ML20094G540

Submits Response to Request for Addl Info Re NRC Ltr & Original Amend Requested .No Change to Reactor Operating Conditions Being Proposed

ML20094G540
Person / Time
Site:	University of Texas at Austin
Issue date:	11/11/1995
From:	Bauer T TEXAS, UNIV. OF, AUSTIN, TX
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9511130088
Download: ML20094G540 (10)

Text

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.) 3 DEPARTMENT OF MECHANICAL ENGINEERING i M My THE UNIVERSITY OF TEXAS AT AUSTIN ung4y

'\g NuclearEnginemng Trad>ingLaboratory*($12)471-5787 FA November 11,1995 T

Document Control Desk i US Nuclear Regulatory Commission Washington DC. 20555

Subject:

. Response to Questions

! NRC letter Aug 4,1994 Docket 50-602

Dear Sir:

The following information is in response to the Request for Additional Information letter dated 8/2/94 and the original amendment request dated 25/1/95. The I amendment request and response to questions correct language in the original 1 Technical Specification. No change to the reactor operating conditions is being proposed.

i Sincerely, h 9. h T.L. Bauer Assistant Director / Reactor Supervisor Nuclear Engineering Teaching Laboratory J

Enclosures:

Affidavit Response to Questions

TS amendment pages 14,15,44 cc

R. Charbeneau B.W. Wehring K. Diller NRC Region IV l D.Klein QY 1 l

. 13000W - si Strut Address: 10100 Burnet Road Austin, Texas 78758 Mail Address: Balcones Research Center Bldg.159 Austin, Texas 78712 ,

9511130088 951111 PDR ADDCK 05000602

_ (P _ PDR

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of & j The University of Texas &

at Austin & Docket No. 50-602 J.J. Pickle Research Campus &

Nuclear Engineering Teaching &

Laboratory &

AFFIDAVIT I

Mark G. Yudof being duly sworn, hereby deposes and says that he is Executive Vice President and Provost, The University of Texas at Austin; that he is duly i authorized to sign and file with the Nuclear Regulatory Commission the enclosed Response to Questions (NRC letter 8/2/94) regarding Technical Specification 3.2.2, for docket 50-602; that he is familiar with the content thereof; and the matters set forth therein are true and correct to the best of his knowledge and belief.

l7 A Y Mark'G. Yudof /

l Executive Vice President and Provost Subscribed and sworn to before me, a Notary Public in and for the State of Texas, thi-3 # dayof Modem ber ,1995

'\ W N . L L m i NOTARY PUBLIC in ark for the S@e of Texas f _ _ _ _ _ _SHARdN

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Response to Questions Docket 50-602 ,

Amendment Request 25/I/93 The amendment request of 5/1/93 is being made pursuant to 10CFR50.90 as l 1.

c noted in the US NRC Request for AdditionalInformation 8/2/94. The reference to 10CFR50.56 (letter 5/1/93), should be changed to 10CFR50.90.

2. Clarification of TS 3.2.2 regarding automatic mode interlocks is the purpose of this amendment request. Operation of the automatic mode is not a Technical  :

Specification reportable occurrence, therefore reporting according to 'IS 6.6.2.2 is not a requirement. A reference to TS 6.6.2.2(b) was made to acknowledge the fact that some automatic mode operation of the reactor did occur prior to a determination by the licensee that the terminology of the Limiting Condition for Operation in TS 3.2.2 was I not consistent with the system design and operation. As noted in the licensee's amendment request, no auto;natic mode (or square wave) operation will occur until a j correction is made to the terminology in the Technical Specifications. No change is being made to the control system design.

3. The SAR describes the reactor operating modes in section 6.1.4. A general description of the automatic mode is presented on page 6 - 12. Detailed information about of the control rod system design, including operating characteristics, configuration and calibration, are found in the ICS System Operation and Maintenance ,

Manual, Control Console Operator's Manual and notes in the ICS System files. Servo t

calculations that control the regulating rod in the automatic (and square wave) modes are done by a control system digital algorithm. All other rods remain in manual control mode during the automatic control of the regulating rod. Configuration of the servo 1 1993 Amendment Response

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calculation control algorithm provides limits on the control signal magnitude, limits on l the reactor period and a scale limit for the regulating rod drive speed. Output of the servo calculation has a full scale digital limit ofi32768 (i5 volts). This signal scale ligtit ,

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4 applies to both manual and automatic mode operation. The scale limit represents the maximum rod speed and is the same as the manual insertion and withdrawal rate of the 4

3 regulating control rod drive. The automatic control cannot exceed this value but will in i

general be less than the scale limit. Digital constants further define the other two

maximum limiting conditions of the automatic mode.

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i I The following data summarizes current operating data for the regulating control j rod.

l Regulating Rod Calibration Data i

! control rod control rod peak maximum i

withdrawal drive speed (2) differential withdrawal l

year time (1) reactivity (3) rate (4) i l (seconds) (units /sec) (c/ unit) (%Sk/k/sec)

I i 1995 33.8 28.4 0.666 0.13 1 i

) 1994 34.8 27.8 0.660 0.12

! 1993 33.5 28.7 0.654 0.13 1992 34.5 27.8 0.657 0.13 j l I (1) 0 - %0 units for full rod withdrawal  ;

I l (2) speed in manual mode at control maximum (3) function fit to rod calibration data i

(4) 100e = 0.7% Sk/k l

2 1993 Amendment Response

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a. Magnitude of the limiting period is 4 decades per minute or a factor of "e" i each 6.5 seconds. In the servo algorithm an error limit of 20% of the demand power combines with a factor of 20 and the derivative constant of one to drive the control rod to a stop if the period is 4 decades per minute.

A limit twice this rate,8 decades per minute is used in the square wave mode for the first 300 cycles.

b. The limiting period is set by configuration parameters in the digital control system. Surveillance checks of the control system verify the automatic mode limiting period of ~6.5 seconds with a statistical accuracy 1 to 2 seconds.

c. Safety considerations for the limiting period in the servo calculations include two automatic control parameters, the control rod drive speed and the reactor rate of power change. Design of the servo calculations limits the controllable regulating rod speed in the automatic mode to rod speed ,

1 values no greater than that available in manual mode operation. At this value the reactivity insertion rate does exceed 0.15% Sk/k/sec significantly less than the TS 3.2.1.c limit of 0.2% Sk/k/sec. The limit on reactivity insertion rate (rod speed) in the manual mode is necessary to provide sufficient reaction time for manual control of the reactivity.

Automatic mode control applies an add'tional limit on the reactor period to compensate for the fact that an operator will not be making the manual changes necessary to respond to the reactor rate of power change. A limiting period to control the reactor rate of power change assures that automatic control actions do not exceed those that can occur in the manual mode. Another consideration for the limiting period is the amount of reactivity insertion that can occur if one of the other control rods moves in the up direction. At the limiting period condition the regulating rod stops 3 1993 Amendment Response

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moving, therefore any increase in the reactor period will cause the 9

1 regulating rod to move down maintaining the limiting period.

1-l l i- 4. At the limiting condition,4 decades per minute, the regulating rod stops, moving i neither up or down. A reactivity insertion of .33% Sk/k would create the equivalent i

j stable reactor period. Pressing a shim rod control "up" button while the reactor power

! is being increased in the automatic mode at the limiting control rate will cause the following reactor response.

! a. The shim control rod will move up. Approximating the reactor response as a prompt jump a change in reactor power of 40% would occur for a one i

second movement of the control rod if power coefficient is negligible and 4 no action is made by the automatic mode control. At the peak rod worth a

! shim rod willinsert about 0.1% Sk/k in one second. A stable reactor

! period of ~ 3 seconds would occur after a one second movement of the  ;

shitn :od without any response from the automatic control. l

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b. As the automatic control detects the period increase, exceeding the l

! limiting value, a control output signal will go negative driving the t

regulating rod down. The change in the period combines with the l

j difference between the current and demand power to control the down

motion of the rod until the demand power condition is met. At the  !

1 i maximum drive down speed the reactivity change is roughly equivalent to that of the shim rod.

! c. Automatic mode control will maintain the reactor period at the limiting 1 period condition only if the error signal exceeds 20% of the demand  ;

i signal. A progressively shorter period limit applies as the automatic mode i i

a approaches the setpoint for demand power until the period becomes infinite at the control point.  ;

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5. Pages 14 and 15 of the University of Texas Technical Specifications have been revised to clarify the application of the four modes of control in 'IS 3.2.2, TS 3.2.3 and TS i

! 3.2.4. The effective mode column for manual control has been changed to show Manual i i (M), Automatic (A), and Square Wave (S) control. The effective mode column for Pulse i (P) mode remains the same. A note at the bottom of each table defines the use of M, A, ,

! S and P. A note to the table in TS 3.2.2 removes the regulating rod from interlock i

{ requirements when in the automatic mode.

i j 6. Amend section A.3.2.2 paragraph 5 (page 44) of the Technical Specification bases l to read as follows:

( i j Auto mode is a special condition of the manual mode with autolaatic control of the regulating rod. The simultaneous withdrawal interlock does not apply to the regulating ,

! rod in auto mode so that the up or down manual operation of rods other than the

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regulating rod can occur. The servo control calculations apply a limitmg penod (4 ,

i decades / minute) to assure that two rods moving in the up direction do not exceed a 1

i safe control condition. Square wave mode is also a special case of the manual mode with automatic control except that pulse logic applies to the initiation of the auto mode l f

I condition.

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1 5 1993 Amendment Response i

' Revision 1 Technical Spscifications 3.2 Reactor Control and Safety System 3.2.1 Control Assemblies Specification (s)

The reactor shall not be operated unless the control rods are operable, and j

a. Control rods shall not be operable if damage is apparent to the rod or drive assemblies,

b. The scram time measured from the instant a simulated signal reaches the value of a limiting safety system setting to the instant that the slowest scrammable control rod reaches its fully inserted position shall not exceed 1 second.

c. Maximum reactivity insertion rate of a s t.andard control rod shall be less than 0.2% Ak/k per second.

3.2.2 Reactor Control System Specification (s) l The reactor shall not be operable unless the minimum safety interlocks are operable. The following control system safety interlocks shall be operable:

I l Interlocks Number Effective Mode

• l Rod Drive Control Ooerable Function M. A. S P

a. Startup Withdrawal 4 prevent rod X Standard control rods withdrawal for Transient control rod less than 2 counts per see

b. Simultaneous Withdrawal 4 prevent rod X Standard control rods withdrawal for Transient control rod two or more rods

c. Non pulse condition 1 prevent withdrawal X Transient control rod for drive not down except square wave

d. Pulse Withdrawal 3 prevent withdrawal X Standard control rods of non pulse rods

e. Transient Withdrawal 1 prevent rod X Transient control rod withdrawal for more than 1 kilowatt power

• Modes are: (M) Manual, (A) Auto, (S) Square Wave, and (P) Pulse Note: Regulating rod has no simultaneous withdrawal interlock in the automatic mode.

12/90 Amendment 10/95 Page 14

'Ravision 1 Technical Spscifications 1

l 3.2.3 Reactor Safety System 1

Specification (s)

. The reactor shall not be operable unless the minimum safety channels 1 are operable. The following control rod scram safety channels shall i be operable.

4 Number Effective Mode *

- Safety Channel Operable Function M. A. S P

! i i

a. Fuel Temperature 2 Scram at $550'C X X i

b. Power Level 2 Scram at $1.1 Mw X Pulse Power 1 Scram at $2000Mw X

c. High Voltage 2 Scram on loss X X

d. Magnet Current 1 Scram on loss X X

e. Manual Scram 1 Scram on demand X X l Console Button l f. Watchdog Trip 2 Scram on loss of Microprocessor scan rate timer reset X X

• Modes are: (M) Manual, (A) Auto, (S) Square Wave, and (P) Pulse 3.2.4 Reactor Instrument System i

l i Specification (s)

! A minimum configuration of measuring channels shall be operable. The J following minimum reactor parameter measuring channels shall be operable:

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Number Effective Mode l Measurine Channel Ooerable M. A. S P

a. Fuel Temperature 2 X X

b. Power Level 2 X

c. Pulse Power 1 X ,

d. Pulse Energy 1 X 1 1

• Modes are: (M) Manual, (A) Auto, (S) Square Wave, and (P) Pulse 12/90 Amendment 10/95 Page 15 1

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• Ravision 1 Technical Spscifications

. Two basic interlocks control rod movements for the pulse mode. The interlock to prevent withdrawal of the motor driven rods in the pulse mode is designed to prevent changing the critical state of the reactor prior to the pulse. A power level interlock controls potential fuel temperature changes by setting a limit of less than 1 kilowatt for initiation of any pulse.

Interlocks applicable to the transient rod determine the proper rod operation during manual mode and pulse mode operation. The non pulse condition interlock determines the allowable position of the rod drive for actuation of the FIRE switch. Actuation of the switch applies the air impulse for removal of the transient rod from the reactor core.

Auto mode is a special condition of the manual mode with automatic control of the regulating rod.

The sinnaltaneous withdrawal interlock does not apply to the resulating rod in auto mode so that the up or down manual operation of rods other than the regulating rod can occur. The servo control calculations apply a limiting period (4 decades / minute) to assure that two rods moving in the up direction do not exceed a safe control condition. Square wave mode is also a special case of the manual mode with automatic control except that pulse logic applies to the initiation of the auto modo condition.

A.3.2.3 Reactor Safety System Applicability These specifications apply to operation of the reactor safety system.

Objective The objective is to determine the minimum safety system scrams operable for the operation of the reactor.

Bases Safety system scram functions consist of three types. These scram types are the limiting safety system settings, operable system conditions, and the manual or program logic scrams. The scrams cause control rod insertion and reactor shutdown.

Scrams for limiting safety system settings consist of signal trip levels that monitor fuel temperature and power level. The trip levels are conservative by a significant margin relative to the fuel element temperature safety limit.

Operation without adequate control and safety system power supplies is prevented by scrams on neutron detector high voltage and control rod magnet current.

l l Manual action of the scram switch, key switch, or computer actuation of watchdog timers will initiate a protective action of the reactor safety system. Either of two watchdog circuits provide updating timers to terminate operation in the event that key digital i

processing routines fail, such as a display system. Each watchdog l circuit with four resettable timers contains one trip relay and monitors one microcomputer.

12/90 Amendment 10/95 Page 44