ML13073A122

Texas A&M University, Additional Clarification to Responses to NRC Request for Additional Information Regarding the Review of AGN-201M Research Reactor License Renewal

ML13073A122
Person / Time
Site:	Texas A&M University
Issue date:	03/06/2013
From:	Hassan Y Texas A&M Univ
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME1588
Download: ML13073A122 (8)

Text

DWIGHT LOOK COLLEGE OF ENGINEERING Department of Nuclear Engineering AlmTEASAM March 6, 2013 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Docket No.50-059

SUBJECT:

Response to "Texas A&M University - Additional clarification to responses to NRC request for additional information regarding the review of the Texas A&M University AGN-20 1M research reactor license renewal (TAC No. ME 1588)"

In response to the letter dated December 6, 2012 the following remarks have been provided for clarification. If you have any questions, please do not hesitate to contact me at: (979) 845-4161, or email at y-hassan(2btamu.edu.

I declare under penalty of perjury that the forgoing is true and correct. Executed on March 6, 2013.

Best regards, Yassin A. Hassan, Ph.D.

Department Head and Sallie & Don Davis '61 Professor in Nuclear Engineering Professor in Mechanical Engineering

[Enclosure]

337 Zachry Engineering Center 3133 TAMU College Station, TX 77843-3133 Tel. 979.845.4161 Fax. 979.845.6443 nuclear.tamu.edu

Texas A&M University AGN-201M License No. R-23 Docket No.50-059 Responses to Additional Clarification RAI Questions 6,7,8,9,11,13,14,15,17,20,21,24,25 and 29

6. Hardware:

Four input/output PCI cards are used in the "AGN Computer". The operating system is installed on a RAID hard drives. This would ensure safety of recorded data in case of hard drive failure.

Four cards used are as follows:

• PCI-WDT500 - contains a watchdog timer and computer power supply monitor

• PCI-AOB4/12 - contains double-buffered digital-to-analog converters (DACs) that provide independent analog output channels of 12-bit resolution. In addition contains 16 digital I/O Lines.

• CIO-DIO24 - digital I/O board

• PCI QUAD-04 DAS - is used to receive signals from optical Encoders located in the four rod drives.

The design for the console upgrade was built upon the existing logic. Existing logic of the console controls has been updated in implementation using Data acquisition and software systems within the "AGN Computer". Channel 3, Channel 2 and Period information are provided through the "AGN computer". Digital inputs received by the "AGN Computer" are as follows: Engage, rod down, carriage down, fine rod down, carriage up. Calibration programs have been created and are initialized at every startup of the system. For safety, the program is implemented using basic logic of the original console. A system timer keeps track of the delay of each operation. In case of extra delay or failure of the timer, a watchdog timer located on a separate PCI card will restart the system (creating a loss of signal, which in turn will SCRAM the reactor). Test program has been created in order to test the operations of the program including the test of the timer itself.

Following are the alarm output provided by the computer: Log Low, Log Power, Linear Low, Linear Power, Period and Scram. "Scram" alarm output by the computer is in parallel with hardwired Scram signal. All of the alarm outputs from the computer will automatically trigger the Scram at the same time. Alarm output is set "low" when active; this ensures scram in a case of a signal loss.

7. The LCO for the skirt monitor scram will be placed in section 3.2 vice 3.4 of the technical specifications. The LCO will be inserted and numbered as 3.2.i. The remaining three specifications will be renumbered 3.2.j, 3.2.k, and 3.2.1 respectively.

8. Period Meter data is processed by the "AGN Computer" with a 0.1 second delay, and every 0.1 second. The VBA function first filters out any extremely small log power values (to keep the logo function numerically stable) and then averages 20 recent power values. Then the logo calculates the reactor period, and sends it (after converting to a proper binary form) to the external indicator. If the period value is shorter than 5s, it sets a flag to scram the reactor. The function reads as follows:

I0 ' 12 ' 14 1 16 IS8 110 ' 112 ' 114 ' 116 ' 118 Private Sub PeriodMeter(LogPower, TimeStamp)

Static Readings(100) As Single Static T..a..mp 00) As Single Static Fitter(100) As Single Dim FilterSteps As Integer ' 1 to 100 CurrentPower = LogPower If CurrentPower < 0.000000000000001 Then CurrentPower = 0.000000000000001 Readings(O) = CurrentPower T~tn3p(O) TimeStamp l-lmeSpan =40 If Readings(TimeSpan) < 0.00000000000001 Then Readings(TimeSpan) = 0.00000000000001 FilterSteps = 20 Filter(O) = Readings(O) / Readings(TimeSpan)

For i = FilterSteps To I Step -1 PF = PF + Fitter(i - 1)

Fifter(i) = Filter(i - 1)

Next i FilterOut = PF / FilterSteps x = Log(FilterOut)

If Abs(x) < 0.000000000000001 Then x = 0.000000000000001 Period = CrStamp(0) - TStamp(TimeSpan)) / x Filter(0) = Period For i = 100 To 1 Step -1 'UPDATE ARRAYS Readings(i) = Readings(i - 1)

Next TStap.) . - 1)

If Abs(Period) < 0.000000000001 Then Period = 0.000000000001 v = 3.1 * (4095 - 376) 1 Period + 376 If v > 4095 Then v = 4095 If v <0 Then v = 0 b = 255 And Int(v /256) a = 255 And Int(v)

OutPortB AlOBase + 4, a OutPortB AlOBase + 5, b If PeriodBypass = True Then Exit Sub If Period > 0 And Period --- 5 Then PeriodAlarm = True Else PeriodAlarm = False End Sub

9. Output of Channel #3 detector is first received by the picoammeter. From the picoarnmeter the data is received by the "AGN computer" through serial interface using PCI Data acquisition card. Every 0.1 seconds the value is compared to the set point.

Given the worst case of detector output arriving to the input of the computer at the beginning of the new cycle, there can be up to 0.2 second delay before scram signal is initiated. The system timer is constantly compared to watchdog timer. In a case there is a greater delay detected during a cycle, scram signal will be generated. Processor demand and use is maintained below 20% use. The processing speed of the processor is ensured to be greater than the computation demand of the system. The processor installed is 3.0 Ghz Dual core capable of more than 2000 million instructions per second using visual basic compiler. The operating system is capable of multithreading, which allows to send separate instructions to both cores of the processor simultaneously.

Other:

Channel 1 is displayed directly from the counter.

Linear power, log channel and period meter data encounter a 0.1 second delay. The program is run on a set timer. Every 0.1 seconds the timer sends an interrupt to the processor, which in turn will process the data for linear power, log channel and period meter. With a 6 second delay linear graph, log graph, time line, linear trace and log trace are updated. Digital inputs, watchdog and alarm outputs are processed with a delay of less than 0.1 seconds.

11. Previously, when an out of specification input was received from the shield water level float, shield water temperature probe the interlock relay would open removing power from the scram system, thus causing a reactor scram or preventing a reactor start up until the condition was clear. During the console upgrade, the interlock relay was not incorporated.

Instead the scram functions that were previously managed by the interlock relay have been incorporated on the scram circuit.

13. Modify LCO 3.2.1 (formerly 3.2.k) 3.2.1 The watchdog timer shall be operable during reactor operations.

The AGN computer is protected against software failure through use of a watchdog counter/timer circuit. The method used by the WDG-CSM card to detect loss of computer function is as follows:

1. A type 82C54 counter/timer is used. This chip contains three 16-bit counters. A number greater than zero is set into the chip's counters. The Watchdog is armed by software command and both counters begin counting down. As long as the computer is operating properly, both counters will be periodically reloaded to their original

programmed values by the application program before both counters have counted down to zero.

2. If the software fails to reload the counters, then both counters continue counting until zero is reached (timeout). When the counters 0 and 1 reach zero, either the power-good line is held low for approximately 16 milliseconds (performing a hardware reset) through a relay contact, or external lines (either relay contacts or a de-bounced opto-isolated switch) are active. When a reset condition occurs, the reset circuit is active until a reset pulse returns from the system bus or power is cycled to the system.

14. When members of the general public are present in the reactor room (students) during operations, the power level is limited to ensure that ALARA principles are followed.

Students are present in the reactor room during operation for only two reasons: during laboratory experiments and student reactor operations. Prior to students entering the reactor room during operation, lab specific training is held to ensure that ALARA principles are followed and that the students are aware of the radiation field.

Additionally, the methods of time, distance, and shielding are emphasized to the students.

Students are supervised at all times when inside the reactor room.

During classroom experiments students adjust relative detector positions in an access port and limit the time that they are near the reactor while operating. After adjustments are made, the students leave the reactor room. Classroom experiments that involve students in the reactor room are conducted at powers below 1 watt; typically less than 500 milliwatts to ensure ALARA principles are followed. Students also participate in reactor operations at the control console during individual operating periods of less than one hour. Student operations are conducted with the student at the control console during the entire period.

Facility phantom monitors consist of 1 gallon water jugs with a dosimeter badge attached to monitor for general radiation levels in the reactor room and adjacent room. One additional dosimeter is located at the control console to monitor radiation levels at the console.

Facility personnel constitute any employee that is directly involved with operations of the AGN reactor which includes all licensed senior reactor operators (SRO), reactor operators (RO), and reactor trainees. Facility personnel are required to complete a radiation safety course prior to issuance of dosimetry. Texas A&M Environmental Health

& Safety provides this course to personnel upon request and also requires an on-line refresher course every two years. Personnel are badged with dosimeters capable of detecting photon, beta, and neutron exposure. Currently the University employs Luxel+

dosimetry services to monitor personnel. Additionally, all facility personnel also wear a direct reading dosimeter, commonly referred to as a pocket ion chamber (PIC). Currently the University uses Arrow-tech direct-reading dosimeter with sapphire window, model W138 (0-200mR).

15. From 10 CFR Part 20 Appendix B, Table 2, Column 1, the effluent concentration of 1 x 10-8 lICi/ml. As stated in 10 CFR Part 20 Appendix B, "The concentration values given in Columns 1 and 2 of Table 2 are equivalent to the radionuclide concentrations which, if inhaled or ingested continuously over the course of a year, would produce a total effective dose equivalent of 0.05 rem (50 millirem or 0.5 millisieverts)." Thus the following conversion factor will be used to convert the full power equilibrium concentration of Ar-41 in the reactor room to annual doses for occupational workers and members of the public:

50 mrem yr 1 *10-8 Im An occupational worker exposed to the 5 watt thermal power equilibrium Ar-41 concentration of 2.56 x 10J° "tCi/ml in the reactor room for 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> per year will receive an annual dose of 0.292 mrem from Ar-41 as calculated below:

/_lyr. ) ( 10lltCi'/ 50 mrem

___yr___l =.9me 2000 hr ) * ( 2.56. 1010 i - 0.292 mrem The annual dose from Ar-41 received by a member of the public standing in the reactor room exposed to the 5 watt thermal power equilibrium Ar-41 concentration continuously for one year is 1.28 mrem as calculated below:

50 mrem 1 year *256" 10-10 *m = 1.28 mrem (2.5 Ii~) (1 1O8 m l)

17. Students are present in the reactor room during operation for only two reasons: laboratory experiments and reactor training operations. During these times power level is limited to ensure that ALARA principles are followed. Prior to students entering the reactor room during operation, lab specific training is held to ensure that ALARA principles are followed and that the students are aware of the radiation field. Additionally, the methods of time, distance, and shielding are emphasized to the students. Students are supervised at all times when inside the reactor room and are issued a direct reading dosimeter prior to entry.

During student training operations, the reactor operator is responsible to ensure that the student does not leave the area behind the console. This ensures that the student is in a low radiation field during operations. For laboratory experiments, the course instructor or the senior reactor operator directly supervises any student that enters the reactor room.

20. Pursuant to License Amendment 10 the 2% step reactivity increase was not considered in the analysis related to dose limits. As stated in the Safety Evaluation Report for Amendment 10, "the most severe accident that could be postulated from operation of the AGN-201M reactor at 5 watts would result from the instantaneous addition of 1% delta k/k in reactivity."

21. Modify T.S. 1.19 1.19 Reactor Shutdown - The reactor shall be considered shutdown if it is subcritical by at least one dollar (0.75% Ak/k) in the reference core condition with the reactivity worth of all installed experiments included and the following conditions exist:

(a) All control rods fully withdrawn from the core and (b) The console key switch is in the off position, and the key is removed from the lock and under control of a licensed operator.

24. The rod drive cable interlock was originally intended to prevent operation of the reactor with a rod drive Amphenol disconnected. Without the rod drive cable interlock the operator would conceivably attempt to startup the reactor without control of the disconnected rod. There would be no other way for the operator to know that the rod cable was unplugged other than this relay. The upgraded control console solves this problem with a digital substitute. With the current console design, the operator will know that a rod is unplugged prior to startup by simply looking at the computer screen. If a rod cable is unplugged, none of the associated indications (rod engaged, rod down, rod position) will be present for the affected rod. If the rod plug were to be unplugged during reactor operation, the affected rod would scram due to a loss of magnet power. Given the abnormal condition, the operator would perform a manual scram of the reactor. This worst case scenario would result in a negative reactivity insertion and would be considered fail safe.

The relay chassis interlock was associated with the actual Amphenol plug that connected the interlock system to the scram system. If the Amphenol was unplugged the interlock system would no longer input into the scram system. Since several protective features were previously associated with the interlock system, their protective function would be removed. These protective features have been incorporated into a hardwired system, with no "quick" disconnect. As a result of the hard wiring of these protective features, the relay chassis interlock was not incorporated into the new control console.

25. The seismic displacement safety channel is not calibrated but an operability check is performed annually. This test is consistent with the other three AGN reactor facilities.

This is done by using mechanical force (a rubber mallet) to perturb the earthquake sensor.

In this manner the alarm circuit will energize and a scram signal is received. This safety feature is an original design feature of the AGN reactor and is described by Biehl in Elementary Reactor Experimentationas:

In the event of an earthquake of horizontal amplitude greater than 1/16 inch, the earthquake switch will shut down the reactor. The safety rods are spring loaded and operate very nearly independently of the gravitational field orientation. Thus this safety system makes the reactor safe even in a major tremor.

29. Add T.S. 3.4.f(3) 3.4.f(3) The core tank shall be sealed during reactor operations.

This LCO will be verified during the prestart up checklist by verifying that the thermal column is in place.