ML20034C776

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Issue 55 to Abnormal Operating Procedure AOP D-1, Single Circulator Trip
ML20034C776
Person / Time
Site: Fort Saint Vrain Xcel Energy icon.png
Issue date: 04/19/1990
From:
PUBLIC SERVICE CO. OF COLORADO
To:
Shared Package
ML20034C092 List:
References
AOP-D-1, NUDOCS 9005100029
Download: ML20034C776 (5)
v • d • e


Text

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I AOP D-1 Issue 55

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O $9tVICO' Public FORT ST. VRAIN NUCLEdR CENERATING STATION Page 1 of 2 PUBUC SERVICE CORSP'ARMf OF COLORADO k

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SINGLE CIRCULATOR TRIP "El'*"YCd..e Uni AUTHORR$D U} "g.K _hw 8Y E$iew PORC 8 7 7 APR 111990 E'ly',C7'V'4 %

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PDR FORM 10)372 22 3842

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Issue 55 Page 2 of 2-(D-1)'

SINCLE CIRCULATOR TRIP Ol' ONE CIRCUt_ATOR TRIP IN EACH 1.OCP SYPPTCM-ACTBON MATRIX l

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1 SYMPTOMS I

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1.3 8.

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IHelium IHellum IHelium I

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ACTIONS ICi rcula tor ICi rcula to r ICi rculator i

I ISpeed High I Penetra t ion ILoss or i

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IPressure High IBearing Waterl l

IIA 105A 1-1 11A 105A 4-2 ITA 105A 2-2' I-1 IIB 105A 1-3 118 105A 4-4 118 105A 2-4 I

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OPERATOR ACTION I

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i 1.1 Ensu re i

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I penetration inter-I I

XX l-1 I space block valve i

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l' closed.

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8 circulator water i

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8 speed, water turbine I I

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I Inlet,. and water., -l i

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. I valves close.

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t 1.3 Veri fy/ set

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. 1 circulator brake and I I XX 1

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1. seal and isolate i

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- 1 auxiliaries.

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i 1.4 Monitor critical I-4-

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AOP APP D-1

. Issue 55 APublic FORT ST. VRAIN NUCLEAR GENERATIND STATIOlQage 1 of 3

%F Service

V INTRODUCTIO.N Circulator trips are initiated by the Plant Protective System (PPS) to protect the circulators and associated equipment against various I auxiliary equipment and control system failures.

I When the cause of the trip is loss of bearing water pressure, all the circulator auxiliaries are isolated.

In this event, the circulator brake is applied when the speed has coasted down to 700 rpm. Twenty seconds later, the static shaft seal:is automatically applied.

DISCUSSION OF SYMPTOMS 1.1 Helium Circulator Speed High.

Speed sensors monitoring shaft speed actuate the circulator trip logic system when circulator speed exceeds l

8,800 rpm. Actuation of at least two of the three sensors is required to cause trip.

Excessive circulator speed is an indication of a speed controller failure or other circulator system-failure necessitating rapid shutdown of the circulator. The speed sensing system response and trip setting are chosen so p

that, for t"e case of the maximum overspeed situation

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possible (It ss'of restraining torque), the circulator speed will rsmain within design _ limits.

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1.2 Helium Circulitor Penetration pressure High.

pressure exceeding 810 psig in the circulator penetration will actuate pressure switches. Actuation of at least two of the three switches is required to cause trip.

Circulator penetration overpressere is indicative of a I

pipe rupture within the penetration. A circulator trip is initiated and the purified helium pressurizing line to the penetration is closed to prevent moisture backflow into the purified helium system. The relief of the overpressure is handled by the circulator penetration relief valves. The trip point is set above normali operating pressure but below the circulator penetration relief valve setting.

I 1.3 Helium Circulator Loss of Bearing Water.

Pressure switches sensing the difference between primary

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coolant pressure and' bearing water pressure actuate at a 3

differential of 475 psid. Actuation of two of the three J

switches is required to cause trip of the steam drive and prevent automatic water turbine start.

a FORM 101372 22 3643

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l AOP APP D-1 1

Issue.55' O PUD llC FORT ST. VRAIN NUCLEAR GENERATING STATIOAage 2 of 3 VGF Service

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NOTE: After a loss of normal bearing supply (loss of all.

three pumps in-a loop) the NBW isolation valves

(-1) and the flow control valves close to prevent re-establishing normal bearing water on top of back-up bearing water. These valves must be shut (on controller /handswitches) in order to re-open.

Loss of bearing water is potentially damaging to the helium circulator. The trip point is set:to ensure that the normal and auxiliary bearing water sources are available; if not, the circulator is tripped. The-line to the bearing water accumulator opens automatically, due.te reversal of differential pressure across a check valve, to allow use of the stored water.during circulator coast down.

DISCUSSION OF OPERATOR-ACTION I

2.1 Ensure penetration interspace block-valve'c'osed.

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High penetration pressure indicates a bearing water pipe.

leak in the penetration. The purified helium penetration I

interspace block valve is shut automatically to prevent I

water from backing'up the line and getting into'the

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purified helium system. The operator acts as a backup to y

the PPS.

I 2.2 Ensure Tripped Circulator Water Speed, Water Inlet, and-I Water Outlet Block Valves Close.

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.This step. verifies proper circulator shutdown by PPS..

I 2.3 Verify / Set circulator brake and;se,al and isolate u

circulator auxiliaries.

1)

The circulator must coast down to less'than 700 rpm before brake will set. The: static seal is inhibited from setting by a 20 second time delay after the brake is applied.

The static seal will be damaged if applied while the shaft is turning. The circulator brake is provided to stop the shaft when it is necessary as a result of dynamic seal or bearing malfunction.

2)

Isolate circulator auxiliaries.

By isolating circulator auxiliaries, any leakage in l

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bearing water piping or buffer helium piping will be stopped.

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FORM (Ol372 22 3643 i

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A0P APP 0-l' Issue ~55 Public FORT ST.' VRAIN NUCLEAR GENERATING STATIOkage 3 of 3 l*

OService*

Pusuc senvece couramy or cotonaoo 1

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l-l 2.4 Monitor Critical Safety Functions Per E0P's.

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Monitor critical safety functions per E0P's and perform l~

steps of E0P's as required.

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FORM t01372 22 3M3 l

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