Systems Exam 2 - LTOP

Question 1

Temperature at which PORVs automatically arm for LTOP

Answer 1

≤350° F

(automatically disarm >350° F)

Question 2

How many PORVs are required to prevent overpressure?

Answer 2

Only one

Question 3

A single PORV has adequate relief capability to prevent overpressure if the transient is limited to:

Answer 3

1. starting an idle RCP with secondary water temperature
   ≤ 50°F above RCS CL temperature
2. the start of 2 charging pumps and their injection into a water solid RCS

Question 4

TS 3.4.12 requirements for LTOP

Answer 4

→2 RHR suction reliefs (lift @ 450 psig ± 3%), or
→2 PORVs, or
→1 of each
→0 SI pumps capable of injecting
→2 charging pumps capable of injecting
→0 accumulators capable of injecting

If these requirements are not met, then the RCS must be depressurized and a 2.98 sq in vent path must be made in the RCS pressure boundary.

Question 5

Describe the LTOP circuitry by train

Answer 5

Each train consists of 4 inputs feeding 2 auctioneered low circuits with 1 train providing input into a setpoint generator and the other supplying the permissive to open the opposite train’s PORV.

Question 6

Train A LTOP Inputs

Answer 6

For PCV-455A:
→T-hot 413A (Loop 1)
→T-hot 423A (Loop 2)
→T-cold 433B (Loop 3)
→T-cold 443B (Loop 4)
→PT-405 (Loop 1 WR pressure)

Temperature arms Train B, but pressure operates Train A

Question 7

Train B LTOP Inputs

Answer 7

For PCV-456:
→Tcold 413B (Loop 1)
→Tcold 423B (Loop 2)
→T-hot 433A (Loop 3)
→T-hot 443A (Loop 4)
→PT-403 (Loop 4 WR pressure)

Temperature arms Train A, but pressure operates Train B

Question 8

LTOP is required when any CL temperature is…
(TS 3.4.12)

Answer 8

≤ 320°F

Question 9

When LTOP is required by TS 3.4.12, the following is also required to ensure no heat transients beyond LTOP capability occur:

Answer 9

1. render all SIPs and one charging pump incapable of injection
2. close and deactivate SI accumulator discharge valves
3. preclude the start of RCPs if secondary water temperature is > 50°F above primary

Question 10

Per TS 3.4.12, LTOP applies Mode 4, 5, and 6 (when RV head on), but does not apply when all RCS CL temperatures > 320°F and all of the following are met:

Answer 10

1. at least 1 RCP operating
2. PZR level ≤ 92%
3. Plant heatup rate is limited to 60°F per hour

Note: LTOP will still arm ≤350°F

Question 11

When is LCO 3.0.4.b not applicable regarding LTOP?

Answer 11

When entering MODE 4

Question 12

Which PORV opens faster on NOP/NOT overpressure? Which PORV opens faster on LTOP actuation?

Answer 12

Overpressure: PCV-455A, due to the PI Controller
LTOP: They open simultaneously

Question 13

What are the LTOP PORV setpoints for different temperatures?

Answer 13