs:    > 50 K;azimuthal ∆T:   < 60 K;tests performed without reflood.FR2 test channelelectrically heated rod BSS9 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, Karlsruhe(sample BSS 23:Tburst=810°CPburst=85 bar)FR2 in-pile single rod tests with electrical heating:axial changes of circumferential strain 10 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheFR2 in-pile single rod testsE. H. Karb, M. Prüßmann, L. Sepold, P. Hofmann, G. Schanz. KfK 3346, March 1983test roddesignpre-irradiation history of rodswith burnup20 GWd/tUType of Tests Test seriesNumber of irradeated rodsNumber of testsBurnup(MWd/tU)Range of internal pressure at steady state temperature (bar)Calibration, Scoping A 0 5 0 25 -100Unirradiated rods(Main parameter: Internal pressure)B 0 9 0 55 - 90Irradiated rods(Main parameter: Burnup)C 6 5 2500 25 - 110E 6 5 8000 25 - 120F 6 5 20000 45 - 85G1 6 5 35000 50 - 90G2/3 6 5 35000 60 - 125Electrically heatedfuel rod simulators (Main parameter: Internal pressure)BSS 0 8 0 20 - 110The same test scenario as for electrically heated rods (BSS),but with nuclear heating.Tests performed without reflood.11 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheFR2 in-pile single rod tests:cladding oxidation close to the burst openingNo influence of irradiation on the oxide growth was indicated (up to 35 GWd/tU)Close to the burst opening, the thickness of the inner oxide layer was similar to outer oxideEssentially no oxide was found on the inner surface more than about 100 mm from the burst locationThe observed oxidation did not influence the circumferential strain12 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheFR2 in-pile single rod tests:no influence of irradiation (<35 GWd/tU) on burst parameters13 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, Karlsruheno influence of irradiation on burst shapeneutron radiography: lost of shape of fragmented pellets after ballooning (rod F1, burnup 20 GWd/tU)FR2 in-pile single rod tests:shape of claddings and pellets at ballooning positionsFuel pellet fragmentation did not affect the cladding deformation processNo influence of fission products on cladding burst strain was detected14 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, Karlsruhemax 4 mmPlenumspringResults of the FR2 in-pile single rod tests: out-of-pile results[Chung], showing significant bending below 840°C (-Zr(O))and negligible values above 840°C, were not confirmed bythe in-pile tests. However, the orientation of the rod bendwas consistent with out-of-pile results, i.e., the rupture wason the inside of the bend.Axial cladding contraction and growthdepends on temperature:results of later REBEKA tests with singleZry-4 tubes surrounded with heaters;rod length 500 mm;heating rates 1…30 K/sSingle rod tests: change of axial cladding dimensionsand rod bending15 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheOut-of-pile bundle tests FEBA on investigation of coolabilityof bundles blocked by ballooning simulatorsP. Ihle, K. Rust.  KfK 3657, March 1984cross section of FEBA bundlewith 5x5 rodsFEBA rod simulatorFlooding Experimentswith Blocked Arrays:8 electrical heated bundle simulators, length 3.9 mOutcome: Blockage of rod clusters up to90% don’t affect their coolabilityfor flow rates 2…6 cm/s; Grid spacers increase the coolingeffectiveness.FEBA test scenario16 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheFEBA: clad temperature evolution17 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheOut-of-pile bundle tests SEFLEX on influence of clad-fuel gaps and coolability of bundles blocked by pre-ballooned cladsP. Ihle, K. Rust.  KfK 4024, March 1986Fuel Rod Simulator Effects in Flooding Experiments:4 electrical heated bundle simulators with Zry-4 clads, length 3.9 m.The required outer shape of the balloonedZircaloy claddings was produced in afurnace by heating up the pressurizedcylindrical tubes placed in correspondinglyshaped molds.Outcome: Ballooned Zircaloy claddings,forming e.g. a coplanar 90%blockage, are quenchedsubstantially earlier than thickwallFEBA stainless steel blockagesleeves, and even earlier thanundeformed rod claddings. Rods with Zry-4 clads exhibitlower peak cladding temperaturesand shorter quench times duringreflood than gapless heater rodswith FEBA steel claddings.SEFLEX (REBEKA) rod simulatorSEFLEX bundlesPeak cladding temperatures and quench timesof SEFLEX (Zry) and FEBA (SS) bundles 18 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, Karlsruheradial structure of REBEKA rod “cosines” axial power profileOut-of-pile REBEKA bundle tests (1978-1987) on Zry-4 clad behaviour under LOCA conditionsK. Wier, KfK 44407, May 1988;F. J. Erbacher, H. J. Neitzel, K. Wiehr:  KfK 4781, August 1990allocation of thermocouplesREBEKA-5 post-test appearance:burst positions19 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheREBEKA 1 REBEKA 2 REBEKA 3 REBEKA 4 REBEKA M REBEKA 5 REBEKA 6 REBEKA 7pressure, bar 60 55 51 53 70 68 62 57burst T, °C 810 870 830 830 754 800 790 790strain, % 28 54 44 46 63 49 42 55blockage, % 25 60 52 55 84 52 60 66burst region, mm 95 203 242 28 242 140 200REBEKA test matrix20 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheOutcomes of REBEKA program comparison of FR2 data with REBEKA burst ctriterium The cooling effect of the two-phase flowincreases the temperature differences on thecladding tube circumference and limits in thisway the mean circumferential burst strains tovalues of about 50%. The circumferential burst strains of Zircaloycladding tubes are kept relatively small due totemperature differences on the claddingcircumference and the anisotropic strainbehavior of Zircaloy.21 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, Karlsruhe Isothermal single cladding tests TUBA given conservative values on maximal burstparameters (dependence of stress burst life on temperature and pressure) Rod bending was observed only at temperatures below phase transition α → α+β in Zircaloy-4 material (810°C) Single rod tests FABIOLA with temperature transient confirmed observation of isothermaltests: minimum of burst strain lies in α+β-region at 900°C Single rod FR2 in-pile tests up to burn-up of 35 GWd/tU showed that 1) Fuel pelletfragmentation did not affect the cladding deformation process; 2) No influence of fissionproducts on cladding burst strain was detected The observed oxidation degree did not influence the circumferential burst strain Conclusions of out-of-pile tests REBEKA, SEFLEX and FEBA on bundle thermal-hydraulicbehaviour: 1) The cooling effect of the two-phase mixture which is intensified duringreflooding increases temperature differences on the cladding tube circumference and thuslimits the mean circumferential burst strains to values of about 50%; 2) An unidirected flowthrough the fuel rod bundle during the reflooding phase causes maximum cooling channelblockage of about 70%; 3) The coolability of deformed fuel elements can be maintained up toflow blockages of about 90%.Summary of single rod and bundle tests (not pre-oxidised claddings)performed between 1978 and 1987 22 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheObjective and resultsInvestigation of ballooning, burst and secondary hydrogenuptake of the cladding under representative design basisaccident conditionsDetailed post-test investigation of the mechanical propertiesof the claddings to check the embrittlement criteria andmeasurement of residual ductilityTwo experiments with Zircaloy-4 bundles were performed upto now as commissioning and reference testsFour bundle tests with non- and pre-hydrogenated M5® andZIRLO™ claddings will be performed up to 2015hydrogen bands inside claddingdetected with n0‐radiographyrupture of cladding during tensile testsdue to stressconcentration(rods with CH<1000wppm)Bundle experimentsof the new QUENCH-LOCA seriesdouble ruptures due to hydrogen embrittlement(CH<1000wppm)Zircaloy-4 rods23 / 2319.11.2013 J. Stuckert – LOCA overview KfK-FZK-KITQWS-19, KarlsruheThank you for your attentionhttps://www.iam.kit.edu/wpt/loca/http://www.iam.kit.edu/wpt/471.phphttp://quench.forschung.kit.edu/AcknowledgmentThe on-going QUENCH-LOCA experiments are supported and partly sponsored by the association of the German utilities (VGB).

Overview of LOCA tests performed at KIT during last 30 years

https://publikationen.bibliothek.kit.edu/240093449/3816412

Overview of LOCA tests performed at KIT during last 30 years

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