ML20113G468
| ML20113G468 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 04/11/1990 |
| From: | Bur K GEORGIA POWER CO. |
| To: | |
| Shared Package | |
| ML20092F288 | List:
|
| References | |
| CON-IIT05-209-90, CON-IIT05-210-90, CON-IIT5-209-90, CON-IIT5-210-90, RTR-NUREG-1410 PROC-900411, NUDOCS 9202210414 | |
| Download: ML20113G468 (10) | |
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!D $0t CEO iO3TLE TEL '0: 1-105-17f ~i!!
u?i. F01
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j fj il GEORGIA POWER COMPANY luverness Building 40 P.O. Bor 1295 Birmingham. Alabat: 35242 TELECOPY COVER SHEET 50NOPC0-V0GTLE -- 4TH F1.00k Telecopiert (205)-877-7885 Vertiy (205)-877-7897 DATE:
Aoril ll, 1990
!WMEEP. OF PAGES:
6 (Lxcluding Cover Pagej PICIPIENT:
Please nor,ify us if you have problems receiving this telecopy.
FROM:
Toa NAME: Lenneth S. Curr NAgg Al Chaffee EXTt3SIcN: (205) 877-7836 ErTrysley 1.0 CAT 10N Birmingham. AL LOCATION:
NEC TELEC0?!ER #:
(1nii aop ntn7 Verify:
(301) 492-0802 SENDER; $hould this document be returned to you af ter tg has been sent?
1YES NO COMMENTS:
pie ne review and tenvida coments to Lewis k'ard (205) 877-7802 or Ken Bure (205) 877-7836, 9202210414 920116 PDR ADOCK 05000424 S
.,u -n
- < ca :; u :: e :t-os:LE TEL C ;-: !- F7-7:10 c?M F D; f
M_1E1IEMERLIISLAlltlHC Ehuth_htitLhter Te-oeratm_Michltlidili1LCnlmin A.
Perform a reliability evaluation of two new temperature ;mches (Calcon Model A%00),
used for Jacket Water High Temperature switches on the Vogtle Llectric Generating Plant (VEGP) emergency dicsel generators.
The purpose of the evaluation is to determine switch setpoint repeatability due to several factors which are outlined in the following test sequences.
Additional
- tests, based on results of thess tests, may be added by approval of the GPC test monitor.
B.
Test Sequence:
1.
Record serial and model numbers, and other pertinent data from the instruments, prior to performing any disassembly or removing the sensor from its thermowell.
2.
Remove the sensor from the thermowell and determine the as-found condition of the spacer-tube (how loose, whether or not lock-tite on threads, etc.).
If the spacer-tube was not tight, mark th ' as-received position, then tighton the tube.
3.
Connect air supply and test instrumentation to the switch to simulate installed configuration (approximately 60 psig clean, dry air through 1/4 in. tubing and 0.028 in. orifice).
Connect test instrumentation to provide continuous recording of air pressure at sensor after the orifice, bath temperature P channels -- one in a well, and one in the bath) and time.
4.
Perform s calibration of the switch in its thermowell using the attached calibration procedure.
Set the switch 0 200 t 20f.
lhis calibration is to remain in effect for the subsequent tests.
5.
Perform setpoint tests to measure setpoint and reset sensitivity to the following parameters.
The attached test procedure should be used to determine the trip and reset points.
a.
With the sensor installed in the thermowell, check the trip and reset point under the following conditions:
(60 psig air supply, slow rate of temperature change (e.g.
10f/ minute)).
Remove the senser from the thermowell and insert it directly in the bath, and repeat the trip and reset test.
Repeat the above cycle 2 additional times to check for changes in trip and reset points.
b.
Withthesensorinstalledinitsthermodellundervarying rates of temperature change (approximately 2,4, 6, 10, 1.2
i p r-it '90 c m ; :N E:ce :C-4 W LE TEL t 01 l,-ICT-177.'iI" and 200f/ minute, with 60 psig air supply pressure).
c.
With the sensor installed in its thermowell, with a slow rate of temperature change (- 10F/ min.), with various air supply pressures (55 and 65 psig).
d.
With the sensor installed in its thermowell, with slow rate of temperature change (-
10F/ min.), 60 psig air
- pressure, determine the effect of vibration vs.
static conditions on the setpoint.
c.
With the sensor installed in its thermowell, with a slow rate of temperature change (~
10F/ min.),60 psig air pressure, determine the effect of a change in ambient air temperature of approximately : 200F on the setpoint.
f.
With the sensor installed in its thermowell and the bath temperature near, but just below the switch setpoint, determine the switch response to a rapid reduction in temperature (approximately100 Fin 1 minute).
g.
Determine the effect of tightness of the setscrew used to attach the sensor in the thermowell on trip / reset point.
6.
Determine the effect of spacer-tube looseness by returning the tube to the position noted in step B.?.
If the tube is not loose, then loosen it until it can be easily moved by light finger pressure.
Install the switch in its thermowell and recalibrate it using the attached procedure.
Check the trip and reset points (at 10F/ minute, 60 psig air) with the sensor inserted in the thermowell and with the sensor inserted directly in the bath, as performed in B.S.a above.
Perform each test a minimum of 3 times.
Ph3se 11.-
Testing will consist of analysis work on 7 temperature switches to determine the cause of failure.
The test method will be determined af ter the Phase I work is complete.
(A100N REPRESENTATIVI California Control Company (CALCON)
Cary Hazelitt 1334 Callens Road Ventura, CA 93003 (805) 650-1597 Mr.
Gary Hazelitt was on site (VCGP) and did some initial testing and instructed site personnel on proper calibration methods.
He is a good source for information on these switches.
a
j Acc-: 1*ic 3:N
- Ea:L: - @ TLE
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u?M F04 ATTACHMENT 1 TEST PROCED'JRE 10R SETTING HIGH 1[MPEPATURE JACKET WATER TRIP SWITCHES (cal. CON - P/N f-573-330) 1.
Install terrporature sensor in bath (See Temp. Bath requirements).
2.
Hook,up Air Supply (60 psig thru.028 orifice and test gauge) to sensor "IN port.
3.
Heat-up Bath to temperature at which sensors are to be set and stabilite.
4.
$ct temperature ', witch to trip by slowly turning split ring clockwise while watching pressure gauge.
While adjusting or checking trip temperature
- setting, lightly tap continuously on the side of the sensor.
This simulates engine vibration and will give a more accurate setting.
When switch begins to trip, the pressure gauge will drip.
The temperature sensor is considered tripped when gauge drops to 70 psi.
5.
Cool temp. bath and note that tortp sensor resets (40 psi on gauge) by 100F below setpoint.
Pressure gauge must reset to within 1 psi of supply pressure by 200F belon setpoint.
6.
Reheat bath (always starting 200f below setpoint) and check trip setting.
Readjust as required to desired setting.
A 20f tolerance is acceptable.
7.
Recheck settings until setting within tolerance is achieved two consecutive times.
l
cu-:: * :-0 ;9::6 ::.i t:'c co-tcGr_s it:. t 0i :-10"-177-7' 55 uT:s FC5 ATTACHMENT 1 PAGE 2 1DLDIRATVPJ BATH REQVJARi[Nis 1.
To test temperature switches accurately, a bath must have heating, cooling and circulating abilities.
2.
Two Temp. switche thermowells are required submerged 3" into the water.
3.
Install Temp. Sensor in one well and a thermometer in the other.
(Seal thers.ometer in well at the top to suppress heat loss.
Thermometer should not touch sides or bottom of wcil).
4 A 60 psi supply pressure thru a 0.028 i.001 orifice thru a test gauge to the sensor is required.
i 1
mrc.21 + N epi d t ri is or<D-t OMLE TEL tci:- M -i~'7-TIIt u?ss FN i
l TEMPERATLMU:
IALCQid i. ~. n....e %
l SENSOAS 7*,'fr' Q 7 P N EU M AT I C f-573-330 BNCTION A
RANot 0 - 40 0 'F
)
DESCRIPTION
- This line of tempuroture sensors l
is designed around Colcon's unique solid phase thermol l
esponsion cells.
Model variations consist of rising i
temperature trip (N.C.), folling temperature trip (N,0.)
j ond extended elemerit units. Optional cod nium plated i
gy i
g.
carbon steel or stainless stee! wells are offered in the l
l",
stondord length units. Minimum wall thickness is 0.053'.
Extended element sensors have 304 stainless steel l
j
( K, diameter, the sensing element stock permits insiollonion wells with 0.119' well thickness.
fseing small in 3
i in small diometer wells. The stroke vs. temperoivro ratio is lineer over the full 0 -400'F temperature range l
ond the element is slied to give on occuroie 100'F i
setting change for each full turn of the odiusting devlee.
l This type of expansion element has more inherent occurocy ond linearity than the bi metal disk type, and I
it connot suffer rupture and loss of fluid such as may i
occur in the filled bellows elements. Actual element hysteresis is opproximately ? Io T F, although service
(
ond installotion factors such as wells, hoot fronsfer fluids, role of temperature chonge, etc. will impose i
l other time and temperatute gradients. The trip point may be offected by supply air pressure chonges (opprox. 0.3 F /4 pst), Units must be instolled in o thermo well end if the unit is positioned within I
4$ of certical. Dow 710 heat transfer fluid may be used. This material has o get tiene of opprox.
I imotely 18 menths at 400'F and oppreciobly longer at lower temperatures. This material must not be l
ollowed to horden in the well and other heot transfer grooses should not be used.
l A P P L IC AT ION
- Thor,e temperature sensors mey be used os a detector in any medio system enmpatible with the temperature ronge of the sensor end the material and pressure limitorions of the I
wells.
E= tended element sensors are useful in
,un m.
mt nn m e. m m mm c.
reaching the center region of pipe fluid flows.
Td"
'Q Q"
i'$y
'"I L Typical uses are on engines, gas compressers, and in the process industry as high and low limit trans-l ducers. Data is ovoiloble relating to pressure and
.h ana c sua vs 1.n ai m c l
velocity rotings. Special wells for very high pres.
anu s mu vs i.n Anst s l
sure service Con be sVpplied.
l r
l AllM41 m il 1/2 1.00 Atul W2 l
ORDERING INFORM AflON. Use the toble l
j n
mu i/a is o
on the right and the outline detoils on the bock of j
gn if, y
j this sheet. Unless otherwise specified, sensors n
,g 33 3,,
g
,g will be shipped factory set and tested at 300*F ll l
(static temperature conditions) with on opplied h
35 psi supply air.
Upon request, special temp-
,g
,g eroture settings well be mode of no odditional cost.
i A small viol of Dow 710 heat transfer fluid is sup-plied with each sensor.
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l'N!?tD STATES NUCLEAR PEGULATORY C0 m!SS!0N OFrlCE OF NUCLEAR REACTOP FFGULATION KASHINGTON, D.C.
20555 June 8, 1982 NRC INFORMATION NOTICE NO. 28 36:
FOSSIBLE SUPDEN LOSS OF RCS INVENTORY DURING LOW COOLANT LEVEL OPERATION Addrestees:
All holders of operating licenses or construction permits for pressurized water reactors (PWRs).
Purposet This infonration notice is.beino provided to alert addressees to the potential for a sudden loss of reactor coolant system inventory while conducting steam generator tube inspections and modifications with hot leg nozzle dams in place.
it is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.
However, suggestions contained in this information notice do not constitute NRC j
reouirements; therefore, no specific action or written response is recuired, rescription of Circumstances:
During the second refueling of Diablo Canyon Unit 1, in the spring of 1988, deficiencies in the procedures to be used during the steam generator tube inspections were identified that could significantly increase the probability uf a sudden esection of reactor _ coolant followed by core uncovery, i
in order for the steam generator tubes to be inspected at Diablo Canyon, they were drained, by drawino air through reactor and pressurizer vents, until the reactor coolant inventory was drained down to the mid-level of the hot leg i
piping (see Figure 11 Lowering the reactor coolant to this level also un-covers the steam generator primary side manways so that they can he removed to gain access to the steam generator hot and cold leg plenums and their re-spective hot and cold leg nozzles.
Nozzle dams are then placed in these steam generator plenum nozzles so that the reactor coolant level can be raised to increase the net positive section head to the decay heat removal pumps without refilling the steam generators, t
If the hot leo nczzle dams were all installed before all of the cold leg nozzle dams were in place, a small-increase in reactor vessel pressure would cause reactor coolant-to be rapidly expelleo from the open cold-leg manwys. This would occur because the increased pressure, unable to vent through the dammed.
up hot legs, would force the coolant down in the vessel, through the cold legs, sno cut of the manways.
A pressure increase of only 2-1/? psio in the vessel
/
88 20047 I)
i 14 PR-V June P. 198P Page ? Of f.
would lower the coolant level to the point where the top of the fuel would begin to be uncovered, with the level of the remainina coolant in the open steam generator located at the bottom of the cold len plenum unway.
Similar mechanisms have been identified at San Onofre Units 2 and 3 in their response to Generic letter 87-l (Reference 1), and by the Westinchouse Owners Group in an onocino enalysis of reactor behavior durinn the shutdown condition.
The possibility of e.iectino coolant by this mechanism can be eliminated by ensuring that a steam generator hot leg plenum manway and its associated hot leg pipe are kept open to provide an adequate vent path whenever any cold leg openings are made.
This can be accomplished by ensuring that a hot leo manway is the first manway to be opened, and a hot leg nozzle dam is the last dam to i
be installed.
In addition, not installing the last het leo nozzle dam until a sufficient vent path is established in the reactor vessel or pressuriter will reduce the possibility of developing a pressure differential which could eject a dam.
. Discussion:
On April 10, 1987, the.Nablo Canyon Unit 2 reactor vessel became pressurited to approximately 7 to 10 psig when the residual heat removal flow was lost for a period of 1-1/2 hours (Reference-M.. Fortunately, during this event the man-ways, although loosened, were still in place and the nortle dams had not yet been fnstalled. Operatino a reactor coolant system that has been drained to a l
low level often involves unusual problems that have a significant proo&bility of cauiing a loss of residual heat removal unless special care is taken.
NUREG-1266 (Reference 3), the repor t of the NPC investigation into the Diablo Canyon event.
discusses a number of t1ese problems.
These include the followino i
The level which is established for draining the steam cenerator tubes is frequently only slightly above the level which will provide an adequate suction head for the residual heat removal pumps.
This marginal suction i
head can lead to-air entrainment due to vortexing at the suction point, which may cause a loss of pump suction.
The temporary reactor vessel level measurement system necessary for this type of operation tends to be inaccurate because of the long lengths of tubing normally used. The possible air entrainment and the surface level variations due to fluid flow at this low level provide additional mechanisms that cause error in the level measurement.
The NPC has documented many instances where residual heat removal Las-been lost, because of loss of pump suction, while the plant was beinn operated at reouted reactor coolant water levels.
Generic letter P7-12 (Reference 11 lists 37 loss-of-decay-heat-removal events, occurrino from 1977 to 1987, that were at-tributed to inadequate reactor coolant system level, i n four cases, includino the inP7 Diablo Canyon event, boiling is known to have cccurred before residual heat removal could be reestablished.'
Althouch small vents are normally established in the reactor vessel head and in the pressurizer before the coolant level h drained down, these ore far toe v
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small to prevent pressurization of the reacter coolant system af ter the toilire pcint is reached.
For the recent steam cenerator inspection at Diablo Canyon, which was initiated 10 days after shutdown, the reactor was prooucing 5 PW of decay heat. This is sufficient to produce 5 lb of steem per seccno, which would require a vent area greater than 12 sauare inches in order to hold the pressure rise to less then 25 psi.
During the 1987 Diablo Canyon event, the reactor, which had been thut down for seven days, reached the boiling point about 1/2 hour after decay heat removal capability was lost. The pressure increased to the 7-to-10-psig maximum value a short time later even thouah small vents were available in the vessel head and pressurizer.
With the hot leg nozzle dams in place the pressure rise would be quite rapid.
Generation of a small amount of steam would be sufficient to procuce the partial pressure of 2-1/? psi necessary to uncover the core by ejecting the coolant throuah the open cold leg plenum manway. This amount of steam could be produced in less than a minute. However, the actual time to produce this pressure would depend on the time to heat the reactor coolant to the higher boiling point and on the rate of toergy deposition in the cold materials in the upper part uf the reactor vessel and, to a lesser extent, in the pressuri7er.
The time required for this to occur would likely be only a few mir.utes.
Loss of residual heat removal capability af ter the nozzle dams are installed and before the vessel level is raised would still result in a hazardous situ-ation, however, more time would be available for operator action before loss of coolant occurred. The nozzle dams used at DiaF'; Canyon are designed to withstand about B0 psi of differential pressure. Approximately 1/2 hour of additional time would be available before the reactor conlant heated up to the approximately 300' F necessary to boil at this higher pressure. However, if a cold leg dam were to be expelled at this point, coolant ejection thrcugh the affected steam generator manway followed by core uncovery would be very rapid.
For this reason, it is prudent to provide a means of venting the vessel with the dams installed. At Diablo Canyon, the schedule for detensioning the reactor vessel head was advanced so that this would be done before the reactor was drained for the steam generator inspection. Although the pressure neces-l sary to lif t the detensioned vessel head, in order to vent the vessei, is less than the pressure required to eject the nozzle dams, this pressure is greater than that which would be required to uncover the top of the fuel by expelling coulant throuah an undammed steam generator cold leg nozzle and the associatea ma oway. Therefore, even with the head detensioned, the hot leg r."les should be left open until all cold leg openings are closed.
Generic Letter 07-12 also identified a comparable frechanism for uncovering the core by pressurization during low coolant level operation. An opening in a cold leg, such as one caused by the opening of a reactor coolant system pump cr a loop isolation valve (in some plants), would vent the space of the af-fected cold leg, maintaining this space at atmospheric pressure. Any pressure i
increase, such as would be caused by boilino in the reactor vessel, would be propagated throughnut the remainder of the reactor coolant system, including both hot and cold sides of steam generator primary spaces.
This cifferential pressure wuuld force the coolant levels in the vessel down while the displaced coulant would be forced up and out of the affected cold leg opening. As with the rechanism already discussed, only about 21/2 psi would be recuireo to L
IN 88-3(
June A. 10FF Pace 4 of a expel the water down te the top of the core with the coolant in the affected cold
-leg at the level of a pump opening. Although in this case sone steam condensation may occur in the steam generators, as the ic67 Diablo Canyon event showed, this will not prevent, pressurization.
Note that this mechanism, involving-coolant expulsion through a cold leg opening, does not recuire plugging the steam gener-ator nozzles. As with the previous rechanism. this hazard micht be eliminated
-by venting the reactor vessel through a large opening, such as a hot leo steam generator plenum manway or pressurizer opening, before opening the cold leo.
The loss of residual heat removal capebility durino low reactor coolant level operation has proven to be a frecuent occurrences leading in several cases to boiling in the reactor vessel.
If this should occur, pressurization of the reactor vessel can lead to sudden core uncovery by the expulsion of coolant through any opening in the cold leg side of the reactor coolant system.
This hazard can be eliminated by providing a laroe vent for the reactor vessel space before opening the cold leg.
No specific action.or written response is required by this information notice.
If you have any questions about this matter, please contact one of the technical contacts listed below or the Regional Administrator of the appropriate regional office.
h wh b &-->r Charles E. Rossi, Director Division of Operational Evel.'s Assessment Office of Nuclear Peactor Regulation Technical Contacts: Paul P. Narbut. PV (805)595-2354 Donald C. Kirkpatrick, NRR (301) 492-115?
Warren Lyon, NRR (301) 40?-0891 Attachments:
.1.
Fioure 1 - Reactor Coolant System
?.
List'of Recently. Issued NRC Information Notices
References:
1.
Generic Letter 87-12 " Loss of Residual Feat Removal Phile the Peactor Coolant System is Partially Filled " July 9.1987 t
IN 87-23. " Loss of Decay Feat Removal During Low Peactor Coolant Level Operation."
3.
NUREG-IP69, " Loss of Residual Heat Removal System. Diablo Canyon. Unit ' "
April 10,1987
Figure 1 REACTOR COOLANT SYSTEM PHESSURIZE9 '
STEAM
' GENERATOR 151*-4 % ~
Y
/
Cl = CENTER LINE SG TUBES\\
w 121*
SG MANWAYS MOTOR s
I EI (D 'O N
114~-11" 115' REACTOR VESSEL
- ~~lI~
-^^^^^^^^^^M^^^^^^^^^^^-r^+-^^^^^^^^^-
- r-COLD LEGe:w.
C N
fv-
- ~.
- C3 = 107 )
~ _ ~ ~ _ ~
PUMP COLD LEG [
HOT LEG
~
~
9 '
--j NOZZLE TOP - 1G2*.11 %~_ -
^ /
RHH(out)
NOZZLE DAM (6n)
DAM b
{
ORE CROSSOVER LEG C3 = 96'-8%~
e
-BOTTOM - BS' 6% ~
,~ _
.. ~..
-_. _