<s>
RELAP5-3D	B-Application
is	O
a	O
simulation	O
tool	O
that	O
allows	O
users	O
to	O
model	B-Application
the	O
coupled	O
behavior	O
of	O
the	O
reactor	O
coolant	O
system	O
and	O
the	O
core	O
for	O
various	O
operational	O
transients	O
and	O
postulated	O
accidents	O
that	O
might	O
occur	O
in	O
a	O
nuclear	O
reactor	O
.	O
</s>
<s>
RELAP5-3D	B-Application
(	O
Reactor	B-Application
Excursion	I-Application
and	I-Application
Leak	I-Application
Analysis	I-Application
Program	I-Application
)	O
can	O
be	O
used	O
for	O
reactor	O
safety	O
analysis	O
,	O
reactor	O
design	O
,	O
simulator	B-Application
training	I-Application
of	I-Application
operators	I-Application
,	O
and	O
as	O
an	O
educational	O
tool	O
by	O
universities	O
.	O
</s>
<s>
RELAP5-3D	B-Application
was	O
developed	O
at	O
Idaho	O
National	O
Laboratory	O
to	O
address	O
the	O
pressing	O
need	O
for	O
reactor	O
safety	O
analysis	O
and	O
continues	O
to	O
be	O
developed	O
through	O
the	O
United	O
States	O
Department	O
of	O
Energy	O
and	O
the	O
International	O
RELAP5	B-Application
Users	O
Group	O
(	O
IRUG	B-Application
)	O
with	O
over	O
$3	O
million	O
invested	O
annually	O
.	O
</s>
<s>
RELAP5-3D	B-Application
is	O
an	O
outgrowth	O
of	O
the	O
one-dimensional	O
RELAP5/MOD3	B-Application
code	O
developed	O
at	O
Idaho	O
National	O
Laboratory	O
(	O
INL	O
)	O
for	O
the	O
U.S.	O
Nuclear	O
Regulatory	O
Commission	O
(	O
NRC	O
)	O
.	O
</s>
<s>
The	O
U.S.	O
Department	O
of	O
Energy	O
(	O
DOE	O
)	O
began	O
sponsoring	O
additional	O
RELAP5	B-Application
development	O
in	O
the	O
early	O
1980s	O
to	O
meet	O
its	O
own	O
reactor	O
safety	O
assessment	O
needs	O
.	O
</s>
<s>
The	O
RELAP5	B-Application
code	O
was	O
chosen	O
as	O
the	O
thermal-hydraulic	O
analysis	O
tool	O
because	O
of	O
its	O
widespread	O
acceptance	O
.	O
</s>
<s>
The	O
application	O
of	O
RELAP5	B-Application
to	O
various	O
reactor	O
designs	O
created	O
the	O
need	O
for	O
new	O
modeling	B-Application
capabilities	O
.	O
</s>
<s>
In	O
particular	O
,	O
the	O
analysis	O
of	O
the	O
Savannah	O
River	O
reactors	O
necessitated	O
a	O
three-dimensional	O
flow	O
model	B-Application
.	O
</s>
<s>
Up	O
until	O
the	O
end	O
of	O
1995	O
,	O
INL	O
maintained	O
NRC	O
and	O
DOE	O
versions	O
of	O
the	O
code	O
in	O
a	O
single	O
source	O
code	O
that	O
could	O
be	O
partitioned	O
before	O
compilation	B-Language
.	O
</s>
<s>
The	O
code	O
was	O
therefore	O
"	O
split	B-Application
"	O
into	O
two	O
versions	O
—	O
one	O
for	O
NRC	O
and	O
the	O
other	O
for	O
DOE	O
.	O
</s>
<s>
The	O
DOE	O
version	O
maintained	O
all	O
of	O
the	O
capabilities	O
and	O
validation	O
history	O
of	O
the	O
predecessor	O
code	O
,	O
plus	O
the	O
added	O
capabilities	O
that	O
had	O
been	O
sponsored	O
by	O
the	O
DOE	O
before	O
and	O
after	O
the	O
split	B-Application
.	O
</s>
<s>
The	O
most	O
prominent	O
attribute	O
that	O
distinguishes	O
the	O
DOE	O
code	O
from	O
the	O
NRC	O
code	O
is	O
the	O
fully	O
integrated	O
,	O
multi-dimensional	O
thermal-hydraulic	O
and	O
kinetic	O
modeling	B-Application
capability	O
in	O
the	O
DOE	O
code	O
.	O
</s>
<s>
Other	O
enhancements	O
include	O
a	O
new	O
matrix	B-Architecture
solver	O
,	O
additional	O
water	O
properties	O
,	O
and	O
improved	O
time	O
advancement	O
for	O
greater	O
robustness	B-Application
.	O
</s>
<s>
RELAP5-3D	B-Application
has	O
multidimensional	O
thermal	O
hydraulics	O
and	O
neutron	O
kinetic	O
modeling	B-Application
capabilities	O
.	O
</s>
<s>
The	O
multidimensional	O
component	O
in	O
RELAP5-3D	B-Application
was	O
developed	O
to	O
allow	O
the	O
user	O
to	O
accurately	O
model	B-Application
the	O
multidimensional	O
flow	O
behavior	O
that	O
can	O
be	O
exhibited	O
in	O
any	O
component	O
or	O
region	O
of	O
a	O
nuclear	O
reactor	O
coolant	O
system	O
.	O
</s>
<s>
There	O
is	O
also	O
two	O
dimensional	O
conductive	O
and	O
radiative	O
heat	O
transfer	O
capability	O
and	O
modeling	B-Application
of	O
plant	O
trips	B-Application
and	O
control	O
systems	O
.	O
</s>
<s>
RELAP5-3D	B-Application
allows	O
for	O
the	O
simulation	O
of	O
the	O
full	O
range	O
of	O
reactor	O
transients	O
and	O
postulated	O
accidents	O
,	O
including	O
:	O
</s>
<s>
RELAP5-3D	B-Application
is	O
a	O
transient	O
,	O
two-fluid	O
model	B-Application
for	O
flow	O
of	O
a	O
two-phase	O
vapor/gas	O
-liquid	O
mixture	O
that	O
can	O
contain	O
non-condensable	O
components	O
in	O
the	O
vapor/gas	O
phase	O
and/or	O
a	O
soluble	O
component	O
in	O
the	O
liquid	O
phase	O
.	O
</s>
<s>
The	O
multi-dimensional	O
component	O
in	O
RELAP5-3D	B-Application
was	O
developed	O
to	O
allow	O
the	O
user	O
to	O
more	O
accurately	O
model	B-Application
the	O
multi-dimensional	O
flow	O
behavior	O
that	O
can	O
be	O
exhibited	O
in	O
any	O
component	O
or	O
region	O
of	O
an	O
LWR	O
system	O
.	O
</s>
<s>
However	O
,	O
the	O
model	B-Application
is	O
general	O
,	O
and	O
is	O
not	O
restricted	O
to	O
use	O
in	O
the	O
reactor	O
vessel	O
.	O
</s>
<s>
Recent	O
developments	O
have	O
updated	O
the	O
programming	O
language	O
to	O
FORTRAN	O
95	O
and	O
incorporated	O
viscous	B-Application
effects	O
in	O
multi-dimensional	O
hydrodynamic	O
models	O
.	O
</s>
<s>
Currently	O
,	O
RELAP5-3D	B-Application
contains	O
27	O
different	O
working	O
fluids	O
including	O
:	O
</s>
<s>
Heat	O
structures	O
provided	O
in	O
RELAP5-3D	B-Application
permit	O
calculation	O
of	O
heat	O
transferred	O
across	O
solid	O
boundaries	O
of	O
hydrodynamic	O
volumes	O
.	O
</s>
<s>
Modeling	B-Application
capabilities	O
of	O
heat	O
structures	O
are	O
general	O
and	O
include	O
fuel	O
pins	O
or	O
plates	O
with	O
nuclear	O
or	O
electrical	O
heating	O
,	O
heat	O
transfer	O
across	O
steam	O
generator	O
tubes	O
,	O
and	O
heat	O
transfer	O
from	O
pipe	O
and	O
vessel	O
walls	O
.	O
</s>
<s>
There	O
is	O
also	O
a	O
radiative/conductive	O
enclosure	O
model	B-Application
,	O
for	O
which	O
the	O
user	O
may	O
supply/view	O
conductance	O
factors	O
.	O
</s>
<s>
RELAP5-3D	B-Application
allows	O
the	O
user	O
to	O
model	B-Application
a	O
control	O
system	O
typically	O
used	O
in	O
hydrodynamic	O
systems	O
,	O
including	O
other	O
phenomena	O
described	O
by	O
algebraic	O
and	O
ordinary	O
differential	O
equations	O
.	O
</s>
<s>
There	O
are	O
two	O
options	O
that	O
include	O
a	O
point	O
reactor	O
kinetics	O
model	B-Application
and	O
a	O
multidimensional	O
neutron	O
kinetics	O
model	B-Application
.	O
</s>
<s>
A	O
flexible	O
neutron	O
cross	O
section	O
model	B-Application
and	O
a	O
control	O
rod	O
model	B-Application
have	O
been	O
implemented	O
to	O
allow	O
for	O
the	O
complete	O
modeling	B-Application
of	O
the	O
reactor	O
core	O
.	O
</s>
<s>
The	O
decay	O
heat	O
model	B-Application
developed	O
as	O
part	O
of	O
the	O
point	O
reactor	O
kinetics	O
model	B-Application
has	O
been	O
modified	O
to	O
compute	O
decay	O
power	O
for	O
point	O
reactor	O
kinetics	O
and	O
multi-dimensional	O
neutron	O
kinetics	O
models	O
.	O
</s>
<s>
RELAP5-3D	B-Application
Sequential	O
Verification	O
writes	O
a	O
file	O
of	O
extremely	O
accurate	O
representations	O
of	O
primary	O
variables	O
for	O
comparing	O
calculations	O
between	O
code	O
versions	O
to	O
reveal	O
any	O
changes	O
.	O
</s>
<s>
The	O
test	O
suite	O
of	O
input	O
models	O
exercise	O
code	O
capabilities	O
important	O
for	O
modeling	B-Application
nuclear	O
plants	O
.	O
</s>
<s>
The	O
ability	O
to	O
simulate	O
movement	O
,	O
such	O
as	O
could	O
be	O
encountered	O
in	O
ships	O
,	O
airplanes	O
,	O
or	O
a	O
terrestrial	O
reactor	O
during	O
an	O
earthquake	O
becomes	O
available	O
in	O
the	O
2013	O
release	O
of	O
RELAP5-3D	B-Application
.	O
</s>
<s>
It	O
allows	O
RELAP5-3D	B-Application
to	O
model	B-Application
reactor	O
systems	O
on	O
space	O
craft	O
,	O
a	O
space	O
station	O
,	O
the	O
moon	O
,	O
or	O
other	O
extraterrestrial	O
bodies	O
.	O
</s>
<s>
There	O
are	O
five	O
different	O
levels	O
of	O
membership	O
available	O
in	O
the	O
International	O
RELAP5	B-Application
Users	O
Group	O
(	O
IRUG	B-Application
)	O
.	O
</s>
<s>
A	O
full	O
member	O
organization	O
is	O
the	O
highest	O
level	O
of	O
participation	O
possible	O
in	O
the	O
IRUG	B-Application
.	O
</s>
<s>
Members	O
receive	O
the	O
RELAP5-3D	B-Application
software	O
in	O
source	O
code	O
form	O
.	O
</s>
<s>
Regular	O
Member	O
organizations	O
receive	O
up	O
to	O
40	O
hours	O
of	O
on-call	O
assistance	O
in	O
areas	O
such	O
as	O
model	B-Application
noding	O
,	O
code	O
usage	O
recommendations	O
,	O
debugging	O
,	O
and	O
interpretations	O
of	O
results	O
from	O
INL	O
RELAP5	B-Application
technical	O
experts	O
.	O
</s>
<s>
Participants	O
receive	O
the	O
RELAP5-3D	B-Application
software	O
in	O
executable	B-Application
form	O
only	O
.	O
</s>
<s>
Single-use	O
participants	O
are	O
restricted	O
to	O
use	O
RELAP5-3D	B-Application
on	O
a	O
single	O
computer	O
,	O
one	O
user	O
at	O
a	O
time	O
.	O
</s>
<s>
They	O
receive	O
the	O
RELAP5-3D	B-Application
executable	B-Application
code	I-Application
and	O
may	O
receive	O
up	O
to	O
5	O
hours	O
of	O
staff	O
assistance	O
.	O
</s>
<s>
University	O
Participants	O
may	O
acquire	O
a	O
license	O
to	O
RELAP5-3D	B-Application
for	O
educational	O
purposes	O
.	O
</s>
<s>
Training	O
participants	O
have	O
two	O
main	O
options	O
available	O
:	O
they	O
can	O
receive	O
a	O
3-month	O
single-use	O
license	O
for	O
the	O
RELAP5-3D	B-Application
code	O
and	O
up	O
to	O
10	O
hours	O
of	O
staff	O
assistance	O
,	O
or	O
a	O
3-month	O
multiple-use	O
license	O
and	O
up	O
to	O
40	O
hours	O
of	O
on-call	O
technical	O
assistance	O
.	O
</s>
<s>
One	O
set	O
of	O
RELAP5-3D	B-Application
training	O
videos	O
is	O
included	O
.	O
</s>
