26.08.2015   Modern Power Station Practice

Caustic/chloride ingress protection

This system is provided to protect the boilers against the ingress of chloride from the CW system or caus­tic solutions from the condensate polishing plants. A high level of protection is required and thus, as far as practicable, two diverse sets of equipment are provided, each using ‘2 out of 4’ logic.

9.11 Heating and ventilating system

There are over 50 separate heating and ventilating systems on Heysham 2, of which about 40 are related to safety and/or contaminated zone systems. Consi­derable effort has been put into ensuring that the standard of C and I design and equipment on these systems is of a comparable level to that employed on the main reactor/turbine-generator plant.

A number of systems are controlled by program­mable logic controllers (PLC) also known as Program­mable Controllers (PC), which implement both sequen­tial and modulating control. These PLCs are linked to a microprocessor, programmed in Cutlass, which provides centralised logging and display.

Table 2.15

Typical AGR tripping schedule

Trip parameters

Trip setting nominal

Redundancy

Comments

fam guardline

1

Pulse count rate high i level onlv)

500 kW

2 out of 4

Flux period (log DO

29 s

(doubling time 20 s)

2 out of 4

3

Excess flux (linear channels) rate and 1 lex el stop 1

200 MW—min up 1000 MW, mm down 0 margin lO^o (40 MW mm)

2 out of 4

4

Excess flux flog DC channels — from l linear output) rate and level stop j

Upper 17 MW

2 out of 4

5

Low reactor pressure l

28.5 bar a

2 out of 4

6

Low reactor pressure 2

28.5 bar a

2 out of 4

7

High reactor pressure 1

44.8 bar a

2 out of 4

8

High reactor pressure 2

44.8 bar a

2 out of 4

9

High CCO temperature rate and level stop

10°C/min up 200°C/min down Q margin 40°C Upper 710°C

2 out of 4 in each case of two separate sets

10

High circulator outlet gas temperature rate and level stop

7°C/min up 7°C/min down Q margin 20°C Upper 320°C

2 out of 4

11

Circulator undervoltage

Less than 3.3 kV for greater than 200 m/s

Two

2 out of 4

12

IGV position

14°

I out of 2 per quadrant into 2 out of 4

13

Any one quadrant extra high circulator outlet gas temperature

370°C

2 out of 3 per circulator

14

High boiler half-unit outlet gas temperature (via quadrant trip initiated)

320°C

2 out of 3 per half­unit into 1 out of 6 per quadrant into 2 out of 4

15

Circulator underspeed (via quadrant trip initialed)

2520 r/min

2 out of 3 per circulator into 1 out of 2 per quadrant into 2 out of 4

16

High CACS demineralised water temperature

(via quadrant trip initiated)

40°C

2 out of 3 per quadrant into 2 out Of 4

17

Two quadrant trips initiated

—

2 out of 2

18

Safety room high temperature

40°C

2 out of 4

19

Impact vibration

10 dB above background

2 out of 4

20

Fuelling machine grab load

U/Ll 1880 kg U/L2 2180 kg O’L 2775 kg ROC 80-85 kg/s

2 out of 3

21

Pile cap air temperature high

130°C

2 out of 4

Distributed sets.

Channel trip if one ther­mocouple rises 30° above ambient of 50° noting two series thermocouples to one input. Local gas temperature at trip 80°C nominal.

T BLE M 5 want’d) Typical ACR mppins schedule

Trip parameters

Trip vetting nominal

Redundancy

Comments

pucrse ■iiuirdline

1 Hi eh. COO temperature rate and level ‘top

identical to item 9 — main guardlme

2 out of 4

‘ £■ v C" fiuv 1 l. r’car ^ "uггr.-1 rate and level stop

Identical to item 3 — mam guardiine

2 out of 4

1 Quadrant trip initiated

—

2 out of 4

Auxiliary guard line 1 Pulse count rate high

500 kW

2 out of 4

Quadrant protection 1 Hall-unit outlet gas temperature high How

з:о°с

270°C

2 out of 3 per half­unit into 1 out of 6 per quadrant

Safety associated

2 Low superheater transition joint metal temperatures

See Note l

2 out of 3 per half­unit into 1 out of 6 per quadrant

3 Circulator underspeed/overspeed

2520 r/min 3220 r/min

2 out of 3 per circulator into 1 out of 2 per quadrant

Safety associated

4 Differential oil pressure across circulator bearings very low

0.75 bar

2 out of 3 per circulator into 1 out of 2 per quadrant

5 Oil level from circulator compartment very high

See Note 2

2 out of 3 per circulator into 1 out of 2 per quadrant

6 Circulator lub oil tank level very low

See Note 2

2 out of 3 per circulator into 1 out of 2 per quadrant

і Circulator high differential pressure

between reactor and motor compartment

4 bar

2 out of 3 per circulator into 1 out of 2 per quadrant

й CACS demineralised water temperature high

40°C

2 out of 3 per quadrant

Safety associated

9 Circulator outlet gas temperature high

435°C

2 out of 3 per circulator into 1 out of 2 per quadrant

SSD initiation

Bulk group 1 insertion

691Щ

Delay timer L.

4.35 s

Votes

I Гпр -.cuing is a function of steam pressure — trip is based on integral level switches with fixed setting

‘ Q = quiescent