RC- Reactor Coolant System Flashcards by Briana Phillips

What are purposes of the RCS? (3)

1-transfer thermal energy to the S/G

2-secondary barrier to the release of fission products

3-provide core cooling

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How does the RCS interface with the CEDMCS system?

CEDMCS controls the direction, rate, and duration of CEA’s

also controls the magnetic jack coils to CEDM’s

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Can CEA motion be controlled automatically or manually?

both

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How does the RCS interface with the RI (Fixed in-core instrumentation system, or FICS)?

measures neutron flux,

coolant temp. in 61 locations

monitors core characteristics to assure we do not exceed allowable limits

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In the RCS, what does the RI system control?

nothing. it only collects data

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How does the RCS interface with the CH system?

maintains pressurizer level,

chemistry control,

boron concentration

provides RCP seal injection

collects RCS discharges

supplies aux spray to pressurizer when normal spray path unavailable

purifies RCS

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What [RC] discharge does [CH] collect?

-RCP seal bleed off

drainage for maintenance

Primary safety valve discharge

identified leakage

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[RC] & [NC] system?

-intermediate water between [RC] and the [PW].

-cooling to:
RCP motor air cooler,
lube oil cooler,
thrust bearing lube oil cooler,
and seal coolers

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[RC] and [SI] purpose? (3)

-emergency cooling
-Rx Shutdown - boron injection
-long and short term cooling

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When does SDC provide cooling for Rx?

-When S/G’s are unavailable

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When does SDC provide long term cooling?

after a LOCA

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RC & NA?

Power for RCPs

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How does the RCS interface with the IA system?

supplies control air to the pressurizer spray valves, controlled bleed-off containment isolation valves, and RDT bleed-off isolation valves

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[RC] interface with [SG] (main steam) and [FW] (feed water) systems?

remove heat from RCS

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How does the RCS interface with the SS (primary sampling) system?

samples PCS loop 1 hot leg, surge line, and pressurizer steam space

used for chemistry and boron control

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How does the RCS interface with the [SE] (Ex-core neutron monitoring)system?

monitors neutron flux from detectors outside the vessel

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How does the RCS interface with the reactor vessel level monitoring system (RVLMS)/QSPDS (SH)?

provides reliable (class) indication of the vessel level online and during accidents

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What is the purpose of the reactor vessel?

contains the core and vessel internals

directs flow of coolant through the core

part of RCS pressure boundary to prevent fission product release

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What are the internals of the reactor vessel? (2)

core support barrel
&
the upper guide structure

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In the reactor vessel, what allows for radial and axial expansion of the core?

the core support barrel assembly

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What components make up the core support barrel assembly?

Core support barrel

lower support structure and instrument nozzle assembly

core shroud assembly

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In the reactor vessel, what supports the upper ends of the fuel assemblies and protects the CEAs from coolant cross flow?

the upper guide structure assembly

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What components make up the upper guide structure assembly?

CEA shroud assembly

upper guide structure support barrel

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Main flow path of RCS within the Rx vessel?

inlet nozzles,
down between vessel wall and core barrel,
through flow skirt section and into lower plenum,
up through core to outlet region, through CEA shroud tubes and through outlet nozzles

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In the reactor vessel, what purpose does the core bypass flow serve?

prevents stagnation of water in low flow areas keeps primary coolant below saturation temp removes gamma radiation heat from core support barrel

What do the surveillance capsule assemblies do?

monitor radiation induced changes in vessel materials

How many CEA's are in the core?

What are the three types of CEAs and how many are there of each?

5 regulating groups (1, 2, 3, 4, 5) 2 shut down groups (A and B) 2 part strength groups (P1 and P2)

What are CEA pellets made of?

Boron Carbide

There are 48 of which CEAs?

12 finger full strength

There are 28 of which CEA's?

four finger full strength

There are 13 of which CEA's?

four finger part strength

How many Fuel assemblies do the 12 finger CEAs interact with?

How many fuel assemblies do the four finger CEAs interact with?

Which type of CEA do the shutdown banks A and B use?

12 finger only

Which type of CEA do the regulating groups use?

12 and 4 finger

What are the major components of the fuel assemblies?

fuel spacer grids upper end fitting hold down plate lower end fitting guide tubes fuel rods

describe the construction of a fuel rod

filled with uranium pellets with a compression spring and spacer disks at each end of a zirconium alloy tube seal welded with end caps and pressurized with helium

Why are fuel rods pressurized with helium?

improve thermal conductivity of pellet to clad gap prevent clad collapse

Why are the fuel pellets "dished" at the ends?

account for thermal expansion and fuel swelling

What maintains the RCS in a sub-cooled condition?

PZR

What acts as a surge volume to minimize pressure changes during load transients?

pressurizer

What prevents the RCS from over pressurizing?

the pressurizer

What is RCS safety limit pressure?

2750

what is the normal RCS pressure?

2250

What is the purpose of the 4 spring loaded safety valves on PZR?

-prevent RCS from reaching safety limit pressure

Where do the four safety valves discharge to?

under the water line in the RDT (reactor drain tank)

What happens if the RDT (reactor drain tank) is over pressurized by up to 10 psi? Over 10 psi?

tank reliefs to gaseous radwaste tank relieves to containment through a rupture disk

PZR ressurizer heaters purpose?

boil the water to increase the mass of steam in the vapor space

# PZR heaters? How many banks are they divided into?

-36 heaters -8 banks

How many of the pressurizer heater banks are back ups? How many proportional banks are there?

6 2

How many heaters are in the proportional pressurizer heater banks?

3 each

How many heaters are in the back up pressurizer heater banks?

banks B1 and B2 each have 3 banks B3, 4, 5, and 6 all have 6 heaters each

How many kW are each of the pressurizer heaters rated at?

How can the pressurizer heaters be controlled?

automatically by the pressurizer pressure control system manually by operator

Where are the pressurizer heaters powered from?

two back up banks are class powered from PGA/PGB all other heaters are powered from NG

What is the purpose of the pressurizer spray system?

to reduce pressure by condensing steam in the vapor space of the pressurizer using subcooled water

Describe Main spray in the pressurizer

subcooled water is supplied from the cold leg of the reactor flow is controlled by diaphragm valves

What pressures are associated with the main spray flow control valves?

start to open at 2275 full open at 2300

describe auxiliary spray in the pressurizer

water supplied from charging pumps two solenoid valves to control flow

Why is Aux spray more effective than Main spray?

[CH] is 110 degrees less Cold Leg temp (555*).

How many spray heads are there for main spray and aux spray?

they share one spray head

Where does the PZR surge line connect the pressurizer to?

Loop 1 hot leg

What is the purpose of the pressurizer surge line?

flow path for coolant surging to or from pressurizer transmits pressurizer pressure to entire RCS

How is main spray bypass flowrate controlled?

manually adjusted to establish a temp differential of less than 70* between cold leg and spray nozzle piping

Why won't the main spray flow function without the RCPs in service?

reactor vessel differential pressure isn't sufficient to maintain spray flow without the RCPs

why is maintaining constant main spray valve bypass flow important?

minimizes thermal shock on: pipes, valves and spray nozzles minimizes thermal stratification in piping keeps chemistry uniform throughout RCS and pressurizer

If the pressurizer spray valve bypass valves are NOT isolation valves, what are they?

metering valves

Describe the sealing mechanism between the reactor vessel and the closure head.

two silver plated inconel, self- energizing, metal O-rings sit in machined grooves on the closure head flange. the outer o-ring is passive until the inner o-ring fails

In reference to the reactor vessel head, what is a self-energizing o-ring?

the O-rings are drilled around the inside allowing RCS pressure to pressurize the o-ring and form the seal

What is the reactor vessel head seal drain valve? Where does it drain to?

When the inner reactor head o-ring starts leaking, causing an increase in pressure between the O-rings, this valve drains the coolant between the O-rings RDT

What two sections of the steam generator interfaces with the RCS?

primary chamber tube sheet and U-tubes

Where is the primary chamber located in the steam generator and what is its purpose?

its in the bottom of the steam generator part of the RCS boundary and directs flow through the steam generator

What is the design pressure and temperature of the steam generator primary chamber?

650*F 2500 PSI

What is the purpose of the steam generator tube sheet and U-tubes? How thick is the tube sheet?

separate primary from secondary sides of the steam generator permit heat removal from the primary side without radioactive material transfer 23.5"

Steam Generator Tube rupture vs primary leakage?

S/G tube rupture -tube penetration is so bad CVCS can't maintain pressurizer level Primary Leakage -CVCS can still maintain pressurizer level

Why is a steam generator tube rupture bad?

Allows RCS to leak into the main steam system allowing radioactive material release

What are the primary functions of the reactor coolant pumps?

RCS boundary provide flow in RCS add heat to primary loop during plant heat ups provide motive force for main spray valves

[RC] pumps powered from class or non-class?

Non-class

RCP oil lift purpose?

-forced lubrication to thrust bearing

How long before an RCP start is its respective oil lift pump started and why? how long after start up will the oil lift pump run?

7 minutes before so the oil can push the thrust bearing pads away from the thrust runner 2 after

What components make up the RCP oil lift system?

oil reservoir, filter, accumulator and oil lift pump

What is the RCP oil lift pump auto feature?

prior to stopping RCP, oil lift pump handswitch must be put to auto-- RCP will stop, oil pump will turn on until operator secures handswitch

What minimizes leakage along the RCP shaft, also being an RCP boundary?

shaft seal assembly

What components make up the RCP shaft seal assembly?

casing, three tandem mechanical pressure reduction seals, auxiliary impeller

What injects water at 6.6 gpm to the RCP shaft seal assembly?

[CH]

What is the total flow through the RCP shaft seal assembly?

22.6 gpm

In the RCP shaft seal assembly, where does majority of the seal water flow get routed to?

through the auxiliary impeller to the journal bearing and lower journal bearing cavity

In the RCP shaft seal system, what is the pressure drop across each of three seals?

42% of system pressure for first two seals, 16% across third seal

In the RCP shaft seal system, where is leakage past the vapor seal directed to?

Reactor Drain Tank

Will the seal bleedoff isolation valves close while the RCP is running?

What is the purpose of the RCP motor flywheel?

increases rotating inertia of the RCP which increases coast down time during LOP to pump motors

What is the purpose of the anti-reverse rotation device?

stops a pump when it reaches zero speed so it can withstand reverse torques

Name the start permissives of the RCPs.

no motor fauls oil lift flow NC water flow RCP seal bleed off valve full open

What are the RCP trips?

under-voltage over-current coast-down less than 600 for a few seconds during start up

What is the tech spec limit for RCS pressure?

2750 psia

What is the tech spec range for pressurizer pressure?

2130-2295 psia

What is the tech spec Tcold RCS loop temperature limit?

545*F

Per tech spec, in mode 1 and 2, how many RCS loops have to be OPERABLE and in operation?

two

Per tech spec, in mode 3, how many RCS loops must be OPERABLE and in operation?

Per tech specs, in mode 4, how many SDC loops must be OPERABLE? How many in operation?

2 1

Per tech spec, How many pressurizer safety valves must be OPERABLE with lift settings between 2450-2549 psia

What is the heat sink to the RCS under normal operations?

Main Steam & Main Feedwater

Where can I get samples of the RCS?

Loop 1 hot leg Surge line Pressurizer steam space

What affect does the data collected from the surveillance capsule assemblies have on the plant?

Can have an effect on allowable heat up and cool down rates and the minimum temperature for reactor vessel pressurization