LEADER Project

LEADER Project

Analysis of Representative DEC Events of the ETDR with RELAP5 and CATHARE

Giacomino Bandini - ENEA/BolognaGenevieve Geffraye – CEA/Grenoble

LEADER 4th WP5 MeetingKarlsruhe, 22 November 2012

2

Outline

Analyzed DEC Transients at EOC ALFRED Modeling Transient Results Conclusions

3

Analyzed DEC Transients

TRANSIENT Initiating Event (t = 0 s) Reactor scram and threshold

Primary pump trip

MHX FW trip

MSIV closure DHR startup

TR-4: Reactivity insertion (UTOP)

Insertion of 250 pcm in 10 s No No No No No

TO-3: Reduction of FW temp. + all pumps stop

FW temp. from 335 °C down to 300 °C in 1 s

2 s, low pump speed 0 s 2 s 2 s DHR-1 at 3 s

(4 IC loops)

TO-6: Increase of FW flowr. + all pumps stop

20% increase in FW flowrate in 25 s

2 s, low pump speed 0 s 2 s 2 s DHR-1 at 3 s

(4 IC loops)

TDEC-1: Total ULOF All primary pump coastdown No 0 s 1 s 1 s DHR-1 at 2 s

(3 IC loops)

TDEC-3: ULOHS All MHX feedwater trip No No 1 s 1 s DHR-1 at 2 s (3 IC loops)

T-DEC4: ULOHS + ULOF

All primary pumps and MHX feedwater trip No 0 s 0 s 0 s DHR-1 at 2 s

(3 IC loops)

T-DEC5: Partial block. in the hottest FA

10% to 97.5 % blockage at hottest FA inlet No No No No No

T-DEC6: SCS failure Depressurization of all secondary circuits

2 s, low second. pressure No 2 s No No

Main events and reactor scram threshold

4

RELAP5 Modeling

Feedwater

Steam

521- 8

531- 8

551- 8 561-8

151-

8

Feedwater

Steam

521- 8

531- 8

551- 8 561-8

151-

8

841 - 4

851 - 8441 -8

801 - 4

811-4831 - 4

815

401 - 8

841 - 4

-

801 - 4

811-4831 - 4

815

841 - 4

-

801 - 4

811-4831 - 4

815

611 - 8

841 - 4

-

801 - 4

811-4831 - 4

815

611 -

711-

731-

741- 4

751 - 8

761- 4

621- 4

641 - 4

771

781 - 8

601- 4

661 - 4

611 -

711- 8

731- 8

741- 4

751 -

761- 4

621- 4

641 - 4

771 -8

781 -

601- 4

661 - 4

611 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781

601- 4

661 - 4

841 - 8

-

801 - 4

811-4831 - 4

815

841 -

-

801 - 8

811-8831 - 8

815

611 -

841 -

-

801 -

811-831 -

411 -8

611 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771

781

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781 -

601- 8

661 - 8

611 -

711-

731-

741- 8

751 -

761- 8

621- 8

641 - 8

841 - 4

851 - 8441 -8

801 - 4

811-4831 - 4

815

401 - 8

841 - 4

-

801 - 4

811-4831 - 4

815

841 - 4

-

801 - 4

811-4831 - 4

815

611 - 8

841 - 4

-

801 - 4

811-4831 - 4

815

611 -

711-

731-

741- 4

751 - 8

761- 4

621- 4

641 - 4

771

781 - 8

601- 4

661 - 4

611 -

711- 8

731- 8

741- 4

751 -

761- 4

621- 4

641 - 4

771 -8

781 -

601- 4

661 - 4

611 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781

601- 4

661 - 4

841 - 8

-

801 - 4

811-4831 - 4

815

841 -

-

801 - 8

811-8831 - 8

815

611 -

841 -

-

801 -

811-831 -

411 -8

611 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771

781

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781 -

601- 8

661 - 8

611 -

711-

731-

741- 8

751 -

761- 8

621- 8

641 - 8

ALFRED Nodalization scheme with RELAP5

8 MHXs

8 Secondary loops Primary circuit

8 IC loops

Steam line

Feedwater line

100

101102109

110

115

060061-8 070

050

020

200 151-8

121-8

131-8

141-8

220

230

210

100

101102109

110

115

060061-8 070

050

020

200 151-8

121-8

131-8

141-8

220

230

210

100

101102109

110

180

060061-8 070

050

020

200 151-8

121-8

131-8

141-8

220

230

210

Feedwater

Steam

521- 8

531- 8

551- 8 561-8

151-

8

Feedwater

Steam

521- 8

531- 8

551- 8 561-8

151-

8

841 - 4

851 - 8441 -8

801 - 4

811-4831 - 4

815

401 - 8

841 - 4

-

801 - 4

811-4831 - 4

815

841 - 4

-

801 - 4

811-4831 - 4

815

611 - 8

841 - 4

-

801 - 4

811-4831 - 4

815

611 -

711-

731-

741- 4

751 - 8

761- 4

621- 4

641 - 4

771

781 - 8

601- 4

661 - 4

611 -

711- 8

731- 8

741- 4

751 -

761- 4

621- 4

641 - 4

771 -8

781 -

601- 4

661 - 4

611 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781

601- 4

661 - 4

841 - 8

-

801 - 4

811-4831 - 4

815

841 -

-

801 - 8

811-8831 - 8

815

611 -

841 -

-

801 -

811-831 -

411 -8

611 -

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771

781

711-

731-

741- 4

751 -

761- 4

621- 4

641 - 4

771 -

781 -

5

CATHARE Modeling

ALFRED Nodalization scheme with CATHARE

Primary circuit

2 Secondary loops (weight 4)

2 IC loops (weight 4)

TR-4: Reactivity insertion (1/3)(RELAP5 – CATHARE Comparison)

Core and MHX powers Core and MHX powers

ASSUMPTIONS: Insertion of 250 pcm in 10 s No feedwater control on secondary side Different fuel rod gap dynamic model in RELAP5 and CATHARE Fuel-clad linked effect fuel expansion according to clad temperature (closed gap)

6

7

TR-4: Reactivity insertion (2/3) (RELAP5 – CATHARE Comparison)

Core temperatures Core temperatures

Total reactivity and feedbacks Total reactivity and feedbacks

8

TR-4: Reactivity insertion (3/3) (RELAP5 – CATHARE Comparison)

MAIN RESULTS: Initial core power peak around 700 MW Maximum clad temperature remains below 650 °C Maximum fuel temperature (hottest FA, middle core plane, pellet centre) exceeds

the MOX melting point of about 2760 °C only local fuel melting no extended core melting


9

T-DEC1: ULOF (1/3) (RELAP5 – CATHARE Comparison)

Active core flowrate Active core flowrate


10




11



ASSUMPTIONS: No feedwater control on secondary side Fuel-clad not-linked effect fuel expansion according to fuel temperature

MAIN RESULTS: Natural circulation in primary around 23% of nominal value Core power reduces down to about 200 MW Initial clad peak temperature at 750 °C; max clad temperature stabilizes around 650 °C

12

T-DEC3: ULOHS (1/3) (RELAP5 – CATHARE Comparison)Core and MHX powers Core and MHX powers


13

T-DEC3: ULOHS (2/3) (RELAP5 – CATHARE Comparison)

Core and vessel temperatures Core and vessel temperatures


14

T-DEC3: ULOHS (3/3) (RELAP5 – CATHARE Comparison)

ASSUMPTIONS: 3 out of 4 IC loops of DHR-1 system in service No heat losses from the vessel external surface

MAIN RESULTS: Core power progressively reduces down towards decay level Maximum clad temperature rises up to about 700 °C after 30 minutes Maximum vessel temperature rises up to about 650 °C after 30 minutes

15

T-DEC4: ULOHS + ULOF (1/3) (RELAP5 – CATHARE Comparison)

Active core flowrate Active core flowrate


16




17



ASSUMPTIONS: 3 out of 4 IC loops of DHR-1 system in service No heat losses from the vessel external surfaceMAIN RESULTS: Natural circulation in primary circuit reduces down to very low value (around 1%) Core power progressively reduces down towards decay level Max T-clad rises up to 800 °C after about 15 minutes and stabilizes around 825 °C Maximum vessel temperature rises up to about 500 °C after 60 minutes

18

TO-3: FW temp. reduction + PP stop (1/2) (RELAP5 Results)

Total reactivity and feedbacks Core temperatures

Active core flowrate (short term) Active core flowrate (long term)

19

TO-3: FW temp. reduction + PP stop (2/2) (RELAP5 Results)

Core decay and MHX powers Primary lead temperatures

ASSUMPTIONS: Loss of one preheater (FW temperature from 335 °C down to 300 °C in 1 s) + primary

pump coastdown reactor scram at t = 2 s on low pump speed signal 4 IC loops in service for decay heat removalMAIN RESULTS: Power removal by 4 IC loops of DHR-1 system is about 7 MW No risk of lead freezing after DHR-1 start-up Lead freezing at MHX outlet is reached after about 2 hours (cold lead at the MHX

outlet to the core inlet without significant mixing in the cold pool above MHX outlet)

20

TO-6: FW flowrate + 20% + PP stop (1/2) (RELAP5 Results)

Total reactivity and feedbacks Core temperatures

Active core flowrate (short term) Active core flowrate (long term)

21

TO-6: FW flowrate + 20% + PP (2/2) (RELAP5 Results)

Core decay and MHX powers Primary lead temperatures

ASSUMPTIONS: FW flowrate increase of 20% + primary pump coastdown reactor scram at t = 2 s on

low pump speed signal 4 IC loops in service for decay heat removalMAIN RESULTS: Power removal by 4 IC loops of DHR-1 system is about 7 MW No risk of lead freezing after DHR-1 start-up Lead freezing at MHX outlet is reached after about 2 hours (cold lead at the MHX

outlet to the core inlet without significant mixing in the cold pool above MHX outlet)

22

T-DEC6: SCS failure (1/2) (RELAP5 Results)

Secondary pressure Total reactivity and feedbacks

Core and MHX powers Primary lead temperatures

23

T-DEC6: SCS failure (2/2) (RELAP5 Results)

Core decay and MHX powers Core and vessel temperatures

ASSUMPTIONS: Depressurization of all secondary circuits (no availability of DHR-1 system) reactor

scram at t = 2 s on low secondary pressureMAIN RESULTS: Initial MHX power increase up to 800 MW no risk for lead freezing Slow primary temperature increase due to large thermal inertia of primary system

and efficient hot lead mixing in the cold pool at MHX outlet before to reach the core inlet

24

TDEC-5: Partial FA blockage (RELAP5 Results)

ASSUMPTIONS: ΔP over total FA = 1.0 bar ΔP at FA inlet = 0.22 bar No heat exchange with

surrounding FAS Flow area blockage at FA inlet

MAIN RESULTS: 75% FA flow area blockage 50% FA

flowrate reduction 85% blockage T max clad = 700 °C No clad melting if area blockage < 95% Fuel melting if area blockage > 97.5% 50% inlet flow area blockage can be

detected by TCs at FA outlet

25

Conclusions

The analysis of DEC transients with RELAP5 and CATHARE codes has highlighted the very good intrinsic safety features of ALFRED design thanks to:

Good natural circulation characteristic, Large thermal inertia, and Significant negative reactivity feedbacks

In all analyzed transients there is no risk for significant core damage or risk for lead freezing large grace time is left to the operator to take the opportune corrective actions to bring the plant in safe conditions in the medium and long term

Documents

LEADER Project