ML19344D399
| ML19344D399 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/03/1980 |
| From: | Swart F PUBLIC SERVICE CO. OF COLORADO |
| To: | Varga S Office of Nuclear Reactor Regulation |
| References | |
| P-80035, NUDOCS 8003120280 | |
| Download: ML19344D399 (37) | |
Text
,
public seMee company oe ed esde March 3,1980 Fort St. Vrain Unit No. 1 P-80035 fir. Steven A. Vargs Acting Assistant Director for Light Water Reactors Division of Project Management U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Docket No. 50-267
Subject:
Modification of Helium Circulator Auxiliary System Gentlemen:
As agreed in our meeting of November 1,1979 with Messrs. Kuzmycz and Williams, this letter forwards the revised System Description which reflects the changes which will be made by our planned Loop Split Modification of the Helium Circulator Auxiliary System.
The attached System Description is in a preliminary form m.
this time and is subject to change since the design for this modification is not complete.
Additionally, the revised PI Drawings which will be attachments to this System Description have not been completed at this time.
Sketch A has been enclosed with this letter for your use in reviewing the System Description.
We are continuing to work toward the scheduled inservice date of January 31, 1981.
If you have any questions, please call.
Very truly yours,
/
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d ln2. '
Frederic E. Swart Nuclear Project Manager FES/FT:pa Enclosures 8003120 EFO
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FORT ST VRAIN NO.SD-21-2 PROJECT PUBLIC SERVICI COMPANY OF COLORADO E
PAGE 1 0F35 HELIUM CIRCULATOR AUXILIARY SYSTEM (SYSTEM 21-2)
SYSTEM DESCRIPTION TABLE OF CONTENTS SECTION HEADING PAGE 1
PURPOSE 2
2 NORMAL OPERATING REQUIREMENTS 2
3 ABNORMAL OPERATING REQUIREMENTS 2
4 EQUIPMENT ITEMS 3
5 REFERENCE DRAWINGS 8
6 FUNCTIONAL DESCRIPTION-NORMAL OPERATION 10 7
FUNCTIONAL DESCRIPTION-ABNORMAL OPERATION 13 8
CONTROL AND SAFETY 16 9
OPERATING PROCEDURE 30 10 PRENUCLEAR HEATING USING WATtR TURBINE CR..ES 30 11 LIST OF SYSTEM ALARMS AND OPERATOR RESPONSE 31 12 NORMAL STARTUP OF CIRCULATOR SERVICE SYSTEM 35 ATTACHMENTS PREUMINARY; ISSUE
SUMMARY
ISSUE DATE PREPARED BY REVIEWED BY APPROVED BY BASIS FOR REVISION l
l
1
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?
e NO. 50-21-2 FORT ST. VRAIN ISSUE PROJECT PUBUC SERYlCI COMPANY OF COLORADO DATE l
PAGE 2 0F 35 1.
PURPOSE The circulator auxiliary system provides a ;upply of high pressure water for helium circulator bearing lubrication and a supply of purified buffer helium to prevent either the inleakage of bearing water into the primary cool-ant or leakage of primary coolant into the systen;.
A water supply is provided to power the auxiliary water-turbine drives.
The system also recovers helium dissolved in water drained from the helium circulators and provides high pres-sure helium to actuate the circulator brakes and static seals.
High pressure helium is also supplied to back up the "0" rings within the circulator to pre-vent intra-machine leakage if the "0" rings leak.
A nitrogen pressurizing system is provided to maintain the water turbine I drives at a higher pressure than the saturation pressure of the feedwater used to drive the water turbine.
2.
NORMAL OPERATING REQUIREMENTS For each helium circulator, the system provides 170 gpm of bearing water (at full speed) at about 1300 psig and 105 degrees F, and approximately 7.4 acfm of purified buffer helium at 1 psi above helium circulator suction pres-l sure and at a temperature of about 100 degrees F.
At full load, this amounts to about 200 lb/hr of helium per circulator.
Approximately 3.7 acfm of helium is recovered from the bearing water leaving the helium circulator drains.
3.
ABNORMAL OPERATING REQUIREMENTS When it is necessary to use the circulator auxiliary water-turbine drives, the system will supply any two auxiliary water turbines with 535 gpm each of feedwater at 2900 psig and approximately 320 degrees F.
If feedwater is not available, condensate at 268 psig and approximately 100 degrees F and a flow rate of abos t 150 gpm each can be supplied to any two of the turbines.
To pre-vent cavitation damage to the Pelton wheels during auxiliary water turbine drive operation, the Pelton Wheel cavity is pressurized with nitrogen to a t
pressure above the saturation pressure of the incoming feedwater thus inhibit-ing flashing and bubble formation.
If the normal supply of bearing water is interrupted, a backup supply of water is automatically provided from the emergency feedwater line to the bear-ings at a differential pressure of about 600 psi above circulator suction pressure and at a temperature of about 140 degrees F.
The flow to the bearings will be about 165 gpm (at full speed).
If emergency feedwater is not availa-ble, bearing water is supplied from bearing water accumulators for sufficient time to safely shutdown the affe( red circulator.
\\
f FORT ST. VRAIN NO. S0-21-2 ISSUE PROJECT PUBUC SERVICE COMPANY OF COLORADO DATE PAGE 3 0F 35 Whenever a circulator is stopped, high pressure helium is used to set the brake when the machine has slowed to 700 rpm and also to set the static seal, which inhibits helium leakage along the shaft.
The flow passages within the circulator are isolated from one another by "0" ring seals.
Should these seals leak due to misalignment and/or thermal-mechanical stresses, high pressure helium at a maximum rate of 50 lbs/hr/ circulator is supplied and prevents fluids from the different flow pas-sages from communicating with one another.
Prior to nuclear core loading, the primary coolant system will be heated to approximately 625 degrees F using the heat of compression from the helium circulators.
The circulator's water turbine drives will power the circulators using boiler feedwater supplied at a flow rate of approximately 3300 gpm at about 3000 psig at the water turbines.
Special Pelton wheels are supplied for the prenuclear heating.
The nitrogen pressurization system is operated during prenuclear heating.
4.
EQUIPMENT ITEMS The helium circulator auxiliary system incorporates the following equip-ment items:
a) Buffer helium recirculators (C-2105, C-2105S, C-2106, C-2106S) b) Recirculator containment tanks (T-2102, T-21025, T-2103, T-2103S) c) Backup bearing water coolers (E-2101, E-2106) d)
Buffer helium coolers (E-2102, E-2102S, E-2103, E-2103S) e)
Bearing water coolers (E-2104, E-2104S, E-2:.05, E-21055) f) Bearing water filter (F-2101, F-2101S, F-2102, F-2102S) g) Bearin wa ter pumps (P-2101, P-2101S, P-2102, P-2102S, P-2106, P-2107 h)
Turbine water removal pumps (P-2103, P-2103S) i) Bearing water removal pumps (P-2104, P-2104S) j)
Bearing water makeup pump (P-2105) l k)
Helium dryer units (S-2111, S-2112) l
t f
FORT ST. VRAIN NO. 50-21-2 PROJECT PUBLIC SRVICE COMPANY OF COLORADO hE PAGE 4 0F 35 1)
Circulator auxiliary chemical injection system (S-2103) m)
Helium recovery compressors (C-2107, C-2107s) n)
Bearing water surge tanks (T-2104, T-2105) o) High-pressure separato's (T-2106, T-2107, T-2108, T-2109) p)
Turbine water drain tank (T-2110) q)
Low-pressure separator (T-2111) r)
Backup bearing water filters (F-2103, F-2103S) s) Gas pressurizers (T-2112, T-2113) t)
Bearing water accumulators (T-2114, T-2115) u) Water chillers (S-2109, S-2109S, S-2110, S-20110S) v)
Emergency bearing water filters (F-2104, F-2104S) w)
Emergency bearing water makeup pump (P-2108) x)
Helium recovery compressor K.0. drum (T-2117, T-2118) y)
Nitrogen compressors (C-2109, C-2109S) z) Seal water coolers (E-2107, E-2107S) aa)
Separator (T-2120) ab) Nitrogen makeup cylinders (T-2119 I
ac) Helium dryer knockout pots (T-
,T-
)
ad) Bearing water makeup filter (F-2105, F-2105S) ae) Backup bearing water accumulators (T-2121-1,
-2,
-3, T-2122-1,-2,-3...T-2124-1,-2,-3) af)
Emergency water boost pumps (P-2109, P-2110)
I ag)
Coalescing filters (F-2108, F2108S, F-2109, F-2109S)
The buffer helium recirculators (C-2105, C-2105S, C-2106, C-2106S) are rotary, liquid-piston (Nash) compressors using water as the liquid.
Each machine has a capacity of about 12 acfm at a 31 psi pressure differential (18 l
FORT ST. YRAIN
.50-21-2 PROJECT PUBLIC SERVICI COMPANY OF COLORADO hE PAGE 5 0F 35 acfm at a 25 psi differential) and is driven by a 20 HP TEFC motor, which is connected to an essential power bus.
One recirculator in each loop operates continuously; the second machine is on standby.
The recirculator containment tanks (T-2102, T-2102S, T-2103, T-2103S) are approximately 2-1/2 ft I.D. x 6'-3" 0.A.L.
The tanks are designed for 875 psig at 150 degrees F (ASME Code, Section III-C) and,ormally operates at 711 psig and 90 degrees F.
Each tank incorporates a separate compartment which serves as a helium / water separator and a liquid reservoir to supply the water require-ments of the Nash compressors.
Each of the two backup bearing water coolers (E-2101, E-2106) is designed to cool 340 gpm of boiler feedwater from 320 degrees F to 140 degrees F.
Pnis cooler is a shell and "U" tube type exchanger with the tubeside designed for c
2500 psig and 320 degrees F.
The shell is designed for 15g psig and 200 de-grees F.
Design heat load for each exhcanger is 30 6 x 10 Btu /hr.
The heat 2
transfer surface area for each exchanger is 1120 ft.
The coolers are built to the ASME Code,Section VI,II and TEMA Standards, Class R.
The buffer helium doolers (E-2102, E-2102S, E-2103, E-2103S) are Graham Heliflow-type, shell and coiled-tube exchangers.
These coolers are designed for 875 psig at 200 degrees F (tubeside) and 100 psig at 150 degrees F (shellside).
The heat load is about 45,000 Btu /hr each.
The coolers are built to the ASME Code,Section VIII.
l The bearing water coolers (E-2104, E-2104S, E-2105, E-21055) are shell and tube type exchangers.
The coolers are designed for 2100 psig and 150 degrees F tubeside, and 100 gsig and 300 degrees F shellside.
Design heat load for each 2
cooler is 2.0 x 10 Btu /hr.
The transfer surface is 436 ft.
The coolers are l
built to the ASME Code,Section VIII and TEMA Standards, Class R.
One cooler is normally operating in each bearing water loop; the second cooler is an in-stalled spare.
Each cooler is designed to cool 340 gpm of bearing water from about 117 degrees F to 105 degrees F.
The bearing water filters (F-2101, F-2101S, F-2102, and F-2102S) are each capable of handling a bearing water flow of 340 gpm and of removing particles with a neninal size of 1,0 microns and above.
The filter housing is designed for 2100 psi and 150 degrees F (ASME Code,Section VIII).
One filter is normally 3
in service in the bearing water line; the second filter is on standby.
The backup bearing water filters (F-2103, F-2103S) are each capable of handling a water flow of 680 gpo and of removing particles with a nominal size of 10 microns and above.
The filter housing is designed for 2500 psig and 210 degrees F ( ASME Code,Section VIII).
One filter is normally in service in the backup bearing water line; the second filter is on standby.
The emergency bearing water filters (F-2104, F-2104S) each handle a flow of 44 gpm and can remove particles with a nominal size of 25 microns and above.
NO. 50-21-2 FORT ST. VRAIN PROJECT PUBLIC SHVICE COMPAMY OF COLORADO hE PAGE 6 0F 35 The filter housing is designed for 150 psig and 150 degrees F (ASME Code,Section VIII).
One filter is normally in service; the second filter is on standby.
The bearing water pumps (P-2101, P-21015, P-2102, P-2102S, P-2106, P-2107) are vertical, centrifugal pumps.
Each unit has a capacity of about 340 gpm at a total differential head of abcut 1190 ft (515 psi) and is driven by a 150 HP motor which is connected to an essential power bus.
All three pumps are con-nected in series. Any two pumps are in continuous operation while the third pump is on standby in each bearing water loop.
The turbine water removal pumps (P-2103, P-2103S) will normally' operate at about 1070 gpm at a total differential head of about 272 ft and are driven by 150 HP motors, which are connected to an essential power bus.
One pump is on standby. A larger diameter impeller is required for prenuclear heating, in-creasing the capacity of each pump to 1900 gpm at head of 250 ft (see Para. 9).
The larger impeller diameter will be retained for normal operation.
The bearing water removal pumps (P-2104, P-2104S) each have a capactiy of about 140 gpm at a total differential head of about 260 ft.
Each pump is driven by a 20 HP motor which is connected to an essential power bus.
One pump is on standby.
The bearing water makeup pump (P-2105) has a capacity of about 170 gpm at a total differential head of 1730 ft and is driven by a 150 HP motor, which is connected to an essential power bus.
The emergency bearing water makeup pump (P-2108) is a positive displace-ment pump with a capacity of 40 gpm at a total differential head of 1735 ft.
It is driven by a 25 HP motor, which is connected to the essential power bus.
The coalescing filters (F-2108, F-2108S, F-2109, F-21095) are designed to remove 997, of the entrained moisture in the gas stream.
The filter housings are designed to Section VIII of the ASME Code for 875 psig and 150 degrees F.
The helium dryer units (S-2111, S-2112) are designed to dry 400 lb/hr at full load, of helium (water-saturated at 100 degrees F) to a dewpoint of -70 degrees F.
The units are conventional twin bed dryers, capable of continuous, automatic operation.
The units are of all welded construction with the vessels designed to Section VIII of the ASME Code for 875 psig and degrees F and consist of two dryer beds, a regeneration coolei and two effluent filters.
The circulator auxiliary chemical injection system (S-2103) consists of a 50 gallon tank and a 1/4 HP positive displacement pump.
The pump capacity is i
adjustable from 0 to 5 gph at 900 psig.
The helium recovery compressors (c-2107, C-2107S) are multi-stage, verti-l cal, non-lubricated compressors with an inlet capacity of 18 acfm of
I FORT ST. YRAIN E
PROJECT PUBUC SRVICI COMPANY OF COLOM DATE PAGE 7 0F 35 l
helium at an inlet pressure of 10 psia and a discharge pressure of about 845 i
psig. A knockout pot after the discharge of the final (third) stage of the compressor removes any water condensed during compression and cooling.
Each compressor is driven by a 20 HP electric motor.
One ccmpressor is on standby.
i The bearing water surge tanks (T-2104, T-2105) each have a capacity of ap-proximately 1000 gallons.
The tanks are designed for a pressure of 845 psig at 150 degrees F in accordance with Section III-C of the ASME Code.
The high pressure separatgrs (T-2106, T-2107, T-2108, T-2109) each have a volume of approximately 5.5 ft.
Each separator is designed for 845 psig at 150 degrees F in accordance with Section III-C of the ASME Code.
The turbine water drain tank (T-2110) has a capacity of approximately 5000 gallons.
This tank is designed for 80 psig or full vacuum at 320 degrees F, in accordance with Section VIII of the ASME Code.
Low-pressure separator (T-2111) has a capacity of approximately 950 gallons.
This tank is designed for 50 psig and full vacuum at 150 degree", F, in accordance with Secti.on VIII of the ASME Code.
The gas pgessurizers (T-2112, T-2113) each have a gas volume of approxi-mately 1000 ft.
The tanks are designed for a pressure of 2500 psig at 100 de-grees F in accordance with Section VIII of the ASME Code.
Thebearingwateraccumulgtors(T-2114,T-2115)eachhaveawaterstorage volume of approximately 2 Oft The tanks are designed for a pressure of 2500 psig at 100 degrees F in accordance with Section VIII of the ASME Code.
The water chillers (S-2109, S-2109S, S-2110, S-2110S) are equipped with a 3/4 HP pump which delivers 15 gpm of 35 degrees F water containing 5". ethylene glycol by weight.
Each chiller is capable of removing 45,0000 Btu /hr from the process water.
The chillers are run continuously to maintain a constant source i
of low temperature water.
One unit is on standby for each loop.
The helium recovery compressor knockout drums (T-2117, T-2118) have a capacity of 3.5 gallons each.
They are designed for 50 psig at 150 degrees F in accordance with the ASME Code,Section VIII.
FORT ST. VRAIN IfE PROJECT PUBUC SERVICI COMPANY OF COLORADO DATE PAGE 8 0F 35 The nitrogen compressors (C-2109, C-21095) are rated to pump 120 acfm from 13.5 psia at 150 degrees F to 50 psig at 150 degrees F each.
Each is powered by a 50 HP motor.
One is normally operated; the other is a spare.
The seal water coolers (E-2107, E-2107S) are each rated to remove 240,000 Btu /hr.
The shell side is designed for 225 psig at 450 degrees F; the tube side for 150 psig, 450 degrees F, in accordance with AStiE Code,Section VIII.
The separator (T-2120) separates the seal water from the compressed nitrogen.
It has a capacity of 42 gallons and is designed for 150 psig at 150 degrees F in accordance with the ASME Code,Section VIII.
The nitrogen makeup cylinders (T-2119) are used to store nitrogen for the nitrogen pressurization system.
There are 24 cylinders each holding 224 scf for a total volume of 5376 scf.
The helium dryer knockout pots (T-and T-
) collect condensed water from the coolers (E-2109X, E-2110X) on tne helium dryer units (S-2111, S-2112).
The pots have a capactiy of gallons and are designed for 875 psig at degrees F in accordance with the ASME Code,Section VIII.
The bearing water makeup filters (F-2105, F-2105S) have a capacity of 100 gpm each.
They are designed for 150 psig at 150 degrees F in accordance with the ASME Code,Section VIII.
They will remove particulates 10r and above.
The pressure drops at rated flow are 5 psi (clean) and 50 psi (dirty).
The backup bearing water accumulators (T-2121-1, -2,
-3, T-2122-1, -2, 3...T-2124-1,-2,-3) have a capacity of 10 gallons each.
They are of the bladder type, and their gas side is pre-pressurized to the 500-550 psig range.
They allow a smooth transition from normal bearing water to backup bearing water by supplying less than 6 gallons per minute of makeup water for approxi-mately 3 to 4 seconds.
After the transition to backup bearing water is com-pleted, the pressure in the backup bearing water line recharges the accumula-tors automatically.
They meet the ASME Code,Section VIII requirements.
They are designed for 3000 psig and 180 degrees F.
l The emergency firewater boost pumps (P-2109, P-2110) each have a capacity of 155 gpm at 145 psig and are driven by 40 HP motors.
Either pump will boost firewater to the pelton wheels through the emergency condensate line, or through the emergency feedwater line.
5.
REFERENCE DRAWINGS Process Flow Diagram - Helium Circulator Auxiliary System, PF-21-2
FORT ST VRAIN NO. 50-21-2 ISSUE PROJECT PUBtJC SERVICI COMPANY OF COLORADO DATE PAGE 9 0F 35 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Buffer Helium, PI-21-2 Piping and Instrument Diagram - Helium Circulator Auxiliary System.
Buffer Helium, PI-21-3 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Bearing Water Recirculation, PI-21-4 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Bearing and Turbine Water Distribution PI-21-5 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Helium and Water Recovery, PI-21-6 O
Piping and Instrument Diagram - Helium Circulator Auxiliary System, Circulator C-2101, PI-21-7 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Circulator C-2102, PI-21-8 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Circulator C-2103, PI-21-9 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Circulator C-2104, PI-21-10 Piping and Instrument Diagram Helium Circulator Auxiliary System, Circulator Brake and Static Seal System, PI-21-11 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Water Chillers, PI-21-12 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Gas Pressurization, PI-21-13 Piping and Instrument Diagram - Helium Circulator Auxiliary System, Circulator Brake and Static Seal System, PI-21-14 Piping and Instrument Diagram - Secondary Coolant System PI-22-1 Reference for Emergency Water Boost Pumps)
~.
NO.SD-21-2 FORT ST. m PROJECT PUBUC SEVICE COMPANY OF COLORADO hE PAGE 10 0F 35 6.1 BUFFER HELILN:
Each primary coolant syste[n loop, containing two helium circulators, is serviced by its own buffer helium supply loop.
Each buffer loop recovers approximately 50% of the helium supplied to the circulator seals, separates any water carried over from the circulators, recompresses and dries the helium anc returns it to the circulators at the required buffer sup-ply pressure. Makeup helium from the helium purification system (System 23) is supplied independently to each buffer loop to replace the helium that flows through the upper circulator seals to the circulator suction and into the pri-mary coolant system.
Buffer helium flow to each circulator is controlled at 7.4 acfm (200 lb/hr at full reactor power).
Helium flow entering the labyrinth seal splits so that approximately 50% flows through the upper portion of the labyrinth and into the helium circulator suction, thus preventing outleakage of primary coolant.
The remainder flows through the lower portion of the labyrinth to the helium / water drain, thereby preventing 1 takage of bearing water into the pri-mary coolant system. The helium and water mixture (100 lb/hr of helium and ap-proximately 1 gpm water from the helium /ws ter drain) flows to the appropriate high pressure separator where the helium and water phases re separated.
The water flow from the separator is described in Sections 6.2 and 8.1.6.
Buffer helium leaving each high pressure separator is flow controlled at 3.7 acfm.
With the buffer helium supply controlled at 7.4 acfm and the net flow leaving the circulator controlled at 3.7 acfm, the 50% flow split through the helium labyrinth is maintained. This control scheme is more fully described in Section 8.4.
Buffer helium from the two high pressure separators in each loop (T-2106 and T-2107 or T-2108 and T-2109) is manifolded for recycle via the cor-responding buffer helium recirculators (C-2105 or C-2105S and C-2106 or C-2106S).
Normally, one recirculator in each loop will be in operation with the second machine serving as a standby unit.
Helium flow through the recircula-tors is cooled to 90 degrees F by the recirculator seal water supplied from the, buffer helium coolers (E-2102, E-2102S and E-2103, E-2103S) at 41 degrees F.
This water is in turn cooled by_ the water chillers (S-2109, S-21095 and S-2110, S-2110S).
The helium / seal water flow discharged from each recirculator is separated into gas and liquid phases within the recirculator containment tar.ks (T-2102, T-2102S and T-2103, T-2103S).
Helium from the operating recirculator in each loop flows through the coalescing filters (F-2108, F-2108S and F-2109, F-21095 ).
One coalescing filter in each loop will normally be on-stream with the other serving as a backup unit.
The coalescing filters remove any en-trained moisture in the helium flow which may have been carried over from the recirculator containment tanks.
Helium is then discharged to the helium dryer unit in each loop (S-2111 and S-2112) where the' gas is dried to a dewpoint of -
70 degrees F (less than.35 ppm of water).
The helium dryers are conventional twin bed desiccant units which are automatically controlled by a time-cycle controller for a 16-hour cycle (i.e., a bed is operated for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and is then taken off-stream, regenerated, cooled and maintained, ready to be placed in
FORT ST. YRAIN NO, 50-21-2 PROJECT PUSUC SERVICI COMPANY OF COLOM ISSUE DATE PAGE 11 0F 35 operation when the second bed is taken off stream).
Dry gas for regeneration 1
of the off-stream bed is taken from the outlet of the operating effluent filter on the respective dryer (F-2106X or F-2106SX and F-2107X or F-2107SX), flow controlled, heated and then pased through the bed being regenerated.
Regeneration of the bed is assisted by direct heating of the desiccant by elec-tric heaters.
The regeneration gas is then cooled to remove the moisture col-1 lected from the desiccant and discharged to the suction of the recirculator in the corresponding loop.
A moisture monitor located in the dryer outlet actu-ates an alarn if a degrees F dewpoint is exceeded.
The dried recycle helium from the dryer in each loop is augmented by an equal amount (approximately 200 lb/hr per loop) of the dry helium from the purification system to supply the total requirement of 400 lb/hr per loop (200 lb/hr per circulator) at full load.
Makeup helium from the purification system is admitted independently to each loop of the helium circulator auxiliary system on differential pressure
-~
control (see 50-23). The recycle helium flow from the dryer and the makeup helium from the purification system combine to serve the two helium circulators in the respective loop.
Upstream of the flow controller which admits 7.4 acfm into each machine, there is a helium connection which provides high pressure helium to back up the "0" ring seals within each machine.
This line (for each machine) contains a high flow alarm which alerts the operator when 30 lb/hr per machine is being used as backup for the "0" rings.
6.2 BEARING WATER:
Each primary coolant system loop, containing two helium circulators, is serviced by its own closed loop recirculating water supply.
Each closed loop contains a bearing water surge tank (T-2104, T-2105) which supplies water to the bearing water pumps (P-2101, P-2101S and P-2106 or P-2102, P-2102S and P-2107).
Each surge tank is maintained at an essentially constant differential pressure with respect to primary coolant pressure by an equalizing line which connects to the buffer helium recirculator suction line in its loop.
Thus, the bearing water pumps are required to generate only the pressure differential necessary to force water through the circulator bearings and the supply piping in its loop (about 1030 psi), regardless of primary coolant pressure.
Water discharged from the bearing water pumps is cooled in one of the two bearing water coolers in each loop (E-2104 or E-2104S and E-2105 and E-21055).
Heat picked up by the bearing water as it passes through the circulators is removed in these coolers, supplying the circulators with water at 105 degrees F.
Before entering a circulator, the bearing water is filtered by one of the bearing water filters in each loop (F-2101 or F-2101S and F-2102, or F-2102S) to remove foreign matter with a particle size down to 10 microns. When the operating filter delta P reaches 95 psi, the inlet block valve to the standby filter is automatically opened.
The control scheme employed is outlined in Section 8.1.3.
The filters are backed up by two inline strainers in parallel
4 FORT ST. YRAIN SD-21-2 PROJECT PUBLIC SSYlCE COMPANY OF COLORADO DATE PAGE 12 0F 35 near each circulator for additional protection.
The differential pressure across these strainers is alarmed in the control room and the strainers are manually switched when the pressure drop exceeds 50 psi.
A discussion of the reliability of the piping and valves used for assuring a supply of bearing water to the circulators is covered in Sections 7.2 and 8.2.
Bearing water passes through the circulator bearings and leaves through three separate drains:
the helium / water drain which collects about 100 lb/hr of helium and about 1 gpm of water at full load; the main drain which collects approximately 165 gpm of the 170 gpm total supplied; and the steam / water drain which handles about 4 gp.' (at full load) of water leakage through the steam end of the circulator sha't.
The helium and water mixture -leaving the helium / water drain flows to the high pressure separator.
Helium flow is described in Sections 6.1 and 8.4.
The water is withdrawn from the high pressure separator on level control.
Flow from the main drain is maintained by J control system which receives input from the differential pressures measured between the buffer helium supply and main drain, between the bearing water supply and main drain and from the high pres-sure separator drain flow. These controls are described in Section 8.1.6.
The combined flow from the high pressure separator and the main drain from each circulator is returned by gravity flow to the corresponding loop surge tank (T-2104 or T-2105).
Approximately 166 gpm of the 170 gpm supplied to each circu-lator is thus recycled to the surge tank.
The steam / water drain pressure is controlled at a fixed differential (2.5 psi) below circulator steam turbine exhaust pressure.
Since the drain pressure is always less than main drain (and surge tank) pressure, water leav-ing the drain cannot be returned to the surge tank.
This water (amounting to about 4 gpm per circulator at full load) is therefore routed to the low pres-sure separator (T-2111).
This loss of water from the loop is made up on surge tank level control from the emergency feedwater line via the backup bearing water coolers (E-2101 and E-2106) as described in Section 8.1.1.
To prevent flashing of the steam / water drain effluent in the low pressure separator (T-2111) and thus ensure proper operation of the helium recovery compressors (C-2107, C-2107S) and the helium dryer units (S-2111, S-2112), it is necessary to spray quench the effluent in the 4-inch line leading to the separator.
A constant flow of 30 gpm of emergency condensate (110 de-grees F maximum) is provided to limit the bulk temperature of the water in the low pressure separator (T-2111) to 150 degrees F.
Water from the steam / water drain on each circulator is manifolded into a common header and discharged to the low pressure separator (T-2111)
I which is maintained at about 2 psig by one of the helium recovery compressors (C-2107 or C-21075), which compresses helium evolved from the water due to the reduction in pressure.
The control scheme for maintaining pressure in the low pressure separator is described in Section 8.1.7.
l
FORT ST. YRAIN PROJECT PUBLIC SERVICE COMPANY OF COLORADO hE PAGE 13 0F 35 Each of the helium recovery compressors discharges to one of the buffer helium loops upstream of the coalescing filters (F-2108, F-2108S and F-2109, F-21095) and helium dryer units (S-2111 and S-2112).
Each compressor is sized to handle the maximum quantity of helium which is off-gassed from the water in the low pressure separator.
Normally, only one compressor will be in operation at any time discharging helium to the corresponding buffer loop.
The second compressor serves as a backup unit.
At part load, the primary coolant pressure decreases but to a lesser extent than does the exhaust steam pressure, thereby creating a greater diff-erential pressure between the main water drain and exhaust steam.
This causes a greater leakage of water to the steam / water drain.
At 25% load, the water leakage from the drain increases to about 28 gpm per circulator.
(The total bearing water supply remains constant at 170 gpm.)
Water is removed from the low pressure separator on level control and pumped to the condenser hotwell (normally) or to the deaerator (if the hotwell is out of service) by the bearing water removal pumps (P-2104 or P-2104S).
The level control scheme is described in Section 8.1.7.
7.
FUNCTIONAL DESCRIPTION - ABNORMAL OPERATION 7.1 CIRCULATOR WATER TURBINE DRIVES:
Under certain accidents conditions it becomes necessary ti drive two of the helium circulators (C-2101, C-2102, C-2103, C-2104) with the water turbine drives.
Any two of the water-turbines are powered by feedwater from the emergency feedwater headers at a rate of 535 gpm each'and supplied to the water turbines at a pressure of 2900 psig.
The tu r-bine speed is controlled by throttling the water supply (see Section 8.3).
The initial water temperature will be 320 degrees F (if the accident begins with the plant at full load), grad.ually decreasing to 220 degrees F (deaerator
" pegging" temperature). Water leaving the turbines discharges to the turbine water drain tank (T-2110).
This water is then pumped to the condenser hotwell by the turbine water removal pumps (P-2103 or P-2103S), and should the conden-ser be unavailable, the drains.are pumped to the deaerator.
Steam can be removed from the water turbine drain line prior to water turbine operation via vent valve PV-21120 on the turbine water drain tank.
Use of the uncooled feedwater for driving the water turbines mini-mizes thermal shock to the turbine.
To prevent flashing of this hot water in the turbine cavity and consequent potential cas itation damage to the circulator water turbines during these periods, the turbine cavity pressure is elevated above the water saturation pressure by the addition of gaseous nitrogen.
The nitrogen is supplied to the turbine cavity at a pressure 10-30 psi above deaerator pressure.
This margin above saturation pressure is suffi-cient to prevent excessive cavitation damage to the Pelton wheels.
The ni-trogen added to the water turbine cavity passes upward past the lower circula-
FORT ST. YRAIN SUE PROJECT PUBUC SRVICE COMPANY OF COLORADO DATE PAGE 14 0F 35 tor labyrinth seal cut the steam / water drain to the low pressure separator (T-2111).
During nitrogen pressurization system operation, the gas from the low pressure separator is pumped back to the turbine water cavityJy_one of two 1007, capacity rotary compressors (C-2109/C-2109S) and the Tine to the helium recovery compressors (C-2107 and C-2107S) from the low pressure separator is closed.
Each nitrogen compressor is a liquid-piston type machine, usin as the liquid, and is equipped with a seal water cooler (E-2107/E-21075)g water for removing the heat of compression.
A common separator (T-2120) is provided at the discharge of the operating compressor to separate the seal water and pumped gas. A proper flow of seal water through the compressor is ensured by main-taining a constant differential pressure (50 psid) across the compressor by throttling the separator (T-2120) gas outlet.
Nitrogen leaving the separator is metered and filtered before returning to the turbine water cavities.
The pressure in the low pressure separator is automatically maintained at 5-14 psia by recycling gas from the discharge of the operating compressor (C-2109/C-2109S) to its suction.
In order to prevent the loss of nitrogen due to steam strippiag in the deaerator of the nitrogen-saturated water discharged from the turbine water drain tank, the deaerator vent is isolated, and the deaerator off-gas 's re-routed to the low pressure separator for recovery.
For initial fill of the system and subsequent makeup, gas is added to this cl^ sed loop system from 24 standard gas cylinders with a total capacity of 5,376 S (T-2119).
A pressure control loop adds gas to the system from the gas cylinders, as required, to maintain the turbine water cavity pressure at 10-30 psid above deaerator pressure.
In the case of excess gas inventory due to buffer helium inleakage from the circulator seals, excess gas is vented au-tomatically from the low pressure separator when low pressure separator pres-sure is greater than 16 psia.
A control loop is also provided to maintain a fixed differential pressure between the water turbine cavities and the turbine water drain tank to ensure adequate water drainage from the cavities.
Gas in the cavity is alter-natively vented directly to the low pressure separator or to the turbine water drawing tank to maintain the fixed differential pressure.
During nitrogen pressurization system operation, the turbine water drain tank vent is disabled.
Any venting of the system is accomplished via the low pressure separator vent.
Operation of the nitrogen pressurization system during PCRV depres-surization is similar with the exception that the recirculation around the ni-trogen compressors is controlled to generate a setpoint pressure of 6 to 8 psia in the low pressure separator.
Also the turbine cavity pressure is controlled to 10-14 psi above deaerator pressure, and the controlled differential pressure between the cavities and turbine water drain tank is decreased accordingly.
If boiler feedwater is not available, condensate frem the emergency condensate header can be supplied to arive the auxiliary water turbines.
Condensate, al-
~
FORT ST. VRAIN PROJECT PUBLIC SERVICE COMPANY OF COLORADO h
PAGE 15 0F 35 though available at a pressure (approximately 258 psig) substantially below feedwater pressure, will effectively power the water turbine but at reduced speed. Since the condensate is cold, it. vapor pressure will be too low to permit effective operation of the circulator steam water drain.
As a conse-quence, bearing water will pass through the lower labyrinth, onto the steam turbine wheel and drain into the cold reheat inlet piping. To avoid flooding of the piping with consequent water braking of the circulator by a submerged turbine wheel, a high-capacity trap system is provided (M72100 through M72103).
This system, in parallel installation with the cold reheat inlet steam trap system, has a draining capacity of 40 gpm for each circulator, more than suffi-cient to prevent water buildup in the reheat inlet piping.
The high capacity traps will function only when trap delta pressure is less than approximately 25 psi. Above 25 psid they effectively lock, closed by the force developed across their relatively large orifices.
When the circulators are returned to steam drive, the water remaining in the water turbine cavity is drained via HV-21335 (typical of C-2101) through a steam trap to the trap drain tank (T-7201).
7.2 BEARING WATER:
The bearing water flow to each circulator is ensured by a backup supply of water from the feedwater system.
The feedwater is cooled in the backup bearing water cooler to approximately 140 degrees F with service water and filtered before entering the circulator. A spare filter is provided.
Filters are switched autcmatically on high delta P as described in Section 8.1.3.
If service water is not available to the backup bearing water coolers (E-2101, E-2106), either circulating water or firewater is automatically provided (see SD-46).
Pressure in the backup bearing water supply line is con-tinuously monitored, and automatic action taken if pressure in this line (controlled at 2200 psig) falls below 1600 psig as described in Section 8.1.5.
In the event that the differential pressure between the bearing supply cavity and the main drain of a circulator drops to about 600 psid, a differential oressure controller in the backup bearings water line will automatically admit cooled feedwater directly to the bearings in the deficient loop.
If the lack i
of bearing water is due to low water inventory in the surge tank, the operator can bring the surge tank up to the required level by using the bearing water makeup pump (P-2105) to pump water from the condensate storage tanks or by us-ing the emergency bearing water makeup pump (P-2108) to supply condensate or, in an extreme emergency, firewater.
In the unlikely event that both the bearing water supply and the backup supply are interrupted, the bearing water accumulators (T-2114, T-2115) in each loop will supply bearing water to both circulators for a period of at i
least 30 seconds (at full load).
This time is sufficient to permit the circu-lator speed to drop to 700 rpm at which point the braka is applied and the cir-culator isolated as described in Section 8.6.
7.3 CIRCULATOR BRAKE AND SEAL SYSTEM:
As described in Section 8.6, the circulator shutdown procedure involves the application of a brake to prevent
FORT ST. VRAIN S0-21-2 PROJECT PUBLIC SERVICI COMPANY OF COLORADO DA PAGE 16 0F 35 circulator rotation when the machine is shutdown and the use of the shutdown seal to isolate the circulator auxiliary system from the primary coolant.
The actuation and control systems for both the brake and the static seal systems are similar.
The brake is used to bring the circulator to zero speed while the static seal is an isolation valve.
A high pressure helium accumulator on each circulator supplies the energy required to activate the brake and seal system.
The actuation signal (remote manually or initiated via interlock with the plant protective system) opens a block valve permitting high pressure helium to acti-vate the system.
Two vent valves, in series, discharging to the buffer helium return line, are int.erlocked with the supply valve so that the vent valves are closed (pressurizing and actuating the brake or seal mechanism) when the helium inlet valve is opened.
Conversely, when the helium inlet valve is closed, the vent valves are automatically opened, deactivating the brake or the static seal. An interlock with the plant protective system prevents activation of the brake until the circulator has been tripped and slowed to 700 rpm.
After the brake is set, there is a time delay (to ensure the circulator has stopped) before the seal is set.
The interlock operates on both manual and PPS signals.
A pressure control valve (typically PCV-21119) limits the differential pressure between actuation helium and buffer helium to 400-450 psi, for actuation of the brake and seal.
Low pressure in the helium accumulators is signalled to the control room by a low pressure alarm (PAL-21313) set at 1300-1500 psig.
Control interlocks between the brake and seal are discussed in Section 8.6.
8.
CONTROL AND SAFETY 8.1 BEARING WATER CIRCUIT:
8.1.1 Bearing Water Surge Tank (T-2104, T-2105):
Pressure in each bearing water surge tank is maintained at approximately primary coolant pressure by an equalization line between the 23rge tank and the suction side of the associated buffer helium recirculator.
Control and measurement of the surge tank water level under both normal and abnormal conditions is accorolished in the following manner.
Under normal conditions, a level controller (LC-2135, LC-2136) maintains tank level by admitting cooled feedwater from the backup bearing water line via valves LV-2135-1 and/or LV-2136-1.
This same controller regulates an outlet valve (LV-2135-2, LV-2136-2) to dump water to the low pressure separator if the tank level keeps increasing after the makeup valve has been closed.
A second level controller (LC-21245, LC-21246) serves as backup to the first level controller and beccmes operative on high tank level, a condition which may exist when the bearing water pumps are stopped and the bearings are being supplied with backup bearing water from the feedwater line.
Water cannot be drained to the icw pressure separator from the surge tanks during subatmospheric operation of the PCRV, since the low pressure separator is at a higher elevation.
During this time water can be drained from the surge tanks to the reactor building sump by opening valves HV-21311 and HV-21312.
In addition to the level controllers, each tank is provided with a low level switch (LSL-2137, LSL-2138) which will
- - - = - - - - - - - - - =
NO.SD-21-2 FORT ST. VRAIN PROJECT PUBUC SERVICE COMPANY OF COLORADO hE PAGE 17 0F 35 stop the bearing water pumps and close the pump suction block valve (LV-2137, LV-2138).
This action prevents pump damage chrough cavitation and also pre-vents surge tank depressurization in the event the low liquid level is due to a ruptured pump suction or bearing water supply line.
Both the high and low level conditions are alarmed.
8.1.2 Bearing Water Pumps (P-2101, P-2106, P-2101S, P-2102, P-2107,P-2102S): The three bearing water pumps in each loop are piped for operation in series.
Two pumps (P-2101, P-2106 in one loop and P-2102, P-2107 in the second loop) are in operation while a third pump (P-21015, P-2102S) in each bearing water loop acts as a spare.
Each pump can take suction directly from its affiliated surge tank. Check valves are so placed in the pump bypass lines so that when a pump is started and develops its discharge head, the bypass check valve closes and the process flow is introduced into the second operating pump.
Isolation valves in the pump suction and discharge are locked open to prevent a pump from running dry.
Pump malfunction is indicated by low differential pressure which is sensed across the pumps in each loop (PDT-2133, PDT-2134).
When the pres-sure differential falls below 800 psi, an alam is sounded in the control room and the standby pump is automatically started.
The differential pressure across each pump is indicated in the control room and the malfunctioning pump can be identified for isolation and maintenance.
If for some reason the discharge from the pumps should be shut in, a low flow switch (FSL-21297, FSL-21298) set at 100 gpm will open a low flow bypass line discharging to the bearing water pump suction line.
The bypass is located at the discharge of the bearing water coolers (E-2104/4S, E-2105/55) which remove the heat of pumping. Water flow to the circulators con-tinues uninterrupted and is supplied from the feedwater header as described in Section 8.1.5.
8.1.3 Bearing Water and Backuo Bearing Water Filters (F-2101, F-21015, F-2102, F-2102S, F-2103, F-21035):
Each of the bearing water and backup bearing water lines is provided with a set of two filters, one of which is on stream. When the differential pressure across the operating filter rises to about 95 psi, the inle.t block valve to the standby filter opens.
Then the operator places the handswitch (typically HS-2153) in the standby position, the inlet block valve to the spent filter will close when (and only when) the diff-erential pressure falls below 95 psi.
In this way, the flow cannot be blocked off and the valves are positioned so as to always maintain a differential of less than 95 psi across the filters.
8.1.4 Backup Bearing Water Cooler (E-2101, E-2106):
Service water supply to the backup bearing water cooler is controlled by a temperature indicating controller (TIC-21141) set at 140 degrees F.
The control valve is
FORT ST. VRAIN N.
50-21-2 PROJECT PUBLIC SEVICI COMPANY OF COLORADO hE PAGE 18 0F 35 bypassed by a 2" manual valve which is adjusted to maintain a service water flow sufficient to cool the normal makeup flow of bearing water to the bearing water surge tanks.
The main temperature control valve (TV-21141) on the ser-vice water line is used only when the emergency feedwater is used as backup bearing water.
Two additional temperature switches, set at 150 degrees F and 160 degrees F respectively, actuate valves in the reactor plant cooling water system (System 46) to introduce circulating water or fire water if service water is not available.
8.1.5 Backup Bearino Water Supolv:
A pressure control valve (PV-21195) reduces the feedwater pressure from about 3620 psia (at full load) to 2200 psig upstream of the backup bearing water cooler.
After passing through the backup bearing water coolers and filters, the line branches into two separate lines with each line feeding the two circulators in a loop.
Each of these lines is provided with two differential pressure controllers and a con-trol valve.
One differential pressure controller regulates the pressure diff-erential between the backup bearing water supply and lower pressure of the two associated circulator bearing supply cavities at approximately zero differen-tial pressure when the bearings are being supplied nonnal bearing water.
If normal bearing water sup' ply pressure decreases, tha second differential pres-sure controller increases the backup bearing water supply pressure to maintain a minimum bearing supply cavity to main drain difSrential for the two associ-ated circulators at 600 psid.
Under this conditic,, bearing water flow to the circulator will be at a slightly reduced flow of Mproximately 170 gpm.
Each circulator is provided with redundant bearing supf y cavity to main drain diff-erential pressure transmitters, with the higher output of the two used for control.
Additionally, the controls system receives an anticipatory signal from the switch gear for the bearing water pumps which indicates the loss of a pump and the need for an immediate response from the backup bearing water system.
If the pressure in the emergency feedwater header drops below 1600 psig, an alarm is sounded and the bearing water makeup pump (P-2105) is started and supplies bearing water to the surge tanks on level control through level valves LV-2135-1 and/or LV-2136-1.
Redundant differential pressure switches monitor the differen-tial pressure between the bearing water supply cavity and the main drain of each circulator.
The differential pressure switches are set at about 475 psid and provide an input to the plant protection system (PPS) to initiate the isolation of the circulator service system on the loss of normal W backup bearing water.
On initiation of service system isolation, the circulator steam and water turbines are tripped, and the bearing water accumulators supply bear-ing water until the circulator coasts down to 700 rpm, the brake is set and, after a time delay to bring the circulator to a stand still, the static seal is set and all bearing water supply and return lines are isolated.
During normal operatior the bearing water accumulators (T-2114, T-2115) " ride" on the backup
2 FORT ST. VRAIM PROJECT PUBlJC SERVICE COMPANY OF COLORADO
,$E PAGE 19 0F 35 bearing water supply header which supplies about 4 gpm purge ficw through the accumulator.
This purge flow prevents the water in the accumulator from becom-ing saturated with nitrogen due to valve leakage from the gas pressurizers (T-2116, T-2118) which operate up to 2500 psig.
An alternate source for purge flow is available from emergency condensate header when BUBW is out of service.
The purge flow discharges to the deareator or the condenser hotwell.
On the loss of bearing water, nomal and backup, the PPS closes a block valve in purge outlet line and opens the block valve between the gas pressurizer and water ac-cumulator to initiate the supply of water to the circulator bearings.
The sup-ply lines to each circulator are prcvided with a throttling control valve which maintains the bearing water supply cavity to main drain differential pressure at approximately 425 psid (at full load).
Under these conditions, the bearings are supplied approximately 145 gpm of water which is sufficient to support the bearings.
The setpoint for the differential pressure controller for the accu-mulator water supply valve is programmed with reactor pressures.
In this man-ner the water supply is stretched out at lower reactor pressures consistent with longer time for circulator coast down and lower flow rates required to support the circulator bearings. Alarms are provided in the control room to indicate low pressure in the gas pressurizer, low water level in the accumula-tor, or low purge flow through the accumulator.
8.1.6 Bearing Water Drains:
The bearing water leaving the helium / water drain enters the high pressure separator where the helium and water are separated.
Bearing water is drained from the high pressure separator to the bearing water surge tank on level control.
The flow from the main drain is controlled by a differential pressure controller which maintains the main drain gressure at from 1 to 18 psi above the buffer helium supply pressure.
The setpoint of this differential pressure controller is modulated by water flow out of the high pressure separa-tar and modified by high pressure separator level.
This action is provided to l
maintain an acceptable range of upper water seal flow rates which can be han-died by the helium / water drain and high pressure separator since the water seal resistance varies with circulator speed.
l The steam / water" drain is controlled by a pressure differential controller (PDC-2179, typical) which maintains the steam / water drain 2.5 psi below the circulator steam turbine exhaust pressure.
This will ensure a flow of steam into the steam / water drain cavity.
During nomal operation, the main-drain operates at a higher pressure than the steam / water drain cavity.
In the event that the steam / water drain cavity pressure would approach the main drain pressure due to a higher steam turbine exhaust pressure, a reversal of water flow across the lower water seal is prevented by a differential pressure con-troller (PDC-21339, typical).
This controller overrides the normal steam / water drain control to maintain a minimum differential pressure between the main drain and steam / water drain cavity of 35 psid.
Redundant differential pressure switch monitor the main drain to steam / water drain cavity differential pressure.
The differential pressure switches are set at 5 psid and provide an
.~
l FORT ST. VRAIN
^
E PROJECT PUBUC SERVICI COMPANY OF COLORADO DATE PAGE 20 0F 35 input to the PPS to trip the steam turbine.
This prevents steam from passing across the lower water seal to the main drain which could be harmful to circu-lator seal and bearings.
8.1.7 Low-Pressure Separator:
The pressure in the low pressure separator is controlled at approximately 2 psig by the pressure indicating con-troller (PIC-21570 or PIC-21571) associated with the operating helium recovery compressor. This controller sets the net helium flow from the low pressure separator by regulation of a control valve (PV-21570 or PV-21571) that bypasses helium from the discharge to the suction side of the helium recovery compressor l in operation.
One or the other of these compressors is in continuous operation.
If at some abnonnal condition more helium is being generated than can be handled by a single machine, a high pressure alann is sounded in the control room and the second machine is started when the suction pressure reaches 5 psig.
The second machine is stopped manually when the pressure is reduced to 2 psig.
If for any reason the helium circulator turbines are run on auxiliary boiler steam, the circulator turbine exhaust pressure will be essen-tially atmospheric. At full He inventory, this will result in a flow of approximately 30 gpm from each steam / water drain.
To supply sufficient driving head to drain this flow, the, low pressure separator must be run subatmospheric.
This is accomplished by opening vent valves HV-21572-1 and HV-21574-1 and clos-ing HV-21572-2 and HV-21574-2 to the dryers by closing the recovery compressor bypass valves PV-21570 and PV-21571 and operating the compressor (or compres-sors, if necessary) to reduce the low pressure separator pressure to a vacuum.
Valve HV-21252-2 is closed to prevent LV-21119 from letting nitrogen in the turbine water drain tank backflow to the low pressure separator.
Flashed water vapor from the low pressure separator is vented to the ventilation system via l HV-2.'572-1 or HV-21574-1.
The bypass steam / water drain control valve (POV-21339, typical) opens automatically to accommodate the higher flow to the low preuure separator.
Level control and measurement in the low pressure separator con-sists of five separate level elements.
Due to the wide range of flow that the bearing water removal pumps may be required to handle, a control scheme designed to prevent pump operation at an essentially shut-in condition is employed.
A pressure regulator (PCV-21144) set at 125 psig bypasses pump discharge flow back to-the low pressure separator while the primary level con-troller valve (LC-21115) regulates the net water flow from the tank.
If the water flow exceeds that which can be handled by a single pump (or if the oper-ating pump fails), a level transmitter (LT-21118) senses the resulting high level and initiates startup of the standby pump.
This instrument also ener-gizes high or low level alanns in the control room.
A low level switch (LSL-21116) stops both bearing water removal pumps (and the bearing water makeup pump; see below) on low tank level to prevent cavitation and damage to the pumps.
A high level switch (LSH-21117) closes the valve in the suction line to
FORT ST. VRAIN E
PROJECT PUBLIC SERV 1CI COMPANY OF COLORADO PAGE 21 0F 35 the helium recovery compressors, preventing water from entering and causing damage to the positive displacement compressors and opens valve LV-21118 which drains to the reactor building sump.
The fifth level (LC-21119) set at a higher tank level than the primary level controller element is a level controller, which is used to drain the low pressure separator directly to the turbine water drain tank (T-2110) when the inflow exceeds the capacity of both pumps or both pumps are inoperative.
If the water entering the low pressure separator becomes radi-oactive, an alam is sounded, and the bearing water removal pumps are stopped.
These pumps are isolated and the contaminated water is routed to the liquid waste sump by closing a pump discharge valve (LV-21115) and opening the valve (RV-21251-1) on the line to the liquid waste sump, automatically.
Valve (HV-21252-2) to the turbine water drain tank is closed automatically to prevent contamination of the turbine water drain tank.
Water is drained to the sump until the operator responds to the alam.
The operator activates HS-21252 l which opens the valve (HV-21252-1) to the bearing water makeup pump (P-2105) suction and closes the block valve (HV-21252-5) to the condensate storage tanks.
The low level switch, LSL-21116, will stop the bearing water makeup pump only when HS-21252 is activated. HS-21331 is then activated which remote manually starts the bearing water makeup pump, closes the backup bearing water makeup valves (HV-21331-1 and 2) to the surge tanks and allows the flow valve (FV-21333) in the makeup pump low flow bypass line to accept controller action from flow which FS-21333.
The pump is protected against the possibility of be-ing shut in (LV-2135-1 and LV-2136-1 are closed) by the low flow switch (FS-21333) set at 20 gpm.
This switch opens a low flow bypass discharging back to the low pressure separator.
The operator initiated action (enumerated above) confines the containment water to the closed loop bearing water circuit.
To minimize contamination of the two buffer helium loops when high radioactivity is present, the helium off-gassed in the low pressure separator should be directed by the operator to the buffer loop containing the source of the radioactivity.
Individual radiation detectors on each high pres-sure separator can be used to determine which of the four circulators is providing a path for the primary coolant to enter the buffer system.
The helium recovery compressor which discharges to the contaminated buffer loop should be started and the other recovery compressor should be shut down and isolated. This action will allow radioactive gases in the low pressure separa-tor to be returned to the contaminated buffer helium loop, thereby minimizing the contamination of the other buffer loop.
If it becomes necessary to operate the buffer system without either helium recovery compressor in operation, the low pressure separator can be vented to allow it to operate at atmospheric pressure.
The separator is vented by manually opening one of the pressure control bypass valvr.s (PV-21570 or PV-21571) around 3 helium recovery compressor and lining up the discharge of the corresponding conpressor knockout pot to vent.
If high radioactivity in the low pressure separator is detected by RT-21251, the vent from the knockout
FORT ST. VRAIN E
PROJECT PUBLIC SERVICI COMPANY OF COLOM DATE PAGE 22 0F 35 pot will be automatically shut, blocking the path frem the low pressure separa-tor to the ventilation system.
8.1.8.
Turbine Water Drain Tank:
Pressure in the turbine water drain tank is limited to a maximum of 5 psi by a vent valve actuated by a pres-sure switch (PS-21120) located in the tank inlet line.
This pressure switch is disabled when the nitrogen pressurization system is in operation.
The remainder of the controls consists of five level elements and is analogous to those described in the previous section for the low pres-sure separator. The primary level controller (LC-21114) maintains tank level by regulating the net flow from the tank while a differential pressure con-troller across the pump, set at 125 psid, will bypass flow back to the tank and prevent pump operation at shutin conditions.
A high level switch (LSH-21132) will start up the standby pump while a low level switch (LSL-21113) will shut down either pump to prevent damage to that pump.
A level switch (LS-21130) set at higher than normal level will dump water to the reactor building sump if some condition prevents pumping water in the normal manner.
This action pre-vents a possible pump failure from interfering with the free drainage of water from the Pelton water tu'rbine drives.
All abnormal conditions are alarmed in the control room by a signal from a level transmitter (LT-21129) located on the tank.
The turbine water drain tank ::an be temporarily used as a backup for the low pressure separator if the low pressure separator should be out of service during a plant shutdown.
Flow to the low pressure separator can be diverted to the turbine water drein tank by manually closing valve V-211742 in the inlet line to the low pressure separator and opening valve V-211743 to the turbine water drain tank.
The pressure control system installed in the turbine water drain tank will maintain a 5 psi backpressure on the steam water drains.
8.2 BEARING WATER SUPPLY:
In addition to the safety aspects inherent in the control system, additional safety elements have been added to ensure that the helium circulators are always supplied with bearing water.
The primary safety feature is the duplication of loops in the bearing water supply system.
These identical and separate bearing water loops are provided to supply bearing water to the circulators.
Each of these loops contains spares for the major components.
The bearing water surge tank is provided with check valves on all incoming lines so that. line breaks will not drain or depressure the tank.
A line break on the pump suction line will cause the suction line to be closed on low tank level.
The surge tank is equipped with pressure and level alarms in the control room.
As a further backup, the tank level can be maintained by makeup water from the condensate storage tanks via the bearing water makeup filters and the bearing water makeup pump.
The bearing water makeup self is backed up by the emergency bearing water makeup pump (P-2108) pump it-which takes water either frc'n the condensate system or from a completely different source (firewater), passes it through one of the emergency bearing water filters (F-2104 or F-2104S) and into the surge tanks.
The bearing water lines I
t FORT ST. VRAIN
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PROJECT PUBLIC SERVICI COMPANY OF COLOM OA PAGE 23 0F 35 entering the circulator are provided with flow instruments which alarm in the control room.
These flow signals operate block valves to admit bearing water or backup feedwater to the circulators or to isolate the circulators upon shu tdown.
The closing of these valves can be either initiated or prohibited by the plant protective system.
Inlet t,aaring water lines to the circulators con-tain check valves in the circulator housing as well as remotely operated stop check valves outside the penetration.
8.3 AUXILIARY WATER TURBINE CIRCUIT:
The water turbine drive on each circulator provides each circulator with a backup power source in the event the nonnal steam supply is not available.
The normal supply of water for the water turbine is from the emergency feedwater header which operates at the boiler feed pump discharge pressure.
The emergency feedwater supply lines to the cir-culators in each loop are provided with pressure control valves to reduce the water supply pressure at the inlet to the water turbine speed control valves.
The turbine water supply header is controlled initially at 1000 psig, where the speed control valves are closed by two control valves (PV-21243 and PV-21243-1, typical).
The two valves are split ranged, one controlling the supply header under flowing conditions and the second bleeding off any valve leakage from the first under no flow condition to prevent lifting of the supply header relief valves.
The setpoint of the supply header pressure controller is programmed with the water turbine speed control valve position from 1000 psig to 2900 psig for speed valves wide open.
The programmed water turbine supply header elimi-nates cavitation of the water turbine speed control valves at low flows and l
permits better regulation of the supply header pressure when a pressure of 2900 psig is required which is close to the header relief setting of 3080 psig.
If feedwater is not available to power the water turbine drives, the circulators can be driven at reduced speed using water from the emergency condensate or firewater systems.
Remove manually operated stop check valves 1
isolate the condensate and fire water from the feedwater supply header.
8.3.1 Auto Startup of Water Turbines:
Automatic startup of a circulator's water turoine drive is initiated by a signal from the plant protective system.
The signal will result only when one loop has been tripped j
and the circulators' steam turbine drives in the operating loop have been tripped.
Table II of SD-93-2 lists all the loop shutdown parameters while Table III lists the circulator trip parameters.
(Manual or auto startup of the water turbines in inhibited by any condition which initiates a water turbine trip.)
On signal from the pla,nt protective system, the water turbines required for operation are activated by opening the drain and supply valves, allowing the passage of feedwater through the water turbine drives.
If the circulators are operating on their normal steam turbine drive and lose steam, it takes about 8 seconds to close the appropriate steam valves, open the water turbine valves, and reaccelerate the circulators.
The supply and drain valves are interlocked so that the drain valve is opened before the supply valve can
FORT ST. VRAIN NO. SD-21-2 PROJECT PUBLIC SEVICE COMPANY OF COLORADO hE PAGE 24 0F 35 be opened.
This action prevents overpressuring the water turbine supply and drain piping in the circulator penetration.
A relief valve protects the piping in the event of a valve or control malfunction.
The plant protective system signal also opens an equalization line between the turbine water drain tank (T-2110) and the circulator turbine inlet via the cold reheat line.
When the circulator steam turbine is isolated, the entrained steam in the turbine cavity will condense, creating a partial vacuum.
Equalization will allow gravity draining of the water turbine from the trubine cavity to the turbine water drain tank.
However during nitrogen pres-surization system operation, a differential pressure between the cavity and turbine water drain tank is automatically maintained.
(Sec.8.3.2).
In their close position, the isolation valves (HV-21277-1, -2 and -3) between the tur-bine water drain tank and the cold reheat lines form a double block and bleed arrangement since the differential across them is normally 600-700 psi.
~
The water turbine speed is regulated automatically by a speed controller which varies the flow of feedwater to the turbine to control main steam temperature.
l 8.3.2 Water Turbine Nitroaen Pressurizina System:
The water tur-bine nitrogen pressurizing system is man:Jally placed in service to provide a 10-30 psid over-pressure above the saturation pressure of the turbine water supply.
Hand switch HS-21429 is placed in the recycle position so tnat ni-tragen returned to the low pressure separator via the steam / water drain can be pumped back to the turbine drain cavities.
This action closes the outlet valve LV-21117 on the low pressure separator, opens the low pressure separator return valve HV-21429 to the nitrogen compressors, and opens the block valve HV-21430 on the nitrogen makeup cylinders to the low pressure separator.
Additional in-terlocks are provided to close valve HV-21252-2 since the low pressure separa-tor cannot be drained to the turbine water drain tank which will be operating at a higher pressure and to close valve PV-21120 which non7 ally vents the tur-bine water drain tank at 5 psig.
One nitrogen compressor is started, (HS-21431) which places the other compressor in standby.
A pressure differential controller, PDC-21442, maintains a minimum differential pressure of 50 psid from the compressor suction to the outlet of the separator to maintain the required seal water flow to the compressor.
A low flow switch (FIS-21443, typ-ical) monitors the seal water flow and is used to trip the nitrogen compressor and start the standby compressor.
Water accumulated in the seoarator is drained by a level switch, LSH-21140, and high and low level alarms are provided.
Nitrogen is bypassed to the suction of the compressor to maintain the low pressure separator at 14 psia by pressure controller PC-21443.
Nitrogen is provided form the nitrogen makeup cylinders (T-2119) to initially charge the system through the low pressure separator and to make up any system losses.
A pressure controller, PC-21446, is used to regulate the turbine cav-ity pressure.
The setpoint of this pressure controller is operator controlled to 10-30 psi above the pressure in the deaerator.
Since the press;re con-troller for the turbine cavity is only capable of making up nitrogen to the
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NO. 50-21-2 FMT ST. VM PROJECT PUBLIC SERVICE COMPANY OF COLORADO hE PAGE 25 0F 35 system, the system is vented via a vent valve on the low pressure separator controlled by a pressure switch set at 16 psia low pressure separator pressure.
Nitrogen supplied or recycled to the turbine water cavity is filtered and diff-erential pressure switch PDIS-21449 alarms on high filter delta P.
Any ni-trogen carried over to the deaerator with the water pumped from the turbine water drain tank is recycled back to the suction of the nitrogen compres:;or l
(see 5D-31).
An interlod. is provided via HS-21572 and HS-21574 to insure that the helium recovery compresm vent to atmosphere prior to returr.ing the low pressure separator to nomal sevice.
8.4 BUFFER HELIUM CIRCUIT:
Buffer helium to each circulator is con-trolled by a pair of flow control valves.
The supply valve admits a flow of about 7.4 acfm into the upper labyrinth of the circulator.
The outlet valve regulates the flow of helium leaving the high pressure separator at approxi-mately 3.7 acfm.
0-Low flow of buffer helium to each circulator as well as low flow of helium from any of the high pressure separators is alarmed to alert the opera-tor to the fact that some water vapor may be diffusing into the primary coolant due to insufficient buffer helium flow.
Instrumentation in the form of redundant differential pressure swit-ches is used to monitor any flow, whether it be helium or water, through the labyrinth by sensing the delta P across the lower portion of the helium labyrinth.
Nomal helium flow through this portion of the labyrinth is about 3.7 acfm in a downward (positive) direction.
Any water flow through the labyrinth would be in an upward or negative direction, requiring a reversal in the differential pressure.
If for any reason the helium flow through the labyrinth should exceed the normal rate (a high positive reading), this would be indicative of primary coolant passing through the labyrinth and would be detected by the differential pressure switches.
Any signal from these switches which is sustained for three seconds (to eliminate erroneous signals due to transitory occurrences) initiates a programmed circulator shutdown via the plant protective system and simultaneous inhibits a steam generator dump by the primary coolant moisture monitors.
This signal is inhibited in the PPS such that if one machine in a loop trips out, trip of the second machine is inhibited. Thus, a loop shutdown is prevented in the event that some transient momentarily affects both machines. Manual shutdown of the second circulator is not inhibited.
The helium passing through the lower labyrinth seal in the helium circulator, along with a small amount of water from the circulator bearings, enters the high pressure separator associated with each circulator.
Each high pressure separator is provided with a radiation detector which activates an alann if high radioactivity levels are present in the separator.
Helium lines leaving the high pressure separators in each loop are manifolded and enter one of the buffer recirculators in that loop.
FORT ST. VRAIN
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f PROJECT PUBLIC SERVICI COMPANY OF COLORADO DATE PAGE 26 0F 35 Differential presnre across these machines is controlled by bypassing gas from the discharge back to the suction.
The differential is linearly programmed from 11 psi to 31 psi between 175 and 700 psia PCRV pressure with 11 psid main-tained below 175 psia PCRV pressure.
This variable differential pressure is necessary to ensure that the recirculating buffer helium pressure matches the pres:ure generated by the purified helium compressor (SD-23).
Low flow of helium from the operating recirculator actuates a flow switch which automati-cally starts the standby machine.
Cooling water from the buffer hemium coolers recirculates through the buffer helium recirculators at about 2 gpm.
Low flow of cooling water activates a low flow alarm (FAL-21229, typical) in the control room and shuts off the affected recirculator.
The standby recirculator is au-tomatically started on resulting low helium flow.
Before entering the recirculator inlet, cooling water from the buffer helium coolers is chilled to 41 degrees F by the water chillers.
All chillers, both operating and standby, are run continuously to ensure an instantaneous source of chilled water since it takes approximately one hour from startup for a chiller to reach its design temperature.
Since the saturated helium entering the recirculator containment tank (T-2102/2S and T-2103/3S) is being cooled, water vapor will condense.
Each tank contains a baffle which separates the tank into two compartments.
One compartment conr.ains the helium recirculator.
The other compartment contains recycled water and condensed water.
A demister is located at the helium outlet to help remove free liquid water.
If for any reason water accumulates in the recirculator compartmem an alarm sounds in the control room and the water can be removed manually to a r'loor drain.
High water level in the water compart-ment is prevented by an automatic drain (via HV-21233, typical) to the surge tanks.
In the event that the tank level exceeds the normal range, a level indicating switch (LIS-21'75, typical) will shut down the recirculator and shut the suction valve to prev nt flooding the containment tank.
Downstream of the recirculators, two coalescing filters are '.as*,alled in parallel in each buffer loop.
Normally, one filter in each loop will be on-stream.
Instrumentation is provided which will alarm if a high differential pressure develops across the operating filter, as well as automatically opening the path through the standby filter.
A bypass is located around each helium dryer and is actuated on high differential pressure by pressure differential switer. ; (PDIS-21561 and PDIS-21567) set at psi.
The dryers can also be bypas;ed remote-manually if high moisture content in the outlet helium is indicat!d by moisture monitors (M E-and ME-
).
Alarms sound in the control room on high moisture.
Operation of the buffer helium on dryer bypass is acceptable, except that the recirculating buffer helium stream is now water saturated.
However, the quan-tity of water that could enter the primary coolant (about 0.9 lb/hr) is small
e FORT ST. VRAIN S0-21-2 PROJECT PUBLIC SERVICE COMPANY OF COLORADO h
PAGE 27 0F 35 g
enough so that operation could continue in this manner for about 18 hours2.083333e-4 days <br />0.005 hours <br />2.97619e-5 weeks <br />6.849e-6 months <br /> before exceeding established carbon monoxide and hydrogen impurity limits in the primary coolant.
This allows adequate time to make necessary repairs.
Low buffer helium flow to all four circulators could occur due to loss of the normal purified helium makeup supply from the helium purification system.
This is prevented by a flow control scheme (described in 50-23) which admits helium from the high pressure supply tanks (T-2402) if the purified helium makeup supply flow decreases (by operator action down to 6 acfm and au-I tomatic 6 acfm in each loop).
This stored helium supply is adequate fer ap-proximately 30 circulator-minutes operation at full load and 70 circulator-minutes at 25% load.
If the failure in the normal supply extends beyond this time, operation of the circulators will continue, but trace quantities of water may diffuse into the primary coolant loop.
8.5 BUFFER HELILM LINE FAILURES:
In the event of a line rupture occur-ring in the high pressure separator effluent line upstream of the flow controls in that line, the decrease in separator pressure results in an above-normal helium flow across the lower helium labyrinth which is detected by the diff-erent'21 pressure instrumentation across the labyrinth and results in isolation and shutdown of the circulator (Section 8.4).
The flow control valve supplying heliu.1 flow to the circulator will maintain a flow of 7.4 acfm, thereby pre-ventirg depressurization of the buffer system.
A check valve in the d:iuent line ' rom the high pressure separator downstream of the flow controls will pre-vent back flow of buffer helium due to the line rupture.
If a line from the high pressure separator ruptures downstream of the flow controls, the helium recycle from the associated high pressure separator is lost, resulting in low pressure in the inlet line to the recirculator in that buffer helium loop.
Loss of suction pressure will cause the recirculator discharge pressure to decrease, allowing the check valve downstream of the recirculator to shut. Makeup helium for the circulator seals from the purifi-cation system will increase to supply the total requirement for that buffer loop.
As the recirculator suctfon pressure decreases, a decrease in pressure in the corresponding bearing water surge tank will also be experienced.
Loss of cover gas pressure in a surge tank will result in low bearing water supply pressure to the two circulators in the affected loop, causing backup bearing water flow to be initiated in that loop (as described in Section 8.1.5).
Low flow of normal bearing water will alert the operator that backup bearing water has come on.
The other helium buffer loop and bearing water loop will operate unaffected.
If a line rupture occurs between one of the helium recirculators and the helium dryer, or within a helium dryer, recycle helium flow in that loop will be lost and pressure in the suction and discharge lines of the recircula-tor will be lost.
A check valve downstream of the helium dryer will shut to prevent loss of buffer helium flow to the circulators.
The purification system makeup flow will increase as required to supply the two circulators in the
FORT ST. VRAIN
. SD-2b2 PROJECT PUBUC SERVICE COMPANY OF COLORADO hE PAGE 28 0F 35 loop.
The loss of cover gas pressure in the bearing water surge tank will ini-tiate backup bearing water flow as described previously for the affected loop.
A rupture in the buffer helium supply line to the helium circulators, downstream of the dryer discharge check valve and upstream of the inlet flow control valves, will cause a loss of buffer flow to the two circulators in the affected loop. This will result in the shutdown and isolation of those circula-tors (following the stepwise procedure described in Section 8.6).
Buffer helium supply pressure in the affected loop will be lost due to the rupture; however, buffer helium flow to the circulators in the other loop will continue uninterrupted.
If, due to the excessive makeup flow from the purification sys-tem to the loop containing the rupture, low buffer flow is detected in the other loop, the makeup flow for the operating loop will automatically shift over to be supplied by the high pressure storage tanks.
Rupture of an individual buffer helium inlet line downstream of the flow control valve causes shutdown and isolation of the affected circulator (following the stepwise procedure described in Section 8.6).
A cneck valve within the circulator penetration, backed up by a penetration isolation valve, prevents loss of primary coolant to the atmosphere.
Buffer helium supply pres-sure in the loop will be maintained since the flow control valve will limit the flow of helium out of the system.
8.6 CIRCULATOR SHUTDOWN PROCEDURE:
A circulator is shut down by closing the steam inlet valve to tne circulator's steam turbine drive (or the feedwater inlet valve if tne Pelton water turbine is in use).
The plant protective sys-tem prevents startup of the water turbine dirves when a circulator is tripped.
In approximately 30 seconds after the steam to a circulator turbine drive has been stopped, the circulator speed has dropped to 700 rpm.
At this point an interlock from the plant protective system allows the brake to be applied.
After the application of the brake, a time delay ensures that the circulator is stopped and then the static seal is applied, as described in Section 7.3.
Nomally, when a circulator is shut down, the bearing water and buffer helium flow to it will be maintained.
If, however, complete isolation of the circulator is required, the operator can actuate handswitches in the control room which close block valves on all buffer helium and bearing water lines.
Additional interlocks protect the brake and seal from damage during operation.
The bellows in the brake cannot withstand high differential pres-sures; therefore, a differential pressure regulator associated with each helium bottle (PDV-21199, typical) controls the pressure to 400-450 psid.
In addi-tion, a differential pressure switch (POS-21203) is provided to close the helium inlet valve (HV-21203-2) to limit the differential across the brake bel-laws to approximately 400 psid in case of pressure regulator failure.
50-21-2 FORT ST. VRAIN PROJECT PUBlJC SERVICI COMPANY OF COLORADO hE PAGE 29 0F 35 To prevent the brake from being released when the seal is set a diff-erential pressure switch (PDS-21191) is provided which prohibits the brake from being released until the differential between the seal and the PCRV pressure (reference) is below 50 psi.
Shutdown of any circulator, on loss of both the bearing water and the backup supply, is accomplished with the bearing water accumulators described in Sections 7.2 and 8.1.5.
- 8. 7 CIRCULATOR STATIC SEAL - BACKUP ISOLATION SYSTEM:
The circulator static seal is the normal means used to provide isolation of the circulator auxiliary systems from the primary coolant.
The backup isolation system is supplied to provide isolation in the event of static seal failure, e.g., if the brake and seal system is disabled by a steam line rupture.
The backup isola-tion is accomplished by maintaining a water seal within the circulator bearing cartridge. Water for this water seal is supplied from the normal bearing water system and is controlled by a level transmitter which senses the water level within the circulator bearing cartridge.
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The seal backup isolation system requires operator recognition of static seal failure indications.
It also requires operator action to activate the system.
System operation is automatic following activation.
Static seal failure indications and backup isolation system activation controls are located in the control room.
The level transmitters (PDT-21185, typical) which sense the bearing cartridge water level are connected to a circulator helium-water drain sense port on one side and to the circulator main drain sense port of the other side.
The water leg on the helium water drain side remains constant at the level of the helium-water drain port at the upper end of the helium circulator.
The water leg on the main drain side varies with the water level within the bearing cartridge.
The difference in elevation between the helium water drain and the main drain at the circulator is nineteem inches.
The signal from the level sensor (PDT-21185, typical) is an input to the auto mode of the bearing water controller (HC/ PDC-21185, typical).
The bearing water controller (HC/ PDC-21185, typical) in the auto mode exercises control of the bearing water supply (HV-21185, typical) in response to circulator bearing cartridge water level ane l
controller setpoint.
The suggested setpoint is 10 inches; however, any set-point between 2 and 17 inches is acceptable.
The bearing water controller (HC/ PDC-21185, typical) in the manual mode exercises control of the bearing water supply valve (HV-21185, typical) in response to manual adjustment of the controller output.
Auto mode of the controllers (HV/ PDC-21185, typical) is used only in the event of circulator static seal failure.
The bearing water supply isolation valve hand switches (HS-2187-1, typical) are three position switches instead of two position.
The three posi-tions are "open", "close" and "S.D." for shutdown.
The "open" and "close" functions remain unchanged.
The "S.D." position opens the bearing water supply
l FORT ST. YRAIN 50-21-2 PROJECT PUBLIC SERVICE COMPANY OF COLORADO PAGE 30 0F 35 isolation valve (HV-2187-1, typical) if, and only if, a circulator trip condi-tions exists.
The "S.D." position allows the valve to fail open by opening the
" energize to close" circuit of the valve.
The "S.D." position is used only in the event of shutdown seal failure.
A buffer seal indication (PD-121389, typical) of higher than 80 inches subsequent to shutdown seal application is sufficient cause to assume that the circulator static seal has failed, and that immediate action be initi-ated to activate the backup isolation system.
9.
OPERATING PROCEDURE To be initiated when a buffer seal (buffer-midbuffer) indication of more than 80 inches is seen subsequent to shutdown seal application after circulator shutdown either from PPS action or planned shutdown.
1.
Verify that the Learing water control valve (HV-21185, typical) is closed as evidenced by zero output of the controller (HC/ PDC-21185, typical) in manual mode.
2.
Open the bearing water supply siolation valve (HV-2137-1, typical) by placing the hand switch (HS-2187-1, typical) in the "S.D." position.
3.
Switch the bearing water controller (HC/ PDC-21185, typical) to " Auto" mode.
Adjust the set point to 10 inches.
The buffer seal delta P should return to approximately zero thus indicating an effective water seal.
Some oscillation of the buffer seal delta P around zero is expected as the water level in the circulator varies.
10.
PRENUCLEAR HEATING USING WATER TURBINE DRIVE 1 Prior to fuel loading, the primary coolant loops will be heated to about 625 degrees F utilizing, the heat of compression from two helium circulators.
Initially, the circulators will be powered by specially designed water turbine drive.
A total of 3330 gpm of feedwater at a pressure of approximately l
3000 psig at the turbine inlet (1665 gpm to each water turbine drive) will te l
provided.
All four circulators can be operated at about 830 gpm for checking of parallel operation of the circulators.
The prenuclear heating operation utilizes the same emergency feedwater lines as are used in normal operation of the water turbines (Sections 7.1 and 8.3).
The lines are rated for 3900 psig and 4500 psig to accommodate the higher pressures used during prenuclear heating.
The valves used during prenu-clear heating are rated at USAS1500 lb Class which are good for about 3500 psig.
The valves and piping are protected against overpressure by relief valve V-9905 set at 3400 psig.
This valve will be removed and the nozzle capped af-
NO. 50-21-2 FORT ST. VRAIN PROJECT PUBLIC SERVICE COMPANY OF COLORADO hE PAGE 31 0F 35 ter prenuclear heating.
Relief valves V-21522 and V-21523 (set at 2500 psig for normal operation) are not installed in the feedwater lines until after pre-nuclear heating.
11.
LIST OF SYSTEM ALARMS AND OPERATOR RESPONSE P I, Zone Alerm Cause and Succested Rescanse I
21-2 C-4 FAL-2141 Low flow in a buffer helium recirculator.
Infomation only (IO).
No operation action required (NOAR).
Standby starts auto-matically (SSA).
B-4 FAL-21229 Low cooling water flow to buffer A-4 FAL-21231 helium recirculator.
10.
Stops machine automatically.
C-1 PDAH-21561 Excessive pressure drop through helium dryer unit.
10.
NOAR.
Bypass opens automatically.
l A-2 MAH-Moist helium breakthrough on helium dryer unit.
I0.
Replace desiccant or alter regeneration cycle.
A-1 FAL-21562 Loss of helium supply from purified helium header.
I0.
NOAR.
System 24 auto-matically supplies helium.
C-2 PAH-Monitors rupture disc leakage.
Operator C-2 PAH-must depressurize dryer bed.
C-5 LAH-2145 High water level in recirculator compartment B-5 LAH-21217 of containment tank.
Shut down recirculator and drain tank manually.
D-3 PDAH-21556 Excessive pressure drop through coalescing filter.
10.
NOARD.
Bypass opens automatically.
D-2 LAH-21560 High water level in a knockout pot.
Deter-mine specific pot by local alarm and drain manually.
NO.50-21-2 FORT ST. VRAIN ISSUE PROJECT PUBLIC SERVICE COMPANY OF COLORADC DATE PAGE 32 0F 35 C-2 LAH-21559 High water level in Loop I coalescing filter drain tank.
Tank must be drained manually.
21-3 C-4 FAL-2142 Low flow in a buffer helium recirculator 10.
NOAR.
SSA.
B-4 FAL-21230 Low cooling water flow to buffer helium A-4 FAL-21232 recirculator.
10.
Stops machine automa tically.
C-1 PDAH-21567 Excessive pressure drop through helium dryer unit.
10.
NOAR.
Bypass opens automatically.
A-2 MAH-Moist helium breakthrough on helium dryer unit.
10.
Replace desiccant or alter regeneration cycle.
A-1 FAL-21568 Loss of helfum supply from purified helium header.
IO.
NOAR.
System 24 auto-matically supplies helium.
C-3 PAH-Monitors rupture disk leakage.
Operator C-2 PAH-Must depressurize dryer bed.
C-5 LAH-2146 High water level in recirculator compartment B-5 LAH-21218 of containment tank.
Shut down recirculator and drain tank manually.
D-3 PDAH-21563 Excessive pressure drop through coalescing f f1 ter.
10.
NOAR.
Bypass opens automatically.
C-2 LAH-21566 High water level in Loop 2 coalescing filter drain tank.
Tank must be drained manually.
21-4 C-6 LAHL-21135 High or low water level in bearing water C-4 LAHL-21136 surge tank.
Several Automatic actions possible (see 8.1.1).
No single operator action; diagnosis necessary.
A-4 PDAL-2133 Low head across bearing water pumps.
A-2 PDAL-2134 10.
NA0R.
SSA.
C-4 LAL-2137 Low bearing water surge tank level.
C-2 LAL-2138 10.
NOAR.
Automatic stop of bearing water pumps and closure or tank outlet valve LV-2137 of LV-2138.
- 0. 50-21-2 FORT ST VRAIN PROJECT PUBLIC SERVICI COMPANY OF COLORADO PAGE 33 0F 35 B-5 FAH-21209 Line break, backup bearing water to surge tank.
A-3 FAH-21208 10.
Operator should isolate at V-21456 or V-2145 8.
B-6 PDAH-21393 High pressure drop across emergency bearing water filters, stops makeup pump P-2108.
Operatc r should switch filters, clean dirty filter.
A-6 PDAH-21399 High pressure across bearing water makeup filters Operator should switch filters, clean dirty filte r.
21-5 D-4 FAL-21297 Low flow from bearing water pumpgs-10.
C-4 FAL-21298 Bypass opens automatically.
D-2 TAH-21249 Bearing water cooler malfunction.
10.
C-1 TAH-21250 C-4 PDAH-2155 Excessive pressure drop across bearing water C-2 PDAH-2156 or backup bearing water filters.
10.
NOAR.
A-3 PDAH-21190 Operator should clean filter.
A-2 PAL-21189 Low emergency feedwater pressure.
10.
NOAR.
Starts backup bearing water pump.
B-4 TAH-21142 High emergency feedwater temperature.
10.
NOAR.
Automatically introduces circulating water to cool backup bearing water cooler.
21-6 D-5 LAHL-21118 Low pressure separator level outside normal D-5 LAH-21117 High level in LPS.
Closes LV-21117, stops helium recovery compressors.
D-4 LAL-21116 Low level in LPS.
Stops bearing water removal pumps.
D-5 LAH-21118 Law level in LPS.
SSA pump.
C-5 RAH-93267 Alarms high radiation in LPS.
Low pressure separator level control discussed in 8.1.7.
Automatic action listed above, operator action depends on diagnosis, i.e., no single action is appropriate.
LAHL-21129 Turbine water drain tank level outside LAH-21132 nomal range.
High level in TWDT.
SSA pump.
See 8.18.
Operator action depends on diagnosis.
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f 0.S0-21-2 FORT ST. YRAIN PROJECT PUBLIC SERVICI COMPANY OF COLORADO
$E PAGE 34 0F 35 C-4 PAH-21106 Low pressure separator pressure high.
I0.
NOAR.
SSA helium recovery compressor.
C-2 LAH-21576 High water level in knockout pot.
C-1 LAH-21577 Tank must be drained manually.
A-2 LAH-21573 A-1 LAH-21575 21-7 0-5 FAHL-2167 Buffer helium inlet flow outside normal (typical) range.
10.
C-5 FAHL-2183 Bearing water inlet flow outside normal range.
10.
B-6 FAH-21137 Emergency feedwater flow too high, line break.
Operator should close V-21456 or V-21458.
B-6 PAL-21283 Low pressurizer pressure.
Refill with nitrogen.
B-5 LAL-21287 Low accumulator level.
Check PDV-21285-2 and/or open V-218C8.
B-5 FAL-21343 Flow through accumulator too low, check PDV-21285-3 and/or open V-21808.
C-2 PDAHL-2175 Main drain to buffer helium supply differen-tial pressure outside normal range.
10.
A-3 PDAHL-2179 Steam turbine to steam water drain differen-tial pressure outside normal range.
10.
D-1 LAHL-21121 High pressure separator level outside normal range.
10.
D-2 FAHL-2171 Buffer helium outlet flow outside the normal range.
10.
C-6 FAH-21377 High helium flow to back up "0" rings.
10.
l C-1 RAH-High radioactivity in high pressure separator.
Operator must shutdown and isolate circulator.
21-11 C-2 PAL-21313 Low helium pressure for brake and seal 14,(typical )
actuation.
Refill or replace helium bottle.
e e.
FORT ST VRAIN NO, 50-21-2 PROJECT PUBLIC SERVICI COMPANY OF COLORADO hE PAGE 35 0F 35 21-12 A-4 TAH-21368 High temperature on chilled water.
(typical)
Denotes chiller malfunction.
21-13 C-1 PAL-21467 Indicates low pressure in N cyl inder. 10.
2 D-1 PDAH-21449 High differential across strainers. Switch to clean strainer, clean dirty strainer.
12.
NORMAL STARTUP 0F CIRCULATOR SERVICE SYSTEM In the shutdown condition of the service system for circulators, all sup-ply and returr valves will be closed and the circulator brake and seal will be set. The following general procedures indicate the steps taken to place the service system into operation: The bearing water pumps are placed in opera-tion, recirculating water to the surge tanks via the low flow bypass system.
The buffer helium recirculators are operating on their bypass under differen-tial pressure control. Makeup buffe: helium is available from either the purification or helium storage systerc.
The throttling control valve in the normal bearing water supply line is r nually closed which pemits the bearing water isolation valve to be opened. The buffer helium supply and the helium water drain isolation valves are opc ed and one half normal buffer helium flow is established in the recirculation Nop.
The main drain is opened and water is slowly admitted to the bearing hoe.ing by the throttling valve in the normal bearing water supply line to establish the main drain differential pressure control.
Following the full admission of bearing water with the throttling valve opened, the steam / water drain isolation valve is opened. When stabilized conditions have been reached, in the steam / water drain, the static seal is released and the buffer helium supply flow is increased to normal to provide an approximately equal distribution of helium to the reactor and the helium / water drain.
The emergency bearing water and accumulator supply isolation valves can be opened to insure a backup and shutdcwn source of bearing water.
Upon the release of the circulator brake, the service system is restored to operationand the steam and water turbine trip circuits should reset permitting operation of the circulator on either steam or water drives.
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