ML18022A464

Forwards Addl Info Re Turbine Overspeed Testing at Facility Per ACRS Request Requiring Submittal of Structured Test Program for Evaluating Turbine Overspeed Protection.Startup Test Procedure 1-9103-S-27 Encl

ML18022A464
Person / Time
Site:	Harris
Issue date:	11/21/1986
From:	Zimmerman S CAROLINA POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML18022A466	List: ML18022A464 ML18022A469
References
NLS-86-426, NUDOCS 8612040370
Download: ML18022A464 (2)

Text

CPKK Carolina Power 5 Llghl Company SERIAL: NLS-36-026 INv 2l Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation

'Jnited States Nuclear Regulatory Commission Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLAi JT DOCKET NO. 50-000/LICENSE NO. NPF-53 TURBI'~E OVERSPEED TESTING

Dear 0'.r. Denton:

Carolina Power R Light Company (CPRL) hereby submits additional information concerning turbine overspeed testing at the Shearon Harris Nuclear Power Plant (SHNPP). This information is submitted in response to a request from the NRC Advisory Committee on Reactor Safeguards (ACRS) requiring the submittal of a structured test program for evaluating turbine overspeed protection prior to full-power operations.

Attached is a copy of Startup Test Procedure I-9103-S-27r "Turbine Overspeed Trip "Test". This startup test will be conducted during power ascension testing. In addition, the following information concerning the turbine overspeed protection at SHNPP is submitted for your review. Three overspeed protection functions are provided on the SHNPP turbine:

(I) Auxiliary governor control/load drop anticipation - setpoint of 103 percent of rated speed, (2: Mechanical overspeed trip - setpoint of 110 percent of rated speed, (3) Electrical overspeed trip - setpoint of 110 percent of rated speed.

The auxiliary governor control function controls turbine speed without a turbine trip ln the event of a full load rejection. When the setpoint is reached, the governor and interceptor valves close. Then, the interceptor valves cycle open and closed until the entrained steam/energy is released to the condenser. When speed decreases to rated speed, the interceptor valves remain open, and the governor valves begin controlling speed. Overspeed is limited to the roll-up immediately following auxiliary governor control action. Reducing the setpoint below 103 percent of rated speed would create the risk of spurious auxiliary governor control action during normal turbine speed oscillations. If the auxiliary governor control logic fails, turbine speed will increase to approximately 110 percent of rated speed. At this speed, either the mechanical or electrical overspeed protection system will operate. Both systems have the same setpoint (110 percent of rated speed) and provide redundant protection against turbine overspeed. Either system may activate first depending on particular instrument/device tolerances. Both the mechanical and electrical overspeed trips cause all of the turbine steam valves (governor, throttle, reheat stop, and interceptor) to close. These turbine steam valves are very fast-closing valves, and closure of these valves occurs near simultaneously to minimize roll-up. The closing of these valves stops aP steam flow through both the high pressure and low pressure turbines.

P 8612040370 861121

~PDR ADGCK 05000400 PDR k-.

payene>< re siree ~, r IS ~ Rcl e p N C ? 6

I Office of Nuclea eactor Regulation NLS-86-ii26 / Page 2 The mechanical and electrical trip setpoint of 110 percent of rated speed is chosen for tv o reasons: (I) to prevent the turbine from reaching the design overspeed of 120 percent taking into account expected roll-up following turbine trip, and (2) to prevent a turbine trip after auxiliary governor control action due to the normal roll-up following the control action. Reducing the trip setpoint below 110 percent would create a situation in which a turbine trip would occur even though the auxiliary governor control had functioned as designed. This is an undesirable situation. The roll-up of the turbine following a trip at the star tup test power level is ex ected to be I to 2 percent of full power speed. The reduced steam flow results m minima entrained energy which can be converted to rotational energy after steam valve closure. The roll-u followin a tri a; full power has been calculated by Westin house based on auxiliary governor contro percent of rated speed. Specific roll-up data has not been supplied for a trip at 110 percent of rated speed. However, Westinghouse has stated that roll-up following a trip at 100 percent will not result in a turbine speed above the 120 percent design overspeed limit.

Based on the overspeed protection system design described above and the satisfactory completion of the attached startup test, turbine overspeed protection at SHNPP will be demonstrated to be adequate. If you have any questions on this subject or require

-additional information, please contact me.

Yours very truly, S.. Zi mern;an nager Nuclear Licensing Section SRZ/3DK/kts (50603DK)

Attachment cc: Mr. B. C. Buckley (NRC)

Mr. G. F. Maxwell (NRC-SHNPP)

Dr 3. Nelson Grace (NRC-Rll)

Mr. R. 3. Giardina (NRC-PAPS)