ML19256F133
| ML19256F133 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 11/15/1979 |
| From: | Moody D Maine Yankee |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| WMY-79-133, NUDOCS 7911210464 | |
| Download: ML19256F133 (6) | |
Text
-
' ",c== mn=~__
gg wm f
I l
\\
1 L
LJ
' MNHE HARHEE A355FD'EEC.TU'.W'*
$ * ((
ENGINEERING OFFICE WESTBORO, MASSACHUSETTS 01531 S17-366-9011
%* % w e B.3 2.1 WMY 79-133 November 15, 1979 United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Office of Nuclear Reactor Regulation Mr. Robert W. Reid, Chief Operating Reactors Branch #4
References:
(a) License No. DPR-36 (Docket No. 50-309)
(b) NRC Letter to Maine Yankee dated September 11, 1979
Dear Sir:
Subject:
NRC Request for Information Regarding the Potential For Steam Generator Water Hammer The enclosed information is in response to your letter, Reference (b),
regarding steam generator water hammer.
We trust this information adequately addresses your concerns; however, if you should desire additional information, please contact us.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY D$4' C.31 Donald E. Moody Manager of Operations RPB/dmp Enclosures 1380 186 7911210 464-
Enclosure Page 1 l
QUESTION 1 Provide information that demonstrates that the feedwater system and steam generator water level at your facility have been subjected to those transient conditions that are conducive to water hammer, i.e., the addition of cold feedwater or auxiliary feedwater to steam-filled feeduster piping and feedring.
See NUREG 0291, Page 4 that was forwarded to you on September 2, 1977 Include the following:
1.
Describe the expected behavior of steam generator water level as result of reactor trip from power levels greater than 30% of full power.
Include actual plant measurements of steam generator level and other available related data such as feedwater flow and auxiliary feedwater flow.
f 2.
Trovide the number and causes of loss of feedwater events during the operational history of the plant.
You may refer to material submitted previously.
3 Provide the number and causes of loss of off-site power events during the operations history of the plant.
RESPONSE 1 1.
Maine Yankee steam generators operate on a constant water level program with normal level being maintained at approximately 66 2/3% of indicated narrow range level.
This level represents a height of water of approximately 60 inches above the centerline of the feedring which is located at approximately 35%.
Following a reactor trip from full power, steam generator water levels drop to as low as 10-12% indicated level due to the collapsing of steam voids.
Concurrent with a reactor trip, the steam generator water level control system automatically ramps the main feedwater regulating valves to the closed position in less than 10 seconds.
Additionally, the feedwater regulating bypass valves are automatically positioned to provide approximately 5% of normal full load ficw.
As steam generator water level returns to normal, the operators normally override the automatic 5% flow signal to the bypass valves and place the bypass valves' controllers in automatic which stabilizes level back at the normal level.
The attached Figure 1 shows actual steam generator level response to a full load trip.
i380 187
Enclosure Page 2 2.
In Maine Yankee's operating history there have been only two occasions of a complete loss of main feedwater flow.
The first occurred on November 14, 1972 at an initial power level of approximately 33%.
Bearing problems on one of the main feedwater pumps necessitated the starting of the other main feedwater pump.
However, the second feedwater pump's discharge valve could not be opened.
The reactor and turbine were manually tripped, the main feedwater pumps were secured, and an auxiliary feedwater pump was started to maintain steam generator water levels.
The second complete loss of main feedwater occurred on August 31, 1978 when a fault in one of the station's main transformers resulted in a plant trip and a loss of offsite power.
Again an auxiliary feedwater pump was started and normal water level was reestablished in the steam generators.
In both the above cases, cold auxiliary feedwater was established, at a flowrate less than sufficient to maintain the feedring filled, and in neither case did water hammer occur.
3 The only occurrence of a loss of offsite power occurred on August 31, 1978 as described in the response to Item #1.2 above.
QUESTION 2 If administrative controls have been adopted to limit the flow of auxiliary feedwater for the purpose of reducing the probability of water hammer, show when they were adopted and give the answers to Items 1.1, 1.2 and 1.3 for before and after such controls were established.
RESPONSE 2 No administrative controls have been determined to be necessary to limit the ficw of auxiliary feedwater for the purpose of reducing the probability of a water hatser.
QUESTION 3 If administrative controls have been adopted to limit the flow of auxiliary feedwater for the purpose of reducing the probability of water hammer, show that an adequate water inventory and flow will be maintained to accomodate all transient and accident conditions.
RESPONSE 3 Not applicable. See response to Item 2.
}gg
Enclosure Page 3 QUESTION 4 If auxiliary feedwater flow in your facility is not at present initiated automatically for ncrmal and accident events, present your evaluation of whether automating the actuation of auxiliary feedwater might increase the probability of inducing steam generator water hammer.
One of the signals that would automatically initiate the flow of auxiliary feedwater would be the steam generator low water level.
This set point should be above the top of the main feedwater sparger to reduce the probability of steam generator water hammer.
RESPONSE 4 The auxiliary feedwater flow at Maine Yankee is not initiated automatically for normal and accident events.
An evaluation on whether automating the actuation of auxiliary feedwater versus an increase in the probability of inducing steam generator water hammer is required by NUREG-0578.
Maine Yankee will address the above Question 4 when we submit to the NRC the detailed design for automating the auxiliary feedwater system as required by NUREG-0578.
QUESTION 5 Describe the means that will be used to monitor for the occurrence of steam generator water hammer and possible damage from such an event.
Include all instrumentation that will be employed.
Describe the inspections that will be performed and give the frequency of such inspec tions.
RESPONSE 5 Based on plant operating experience and the design of the steam generator feedwater system, !bine Yankee has determined that it is not necessary to have a dedicated means/ system to menitor for the occurence of steam generator water hammer.
As described in the response to Item 1.2, Maine Yankee has experienced plant trips which had resulted in the steam generater water level dropping belcw the feedring and in none of these instances did water hammer occur.
The feedwater piping and feedring were originally designed to prevent the occurence of waterhammer frem this type of incident.
The design of the feed system minimized the horizontal piping run outside each steam generator and vent holes were provided in the top of the feedring.
Previous plant inspections of the steam generators and 100 percent inspection of the feedwater piping supports and hangers and 100 percent radiograph of all welds on the feedwater piping located inside containment, (done in response to I & E Eulletin 79-13), verifies that the uncovering of the feedring in these instances had no effect en the feedwater syster.
Future inspecticns x;11 be done en the safety class portions :f the stear generater feedwater piping as part Of the plant Inservice :nspe::icn Program.
These periodic inspecticns will be done in accordance with ASME Sectict XI, subsecticn '. ;p WC,,
y,z C
N pu ih SNbk Y>q q d ec m. en Uld79 A'umy
Enclosure Page 4 QUESTION 6 Describe the reporting procedures that will be used to document and report water hammer and damage to piping and piping support systems.
Such reports were requested in our letter to you dated September 2,1977 RESPONSE 6 Significant operating abnormalities or deviations from normal or expected performance of plant equipment, as deternined by the Plant Manager are reported to high management as Plant Information Reports (PIR).
PIR's are available at the plant and are routinely reviewed by NRC and I & E personnel.
Therefore, Maine Yankee sees no need to provide any additional reporting procedures that will be used to document the report water hammer and damage to piping and piping support systems.
1380 190
i.-...
~
t,.
c.i..
... ~.,v.>.
f t.
.f *.
$ ENCL.OSURE
+.x
- v..,
3,,.
v., - r.,
.c s
e
,a
- j-.- Q Q
.. w y-'--.$.
.c d..
,-,a..o.,,
6
.' r',..
l
.\\., )'q.
3 j
>. g en.
,... 34
. ;., n
)
8
,t
' \\ -o.,
ig
- 4.., j.
? s; 4x i
4-.
.s s
e s... (-
e si..
s a
9:'
s cI i
i
.. '.g4' J'-
- g-1 's r
.4.
a
=k
'. I b, e
e a.
.p J
.gg'
.P
'.t.
. ). ',
r s
1 e t 1
g-li
. !..'s,.
s o
./..
o j.
j
'.4/_
, h N.. a
' 's.
. tv.t -
e'
- i
. g's
,af e
.,g. -,.,
r a
- '(.,
,.y
.g
. w
,,.g.'
3.
.p-Y,. 4 d
g; e
e.
.s
,t,
. G..
4-o 4..,.,.
.s e
."), t p.,
i
. ?g,. j f '. i
' _- r.
s g. p.
.. ty
..e.,,
1
/
3
,. H...
.."..s,.
.e....
s i
e r..
..~
u,.
l e
, w :: 7.g.r '
. '.-t
.r.
n;
. 3
- g...e..
g
?,7 g... - t.'m;
. m.,,.
a
...a,.r. h.c
. ee
..A 4 +v.,.
a-l' g-8
.i.
.w c__
i n., _._m_
..___.w___._..._.rw.._.._,_.._..a.._____._
_. _, o. _.u._._. __
.,___ _ m_._. _.. _.. =.
. _ =
3
_ _....,....m.,
,...-m.;_._._..e._,.._.._..__._.
...-. _ = = _., _,._
.... _.. -_s__.~.. ____
r_-
_.._...___-_m,_==..= _=_.m
_=_u--.= :.- -
c.. L-m....i _ _%. _..
.. }:
.g
_ _..= =..._"..:~.! -_: :..
n._==_=..__--.,_.._=.._=._=_..._.=_r.=..=..
2.
c.:.
.... =
a_
.y
_.._a_.._._.__.._..~_._.._._._.___ _ _ _.__
..j..-.
_. _. a._ _. _. _ _ _. __ J. _, _.......__.._._._.
_ _ _ - ~.
.n....
_~n...._...._._._._.. _ _...
.,.r
=.. _.._....._.. _.__ _-..... _. _. _ _ _ _.__.
.i.,.__.._
i.e._.e=.=.
..._ s c
.../...~,_
.....,...g..,.
.> _._._._...,._. _. __..__ _ g _,
...,.%/
_.J,.
g,
--m w
g
.-,-e= - - - -
- f '.- '
%..=*- W.J.ak. s".M,peWym.4she e.@' Web. ew e b.M. Wt,*ar h.M,._'.'~._e'.*'.**52.I'~'I'~.~~*'.~Ce.*~"."****.U.'I.~."I~,'.3 9
e.
.a
.g p-b.eM
..s a.
.{.
aw= _. J,.___,..J=m_._
..._.,_.t...e...-=._
. ar e.
{,...
..g..
..4.,...g..
s, e..
g
._._..i_.,....
. _... c...
g a4g
..,e,
.. ~....
--.._4._._-...
s.
.g
._._.._-..v.)..___.___~_.,...._.._._.r_._.-.-
_ 3. 3:,,
...._.._...t
.f. _..
.=.=
7
._.,_._.L.
L,
_....3.....9_-.m e.-m
[
a g..
... ~,.., -.....
... i
$- - ~. - _
I
_.._.i --.
mg_._-,
p.**
w
.. =..
.. t.d w.._...
-. _.,.....5,...
.c.
,.E 4
..g.
.--.,,.,...g_
[..g..
.......,.u.
.g
.a
....%,a....._......,...-
..-.. + w -.
a,..
g,
.._s.........,....-s....a_...-...._.._.a...~...4..-
.m..,
.,,4,
_-._.....1
..... -. ~., _-. ~--.....,. n
..,...-.....-s7...-
ew-s-f
).- -....
-.1
,..- _...._4..e -*..~.-. -..._ _ _
a
.,....,.s.
s..,.
,...s..-. - ~ -....
..s.m..,...,
g....a.......-
.e....e:.-._. -.-.....-
....-...-q,-,--...L.6._
==....-.e..
.~....
.p._.,....,~,..,
s.
f
...,...-..,..--....,......s.e...
&..g,. _ -..
- .,..),...,'.._.-
..,.s4-
~._
a
.e.n
....a_
. e......
..-.---...-....-,,1,..s,.--..
.m
.s.,.-.
. -_. -.\\...._.
~...i.........v...,,.~,,..--..,
.,. ~ = -
t_.,.
.-a f.-
....w.. ~ -.- -
. ~ -.
6........=.,.,.-
...3~~C4-........
-.~.
-. -... ~^,
ns.,
s
-.C.
.- ?.. s~~.; 4*
,,.. <........ -... - - - - ~ ~ -.. -. -...
.-~~~~~^y'.a....-
...a-,...-
- '.w.*."."1*~*~--~~~
. ~ - ~. - -. - ~ -e.-v
^^
. ~ -...n..
.. q
.c
/.
...in...J..
w
?. C. ?. \\....y... -.
. ~- ---.......v,...
. ~ L.
t.
.r.-
s.
,i,
.... -.... --...(.
... - ~. _-._. _.. _...... -
-6
),
.....~.)..-
v-a-.....
.~a.
.,... ~ -
- =.
...=.
.---s..<..,, - -
-a..
-a.
.,.,,.o,,. _.,.
...,.I.,.,.,......
,,4,..-....-.. -
~
,.6-.-
~....
-*,J
-c.. -
6 3
r,
...s..
..LI.........e....s~.
i.
-,.u~..n..
r.-....-
..%.y. go u
... e....LA.. -
.. ~
.1.-.s..~..o.
.-.~...
..,... _ _...-s
. i
.~.
- - - - - =..
.i.., -
~ - _ -.
-4
.__..P...-....,.. -.. -....
p
,..a...,..,..-.
,-.--.3.--.... - -
.. ~. -,. *....
. ~. _ -..
a_,,. = :. _..v :=..
=~..n.=... -. n..
. - -......, -.--.-.w.. -m.. <.. t.... at =.. _ a....c...
e
=-
~
~ m. : ~..
s
...~.
y,.n
. ~.
. ~..._-
.p ~,,..
..... _.- ~-.. -...
.....= --- -...
s
..-v-
- - - ~ - - - -. -........
t
__ s.~._.r_-- _.._...-_.._..-....,. - - -
. -. c
-.c i ' o l O'. O :.4 W:Q.. O.; & 0 - <') ' O ' O O. O O '^D d O 0 00.O O C ' O ' _0' e')
C O y
ggw Q.
w
..;.4.wmMWspu wmeA.ourwetw..
s
.9 "t
)
I.
- /
/
FIGURE 1380 191 i,
+
I r
,