Systems Exam 4 - Steam Generator Blowdown

Question 1

SGBD HELB Isolation Valves u-HV-2397A through 2400A

Answer 1

→AFW Auto Start, Train B
→HELB, Train B (120,000 lbm/hr, 240 gpm)
→valves fail closed on loss of power or air
→powered from uED2-1

HELB & SGBD Isolation - “AH, PHART.”

Question 2

SGBD Isolation Valves u-HV-2397 through 2400

Answer 2

→Train A uED1-1
→Train B uED2-1
→fail closed on loss of power or air
→failure of either train solenoid will result in closure of valves

Valves Close On:
→P - Phase A (train related solenoid)
→H - HELB, Train A (120,000 lbm/hr, 240 gpm)
→A - AFW auto start (train related solenoid)
→R - Rad Hi SGBD Sample Rad Monitor (RE-4200), Train A
→T - Temperature Hi >150°F downstream of SGBD HX, Train A

HELB & SGBD Isolation - “AH, PHART.”

Question 3

What is the max flow through SGBD filters?

Answer 3

→360 gpm per filter before resin beds
→both filters normally in service

Question 4

What sort of leakage are the SGBD demins designed to handle?

Answer 4

20 gpd primary to secondary leak with RCS activity equivalent to 1% fuel defect

Question 5

→Max blowdown flow per SG?

→Max blowdown flow total (all 4 SGs combined)?

Answer 5

→150 gpm

→600 gpm

Question 6

What is the max flow through SGBD bottom nozzles on the SGs?

Answer 6

→Unit 1 - 104 gpm
→Unit 2 - 35 gpm

Difference is due to difference in SG material wear properties.

Question 7

How is flow rate from SGs to SGBD controlled?

Answer 7

→flow after HX throttled to ~200 psig through PV-5180
→manually controlled at CB-08
→this is what starts/stops flow when aligning

Question 8

Once SGBD passes through the containment penetration, how many valves does each blowdown line have?

What are they?

Answer 8

Each line has three valves:
→SGBD Isolation Valves (CIVs) u-HV-2397-2400 (“PHART” Valves)
→HELB Isolation Valves u-HV-2397A-2400A (“HA” valves)
→flow balancing valves HV-5175-5178

Question 9

Supplemental SG Blowdown Valves HV-2440 through 2443

Answer 9

→not always required to be open for U1 since bottom blowdown rate is much higher
→fail open AOVs
→position indication from ZL lights on MCB
→no auto functions

Question 10

How would the loss of SGBD affect the plant?

Answer 10

→SG pressure/temp rises (provides more steam to main turbine)
→turbine control valves would close due to control circuit sensing that load has increased with no change in steam demand
→amount of energy removed by Main Turbine remains the same; RCS temp would increase
→Rx power would go down due to negative reactivity from temp increase
→600 gpm flow ≈2.5% Rx power

Question 11

SGBD Relief Valves

Answer 11

→HX Outlet Relief SB-0040 lifts at 1200 psig
→relief downstream of PV-5180 (controls flow) lifts at 280 psig (alarm at 159 psig)
→both relieve to main condenser

Question 12

SGBD High D/P Alarms

Answer 12

→HX outlet filter Hi D/P 25 psid
→cation resin trap Hi D/P 50 psid
→mixed bed resin trap Hi D/P 50 psid

Question 13

How does SGBD discharge location affect flow?

Answer 13

→when flow is directed back to HX (to Heater Drains via HDT-01), Condensate = SGBD flow (preferred)
→when flow is not directed back to HX (going to Main Condenser, CST, or Turbine Bldg Sump), Condensate = 2x SGBD flow
→maintain condensate temp 35°F below Heater Drain Tank temp
→prevents flashing to steam

Question 14

What are the temperature limitations for SGBD?

Answer 14

→outlet temp from SGBD HX should be maintained <130°F to protect demin resin from damage