ML20235E275

From kanterella
Jump to navigation Jump to search
Forwards Summary of HPCI Problems Experienced During Startup Testing, Per Region III Request
ML20235E275
Person / Time
Site: Monticello, 05000000
Issue date: 10/18/1971
From: Duncanson R
NORTHERN STATES POWER CO.
To: Morris P
US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20235B311 List: ... further results
References
FOIA-87-111 NUDOCS 8709280042
Download: ML20235E275 (5)
v • d • e


Text

I Reguttery File Cy.  !

NSF NORTHERN STATES POWER COMPANY l Minneapolis, Minnesota 55401

&  % l d.!'

(a:o 9gf -  !

October 18, 1971 g'A gd l f  !

Qro . Qg.)^ e f ?lh' S

'Ey4 )

h l I

Director Dr. PeterofA.

Division Morris, Licensing Reactor i United States Atomic Energy dommission I Washington, D.C. 20545

{

Dear Dr. Morris.

10NTICELLO MJCLEAR GENERATIfG PLANT Docket No. 50-263 License No. DPR-22 Summary of HPCI Problems Experienced During Startup Testing As requested by the Region lli Division of Compliance Office, we are forwarding the attached report, " Summary of HPCI Problems Experienced During Startup Testing" for your information.

Yo,u. very truly,

\ N

/

o n'

NW R.0. DuncansIn, Jr. , P. E.

Gen. Supt. of Power Plants Mechanical f, Chairman Monticello Safety Audi t Commi ttee OCT2133,h. )

ROD /caf -

Attachment co i

0709280042 070921 4612 PDR FDIA MENZO7-111 PDR

,h ~ , rn g;y
;(

+

aondne wit.s: u;ut lO~$ Y October 16, 1971 l

~

MONTICELLO NUCLEAR GENERATlfG PLANT

, Summary of HPCI Problems Experienced During Startup Testing This report summarizes the problems encountered while testing the HPCI system during thelMonticello Nuclear Generating Plant Startup Test Program.

The pre-operational testing of the HPCI system was perforned during Januaryled.

1970.. During this time all valves were tested, instrumentation was calibra and functionally tested, all control logic was tested.and the turbine was operated using 80 psi heating boiler steam. The heating boiler steam supply was insufficient to operate the machine under load, consequently, .the turbine

! governor could not be tested. A complete test that demonstrated machine performance at design conditions was not possible until high pressure steam  ;

was available from the reactor.

As a result of FPCI testing performed at other G E plants, the Monticello HPCI l

flow controller was modified in January of 1971 prior to initial plant heatup.

" Tracking" capability was added, wherein the flow controller output could be held at a' preset value during periods when the turbine was shutdown. Previously, L the controller output would integrate to a 50 Ma " saturated" condition during shutdown periods,- thereby causing unacceptable overspeed conditions during the -

automatic fast startup transient. The tracking signal is released when-the i turbine stop valve leaves the closed position, and the. controller output integrates to the value required to satisfy input demand.

A design error was found and corrected involving an air operated pressure control valve which had been installed on the system cooling water loop. The valve was replaced with a self-actuated pressure control valve.

Initial startup testing of the FPCI system was started on February 20, 1971. '

The following problems were corrected during.this initial test period:

1. The flow controller " tracking" station was found inoperable due to a ground loop between the controller and the electronic governor.

The ground loop was corrected, the' controller trackirg capability was j

demonstrated.

2. The " tracking" modification affected the ability of the controller to provide a "bumpless" manual to auto transfer. This was eventually corrected by further modifications to the controller.
3. The pump discharge flow orifice sensing lines were found reversed and were corrected.
4. The local " Turbine Trip" capability using the overspeed trip valve would not operate. The hydraulic oil dump pipe from the turbine stop valve was

. replaced with tubing, increasing the flow area. The oil pump suction piping was carefully sealed to prevent air inleakage that would cause oil pump cavitation.

u l

r . _2_

5. . The torus level switches that cause HPCI suction transfer from the-Condensate Storage Tanks to the torus on high torus water level had to b'e remounted to eliminate. vibration induced trips. A transfer would result

. -on machine startup as turbine exhaust flow caused.the exhaust piping and I torus to vibrate.

The' switches were also found installed about four feet above the proper.

trip point...The switches were moved to the correct elevation and supported from the building wall.

6. A broken. resistor was found in the auxiliary oil pump starting circuit which delayed the start of the auxiliary oil pump and therefore the starting time of the turbine about 3-4 seconds. This was repaired.
7. HPCI- steam-line ' isolation due to initiation of the high steam flow sensors would occur after the 45 second time delay. The switches were calibrated and a new trip point was set based on the observed differential pressure at design conditions.
5. The " test-return" piping vibrated excessively during operation. Additional piping supports were installed.
c. At the 1000 psi steam pressure condition, the stop valve opening time was l excessive. An adjustment was made to the pilot valve to reduce the steam L pressure on the. stop valve balance piston which improved the opening time.

l-

10. Initial testing uncovered problems regarding compatibility between the l

flow control signal, the electronic governor system, and the turbine hydraulic control, system. The following changes were made:

a. A new amplifier printed circuit board was installed to improve slow turbine speed measurement.
b. New " frequency-range" capacitors were installed to cover the required turbine speed range.  ;
c. Isolation transformers were installed to isolate the input and output signals within the electronic governor.

After correcting the above problems, test activity resumed on the HPCI system, ard " operational" status was finally achieved. However, gain and stability adjustments on the electronic governor were at their limits, the adjustments and system control was still on on the the electronic governor primarily edge of instability, were nearthe their limits,f result o a " noisy" flow control signal.

Ft.rther testing on the HPCI system to optimize flow controller proportional band and reset settings was performed from March 21 to March' 24 at reactor pressures ranging from 170 psi to 350 psi. As of March 24 the system was operating satisfactorily at reactor pressures up to 350 ps,ig. During the plant outage following this testing, modifications in the flow controller to allow "bumpless" manual to auto transfer were permanently wired.

G

__ _ . - _ _ 4

When the HPCI syste was. tested at 650 psig on April 17, the flow did not come -

up to 3000 gpm with!- the desired 25 seconds and a 400 gpm peak to peak n instability was noted in pump flow. A few adjustments were made to the . flow -

controller and gove or without success. The decision was'made to declare the system inoperable.

.in order to correct -he instability problems, the flow controller was converted to a pure " integral" controller by removing the proportional band feature. A new electronic governor was installed which incorporated the following permanent modifications:

1. New amplifier p-inted circuit board was installed to obtain wide speed range control and to :nprove gain and stability adjustments.
2. New " frequency-range" capacitators were installed to cover the required l

. turbine speed range.

3. Isolation transformers were inst'alled to provide isolation between the speed input signal, -he convertor circuit board, and the tachometer printed circuit board.
4. The signal convertor was modified to reduce load on the output loop of the flow controller, it was also noted that the present signal converto'rs used ceramic resistors which were dipped in epoxy, an unacceptable condition which resulted ir overheated comp:nents.

The hydraulic syster was modified as follows:

a) The 1/8" choke orifice in the 100# hydraulic system was removed.

b) The hydraulic bypass on the stop valve was renoved.

c) The'30# pilot valve supply orifice was changed from 5/32" to 3/16" diameter.

HPCI testing following the above modifications revealed the following two problems which  !

had to be corrected..  !

a. A steam leak from the turbine valve chest cover required removal of the  ;

cover for inspection. The steam chest flange faces were stoned to renove I imperfections from the '; jacking" bolts. The . steam leak was apparently the result of relaxed torque on the steam chest bolting.

b. The governer hydraulic actuator was renoved and inspected because of faulty operation and found to be fouled. Oil samples were taken revealing high part icle co.:nt. The turbine oil system was drained, cleaned and flushed and a new hydraulic actuator was installed. Turbine oil samples are presently analyzed every six months.

Following some initial difficulty in calibrating the new electronic governor,the HPCI system was successfully tested throughout its required pressure range on May 2 and 3, 1971. Test reruits are tabulated below.

H i

, j

. i' Tests. Conducted 5/2/71.Th'ru .5/3/71 .

Tesi No. ,,,1 , ; _2,,, _3 ,, 4 _5,_ ..

Reactor Pressure, psig_ '170 3 39 .'650- 1000' 1000 Pump Discharge Pressure, 'psig _ 340 410 - -748 ~ 1060 1175 Punp Flow Rate GPM. 3100 3050 3100 3070 3100.

Flow Start, seconds. 5.5 6.0 6.0 ' 6.0 5. 5 Controller Ramp Start, seconds' 5. 5 6.0 6.0 6.0 . 6. 5 Controller @ Req'd Output, seconds 16.5. 16.5 18.0 21.0' 20.0 Time'io 3000 GPM,-seconds 17.0 17 0. 19.0 ,22.0 20.0 NOTE: Times indicated are from the time the steam supply.

, valve starts to open and are recorded to the nearest 0.5 second.

I I

-- - -- - -

Retrieved from "https://kanterella.com/w/index.php?title=ML20235E275&oldid=3191878"