MELCOR 2.1 Leak Path Factor

Sandia National Laboratories is a multi
-
program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary

of Lockheed
Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE
-
AC04
-
94AL8500
0.

MELCOR 2.1 Leak Path Factor
Assessment and Guidance

David L.Y.
Louie

dllouie@sandia.gov

LPF Application of MELCOR


MELCOR is being developed by SNL for the Nuclear
Regulatory Commission (NRC). Details about the
development of MELCOR from the previous MELCOR
presentation were discussed in this workshop .


Even though MELCOR is developed for reactor applications,
but because of the modular in nature, a user can select
certain modules (packages) to be used in LPF applications.


MELCOR is a DOE Toolbox Code for LPF applications


DOE nuclear and nonnuclear facilities for many years


MELCOR 1.8.5 is designated version (which is an obsolete)


Many users have used MELCOR 1.8.6, but requires additional
validation and verification procedures


MELCOR 1.8.6 is unsupported by SNL, so that much of the effort can
be devoted to the development of MELCOR 2.0 and beyond.


2

Code Version Differences


FORTRAN language has been used in the life of the MELCOR
code development; however, beginning with Version 2.0, the
version of FORTRAN has been switched from FORTRAN77 to
FORTRAN95 to ensure future developments in terms of
extensibility and maintainability.


Beginning with Version 2.0, there is a significant change in the
code architecture, even though most the 1.8.6 algorithms
were kept intact.


The original Version 2.0 was developed using the object
-
oriented
approach in terms of input and calculated variables, which contributes
the input format changes beginning with this version.


The new input format utilizes the “block input” approach in different
levels of inputs: program[MELGEN, MELCOR], packages[CVH, FL, etc.],
and objects [CV_ID, etc.] .

3

4

Switching to MELCOR 2.1


S
ome re
-
training may be required for using the “block input”
approach for the MELCOR 1.8.6 users.


Easy
-
to
-
use converter, which allows the decks developed in
Version 1.8.5 without the “COR” package, and Version 1.8.6
to be converted into MELCOR 2.1.


Symbolic Nuclear Analysis Package (
SNAP
) developed by Applied
Programming Technology, Inc. for NRC


There is a plug
-
in for MELCOR


The use of SNAP requires a license agreement with NRC


Some users may find CVH thermodynamic input difficult to
use. To help this, an alternative Input,
CV_THERM
, restores
some of the Version 1.8.6 features.

5

Assessments


The assessment task is in progress at SNL
–

Volume III
(Demonstration Problems) of the manual is being developed.


Appendix A of this manual devotes for the non
-
reactor
application


This appendix addresses a finding for MELCOR with the gaps analyses
conduced by DOE in 2004, which indicated inadequate sample
problems for LPF specific cases.


Much of the thermal hydraulics and aerosol physical models of
MELCOR are assessed using experiments tailored for reactor
applications.


For LPF applications, we try to verify the MELCOR results from the
previously reported calculations done, such as those results reported
in the DOE MELCOR guideline report, and other reports, such as from
LA
-
UR
-
03
-
7945 by Jordan and Leonard.

6

MELCOR LPF Results (%)* from MELCOR Guidance Report

Test
Problem

Reference Value from
interpolated from
(figures) in Guidance
Report

1.8.5

1.8.6

2.1

Appendix C

~8.1 (7
-
6)

8.13

8.10

8.09

Appendix D

~0.39 (7
-
12)

0.39

0.39

0.39

Appendix E

~26.3 (7
-
18)

26.66

26.64

26.63

Appendix F

~0.43 (7
-
21)

0.43

0.43

0.43

Appendix G

1000 g

100g

10g

1g



~11.58 (7
-
26)

~12.03 (7
-
26)

~12.09 (7
-
26)

~12.09 (7
-
26)



10.42

10.79

10.83

10.83



10.39

10.75

10.79

10.79



10.38

10.74

10.78

10.78

7

*
1.8.5
is calculated using the official release version RL, 1.8.6 is calculated using the official
release
version
YV 3404, and 2.1 is calculated using revision 1570.

MELCOR Results
–
Example 3

of LA
-
UR
-
03
-
7945
#

8

Case

Crack
Width
(mm)

Wind
Speed
(mph)

Smoke
Generated
by Fire (kg)

HEPA Collect
Efficiency (%)

MELCOR LPF Results (fraction)*

1.8.5
Reference**

1.8.5

1.8.6

2.1

1

0.5

30

None

99.98

3.9
×
10
-
3

3.0
×
10
-
3

3.0
×
10
-
3

3.0
×
10
-
3

2

1

30

None

99.98

9.3
×
10
-
3

7.5
×
10
-
3

7.5
×
10
-
3

7.4
×
10
-
3

3

2

30

None

99.98

2.0
×
10
-
2

1.7
×
10
-
2

1.7
×
10
-
2

1.7
×
10
-
2

4

5

1

None

99.98

5.1
×
10
-
2

4.5
×
10
-
2

4.4
×
10
-
2

4.4
×
10
-
2

5

0.5

10

None

99.98

2.8
×
10
-
7

1.2
×
10
-
7

2.3
×
10
-
7

2.3
×
10
-
7

6

0.5

20

None

99.98

1.1
×
10
-
4

7.2
×
10
-
5

7.6
×
10
-
5

7.4
×
10
-
5

7

0.5

30

None

99.98

1.0
×
10
-
3

9.6
×
10
-
4

9.6
×
10
-
4

9.3
×
10
-
4

8

0.5

30

10

99.98

2.6
×
10
-
5

2.8
×
10
-
3

2.8
×
10
-
3

2.7
×
10
-
3

9

0.5

30

25

99.98

1.1
×
10
-
5

2.5
×
10
-
3

2.5
×
10
-
3

2.4
×
10
-
3

10

0.5

30

50

99.98

3.9
×
10
-
3

2.1
×
10
-
3

2.1
×
10
-
3

2.0
×
10
-
3

11

0.5

30

None

99.95

3.9
×
10
-
3

3.0
×
10
-
3

3.0
×
10
-
3

3.0
×
10
-
3

#
LA
-
UR
-
99
-
2513 (C. Shaffer and M. Leonard)

*
1.8.5 values are using the official release version RL, 186 values are calculated using the official release version YV 3404,

an
d 2.1 values are
calculated using official release version RL NL 4261.

**1.8.5 reported values from Table 4
-
2 of LA
-
UR
-
03
-
7945

Useful Features in MELCOR 2.1


Physical Models:


Counter
-
current flow model (FL_CCF card)
–

allows coupling of two
paths through momentum exchange using Epstein
-
Kenton
correlations
–

mainly for natural circulations


Benchmark against
CFD code


Can be used to address the counter
-
current exchange of combustion
gases through open doorway in a fire scenario


Turbulent aerosol deposition model (RN1_TURB) [optional input]
–

models the aerosol deposition in pipes or ducts
-
the turbulent flow
regime. (cautions should be placed when applying this model for the
LPF applications, because the benchmark is done for the reactor
accident conditions)

9

Useful Features (continued)


Enhance Features:


Aerosol deposition deactivation flag
(RN1_ADFG card) [optional input]
–

allows to switch off deposition
models, such as gravitational,
thermophoresis

and diffusive settling


Filter model
–

flexible enough to permit the user to model a variety of
aerosol or vapor deposition, flow and degradations in filters
–

via
control functions


Spray model
–

Because of the generality of the spray inputs, the spray
model can be used to simulate the fire sprinkler system
–

reduce
thermal condition of the accident and to scrub radionuclides/aerosols
to minimize the LPF value.





10

Useful Features (
concluded)


Utility Features:


Common block feature
“(((name block” and ending with “)))” can be
used to allow a single input file to simulate a number of different runs,
especially good for sensitivity studies.


ResultsReviewer

Utility, in conjunction of the RN input (RN1_VISUAL)
to provide a way to study the aerosols


Example
–

Appendix E

in the MELCOR Guidance Report
–

Simulation for
the
V300

adjacent to the room with the fire and aerosol release.


SNAP simulation
–

Appendix C sample in the MELCOR Guidance
Report
–

aerosol fraction display, with evacuation door simulated.

11

Conclusions


MELCOR 2.x represents the latest version of MELCOR, which
should be used by the safety basis community for the LPF
applications.


Assessments of this current code version show results that
are consistent with MELCOR 1.8.5, the current DOE Toolbox
code.


With the enhancements to be included in this code version
and beyond, the safety analyst should be benefited.

12

Future Development of MELCOR


Desired improvement:


Hot gas layer modeling for simulating fire scenarios should be added.


Currently MELCOR only models deflagration of hydrogen and carbon
monoxide, combustion of other solid, liquid and gas (including user
-
defined type) should be added.


MELCOR may be used in the development of a fuel
reprocessing source term analytical tool for NRC


Empirical correlations for aerosol generation size/mass and wall
failure phenomena from liquid explosions and liquid criticality events


Additional development model may be included in the effort that
could be benefited for the DOE safety basis community for the LPF
applications.


13

Questions?




14

SNAP Interface

15

return

Example 3 of LA
-
UR
-
03
-
7945

Brief Description


Fire occurs in the
lab


Source: 1 g PuO
2


Sensitivity Studies


Leakage
–

door gap size


Wind speed


Smoke


Filter efficiency

Nodalization: 55 CV multi
-
level problem

16

RETURN

Referenced from LA
-
UR
-
99
-
2513
(C. Shaffer and M. Leonard)

Thermodynamic Input Options

CV_ID

‘VOLUME

ONE’

‘RCS’

CV_ARE

NOCF

12
.
5

CV_THR

NONEQUIL

FOG

ACTIVE

CV_PAS

SEPARATE POOLANDATM
SATURATED
ATURATED

CV_PTD

PVOL

7
.
0
E
6

CV_BND

ZPOL

9
.
5

CV_VAT

2

!N

CVZ

CVVOL



1

0
.
0

0
.
0

!

Bottom

at

0

m



2

10
.
0

150
.
0

!

150

m
3

total

volume

CV_ID

‘VOLUME

ONE’

‘RCS’

CV_ARE

NOCF

12
.
5

CV_THR

NONEQUIL

FOG

ACTIVE

CV_THERM 1



1
PVOL 7.0E6 ZPOL 9.5

CV_VAT

2

!N

CVZ

CVVOL



1

0
.
0

0
.
0

!

Bottom

at

0

m



2

10
.
0

150
.
0

!

150

m
3

total

volume

Current Input Format

Alternative Input Format via CV_THERM

17

RETURN

Typical SNAP Conversion


IMPORT input file (version 1.8.5 without COR or version 1.8.6)


Selected version to be converted (i.e., 2.1)


Export input file


18

RETURN

Nodalization of Appendix E Sample

19

RETURN

Reactor Hot Leg Natural Circulation

20

NUREG
-
1922

RETURN