MMD (µm) MMD (µm)

(1)

OVERVIEW OF MELCOR ACTIVITIES IN CIEMAT (2011)

C. Lopez , M. García, B. Otero, LE. Herranz Unit of Nuclear Safety Research

CIEMAT, SPAIN

(2)

• Containment thermal-hydraulic and aerosol behavior.

LWR (Phebus-FP project) MELCOR 1.8.6 YV 3084 SFR (CP-ESFR project) MELCOR 1.8.6 YV 3084

Scenarios Addressed

• Plant analysis.

BWR3 (Spanish CSN) MELCOR 1.8.6 YV 3084

• Fuel degradation in the presence of air.

SFP (OECD-SFP project) MELCOR 1.8.6 YV 3084 SFP

(3)

• Plant analysis BWR

• SFR-ABCOVE

• Phebus FPT3

184 185 186 2.1

On it On it COR

Converter COR

Converter

186 2.1.1576

SNAP SNAP

SNAP post pro SNAP post pro SNAP running SNAP running

Inputs updating

(4)

• OECD-SFP project: extension to PWR fuel assemblies

• Phebus-FPT3 Benchmark (Sarnet 2)

• Extension of validation against SFR available data (source term)

• Analysis of SGTR scenarios

Stress the need of a SNAP course, not easy to handle

Further work and final remarks

(5)

THANK YOU FOR YOUR ATTENTION

(6)

<Diagnostic Message> Time= 3.6644E+04Dt= 9.4609E-01 Cycle= 36593 (CVH) Attempted cycle advancement was unsuccessful - DT reduced to = 4.4202E-01

Melgen OK!

ERROR-melcor Melgen OK!

ERROR-melcor

v2.1.1576

(Unoptimized)

v2.1.1576

(Unoptimized)

v2.1.4206 v2.1.4206

WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Diagnostics during input processing TF package:

NO errors during input processing TF package

WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Diagnostics during input processing COR package:

WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Diagnostics during input processing TF package:

NO errors during input processing TF package

WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW Diagnostics during input processing COR package:

ERROR-melgen ERROR-melgen

Inputs updating:

(7)

1. BWR3-Mark I

Accident Sequence

- SBO

- High pressure ( ~75 bar ) - 6 SRVs available

- High pressure ECCS and

IC unavailable

(8)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0 1 2 3 4 5 6 7 8 9 10 11 12

Time (h)

MMD (µm)

MMD_DOME C1 MMD_DOME C12

Updating with the MELCOR BMP (Nureg/CR-7008) Revision of the aerosol characterization:

0.0 0.5 1.0 1.5 2.0 2.5

0 1 2 3 4 5 6 7 8 9 10 11 12

Time (h)

MMD (µm)

MMD_WW C1 MMD_WW C2

1. BWR3-Mark I

RPV WW

Range of size, shape factors, sticking coefficient…..

1-50 µm

0.1-10 µm

(9)

DTmax, DTplot

1. BWR3-Mark I

0 500 1000 1500 2000 2500

2 2.5 3 3.5 4 4.5 5 5.5 6

Time (h)

Temperature (K)

C1-Ring1 C1-Ring2 C1-Ring3

1 2 3

(10)

• Zr air oxidation leading to cladding ignition

• Prototypic BWR FAs (electrically heated with MgO fuel substitute) in prototypic SFP racks (SS walls with neutron absorber layer - Boraflex)

• Assemblies arrangements

− 1x1: “hot-neighbor” situation → ignition axial propagation

− 1x4: “cold-neighbor” situation → ignition radial propagation

2. SFP

(11)

Base Case

Hydraulic model Oxidation model

S

_lam

Breakaway Transition Pre- rate

k LF k

_ox-air

CVH nodalization

Coarse Fine

n = 6 n = 13 τ

*

( )

Re

^LAM _H _S

S L F A k k

D A

⋅ ⋅

= + ⋅

( )

0 . 1 LF

LF α LF

k 1 α

k k α

max max

post pre

Trans

−

= −

⋅

− +

⋅

=

∫ ^′ ^′

= ^t

0

t τ d LF t

42.04 12.58

10 τ ≅ T

Base Case, n=10

2. SFP: Modeling studies

(12)

The coarse nodalization leads to different results in spite of preserving total hydraulic losses The variation of S

_LAM

in the range of the experimental uncertainty sligthly affects the results The variation of k in the range of the experimental uncertainty hardly affects the results

The coarse nodalization leads to different results in spite of preserving total hydraulic losses The variation of S

_LAM

in the range of the experimental uncertainty sligthly affects the results The variation of k in the range of the experimental uncertainty hardly affects the results

BWR 1x1 BWR 1x1

2. SFP: CVH nodalization and hydraulic model

(13)

Heavily parametrized (slight variation of τ correlation)

The BC does not seem to represent the actual oxidation phenomena

Best estimate is achieved by accelerating pre-breakaway kinetics and making abrupt transition Heavily parametrized (slight variation of τ correlation)

The BC does not seem to represent the actual oxidation phenomena

Best estimate is achieved by accelerating pre-breakaway kinetics and making abrupt transition BWR 1x4

BWR 1x4

LF_max LF_max LF=1.0

LF=1.0 LF=1.0 LF=1.0

2. SFP: Zr air oxidation model

(14)

Focus:

Project: EU-ESFR (SP3 - Safety)

Scenario: ABCOVE Program

CSTF Facility

AB5 Na spray fire

AB6 NaI + Na spray fire

AB7 Na pool fire – NaI injection

In-containment Aerosol dynamics

3. SFR

(15)

3. SFR: modeling challenges

CB

Q

_ch

+ Q

_s

CB

Q

_ch

+ Q

_s

100% atm 100% atm

0 500 1000 1500 2000 2500 3000 3500

0 1000 2000 3000 4000 5000

Time (s)

Energy Source (MJ)

TF TF

Q

_ch

Q

_ch

Q

_s

To account for the ∆ T between the aerosols and the atmosphere

Q

_s

To account for the ∆ T between the

aerosols and the atmosphere

(16)

CIEMAT Q

_ch

CIEMAT

Q

_ch

50% atm + 50% ‘Fire ball’ 50% atm + 50% ‘Fire ball’

(TF)

(TF) (HS) (HS)

Fire ball hypothesis

(HS rectangular, vertical)

Fire ball hypothesis

(HS rectangular, vertical)

• Shielding effect

• HS surface

• HS thickness

• HS density

• HS Cp

• Shielding effect

• HS surface

• HS thickness

• HS density

• HS Cp

A dense & compact mass to preserve the thermal

capacity and thermal inertia of the hot aerosols cloud A dense & compact mass to preserve the thermal

capacity and thermal inertia of the hot aerosols cloud

3. SFR: modeling challenges

(17)

300 350 400 450 500 550 600 650 700

0 1000 2000 3000 4000 5000

Time (s)

Temperature (K)

AB5 100 % atm Fire Ball approx

3. SFR: modeling challenges

(18)

Objective FPT3 test:

Flow Fuel Containment

Steam poor (steam starvation)

BR3 24.5 GWd/tU B₄C control rods

Evaporating acidic sump Recombiners

● Uncertainty analysis to the Th’s and aerosol modeling of FPT3

Aerosols

Iodine source Particle size Density

Th’s: 24 var

Rh

_o

T

_wet-cond

4. Phebus-FPT3

Uncertainty

(19)

MELCOR

93 runs

MELCOR

93 runs

Stochastic approach: Wilks Theory

4. Phebus-FPT3: User tool kit for uncertainty analysis

“93 samplings determine a 95% of the CI with a 95% of CL”

Fortran Applications:

• n samples

• Different distributions

• Time dependent profiles BC

• n samples

• Different distributions

• Time dependent profiles BC

n inputs: Postprocessing:

• n output files

• Defined output variables

• n output files

• Defined output variables

Specific for Phebus-FPT3

(20)

T Vap Time

Vapo mass flow rate