ML19281A564

Responds to 770902 Request for Certain Info Re Water Hammer. Discusses Possible Mods to Water Hammer in Feedwater Sys

ML19281A564
Person / Time
Site:	Calvert Cliffs
Issue date:	11/14/1977
From:	Lundvall A BALTIMORE GAS & ELECTRIC CO.
To:	Desiree Davis Office of Nuclear Reactor Regulation
Shared Package
ML19281A563	List: ML19281A562 ML19281A564
References
NUDOCS 7903210300
Download: ML19281A564 (4)

Text

BALTI M O RE GAS AN D ELECTRIC CO M PANY GAS A N D aLECTRIC BUILDING B ALTI M O R E, M A RY L A N D 21203 Ilovember lh, lo77 ARTM um E. LUN DVALL.J R.

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Office of Nuclear Reactor Regulation U. S. Nuclear Reculatory Co=ission Washincton, D. C. 20005 Attn: Fr. D. K. Davis, Actine Chief overating Peactors Branch F2 Division of Crerating Peactors Sub.i ect : Calvert Cliffs Nuclear Fever Plant Units No. 1 and 2 Docket Nos. 50-317 & 50-318 Waterhanner

. File: L-037 Gentlemen:

Your letter of September 2,1977 recuested certain infomation with respect to vaterha er. As you are aware, in "av, lo75 Unit 1 exterienced a damaging vaterhanner in the feedvater systen. "'his is well documented in the report of your principal consultant, CREAVE.

Since that time, we have demonstrated by testing on both units, that the no mal operating water level in the steam generators can be reestablished uti-li ine the auxiliary feedvater system at a rate of less than 1.2 inches per ninute. Plant operating procedures have been established to trovide the necessary controls to ensure the use of the auxilie.ry feedvater systen. In addition, the oterating license also requires the use of auxiliary feedvater for this purrese.

Pecause of these control.s, the successful testing and actual creration of the auxiliary feedvater under these conditions, modifications to the riant are not required. We have demonstrated that this natter does not ecnstitute a sig-nificant safety issue and that any resultant risk to the health and safety of the tublic is acceptably stall.

• here is, however, an economic penalty associated with the use of the auxiliarv feedvater in that it takes longer for the nlant to recover fron a riant trip. Modifications to the plant are being considered to shorten this recovery time. Such modifications vould probably entail convertine the feedvater sparrer inside the steam generators to a "too discharge" design.

13D MIG 36G

L. Provide a summary of the pertinent water hanmer experience at the Calvert Cliffs Plant including the results of tests relating to water hammer in the steam generater or feedvater systems.

Pennonse:

a) Please refer to our letter dated 11/lk/77 (attached), which addresses the subject of water ha=ner experience.

b) Following the modifications to the Unit No. 2 steam generator main feedvater rings, a test was conducted (on SG No. 22) to demonstrate the effectiveness of the modifications in preventing water hamners.

The basic test procedure was as follovs:

1) Initial Conditions:

Hot Shutdown (RC temperature 525 F)

Four Reactor Coolant Pumps operating Steam Generator level 0" + 10" Main Feedvater operating _

2) Stop all feedvater flow

3) Initiate bottom blevdown to -85" actual level h) Wait 15 minutes (to allow any design leakage from the feedring to occur).

5) Reinitiate feed flow vith a control valve opening of 33%.

6) Do not allow RCS cooldown by more than 80 F.

7) Stabilize SG level at 0 + 10 inches.

6) Heatup RCS to original temperature.

9) Acceptance Criteria: No appreciable feedvater pipe motion or water ha=mers as detected by visual / aural observations and temporary loose parts moni+cring installation during feedvater injection.

10) Results: Satisfactory in accordance with acceptance criteria,

3. Discuss the operation of the main and auxiliary feedvater systems under norr.al and transient conditions including safety injection actuation.

Pesconse:

The operation of the main and auxiliary feedvater systems is described in FSAR Sections 10.2.2, 10.2.3, and 7.h.5 and in Response 1 above. During normal and most transient operations, the main feedvater system supplies feedvater to the main feedvater rings of the steam generators. The source of this water is the main condenser hotwells. The flow path is shown on FSAR Figure 10-9 and is described in detail in FSAR Section 10.2.2. In the event of a reactor or turbine trip, the main feedvater regulating valves shut and feed flow ramps down to 5% of full flov via the feedvater bypass valves. Otherwise, normal main feedvater is always available except during some casualty which specifically precludes it, such as a feedpump trip or related occurrence.

Auxiliary feedvater is not automatically initiated. The operator can at any time control operation of the two auxiliary turbine-driven feedvater pumps and position each auxiliary feedvater regulating valve. Remote control of auxiliary feedvater is available except when control air is lost, in which case manual control vould be accomolished at the pump.

There is no direct actuation effect on main or auxiliary feedvater as a result of a Safety Injection Actuation Signal except the already mentioned ramp-down of main feedvater to 5% flow in the case of a plant trip.

t

2. Provide a description of the auxiliary feedvater system and piping geometry including all signals that initiate operation of all pumps and valves, sources of auxiliary feedvater and injection points, and sources of energy for all pump and valve operations.

Response

a) Reference FSAR Sec. 10.2.3 b) Auxiliary steam generator feed pumps are powered by steam from the main steam system or the auxiliary boiler steam system.

c) Auxiliary steam generator feed pump steam isolation valves MOV 7070 and MOV h071.

1) Manual open and close from control room switch.

2) MOV's powered from kB0 V Class 1E motor control centers.

d) Auxiliary feedvater regulating valves CV h511 and CV h512.

1) Manual control from hand indicating controller (HIC) in control room.

2) HIC povered from 115 VAC instrument bus which is fed from h80 V Class 1E =otor control centers.

3) The control valve actuator is nevered by compressed air from the instrument air system.

e) Che sources and injection points of auxiliary feedvater (as shown on FSAR Figure 10 o) are: Source: Condensate Storage Tank Inj ection : Auxiliary Feedvater Ring

b. Three Element Control In this mode feedvater flow is cummed with steam flow to produce a flov error signal. This signal is su=med with level error to generate a final signal to open or close the feedvater regulating valve. A proportional, plus reset, controller is used in this circuit so that for a zero input the controller vill still have an output. The reset controller gives this output and is used to hold the feed regulating valve in its new position.

c) Regulating Valve Control and Mode Transfer The feedvater regulating valves and the bypass valves are controlled from the three element controller and the single element controller (respectively) located on the condensate and feedvater control panel (lC03). Transfer from single to three element control by going to auto on the three element controller and to manual on the single element controller then shut the bypass valve with the single element controller. To transfer from three element to single element control place the single element controller in auto, then place the three element controller in manual hold and shut the feedvater regulating valve.

d) Lens of One Level Detector Upon the loss of one level instrument (either LT 1105 or LT 1111) a switch may be positioned to switch all level functions to the other level detector.

e) A pressure transmitter sensing the D/P drop across the feed regulating valves sends a signal to a manual / auto loading con-troller on 1C03. This controller is set to maintain approximately 105 psig across the feed regulating valves and sends an error signal to control feed pump turbine speed when the feed pump turbine is in auto speed control. As power level increases /

decreases and the feed regulating valve opens / shuts, the correct feedvater differential pressure vill be maintained to insure flow into the steam generator.

g) The clearance between the feedvater sparger no::le O.D. and the Steam Generator no::le I.D. is: 15 mils nominal ( .015") and 25 mils maximum (.025")

h) The feedvater ring vents and discharge ports are shown (as modified) on enclosed draving 200-287.

, f) Feedvater control and t ypass valves controls

1) Punctional Description The feedvater control system vill automatically control steam generator level above 15% power using a three element mode of control (feed flow, steam flov and steam generator level) . When the plant is below 15% power a single mode of control (level only) vill be selected and the feedvater bypass valves vill be centrolled from the manual loading station to automatically maintain steam generator level. During start up or low power operation, leakage through the closed steam generator feedvater valves may be greater than stea= flow. In this case the upstream stop valves vill be closed.

The feedvater regulator override units are arranged to perform two functions:

a) Upon a turbine trip, within the operating range the main feed valve vill shut and the bypass feedvater valve vill open to a fixed point (5% of full power feedvater flow). The main valve vill shut either in manual or automatic. The bypass valve vill come to the preset position only in manual. A trip override is provided to restore manual control to the bypass velve.

b) When contacts are closed on high steam generator level, in Lia 1105 cr 1106,'the respective override units vill open circuit the analog signal to the electro-pneumatic transducer, causing the feedvater regulating valve to close.

The outputs of the two controllers (when in " auto" mode selection) vill be used to provide electrical analog signals to electro-pneumatic transducers, which provide air signals to position feedvater regulating control valves.

The set point generator / manual loading stations vill contin-ually indicate the outputs to the electro-pneumatic transducers, with the transfer switch in either the manual or auto position.

2) Operation

a. Single Mode This mode is used below 15% power where you do not have shrink and swell effects to give false indication of true steam gener-ator level. In single control, steam generator actual level is compared with a level setpoint and gives an output to control the feedvater bypass valve. This controller is used for startup and shutdown.

Enclosure (1)

RECUEST FOR ADDITIONAL I!,T0mMTION CAINERT CLIFFS UUCLEAR POWER PLAC UNITS 1 AND 2 STEAM GE'iERATOR WATER FJM!ER

1. Provide a description of the feedvater system and pertinent piping geometry including all condensate and feedvater pump trip signals ,

feedvater isolation signals, feedvater valve controls, feedvater valve bypass controls, feedvater sparger vents and discharge ports and clearance between the feedvater sparger nozzle 0.D. and steam generator nozzle I.D.

Resnonse a) Feference FS AR Sec .10.2.2, Sec. 10A.h.l.

b) Condensate pump trip signals

1) manual stop switch in control room

2) auto stop from overload c) Condensate booster purp trip signals

1) manual stop switch in control roc =

2) auto stop from lov oil pressure after time delay

3) auto stop from suction pressure h) auto stop from overload d) Feedvater pump trip signals

1) manual trip

2) auto trip from exhaust valve closed

3) auto trip from bearing lube oil low pressure b) auto trip fror thrust year

5) auto trip from low pump suction

6) auto trip from high pump discharge

7) auto trip from hydraulic coupling disengaged

8) auto trip from lov vacuu e) Feedvater isolation valves MOV h516, h157

1) manual close from control roon

2) auto close from steam generator isolation signal

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Page 2 In view of the above and as indicated by our letter dated November lb, 1977 (see Response No. h), we vish to state that our under-lying objective in removing License Condition 2.C.3 is to allow recoveries from reactor trips (where feedvater flow is not interrupted) on the main feedvater system rather than be limited to 1.2 inches per minute on the auxiliary feedvater system. This vould result in a significant time savings in getting the plant back on line. Other transients which cause the water level to drop below the feedvater ring without the accompanying loss of main feedvater flow are relatively infrequent. In such cases, ve also propose to continue feeding on the main feedvater system since such trans-ients are sufficiently similar to a reactor trip. If the transient results in a loss of main feedvater, we propose to shift, as ve have been doing, to auxiliary feedvater and to limit the rise rate to 1.2 inches per minute.

We have determined that this submittal constitutes additional and supplementary information pertaining to a previous request for amend-ment, and that no additional fee is required pursuant to 10 CFR Part 170.

If you have any questions pertaining to our responses or the naturc of our request, please contact us.

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Very truly yours, .

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cc - J. A. Biddison, Esquire G. F. Trowbridge, Esquire Messrs. E. L. Conner, Jr. - NRC P. W. Kruse - CE J. W. Brothers - Bechtel