Experimental Study of the VVER-1000 Fuel Rods Behavior under … · 2018. 3. 2. · Several...

Experimental Study of the VVER-1000 Fuel Rods

Behavior under the Design-basis RIA and LOCA in the MIR reactor

A.V.Alekseev, A.V.Goraychev, O.I.Dreganov, A.L.Izhutov,

L.V.Kireeva, I.V.Kiseleva, V.N. Shulimov

Since 2001 RIAR has been conducting irradiation tests in the MIR

reactor under the design basis loss-of-coolant accident (LOCA) and

reactivity-initiated accident conditions (RIA), which are targeted at

obtaining experimental data on the VVER-1000 fuel performance under

these conditions. Each experiment confined itself to examination of

fuel, fuel-cladding interaction and analysis of gaseous fission products

release from irradiated fuel.

2

Several experiments were

carried out under both the

RIA and LOCA conditions

with the use of the VVER-

1000 fuel rods operated at

nuclear power plants and

attained a burnup of 40 to

70 MW·d/kgU.

RIA tests:

testing methodology and experimental data

Main parameters of RIA tests attained in power pulse reactors

3

Number of fuel rods

under testing

Fuel burnup,

MW day/kg U

Power pulse half-width, ms

Peak radial average

enthalpy, 105J/kg

IGR 8 50 750 – 900 2.5 – 11.1

BIGR8 50 2 - 4 4.8- 7.8

4 60 2 - 4 5.2- 6.9

RIA tests:


Changes in the temperature in the center of fuel stack for irradiated fuel rodlet (a) and

radial average enthalpy (b) of irradiated fuel as a function of time at different parameters

of pulse: 1- calculated profiles for the VVER-1000 fuel; 2-3 – calculated profiles for

pulse irradiation tests in the MIR reactor at a linear heat generation rate of 250 W/cm

(initial value), pulse amplitude of 3.25, ԏ=0c(2); ԏ=0.5s(3).

4

200

400

600

800

1000

1200

1400

0 5 10 15

Time, s

1

2

3

Т,оС

а 5.0E+4

1.0E+5

1.5E+5

2.0E+5

2.5E+5

3.0E+5

0 5 10 15

Time, s

E,

10

5 J

/кg

0.5

1.0

1.5

2.0

2.5

3.0

12

3

b

RIA tests:


Fuel Test Rig :

1 – test channel vessel;

2 – hydraulic power drive;

3 – pressure gage;

4 – fuel rods;

5 – in-reactor direct-charge detector;

6 – movable absorber screens;

7 – flow spreader;

8 – thermocouple attached in the

center of fuel stack,

9 – thermocouple in the coolant;

10 – cladding attached thermocouple

5

Rea

ctor

core

4

1

2

6

7

Core mid-plane

8

59

5

10 3

RIA tests:


6

Parameters Test #1

Test #2

Test #3

Test #4

Test #5

Bundle of fuel rodlets

Un-irradiated fuel rods 1 1 1 1 1Re-fabricated rodlets 2 2 2 2 2Burn-up of re-fabricated rodlets, MWd/kgU ~60 ~50 ~60 ~70 ~60

Instrumented fuel bundle

Thermocouples exposed to coolant:- at the inlet of fuel bundle;- throughout the fuelled length of rod ;- at the outlet of fuel bundle

111

111

111

111

111

Thermocouple in the center of fuel stack (un-irradiated fuel)

1 1 1 1 1

Thermocouple attached on the cladding of un-irradiated fuel rod

2 2 1 - 2

Thermocouple in the center of fuel stack of the rodlet

2 2 1 1 2

Direct-charge detector 1 1 2 2 1Gas pressure transducer inside the rodlet plenum - - 1 1 -

Main Specifications of Fuel Rodlets for the RIA Simulation Experiment

RIA tests:


7

Main Parameters of the RIA Simulation Experiment

Parameters Measure-ment units

Test #2

Test #3

Test #4

Burn-up of re-fabricated rodlets MWd/kgU 48 59 67Initial average linear heat generation rate throughout the length

Un-irradiated fuel rodW/cm

270 210 175Re-fabricated rodlets 230 205 140

Pulse amplitude at the level of thermocouple attachment

Un-irradiated fuel rod - 3.32 3.36 3.23Re-fabricated rodlets - 3.32 3.14 3.23

Pulse half-width с 1.75 1.58 2.9Time of screen movement (time of pulse rise) с 2.0 1.2 0.4

Peak temperature in the center of fuel stack at the place of thermocouple attachment

Un-irradiated fuel rod

оС

1670 1318 1508

Re-fabricated fuel rodlet #1 1458 1406 1173

Re-fabricated fuel rodlet #2 1468 - -

Calculated hMAX of fuel stack Un-irradiated fuel rod

105 J/kg

5.3 4.1 4.0

Re-fabricated fuel rodlet #1 4.9 3.9 2.8

Re-fabricated fuel rodlet #2 4.8 - -

Enthalpy increment of fuel stack in pulse

Un-irradiated fuel rod

105 J/kg

2.0 1.6 1.7

Re-fabricated fuel rodlet #1 2.0 1.5 1.1

Re-fabricated fuel rodlet #2 2.0 - -

RIA tests:


8

a) b)

Fission gas release as a function of the peak temperature (a) and peak fuel enthalpy (b).

0

5

10

15

20

25

30

1000 1500 2000 2500

Peak fuel temperature, оС

Fis

sio

n g

as r

ele

ase,

%

IGR_50 МВт*сут/кгU

BIGR_50 МВт*сут/кгU


MIR_50 МВт*сут/кгU




0

5

10

15

20

25

30

2E+05 3E+05 4E+05 5E+05 6E+05 7E+05

Peak fuel enthalpy, J/kg UO2F

issio

n g

as r

ele

ase,%

IGR_50 МВт*сут/кгU





NSRR_70 МВт*сут/кгU

60 МВт*сут/кгU

50 МВт*сут/кгU

LOCA tests:


9

200

300

400

500

600

700

800

900

-300 -200 -100 0 100 200 300 400 500 600Time, s

Fu

el c

lad

din

g t

em

pe

ratu

re, о

С

I

II

IVIII

I - Evaporation (no longer than 5h)

II - Holding at cladding draying temperature (150-250с)

III(180-200с), IV(60-120с) - Ultimate DBA (phase 2)

No longer than 5h

Temperature scenario of the LOCA simulation experiment

LOCA tests:


10

Schematic arrangement of fuel rodlets, thermocouples and sensors in the test assembly

1

2

34

5

6

7

8

9

1011

12

13

14

15

16

17

19

18

Direct-charge

detector

Thermocouple

inside the fuel

stack

Thermocouple

in the coolant

Thermocouple

attached to the

cladding

Fuel rod

instrumented

with pressure

gauge

Re-fabricated

fuel rod

LOCA tests:


11

Main Specifications of the LOCA Simulation Tests

Test Fuel, number of rodlets in the test assembly

Primary pressure,

MPa

Temperature range,

оС

Dewatering time, min

State of fuel rodlets

Un-irradiated fuel rods

High-burn-up fuel rodlets(burn-up, Wd/kgU)

Intact Failed

BT-2 16 3(50) 1.7 500-940 40 +

BT-3 16 3(58) 1.2 500-820 10 + +

BT-3 LOCA test experimental data

13

BT-3 experiment data: of the direct-charge detector and temperatures of claddings

0

100

200

300

400

500

600

700

800

900

18:05 18:10 18:15 18:20 18:25 18:30

Time, h: min

Te

mp

era

ture

, оС

0

1

2

3

Rec

ord

ing

s o

f th

e d

irec

t-ch

arg

e

tran

sd

uc

er,

mV

z - Distance from the

core mid-plane, mm

Т9 - z=402

T11,Т12 - z=354

Т13 - z=408 Т9

Т11

Т13Т12

direct-charge transducer


14

Gas pressure in un-irradiated (Рunir) and irradiated (Рrefbr) fuel rodlets.


15

Outer appearance of the claddings at the place of fuel failure

Fuel rodlet #2 Fuel rodlet #3 Fuel rodlet #4 Fuel rodlet #13


16

Maximum circumferential strain of claddings in the test fuel assembly (a). Changes

in the cross-sectional flow area of the coolant (b)

LOCA tests methodology of single fuel rods

17

Schematic representation of design

(a), cross-section (b) and fixing of

fuel rodlet (c) in the test rig:

1 - thermocouple;

2 - shroud;

3 - basket;

4 - insulator;

5 - heater;

6 - water supply pipe of the test rig;

7 - pressure gage

a

b

c

Fuel rodlet intended for irradiation testing in the MIR reactor channel: 1 -

ferromagnetic core; 2 - pressure gage; 3 - lower gas plenum; 4 - fuel stack; 5 - upper

gas plenum

Main Specifications of the LOCA tests of single fuel rods

19

Parameter Test 1 Test 2

Outer / inner diameter of standard fuel rod selected for refabrication, mm: cladding

fuel stack9.1/7.93

7.8/09.1/7.93

7.8/0

Maximum fuel burn-up in the fuel rod under test, MW·day/kgU

45 60

Peak cladding temperature, оС 807 750

State of fuel rodlet after testing failed intact

Cladding temperature during cladding failure, оС 770-780 -

Rate of temperature increase during failure, оС/s 3.6 1.2*

Pressure drop on the cladding during fuel failure, MPa 5.0 5.8*

Main Specifications of the LOCA simulation tests with the use

of single fuel rods

Note: * pressure drop and rate of temperature increase for the intact fuel rodlet are given at the

maximum temperature of 750°С achieved during test #2.

Experimental data of single fuel rods testing

18

a) b)

Cladding temperature variation with time (1) at 10 to 20 mm above the middle spacer grid

and time history of gas pressure (2) in the lower gas plenum during tests 1 (a) and 2 (b)

0

100

200

300

400

500

600

700

800

900

11:20 11:30 11:40 11:50 12:00 12:10

Time, h:min

Tem

per

atu

re, оС

0

1

2

3

4

5

6

7

8

9

Pre

ssu

re, M

Pa

1

2

0

100

200

300

400

500

600

700

800

14:05 14:15 14:25 14:35 14:45 14:55

Time, h:minT

emp

era

ture

, оС

0

1

2

3

4

5

6

7

8

Pre

ssu

re, M

Pa

1

2


20

a) b)

Surface appearance of the cladding and X-

ray images taken at place of cladding failure

during test #1* (a) and the maximum

deformation during test #2(b)

Note: * - X-ray image is rotated 90º relative to the

photograph of surface appearance

Profile diagrams of the cladding and fuel rodlets

before (1) and after test #1 (2) and #2(3)

9

9.5

10

10.5

11

11.5

12

0 200 400 600 800 1000

z, mmd

, m

m 2

1

3


21

a) b)

Fuel cladding structure after test #1 (a) at the

rupture cross-section and after test #2 (b) at

the cross-section of its maximum deformation

Grain particle size of extracted fuel

Conclusion

22

On the MIR reactor have been developed techniques and devices for

testing of VVER-1000 high burn-up fuel with simulation RIA and LOCA

design basis accidents. At tests measurements of the coolant, cladding

and fuel temperatures, as well as elongation of fuel eleents and fission

gas relese are providing.

RIA simulation experiment in the MIR test channel relevant to

temperatures and enthalpy of DBA parameters for the VVER-1000 fuel

and satisfactory variation of the main parameters can be achieved by

selecting the appropriate pulse parameters of experiments.

LOCA experiments could be provided for single fuel rods as well as for

fuel assembly with several fuel rods.

Results of investigations are used for qualification of new designs of fuel

and verification of of physical models and codes.

Thank you for your attention!

For further information please contact:

Alexey IZHUTOV

Deputy Director —Science & Research

Тел.: 8 (84-235) 9-81-64

E-mail: [email protected]

Experimental Study of the VVER-1000 Fuel Rods Behavior under … · 2018. 3. 2. · Several...

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Transcript of Experimental Study of the VVER-1000 Fuel Rods Behavior under … · 2018. 3. 2. · Several...