ML18044A289
| ML18044A289 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/19/1979 |
| From: | Frost S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7911270308 | |
| Download: ML18044A289 (16) | |
Text
- General Offices: 212 Wast Michigan Avenue, Jackson, Michigan 49201 * (5171: 788-0650 November 19, 1979 Director, Nu~lear Reactor Re~ulation Att Mr Dennis L Ziemarui, Chief Operating Reactors Branch No 2 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR-20 PALISADES PLANT -
STEAM GENERATOR WATER HAMMER RESPONSE Additional information relating to steam genera'tor water hammer was requ*ested by the NRC on September 12, 1979.
That lett.er requested further assurance that a water hammer will not occur in the future and that surveillance procedures would be adequate to detec*t wate~ hammer or damage from water hammer if it were to occur.
The responses to the six questions asked* by the NRC in !~~September 12, 1979 letter are as follows:
Item 1 Provide information that demonstrates that the fee.dwater 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
~eedwat_er or auxiliary feedwater to steam-filled feedwater piping and.
feedring.
See NUREG 0291, Page 4 that was :for-Warded to you on September 2, i'977.
Include the following:
Response
The information sought in this r~quest is very similar to that requested by letter of May 13, 1975.
Consumers Power's response was submitted to Division of Reactor Licensing by lette:r,of July 16, 1975.-
The information contained in that response adequately demonstrat~s the Palisades Steam Generator Feedwater lines have been subjected to a spectrum of_.reflood rates and sparger uncovered
. periods to induce a FW hammer if it were 'going to occur.
Additional.FW transients have occurred since then which provide added credibility to this position.:*
SG Water Hammer Respo~e (11-19-79) 2 Itein 1. 1 Describe the expected behavior of steam generator water level as a 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.
Response
Expected behavior is described via Exhibits 1 and 2 which were taken from an Exxon Transient Report, XN-NF-77-18, submitted to NRR on July 28, 1977 in preparation for our increase in licensed power limit.
Actual level transients are described via Exhibits 3, 4, and S.
Item 1. 2 Provide the number and causes of loss of feedwater events during the operational history of the plant.
You may refer to material submitted previously.
Response
Ta.ble 1 lists all the plant trips which have occurred as a result of loss of feedwater.
This list includes the date of occurrence, power level.prior to trip and a brief description of the reason for feedwater failure.
Item 1. 3 Provide the number and causes of.loss of off-site power events during the operational history of the plant.
Response
Table 2 lists all the plant trips which have occurred as a result of off-site initiated power transients.
Only two of the events, 77-17 and 77-20, actually resulted in a loss of power.
The other three events caused a transient severe enough to cause a plant trip.
Item 2 lf 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
Administrative controls on reflood rate were adopted on two separate occasions.
The first was on January 10, 1977.
This restriction limited auxiliary feedwater flow rates to 100 gpm if the sparger had been uncovered, following a trip, for more than one minute.. It was found in June of 1978 this
SG Water Hammer Respo~ (11-19-79) reflood rate was only marginally acceptable to remove decay heat and reestablish level, thus the second administrative control was adopted on October 4, 1978.
This control allowed 150 gpm reflood rate while the sparger was uncovered and if plant power was.greater than 75% prior to the trip.
Expected water level behavior immediately following a loss of feedwater or loss of off-site power is not altered by reflood rates.
Auxiliary feedwater is manually initiated and is not assumed to occur before 10 minutes following the trip.
Actual steam generator level recovery is controlled by response time of the operator and feed flow - steam flow mismatch prior to the trip.
Typical before and after, 100 gpm reflood rate restrictions, are attached as Exhibit 3 (prior), and Exhibits 4 and 5 (after).
Note the slower recovery rate on Exhibits 4 and 5.
3 Steam generator level responses for ioss of off-site power before and after
.the reflood rate restriction are attached as Exhibits 6 (prior) and 7 (after).
Tables 1 and 2 contain the operational history for loss of feedwater and loss of off-site power.
Item 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 accommodate all postulated tran~ient and accident conditions.
Response
Auxiliary feedwater flow is administratively limited to less than 150 gpm (100 gpm during the first 15minutes) to each steam generator following uncovery of the feedwater sparger.
Plant experience during a number of complete loss of main feedwater events has shown that this flow is adequate for reactor coolant pump and decay heat removal provided both steam generators are in service.
Although steam generator narrow range level indication has, at times, been lost following a complete loss of*main feedwater event, adequate removal of heat from the primary system was always maintained while feeding at the administrative limit.
There exists some concern that the administrative auxiliary feedwater flow rate limit may not be adequate in the event that only one steam generator can be fed (ie, due to a secondary pipe rupture).
This concern could be addressed by instructing the operator to feed the intact steam generator at twice the administrative limit (300 gpm) if indications of intact steam generator dryout arise. It is felt that any water hammer that may occur as a result of feeding in excess of the administrative limit would not be so severe as to prevent cpntinued cooling with the intact steam generator.
This position is supported by numerous incidents (see resppnse to Item 1) in which one or both feed spargers was uncovered for a significant period of time, and although the
- steam generators were fed at rates sometimes approaching 250-300 gpm, no evidence of feed line water hammer was detected.
In order to provide
SG Water Hammer Respol (11-19-79) additional evidence supporting this position, Consumers Power Company is currently considering performing a water hammer flow threshold test (for rates up to and including the maximum auxiliary feed pump delivery rate) following the current refueling outage.
Item 4 4
flow If auxiliary feedwater flow in your facility is not at present initiated automatically for normal 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
Auxiliary feedwater flow is presently not automatically initiated*at Palisades.
However, it is our opinion that a properly designed system for automatic initiation of emergency feedwater would not significantly change the probability of steam generator water hammer.
Subscale model testing described in NUREG-0291 showed that a flow threshold for steam generator water hammer definitely does exist.
At Palisades, operational experience has shown that the flow threshold is greater than 150 gpm per steam generator.
In all known instances (see response to Items 1 and 2) in which the feed sparger was uncovered for a significant period of time, there has been no evidence of water hammer when feeding the steam generator at the administrative limit of 150 gpm.
Therefore, a system designed to automatically initiate auxiliary feedwater flow on low steam generator level and control flow to less than or equal to 150 gpm should not increase the probability of steam generator water hammer.
Item 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 inspections.
Response
Various conditions, as stated in Response l~ have occurred which would induce water hammer, but Palisades has yet to experience any steam generator water hammer.
For this reason, there will not be any monitoring instrumentation installed.
A visual inspection will be performed in case of any steam generator water hammer problems to assess any damage.
SG Water Hammer Respo~ (11-19-79)
Item 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
Consumers Power Company will report any occurrences of water hammer in accordance with our Technical Specifications and the form attached to the NRC l~tter of September 2, 1977.
Steven R Frost Palisades Nuclear Licensing Enginee.r CC JGKeppler, USNRC 5
S~eam Generator Wate~~mmer Response 11/19/79 li Event Number Date 72-01 1-11-72 72-03 1-12-72 72-04 1-13-72 72-06 2-03-72 72-10 3-27-72 72-14 4-14-72 72-20 7-31-72 72-23 12-21-72 75-04 6-30-75 75-06 7-29-75 76-02 5-10-76 1-10-77 77-03 1-17-77 TABLE 1 PALISADES TRIPS DUE TO LOSS OF FEEDWATER Power Level 5%
5%
Hot Standby 20%
60%
15%
18%
82%
20%
Hot Standby 25%
100%
Cause Feedwater pump trip due to sharp increase in demand.
Operator manually opened the reg valve fully.
(See Event 72-04.)
Feedwater pump trip due to oscillations in suction pressure.
Low suction pressure trip.
(See Event 72-04.)
Feedwater pump trip due to low suction pressure.
Fine mesh start-up strainer had been left in the suction.
Feedwater reg valve failure.
Feedwater pump trip due to high vibration.
Oil filter change out procedure induced air into oil system.
Feedwater reg valve failure.
Defective feedwater pump vibration* sensor caused a pump* trip.
Inadvertent closing of feedwater reg valve.
Feedwater pump trip, rapid demand in feedwater flow caused low pump suction pressure.
Feedwater pump trip, low suction pressure.
Feedwater pump speed control ramped pump to minimum r/min thus insufficient discharge head.
Auxiliary feedwater flow rate restricted to 100 gpm.
Feedwater pump trip, low suction pressure, dump valve on moisture separator drain tank failed open.
120
' 80 40 (f)o w
- r:
u z
-40
-80
-12
-1~
I 3 ~
~
~
u u
PALISADES ** LOSS OF LOAD FROM 2580. 6 MW & 2110 PSIA 3
3/ V" v
/
~
_/
N 8
12 1
CHRN*.>E IN s ! r.RH I 1>t.N.
1-JA It:.~ 1...EVEL.
LUI IP l 2
CHF,tJGE lN SfERi1 I 1>£N. i.JAf£R LEVEL. LOI ~p 2 3
CHRNGE IN PRESSU RIZER l-IATEl ~ LEVEL
--z __
~
1 2
~
~
r1-1---_ -LL__
~
~
16 20 TIME. SEC 24 28 32 36 40 FIGURE 3.65 LEVEL CHANGES IN PRESSURIZER AND SEO.
'100 17 JUN 17 10 *OS *08 STEAM GENERATORS, LOSS OF LOAD - CASE e
Ul Q)
~
~
CD l:tj 'i
~ ::i::
H i b:t H
CD 1-3 "I
I-'
~
CD
!fl
. 'd 0
- s UI CD
~
\\0 I -,.
I
--..,J
-...J I
co O'\\
~ *'
50 0
-50 cr-10
~
I
- __)
z
-15
-20
-25
-3i 10 PALISADES** LOSS*oc ~EEO-WATER FLOW FROM 2580. 6 MW 20
. 30 C~~NGE IN STEAM EN.
~ATER LEVEL. LO *P l CHANGE !N STE~M "EN.
HATER. LEVE~. ~a ~ 2 CHANGE IN PRESSU I2ER HATE. tEVEL.
40 50 60 70 80 T IML SEC FIGURE 3.80 LEVEL CHANGES IN PRESSURIZER J\\ND srn.
764 2'.l.JLJ!'j ? 7 ::.-::22:22 STEAM GENERATORS, LOSS OF FEEDWATER FLOW 90 z
I :z Tl I
'-.J I
t<j
~
H tD H
t-3 I\\)
e C/l c;l
~
~
C1I...,
- i:: I
~
C1I
[II td 0 ::s
[II
. C1I
' I-' *
-.,J
\\0
(.
A s/~ FV f J7f1 Flo'-./
Fie- 070//0702-8
(
(
LtJ 11e I s/~,:-v I S7M Fla~
FR.- 070J/10'1
~;J.:.:.:::.. :-**
. *- *:?t::o+f 94&1 "SU water Rammer. Response EXHIBIT 4 t1l71'9' 179T e
9
. _ _:.:;__;:~~~**3:.,-****--~-* **:*****.:*.~** *----*--*-*r:/'~l p~-r,
- .~* :; *.
SG. Water Hammer Response EXHIBIT 5 10
- ~~~ --*-- **-**
.,---;.-* :~:.~~\\:;~~c*;(*~~*;.--*-f~:~~*~.-~ :- ~~fy~:~-:?-,7.*_--!:~~-::.::,~**,,,_~-~-:)~~--.
--~-~
- --*--. -*-.*.*. :.: _----*- *****:~ *_.* --_- -~ -~:( '-~~~,~-I-c.::, '~~-;'f r-gi~~t~n:~--~~j~
_____.-.,... -~~,'!"] -~-
.\\*-*----***-
- ... -:i~-:.*---*~*-* =*~-~~~-.~--=
I....
- ...
- .::~--
~ *:~~+-~~:.~::_:~:::~~~ -:~~~60:::::.-,~~=~:*:~:~
Steam Generator Water,mmer Response 11/19/79 12 Event Number 77-04 77-07 77-08 77-21 78-02 78-04 78-09 78-10 78-12 78-18 78-24 78-27 79-03 Date 1-18-77 3-24-77 3-27-77 11-27-77 4-21-78 5-11-78 6-07-78 6-0.8-78 6-13-78 9-19-78 10-04-78 10-17-78 12-18-78 3-03-79 Power Level 35%
90%
82%
50%
50%
Hot Standby 23%
20%
83%
86%
84%
88%
100%
TABLE 1 (Contd)
Cause Feedwater pump trip, cause unknown.
(See*
Event 77-08.)
Feedwater pump trip, cause unknown.
(See Event 77-08.)
Feedwater pump trip; faulty low-pressure switch on condensate pump disch.
Feedwater reg valve closed, operator error while transferring from manual to auto.
Feedwater pump trip, defective vibration sensor.
Feedwater pump trip, low suction pressure, condensate polisher y' strainer plugged with powdex.
Feedwater reg valve failed to provide *flow.
(See Event 78-10.)
Feedwater stop valve not opened during start-up sequence.
Feedwater pump trip, severe transient induced by Technician error while maintaining feedwater flow recorder.
Feedwater pump trip, turbine governor failure.
Increased reflood rate to 150 gpm while sparger is uncovered.
Feedwater pump trip, axial position, operator failed to warm LP STM line prior to cutting it in.
Feedwater pump trip, cause unknown.
Feedwater pumps tripped, low suction pressure, moisture separator drain tank dump valve failed open.
Steam Generator Water~mmer Response 11/19/79 i3 Event Number Date 79-04 4-07-79 79-09 8-10-79 79-10 8-24-79 Power Level 100%
88%
91%
TABLE 1 (Contd)
Cause Feedwater pump trip, cause unknown.
Pump vibration trip removed from service.
Feedwater pumps tripped, high axial thrust incorrect main turbine valve test procedure.
Feedwater pump tripped, low suction pressure, valving error while. valving in the condensate demineralizers.
Event Number 72-17 76-05 77-17 77-20 78-13 Date 4-15-72 7-20-76 1-10-77 9-24-77 11-25-77 6-18-78 r
10-04-78 Power Level 15%
93%
85%
85%
84%
TABLE 2 PALISADES TRIPS DUE TO LOSS OF OFF-SITE POWER Cause Lightning stroke to tie line.
Lightning storm, unit ground relay operated.
Auxiliary feedwater flow rate restricted to 100 gpm.
Lightning stroke caused "R" bus to clear.
"R" bus cleared cause unknown.
Lightning stroke.
Increased reflood rate to 150 gpm while sparger is uncovered.
14
r -
I +-
SG Water Hammer Response (11/19/79)
EXHIBIT 6 15
e SG Water Hammer Response (11./79)
EXHIBIT 7 16