ELECTRICALLY HEATED BUNDLES ZOLTN HZER, IMRE NAGY, RBERT FARKAS, NRA - - PowerPoint PPT Presentation

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ELECTRICALLY HEATED BUNDLES ZOLTN HZER, IMRE NAGY, RBERT FARKAS, NRA - - PowerPoint PPT Presentation

Dec 29, 2022 313 likes •540 views

EXPERIMENTAL SIMULATION OF THE BEHAVIOUR OF E110 CLADDINGS UNDER ACCIDENT CONDITIONS USING ELECTRICALLY HEATED BUNDLES ZOLTN HZER, IMRE NAGY, RBERT FARKAS, NRA VR, MRTA HORVTH, TAMS NOVOTNY, ERZSBET PEREZ-FER, MRTON

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SLIDE 1

EXPERIMENTAL SIMULATION OF THE BEHAVIOUR OF E110 CLADDINGS UNDER ACCIDENT CONDITIONS USING ELECTRICALLY HEATED BUNDLES

ZOLTÁN HÓZER, IMRE NAGY, RÓBERT FARKAS, NÓRA VÉR, MÁRTA HORVÁTH, TAMÁS NOVOTNY, ERZSÉBET PEREZ-FERÓ, MÁRTON KIRÁLY, ZOLTÁN KIS, BOGLÁRKA MARÓTI, LÁSZLÓ SZENTMIKLÓSI

HUNGARIAN ACADEMY OF SCIENCES CENTRE FOR ENERGY RESEARCH, BUDAPEST, HUNGARY

GYÖRGY GÉMES, PÉTER HOLECZ, GYÖRGY AUGUSZT

TÜV RHEINLAND INTERCERT LTD., BUDAPEST, HUNGARY The present work was supported by the National Research, Development and Innovation Fund of Hungary (contract number: NVKP_16-1-2016-0014).

19TH INTERNATIONAL SYMPOSIUM ON ZIRCONIUM IN THE NUCLEAR INDUSTRY May 20-23, 2019 Manchester, UK

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SLIDE 2
  • Motivation to perform integral tests
  • Materials of the experimental bundle
  • The integral test facility
  • The CODEX-LOCA test matrix
  • Methods and results of post-test examinations

Outline

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SLIDE 3

LOCA (loss-of-coolant accident)

  • reactor core in high

temperature conditions

  • changes of Zr

mechanical properties

  • ballooning and burst
  • oxidation, H uptake,

embrittlement

  • potential loss of

integrity

Introduction

Small scale separate effect tests

  • important information on the

behaviour of zirconium alloys in high temperature steam

  • data for numerical models

Integral tests

  • demonstration of fuel behaviour under

accident conditions with representative scenarios and materials

2000 4000 6000 8000 10000 12000 14000 200 400 600 800 1000

Temperature (°C)

Time (s)

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SLIDE 4
  • Zirconium materials of VVER reactors
  • traditional E110 tubes produced by electrolytic technology
  • sponge based E110 tubes (E110G)
  • spacer grid from fuel factory
  • E125 (Zr2.5Nb) alloy shroud (2 mm thickness)
  • Alumina (Al2O3) pellets
  • KÉP TABLETTA

Materials

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SLIDE 5
  • 7 rod bundles
  • Hexagonal geometry
  • Hexagonal shroud
  • Electrical heating
  • 600 mm heated length
  • Internal pressurization of rods
  • Test section inlet:
  • steam generator
  • water injection (reflood)
  • Test section outlet:
  • cooler

The CODEX (COre Degradation EXperiment) facility

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SLIDE 6
  • Profilometry (Mitutoyo laser micrometer)
  • Eddy current tests (with a bobbin-probe)
  • Position-sensitive prompt gamma-ray

neutron activation imaging (PGAI) driven by neutron radiography (NR) at the Budapest Research Reactor

  • Measurement of hydrogen content by hot

extraction (ELEMENTRAC OH-p analyser)

  • Four-point banding tests (INSTRON 1195

ensile test machine)

  • Metallography (Reichert optical microscope)

Post-test examination methods

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SLIDE 7

CODEX-LOCA test matrix

Test Simulated scenarios

  • Max. cladding

temperature CODEX-LOCA- 200 200% large break LOCA in the cold leg of the primary circuit with conservative conditions 908 °C CODEX-LOCA- 200B 200% large break LOCA in the cold leg of primary circuit 874 °C CODEX-LOCA- E4 Shutdown LOCA in the cold leg of primary circuit with limited availability of emergency cooling water 1089 °C CODEX-LOCA- SFP1 Spent fuel pool LOCA with steam starvation and with limited availability of emergency cooling water 924 °C CODEX-LOCA- SFP2 Spent fuel pool LOCA with unlimited steam and with limited availability of emergency cooling water 896 °C

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SLIDE 8

reflood from the bottom

  • 2000

2000 4000 6000 8000 10000 12000 14000 16000 100 200 300 400 500 600 700 800 900 1000 1100

CODEX-LOCA-200B CODEX-LOCA-200 CODEX-LOCA-E4 CODEX-LOCA- SFP2

Temperature (°C) Time (s)

CODEX-LOCA-SFP1

T>700 °C 325 s/255 s 737 s 3786 s 4321 s

scenarios selected on the basis of VVER-440 safety analyses

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SLIDE 9

CODEX-LOCA-200:

  • three of the seven rods burst, the degree of oxidation was modest

CODEX-LOCA-200B:

  • none of the rods burst, very little oxidation

CODEX-LOCA-E4

  • the traditional E110 rods were heavily oxidized and fractured, while the sponge based E110

tubes remained intact

CODEX-LOCA-SFP1

  • large deformations took place before burst and no oxidation due to steam starving

conditions.

CODEX-LOCA-SFP2:

  • considerable ballooning on some of the rods

and modest oxidation

State of bundles after the experiments

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SLIDE 10

Post-test examinations

Test Eddy current PGAI NR Profilo- metry Four-point bending Metallo- graphy Hot extraction CODEX-LOCA- 200

+ + + + +

CODEX-LOCA- E4

+ +

CODEX-LOCA- 200B CODEX-LOCA- SFP1

+

CODEX-LOCA- SFP2

+

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SLIDE 11

The axial distribution of cladding diameter was determined for the CODEX-LOCA- 200 bundle

Profilometry

1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

burst burst

  • Max. diamater (mm)

Rod No. burst

Significant deformation wihout burst Si

300 350 400 450 500 550 600 650 700 750 800 2 4 6 8 10 12 14 16 18 20 22 24

Fuel rod internal pressure (bar) Time (s) burst

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SLIDE 12
  • Examination of cladding tubes in as-received conditions – no defects,

measurement of geometric data

  • Examination of cladding tubes after experiment (CODEX-LOCA-200):
  • direct correlation between the expansions and the eddy current signals

Eddy current measurements of intact and failed rods

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SLIDE 13
  • hydrogen distribution along the

longitudinal axis of fuel cladding tubes CODEX-LOCA-200

  • Cladding tubes without opening 80 – 100

ppm and no clear peaks

  • Traditional E110 cladding tubes with burst

the hydrogen 1100 and 1500 ppm

  • Sponge based cladding tube with opening

250 ppm

Neutron radiography

340 360 380 400 420 440 460 480 500 520 540 200 400 600 800 1000 1200 1400 1600

H/Zr mass ratio (ppm) Distance from the bottom (mm)

  • No. 1 Sponge based E110
  • No. 2 Traditional E110
  • No. 3 Sponge based E110
  • No. 4 Traditional E110
  • No. 5. Sponge based E110
  • No. 6 Traditional E110
  • No. 7. Sponge based E110
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SLIDE 14

CODEX-LOCA-E4

  • sponge based E110 cladding tubes, small
  • pening 500 – 700 ppm peaks
  • traditional cladding tubes, large visible

burst and fracture, 6000 – 7000 ppm

  • sponge based E110 cladding tubes larger
  • pening,1600 – 1800 ppm

Neutron radiography

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SLIDE 15
  • The individual

measurements showed large scatter.

  • Several hundreds ppm

variations between different circumferential positions

Hydrogen content by hot extraction

Hot extraction Neutron radiography

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SLIDE 16

CODEX-LOCA-200

  • only one rod, showed brittle behaviour

(bending moment 11.5 Nm, traditional E110 alloy with burst)

Four-point bending tests

1 2 3 4 5 6 7 8 9 10 200 400 600 800 1000 1200 1400

Load (N) Displacement (mm) Rod No. 1. Rod No. 2. Rod No. 3. Rod No. 4. Rod No. 5. Rod No. 6. Rod No. 7.

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SLIDE 17

CODEX-LOCA-SFP1

  • Large deformations before burst
  • No oxidation due to the limited steam

supply

Metallography

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SLIDE 18

CODEX-LOCA-SFP2

  • formed oxide layer was compact on the

sponge based E110 cladding tubes

  • layered structure and spalling on the

traditional E110 tubes

  • both oxide and α-layer thicknesses 10 µm
  • n the external surface, no oxide layer

detected inside

Metallography

4 6 8 10 12 14 16 18 20 390 420 450 480 510 540

Distance from the bottom (mm) Oxide layer (mm) Rod No. 1. Rod No. 2. Rod No. 3. Rod No. 4. Rod No. 5. Rod No. 6. Rod No. 7.

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SLIDE 19
  • The behaviour of traditional and sponge based E110 cladding tubes was

compared in integral LOCA experiments.

  • Design basis cold leg break 200% LOCA scenario for a VVER-440 reactor:
  • the representative pressure and temperature conditions would not result in cladding burst

for this scenario for both traditional and sponge based E110 alloys.

  • LOCA events with limited availability of emergency core cooling water injection

in the shut-down reactor and in the spent fuel pool:

  • the long oxidation times at high temperatures resulted in the formation of oxide scale on

the zirconium surfaces. The spalling oxide scale and high hydrogen pick-up of the traditional E110 cladding resulted in brittle fracture of fuel rods with long oxidation scenarios.

Conclusions 1/2

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SLIDE 20
  • Profilometry examinations pointed out that large deformations may take place

even in those rods under high internal pressure, which did not burst during the high temperature experiment.

  • Using the eddy current technique direct correlation was established between the

expansions and the eddy current signals.

  • The hydrogen content in ballooned region showed the typical two peaks

distribution only in case of long oxidation times. In several cladding tubes with short oxidation times only one peak was observed.

  • According to the four point bending tests the fuel rods after high temperature

LOCA test still had significant load bearing capability and ductility in design basis accident scenarios.

Conclusions 2/2

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SLIDE 21

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