ML19320D423
| ML19320D423 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 07/17/1980 |
| From: | Sylvia B VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| 628, NUDOCS 8007210347 | |
| Download: ML19320D423 (6) | |
Text
.T. -
VIEGINIA EI.ucTure Ann Pownn Co3rrAxy RICRMOND, VIRO 1N ZA 20361 July 17, 1980 Mr. Harold R. Denton, Director Serial No. 628 Office of Nuclear Reactor Regulation N0/MDK:smv Attention:
Mr. B. Joe Youngblood, Chief Docket No. 50-339 Licensing B,anch No. 1 License No. NPF-7 Division of Licensing U. S. Nuclear Regulator. Commission Washington, D. C.
20555
Dear Mr. Denton:
ADDITIONAL INFORMATION REACTOR COOLANT SYSTEM VENTS 1.JRTH ANNA UNIT 2 Attached please find response to your request for information telecopied
. July 1, 1980 from Mr. Drome'.1ck - NRC, to Mr. Grecheck - Vepco, concerning North Anna Unit 2 full power licensing approval.
This response provides sufficient detail to satisfy your request.
Very truly yours, pl a B. R.
ylvia Manager - Nuclear Operations and Maintenance MDK/smv:SX1 Attachment i
cc:
Mr. James P. O'Reilly Office of Inspection and Enforcement l
Atlanta, Georgia 30303 l
e THIS DOCUMENT CONTAINS P0OR QUAL.lTY PAGES 8 0 072~103474.
4 A_DDITIONAL INFORMATION REACTOR COOLANT SYSTEM VENTS NORTH ANNA UNIT 2 Question No. 1 Demonstrate that the vent system is designed to RPS safety grade require-ents.
Include:
a.
Seismic design b.
IEEE-279 requirements c.
Vent valve position in the control room; and d.
Qualification of the vent system to exhaust all possible fluids, i.e., noncondensables, steam, water, and combinations thereof.
Response No. 1 The Reactor Vessel Head "ent System consists of two parallel flow paths with redundant isolation valves in each flow path.
(See attached sketch.)
The valves in each flow path are powered by opposite vital buses.
If one.
single failure prevents a venting operation through one flow path, the second flow path provider a redundant backup.
The two isolation valves in each flow path provide a single failure method of isolating the vent-P ing system.
Each isolation valve is a fail closed normally de-energized valve. With two valves in series, the failure of any one valve or power supply will not inadvertently open a vent path.
The Reactor Vessel Head Vent System ha:: two normally de-energized valves in series in each flow path. As such, power lockout to any valve is not considered necessary.
The Reactor Vessel Head Vent System is seismically designed and supported.
The isolation valves will be qualified to IEEE-323, 344, 382 and meet Regulatory Guide 1,48 (active valves).
The Reactor Vessel Head Vent System is capable of exhausting all possible fluids, i.e., noncondensables, steam, water and combinations thereof.
Each vent valve will have its actual valve position indicated in the control room.
Question No. 2 Demonstrate that the exhaust from the veut system will not impinge on other equipment, that the vent system will vent RCS hot legs and that the vent system exhaust is to a por*. ion of the containment with maximum ventilation and cooling.
Q Response No. 2 The Reactor Vessel Head Vent and Pressurizer Vent will discharge into the refueling cavity surrounding' the reactor vessel in the vicinity of the fuel' transfer canal.
This vent location insures the vent effluent will not impinge on any equipment.
-The reactor. coolant system hot legs are not a high point in the system.
Therefore, no venting is mequired.
The Reactor Vessel Head Vent System will discharge in the vicinity.of the operating level near the middle of the containment.
The region of the containment above the operating level is a large open volume which allows for rapid dispersion of any gaseous vent effluent.
There are no enclosed compartments in this - region of the containment, with the potential to accummulate gase9.
This area is completely enveloped by the containment spray and recirculation spray systems, both of which provide cooling of the : containment atmosphere following a postulated loss of coolant acci-dent.
Question No. 3-Discuss the discharge capacity of the vents.
How does it compare with the guidelines of venting a gas volume of 1/2 the RCS volume in one hour?
Response No.-3 W
The Reactor Vessel Head Vent system is capable of venting 1/2 of the RCS volume of hydrogen (at typical system temperatures) within one hour.
Question'No. 4' Provide criteria ar.d. operator action for venting and its termination. The procedure must also assure adequate decay heat removal via the U-tube steam generators, given possible noncondensables that would obstruct natural circulation heat removal.
The procedures must consider vent capabilities and the spectrum of potential venting conditions.
Include criteria for venting and its termination which assure pressurizer control, natural circulation ' heat removal, reactor pressure and level control prevent. steam flashing and core uncovery, and containment combustability
. requirements.
The procedures must be based on the following criteria:
a.
The plant can meet. the requirements of 10 CFR 50.46 and 50.44 and combustible gas. criteria of Regulatory Guide 1.7 (Rev. 1) and Standard Review Plan Section 6.2.5, and b.
..The're is substantial increase in the plants ability to maintain core c'ooling-and containment integrity for events beyond the design basis.
Response No. 4 sestinghouse is in the process of developing procedures for recommended use. of the ? vent system.
The procedure for how to use the Reactor Vessel
. Head j Vent : system will include criteria for insuring that - Regulatory Guide 1.7 requirements are satisfied.
' The. vent ~ is smaller than the LOCA definition. The system is crificed to 3/8 inch. A break in the piping downstream of the orifice will result in a blowdown of less than the capability of one charging pump.
Operation of the vent system will be based on the current hydrogen con-centration in the containment as determined by the hydrogen analyzers and will be based upon the requirements of 10 CFR 50.44.
- Venting will be independent of the history of the event.
The vent time will be determined from a f amily of curves similar to Figure 1.
The vent time is a function of reactor vessel pressure and the desired increase in containment hydrogen concentration.
The increase in concentration will be restricted to result in a maximum projected containment concentration of three (3) volume percent.
This allows for 0.5 volume percent error in determining the inital hydrogen concentration and 0.5 volume percent allowance for hydrogen generation from other sources.
The curves in Figure 1 are based on venting 100 percent hydrogen at a temperature of 600*F through a three-eights inch orifice. The vent rate was based on isentropic compressible flow througn an orifice.
The flow rate is relatively insensitive to temperature.
If the vent flow is not 100 percent hydrogen, the containment hydrogen concentration will not attain the projected level.
Operation of the vent system can be repeated based on the new reactor vessel pressure and con-tainment hydrogen concentration af ter a specified period of time to allow for attainment of a stabilizied hydrogen concentration.
)
Question No. 5 Provide analyses demonstrating that the direct venting of noncondensable gases with perhaps high hydrogen concentrations does not result in viola-tion of combustible gas concentration limits in containment as described in 10 CFR 50.44, Regulatory Guide 1.7 (Rev. 1) and Standard Review Plan Section 6.2.5.
Response No. 5 See response to Question No. 4.
C
- -.: e........ _ _.
f*
1 55
@ ~-
O O
C 07 v.
- a. te 2 *-
E- $a Q
^
^
c' e
-s 3
LA
~
v tw R: 59 s 5: 5:D LO s'
. )-
2 E E_
3 ef IEl O f
75 is
,5 si. <n _. N e,s.
r2 r-o a
h h 3 9 h,,,
pa.
io 8!
m t
N: g%
i E
1 p.~ g 1
g Mgr 5: I s! M
! L e
R es u=
s
~
e a
s- )
a y
I l
I 5
s 5
o g $.e. -
Q.x f
=
o
~
x
~'t D
g y
n B
=.
a.
Y, b
5 w
'f 7E
?E El la W
p<
m E
y U
L g
o e
l; O
A
'T g
1 3
n
.o v~
n e
~:
Y 9
A 9w i4 6
e
?
(:
X 03 Et R R
i
'y s"
a-j
[a gg j i i i i 4
g
,, =
s..
sk Di "
e-
=.g 3
$s
.e
- d a,e,h C wf g
2 5" gT._
4 l
b AA a.
3.s.
. =s.:
i a
V
,a v
- d 4
hl s
8 "2
TO E'
El
.l b
f
~
WI wW i< >
i h
g' V
.u ---w
^7
["
- d. 8 m
e e
~
g3 4
7
?2 i
e
?. :
. :.> i
~~
b,
- ' E:
.j, :
1.i; ;,y. y.-
y8 i
e p
bli
~'....
v 6
sa y U1 i
{F g il) en s.
d O
c.n
~
~
O
> ~ " '
l >-
r a
' I n I' Ie f th -
l _ Lte:Pd3d,jgWW1CK 3.W q;7 ;p g g#
.i - r-- n, +1WI AJAI.LK837NJ,3i SM JNh.F)W40 :.. -
- r m,3 g,-
3 v.
[ 'T **^,,
m'f.
I i
+ n n
,g e
L O.,.,
i.
u,.s, I
a a.
{.
L I
- .J -i -. '~y w
- 1.,
-h.
. 15
.f
({
..J t.
t
-,.j.
_1 JN Ii i
f 5
3 4(<
i_
t e[.
+
x i
i 6
I.
3' 7.,
c w
r.v
_ I o
1 e
a, m.
e,
._.J _
4 r
1.o f
s.
1 t
t n
s
_ __ __ u1 pr t
gJ 3.r 1 i9.
1
_ P i 4 s 2
I e
pl
-O _-
d.,- t c
+t M
,a
.s
~
. %U a
w 8
1
- mh n l W6
--y n
3-l
.. s 3
m.
.m n
_p-r E.
y
- m..
O I:n
' _ eGamm
! i saa
- ii6 8
f
__. p,,._
..W T'
1 e s +p =
. +
aw_n K
f
'T E
_ _ _ _u__._
&> q
? -
..,A i
-u i
n'4 1__.
f
]
in
- s.
.J i
g
+
i em
+
+
p 2
hl 1
, T E'E
-u s J
4 1
1>
R _.,,,
'Y
? _%1,amO*
9 l}
t 6
f N emas i :
.o
. er i
-- -~~
g 8
'a
_ [
-. 2.~. _ y.} g g
2 U~ - > '~ -
i t
l
/
I E c--f -
r g
m s
,f. -
r m
- -,,, M
- j l c
+ <
- i M
6 f
s_. ;
e, _a e(l r
/.
2
+.
6
=
i g,,_
. I~
_ h _f=0 s?f ~_
A
""~~
+
1 x.
. ~
- e a,
e 6
i aA
('k t he
=
g
- l 0
in --
=
s f_ _
g g
y
?
1 h,3 p
J e st t
i i.
4Ea f
N g
-3 G
j
. M..A 4
- i t
1 e-e r
-s I h _X. _,S..
l -
f f
_6 \\
L
,, m i
a 4_. i \\
- \\
A f w.
X 3
i er*7m"
?
s
- i
\\
\\#-
4/
F.
\\E.
1_
t E
\\-
\\-
T N
E, Xs e E J
t u
Vi
\\-i
\\
\\
F.
J g
e t
i i
.x y
41 - f._7
- 4gg i
\\
\\3
'A-i-/%-/
['i
- ---ii o in 1\\
4 s,c X,,
~
. c-
---<t s,
+d 1
7 -'
1
- \\1 iA
\\ J mil
-i
, s.
s n X
a L
~~
t#
t
\\#
\\
s s
7-a s
.\\
v t
4
- ,3 2-A ('
^
f R
s - e f
f I
ry f
- [f*
-[_ ',
[-[- -
f, l
_ A,/
T l'
~~
1 s
2 1- _f
..u.
l 1
i
-y a.
Og
.y
. l 'i.
. J.a.
1--
4-
~
' ',.- ~,' A -
m, - = -- +-t7 M
-m 5 4-4J
{j 4
- q..;.
j,
.g t.;.r*- -,
O
$ =. g;.- e --
-**.. H ed.~< h 5.s.
I-
..=.....e-
. !._ = eq.,9
.s 2
g
.4..E E i r.:_.
M g
_m'**. - _. ' < - +. -
... n.. n.a a-a
.npa.._,. ;
~.""
D o
o an o
tn
.=.
, n n, to..
c,
~.
J
..