ML18026A393

Requests NRC Approval to Install Mod at Plant Determined to Constitute Unreviewed Safety Question When Evaluated.Util Will Implement Administrative Controls to Ensure Larger Min Vol Met for Diesel E Prior to Tech Spec Change

ML18026A393
Person / Time
Site:	Susquehanna
Issue date:	06/07/1990
From:	Keiser H PENNSYLVANIA POWER & LIGHT CO.
To:	Butler W Office of Nuclear Reactor Regulation
References
PLA-3400, NUDOCS 9006200041
Download: ML18026A393 (7)

Text

ATTACHMENT 3

, Pennsylvania Power 8 Light Company TWO NOrlh Ninth Slreol ~ AllantOWn, PA 18101 ~ 215 I 7705151 June 7, 1990 Director of Nuclear Reactor Regulation R E C 1'. 1 VE O Attention: Dr. W. R. Butler, Project Director Project Directorate I-2 JU'I 1 9 l39Q Division of Reactor Projects U.S. Nuclear Regulatory Commission Washington, DC 20555 SUSQUEHANNA STEAM ELECTRIC STATION UNREVXEWED SAFETY QUESTXON PLA-3400 FILE 7- SO24 Docket Nos'. 50-387 50-388

Dear Dr. Butler:

The purpose of this correspondence is to request NRC approval to install a modification at Susquehanna which was determined to constitute an unreviewed safety question when evaluated per 10CFR50.59. Additionally, PP&L is, taking this opportunity to inform you of administrative controls that have been determined to be required as a result of this modification.

BACKGROUND Two overpressurization events occurred on the 'B'nd 'C'iesel generators during September and October of last year. The subsequent root cause investigation identified low combustion air temperature as a contributor to the diesel events.

The diesel generator combustion air is drawn through an air intake filter and into the compressor section of the turbo-charger. once compressed, th~. combustion air passes through one of the two intercoolers and then into the combustion chambers.

The intercoolers have heating sections, heated by engine jacket water, and cooling sections cooled. by Emergency Service Water

( SW) . The combustion air temperature in the intake manifolds has been measured as low as 35'F. The optimum range of combustion air temperature is between 95'F and 125'F.

June 7, 1990 SSES PLA-3400 FXLE A17-8,SO24 Xt was determined that the low combustion air temperature was attributable to the inability to control ESW flow through the intercoolers. PPGL's present design is for full flow ESW through the intercoolers whenever the diesels are running.

To control the combustion air temperature, an automatic tempexature control valve is being installed on the outlet of the intercoolers and upstream of an existing butterfly valve which will be used for ESW system flow balancing.

A functional description of the proposed modification is provided as Attachment 1 to this PLA.

UNREVIEWED SAPETY DESTIOH The 10CFR50.59 safety evaluation performed for this modification resulted in answering 'Yes'o the question 'Does th~ proposed action create a possibility for an accident or malfunction of a different type than any evaluated previously in the SAR?'he valves being installed are safety related and fully qualified. However, two portions of the control equipment are not immediately available as ' ' The controller module and the dual indicator module will be purchased and installed as commercial grade.

.Xnstallation of these valves creates a new failure mechanism.

The valves themselves could fail and the use of commercial grade components increases the probability that the components will fail.

EVALUATION OP SAFETY We have evaluated the impact of the new valves failing as well as the failure of the associated commercial grade components and determined the modification will not impact plant safety. The modification was de'signed in light of potential failure modes and the need to pxeserve the design basis of the plant.

Xf the controller fails, the most serious effect is closure of the valve, which will reduce to nothing or to a" minimum, the flow of ESW to the intercooler causing intake air temperature to x'ise.

Test data from the engine manufacturer (Cooper-Bessemer) shows that full load can be maintained even with intake air temperatures of 165'F 175'F. Xn the event intake air temperature continues to rise, the modification is designed with a high-high alarm at 160'F which terminates power to the valve

June 7, 1990 SSES PLA-34 00

'ILE A17-8,SO24 causing it to fail safe (full open position). Once this high-high alarm is activated, the valve remains open until a manual reset action is initiated.

The engines are currently configured to allow full ESH flow through the intercooler whenever ESH is running and have shown distress only after repeated starts.

If the controller fails and results in the valve failing in-position the same arguments apply. This failure mode is probably less severe and the time period over which the intake air temperature will rise is longer. Xf the valve fails at a conservative setting the temperature may not rise at all.

The- controller module and dual indicator module for this modification are identical to those used in other non-Q applications at Susquehanna. The equipment is highly reliable and there is little risk being introduced. Also, 'Q'omponents are being procured in parallel and will be installed by year end.

In summary, the worst case scenario associated with this modification is failure of the controller and valves. The arguments above demonstrate that the safety function of the on site power system is not compromised, considering failure of one diesel is an analyzed condition.

He request NRC review this submittal and provide approval by July 13, 1990 which supports installation of the modification on Diesel Generator 'B'.

ADMINISTRATIVE CONTROL OP DAY TANK MINIMUM VOLUME As part of the modification discussed above, PP&L plans to revise the design of the fuel oil system for diesel generators A, B, C, and D to prov'de added cooling to the combustion air. Flowing vents will be added to the fuel injection pumps and the existing fuel oil coolers will be bypassed. As a result of this change.

excess fuel from the pumps will be rerouted to the underground storage tank instead of being returned to the day tank. This added drain on the day tank requires a greater minumum volume to be established in order to meet ANSI N195-1976 requirements.

Currently, the minimum volume specified in the Technical Specifications is not sufficient to support what will be required as a result of the modification; accordingly, we are preparing a proposed change to the Technical Specifications. However, the revised value, since it is greater than the minimum requirement, will not violate the current Technical Specifications. Our 10CFR50.59 review has therefore determined that a. Technical

June 7, 1990 SSES PLA-3400 FILE A17-8,SO24 Specification change prior to the modification is not required as long as we administrative3,y control the day tank volume to the value which we determine to meet ANSX N195-1976. This position was reviewed with the NRC Project Manager and the Sr. Resident Xnspector; please contact us.

if the NRC has any questions on this determination, For your information, PP&L has determined that due to the higher output of the E diesel (the E diesel already incorporates flowing vents), it should also have a higher required minimum volume. Xn order to ensure that ANSI N195-1976 is met for the E diesel, PP&L will implement administrative controls to ensure the larger minimum volume is met until a change to the Technical Specifications can be processed.

Xf you have any questions please contact. Mr. D. J. Walters at (215} 770-6536.

Very truly yours, (Sign.'(Q H. Y(, KEISN H. W. Keiser cc: Document Control Desk (original)

Mr. M. C. Thadani NRC Project Manager White Flint Mr. G. S. Barber NRC Sr. Resident Xnspector SSES DJWQSAFQUES.DJW bcc: W. E. Barberich A2-3 F. G. Butler A6-3 R. G. Byram A6-1 J. M. Kenny A2-4 A. M. Male A6-2 J. Miltenberger A6;1 D. F. Both SSES R. R. Sgarro A2-4 H. G. Stanley SSES D. J. Walters A2-4 SRMS Corr sp. File A6-2 Diesel Team

Attachment 1 to PLA-3400 For simplicity, the following description describes changes on Diesel Generator A. Identical changes will be made on the other diesels, therefore any references to component numbers, etc. must be correlated to the appropriate diesel generator to understand the entire scope of the modifications.

INTAKE AIR TEMPERATURE CONTRO7 The diesel generator combustion air temperature going into the combustion chamber will be controlled in the. range of 95'F to 125'F by controlling the flow of ESW through the intercoolers.

An automatic control valve is added in the common line downstream of the two bias valves. The control valve is a 3" globe valve who position is determined by a ITT Barton Hydramotor Actuator Type NH92. Temperature of the combustion air in the left and right intake manifolds is sensed by RTD's and processed within Bailey 7000 series instrument control equipment located in a ]:--..-

control panel OC 597A. The air temperature inputs from the lefta and right manifolds are compared, the high value selected, and signal sent to the hydramotor actuator to adjust the valve.

Control of the hydramotor actuator and positioning of the control valve is on 0he higher temperature of the two intake manifolds.

The control circuit maintains approximately 110'F in the warmer manifold. In the event the temperature should exceed 160'F in ~ '

either manifold, the control circuit interrupts power to the hydramotor actuator causing the valve to go full open so that there is maximum ESW flow through the intercooler. Once the High-High temperature override circuit is activated the valve remains open until a manual reset action is initiated at panel OC597A.. This feature is to prevent the turbocharger from exceeding the maximum temperature of 1200'F in the turbine portion.

The type NH92 hydramotor actuator is designed to move the control valve to the fail open position when power or control signal is interrupted to the actuator. Power to the actuator is Diesel 120V AC Class 1E power from OC577A located on El. 710'n the Generator A Bay. Power to OC577A is from Class lE MCC OB516 located on El. 677'n the Diesel Generator A bay. The operating mode is selected by and the power supply to the actuator is controlled by two switches on control panel OC597A. A contact of the 4X2 diesel generator start relay closes to energize the actuator motor and relief valve circuit when the OFF-AUTO not .

selector switch is in AUTO. When the diesel generator is running, the 4X2 contact opens to de-energize the actuator motor and relief valves circuit, allowing the actuator spring to move the control valve to the open position and results in full design flow through the intercooler. Full flow when ESW is available

and the diesel is not running permits the removal of any ;.ilt accumulation and a change of water, thereby avoiding the effects

'of any stagnant water corrosion. Placing 0he selector switch in the OFF position disconnects the power supply to the actuator circuit and opens the valve.

A NORMAL-BYPASS selector switch is also provided for operating

, the control valve when the diesel generator is not running. With the OFF-AUTO selector in the AUTO position and the NORMAL=BYPASS selector in the BYPASS position, a contact in parallel with the 4X2 contact is closed, energized the actuator circuit and allowing automatic or manual control of the ESW flow when the diesel is not operating. Placing the selector switch in the NORMAL position opens the parallel contact route of the power supplyo A Bailey 701 controller located in OC 597A on Elev. 677'f the Diesel Generator A bay allows automatic or manual control of the valve. The controller functions include a set point station, controller output indicator and a MANUAL-AUTO selector switch with OPEN-CLOSE pushbuttons. In the AUTO or MANUAL modes the controller provides a 4 to 20 mA DC signal to the valve actuator to control the valve position. 'However, as described previously, the valve will only respond to the control signal when the C.".

AUTO selector switch 'is in the AUTO position and the diesel generator is running or the NORMAL-BYPASS switch is in the BYPASS position. When the controller- is in the AUTO position, the higher input signal from the two intake air temperature sensors is compared to a set point and the output signal to the valve is adjusted to maintain desired temperature. When the controller is in the MANUAL position, the OPEN and CLOSE pushbuttons are used to regulate valve position. A manual handwheel on the actuator

'with a chain is also provided to change valve position when the OFF-AUTO selector switch is in the OFF position. This handwheel/chain operator shall be locked in the valve open position when not being used to control valve position. Full or partial extension of the manual operator prevents the 'electro-hydraulic actuator from operating properly, limiting valve opening to that of the manual operator position.

A green indicating light and a reset pushbutton are provided on panel OC597A to indicate that High-High temperatur'e override of the modulating control circuit has been activated and to allow manual reset to normal control when the temperature drops below 160'F. A seal in circuit prevents automatic return ~..o modulating control when the over-temperature condition disappears. Pressing the pushbutton momentarily interrupts the normally closed contact, allowing power to be restored to the hydramotor actuator if the temperature is below 160'F.

Indication of combustion air tern p erat n h li nd right o

left t manifold oil . X ddi is pxovided e at a valv 1ocation for the plant thee valve operator.

Annunciation is provided on the diesel en ine ane omb F ox less than 95,F common fo ld t th alarm window on 15'F OC521A These Th which three cond is conne t

xou e,a arm n he main control room.

cond3. 3.ons recp111e a o owe by a time delay of a inutes to become act'v ac ive alarms.

1 The time de lay permits the air i i tempexature in the man'f o ld t o r se above the 95 F and prevents spuri u 1 when the conditio

\

occur xmmediately~

The OFF position of the OFF-AUTO h d Proper for Remote Auto 0 eratio