ML20245D693

Annual Rept Illinois Lopra Reactor Aug 1987 - Jul 1988

ML20245D693
Person / Time
Site:	05000356
Issue date:	07/31/1988
From:	Miley G, Pohlod C, Williams J ILLINOIS, UNIV. OF, URBANA, IL
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8810050155
Download: ML20245D693 (8)

Text

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' bniversity Of If 'OiS Department cf College of Engineering

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h at Urbana-Champaign 214 Nuclear Engineering 217 333 2295

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Laboratory l.

103 South Goodwin Avenue l

4 Urbana, IL 61801 2984 l.

9-29-88 1

Director l-l.

Office of Nuclear Reactor Reoulation l

U.S. Nuclear Regulatory Commission Documents Control Room Washington D.C. 20555

Subject:

Annual Report, LOPRA Reactor License No. R-117 Docket No. 50-356 The following is written to comply with the requirement of Section 6.7.f of the Technical Specifications and conditions of 50.59 of 10 CFR 50. The outline follows the numbered sequence of Section 6.7.f of the Technical Specifications.

Yours truly, 0

2 Pa t a CraioS.hohlod, Reactor Supervisor

,yguk kr.JohnG. Williams, Reactor Director

/Chairmh, Nuclear Reac[ tor

[r.beo[reH.Miley, Committee 1

AA Y

. '.M4

+ Dr. Barc G.

nes, Head, De rtme of Nuclear Engineering f0f 1

1 8810050155 880731

{DR ADOCK 05000356 PDC

ANNUAL HEPORT Auoust 1. 1987 - July 31 1988 ILLINOIS LOPRA REACTOR Facility License R-117 1.

SUMMARY

OF OPERATING EXPERIENCE The reactor was scheduled for operations a total of 53 hours6.134259e-4 days <br />0.0147 hours <br />8.763227e-5 weeks <br />2.01665e-5 months <br /> and was in I

actual operation a total of 21.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />. Usaae was similar to what it was in i

the previous reporting period although the pattern of usage was different than the last reporting period. Student Experiments include an " Approach to Critical " fuel loading experiment in the LOPRA and the determination of k

Control Rod Worth by sub critical multiplication. The time involved with l

Surveillance Requirements includes power calibrations, control rod worth

)

determinations and fuel inspections. Scheduled time includes time for activities such as fuel inspections which don't require actual operation of the LOPRA. Over 99.9 % of the enerty listed in Section 11 was oenerated during the two power calibrations performed during this reporting period.

Maintenance performed in this reporting period includes the removal and repair of the LOPRA Compensated lon Chamber (CIC) and the repair of the pulley system used to position the LDPRA Assembly relative to the thermal column.

31 %

Maintenance 15 %

Student Experiments Surveillance Requirements 45 %

Laboratory Measurements j9ff 100 %

Total

.ABULATION OF OPERATIONS T

11.

Hours Critical

• and Eneroy 21.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> 6.33 kW-hrs

• This time includes that for loading fuel elements during the Approach to Critical experiment and sub-critical time durino the control rod calibration. The control rods are calibrated using sub-critical multiplication so that a large portion of the experiment is done with the reactor sub-critical. The actual critical time was about ?.2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or 6 % of the above time.

III. EMERGENCY SHUTDOWNS AND INADVERTENT SCRAMS There was one unplanned scram and no emergency shutdowns during this period. The unplanned scram was due to a trainee (student) switchina error.

The trainee mid-positioned the Range Selector Switch on the Linear Power Channel, resultino in an up-scale response by the Linear Channel Chart Recorder which initiated the scram. Students are routinely advised to make rance changes smartly to avoid switchina problems.

IV.

MAINTENANCE Maintenance on the LOPRA included the removal, repair and re-installation of the LOPRA CIC. This was accomplished by partially unloading the LOPRA core and sendino a diver into the Bulk Shieldina Tank to first remove and later re-l l

- c' -

' install the Guide lube for the LOPRA CIC. The final report on this evolution is attached as an addendum to this report.

Another significant item of maintenance performed during this reportino period was the repair of the pulley system which is used to position the LOPRA core relative to the thermal column.

Several years ago, the anchors that held the pulley system in place pulled away from the south wall and the bottom of the Bulk Shieldina Tank.

WE t7 this occurred, the LOPRA Assembly was manually positioned to allow enough clearance for the boral curtain to be raised and lowered to de-couple the LOPHA when it was shutdown. Four graphite dummy elements were added to the 1-row of the LOPRA to oain back some of the reactivity lost due to the positioning of the LOPRA assembly. This provided twelve to fifteen cents excess reactivity for operation of the LOPRA.

Typically fourteen cents of excess reactivity is needed for 10 kW operation of the LOPRA.

The new pulley system is anchored to the south wall near the top of the Bulk Shieldina Tank and held in place by the tracks upon which the LOPRA Assembly is moved back and forth, lhe LOPRA is free to move over its entire rance of travel.

The last item of maintenance performed durino the reportino period was the overhaul of the Poison Control Rod Position Indication system. This system relied on an obsolete servo driver similar to the one which used to drive the Poison Control Rod servo motor. The replacement for this obsolete driver uses one-tenth the power of the old unit and is electronically superior to the old driver. This unit is less susceptible to electronic noise than the old unit.

V.

CONDITIONS UNDER SECTION 50.59 OF 10 CFR 50 There were no changes to procedures or new experiments during this period. The excess reactivity of the LOPRA core was increased to about 22 cents during this reporting period as a result of the repair of the pulley system f or mnvino the LOPRA Assembly relative to the thermal column. This will allow the flexibility to use the pulsing feature of the LOPRA. This increase leaves the excess reactivity well below the maximum Technical Specification limit of sixty cents.

VI., Vll., Vill.,

RADj0 ACTIVITY Because of the lower power and infrequent use of the LOPRA, its operation does not contribute to the release of effluents. Personnel radiation exposures for the laboratory are oiven in the Annual Report for the Advanced TRIGA Reactor, License No. R-ll5, Docket No. 50-151, dated February 29, 1988.

J J

i

11/20/B'/

lo:

Nuclear Heactor Committee Froms,Craio S. Pohlod Heactor Supervisor bubi: Hemoval of the Compensated lon Chamber (CIC) from the LOPRA Recent operation of the LOPRA CIC has produced a noisy and occasionally erratic sional at hioh power. Operation of the CIC at low power has remained satisfactory.

This behavior sugoests that either the CIC connectors need replacement-or the CIC is becinnino to fail. Attempts to remove the CIC have been unsuccessful.

Deterioration of a piece of rubber which was wrapped around the CIC to facilitate easy removal of the CIC f rom the cuide tube. appears to be the problem. 1he rubber has become brittle and attempts to. move the CIC have caused the rubber to become wedoed tightly between the CIC and the cuide tube, in order to remove the CIC oulde tube, four bolts must be removed from the LOPRA crid plate.

Hemoval of the CIC and ouide tube can be accomplished by moving the

.Northrop Fuel Elements (NFEs) to the TRIGA tank, movino the LOPHA elements into the lruck Bay storace pits, placing a camma shield in front of the Bulk Shielding Tank (BST) Thermal Column and drainino the water from the BST or by placino a gamma shield in front of the BST Thermal Column, movino the NFEs to the southwest corner of the BST and sending down a diver.

For obvious reasons the latter is the most practical approach to the removal of the CIC and its guide tube. The following is a description of how the removal of the CIC and ouide tube will be accomplished.

The following precautions will be taken with regard to removal of the CIC and its cuide tube

1. The NFEs will be moved to the southwest corner of the BST.

2. The area around the southwest corner of the BSI on the Reactor Bay floor will be roped off and identified as a Hioh Radiation Area.

3. The LOPRA Assembly will be moved back from the BST Thermal Column a s

far as practical.

4. A 1" sheet of lead which measures 2' by 3' will be suspended from the l

Overhead Crane and positioned between the BSI Thermal Column and the LOPRA.

l l

b. lhe diver will use an air tank and reculator from Midwest Scuba in Champaign and he shall be certified by the National Association at Underwater Instructors (NAUI).

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6. 1he diver will verify that the air reculator is operable and that there is sufficient air in the tank to accomplish the removal of t h e CIC and its cuide tube and the re-installation of the CIC oulde tube.

Time of the dive will be monitored by a third party.

7. lhe diver shall have a safety line appropriately attached during t h e dive. This line will be attended during the time the diver is in the BSI.

8. 1he H and I rows of the LOPRA Assembiv will be empty except for t h e blue topped graphite dummy elements in the H-3 and H-10 positions.

9. The diver shall wear film badoes, finoer rinos and pocket dosimeters so that the diver's radiation dose can be adequately determined.

10. Efforts to characterize the radiation fields around the LOPRA will continue up to and including the time that the 1" lead sheet between the BST Thermal Column and the LOPRA Assembly is installed.

The diver will enter the BST, remove the four bolts which hold the CIC ouide tube in place, ensure that the CIC and its cuide tube are free of the LOPRA grid plate and exit the BST. If the bolts cannot be removed, attempts will be made to free the CIC from the guide tube by loosenino the clamp around the top of the cuide tube and pulling the CIC out of the cuide tube.

After the LOPRA CIC has been removed from the guide tube and the guide tube has been refurbished, the diver will re-enter the BST, re-install the cuide tube and exit the BST.

l Measurements made around the LOPRA indicate that most of the radiation field at the point where the diver will work is due to camma radiation from the 1RIGA Core streamino throuch the BST Thermal Column. The installation of the 1" thick sheet of lead shrAld reduce the dose from the TRIGA Core by about 70%. Removal of the LOPRA fuel elements is considered unwise as these elements are relatively " cold" and thus removing them would reduce the shieldino more than the source term.

Crude calculations based on the measured doses from the LOPRA fuel elements suqQest that about 30% of the measured radiation field existing at the point where the CIC and cuide tube will be unbolted is due to the LOPRA fuel. With the 1" lead sheet installed the expected radiation field should be 200-400 mR/ hour.

A dose equivalent of 200 mrem is acceptable to the diver.

1 The Health Physicist's evaluation of this evolution is attached.

/

HEALTH PHYSICS APPRAISAL FOR the REMOVAL of the LOPRA COMPENSATED l

1 ION CHAMBER (CIC)

1. Surveys performed using calibrated pocket dosimeters and the"Dosipole".

Cdie detector indicate that the immediate location where the bolts are to be removed are less than or equal to 12 mR/hr deep exposure rate equivalent. However, within 1-2 feet from the bolt locations, exposure rate is approximately 925 mR/hr due to ganana radiation f rom the Triga core and with all fuel elements moved to the southwest corner of the pool. A major portion of an individual's body would lie within this field.

2. It is anticipated that the removal of the 4 bolts attaching CIC guide tube to the LOPRA grid plate will take from 5 to 20 minutes to accomplish while the individual is in this field. After the installa-tion of the lead shield, it is anticipated that the field strength in-tensity will be reduced to approximately 400 mR/hr, using the upper exposure rate as detailed in the attached description. Thus, there is a potential for this individual to receive up to 133 mrem deep dose equivalent as a result of this operation. The maximum whole body dose equivalent for this operation will be 200 mrem.

3. The individual who will be performing this operation is Robert Peach, a reactor operator. His current deep dose equivalent for the fourth quarter is 30 mrem recorded in October, and an estimated upper dose of 60 mrem for the current month of November. It is planned to have a film badge and a pocket dosimeter, sealed together in a plastic bag, and worn at each of the following locations:

a. Head, facing source term.

b. Mid-chest, facing source term,

c. Waist, facing source term.

The normally issued film badge will be worn on the waist, which will be within the region where the highest exposure rate is anticipated.

An additional pocket dostmeter will be worn on Peach's ankle. A ring badge is to be worn on each hand also.

4. Measurements using pocket dosimeters and an ion chamber set on integrate mode, sealed in plastic, will be contirued after Installa-tion of the shield and removal of the H and I rows.

5. Robert Peach will be advised that if there are any problems in bolt removal, he will return to the surface where the problem will be discussed and resolved before submerging again.

6.

In accordance with the UlUC Campus Radiation Safety Manual, approval for this operation is requested since the potential exists for this individual rec Ive more than 100 mrem within a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period.

Prepared By: M Or

. Reactor Health Physicist DATE: 8 b

Approved By:

, Campus RSO DATE:

N

~3 I

3/87 Reviewed By:

, Rx Supervisor DATE:

u H A ooz

l i

11/20/87 To:

Nuclear Reactor Committee From: Craig S. Pohlod Reactor Supervisor Subis Removal of the Compensated Ion Chamber (CIC) from the LOPRA Recent operation of the LOPRA CIC has produced a noisy and occasionally erratic signal at high power. Operation of the CIC at low power has remained satisfactory. This behavior suqqests that either the CIC connectors need replacement or the CIC is beginning to fail. Attempts to remove the CIC have been unsuccessful.

Deterioration of a piece of rubber which was wrapped around the CIC to facilitate easy removal of the CIC from the guide tube appears to be the problem. The rubber has become brittle and attempts to move the CIC have caused the rubber to become wedged tightly between the CIC and the guide tube.

In order to remove the CIC quide tube, four bolts must be removed from the LOPRA grid plate.

Removal of the CIC and guide tube can be accomplished by moving the Northrop Fuel Elements (NFEs) to the TRIGA tank, moving the LOPRA elements into the Truck Bay storage pits, placing a gamma shield in front of the Bulk Shielding Tank (BST) Thermal Column and draining the water from the BST or by placing a gamma shield in front of the BST Thermal Column, moving the NFEs to the southwest corner of the BST and sending down a diver.

For obvious reasons the latter is the most practical approach to the removal of the CIC and its guide tube. The following is a description of how the removal of the CIC and guide tube will be accomplished.

The following precautions will be taken with regard to removal of the CIC and its guide tube

1. The NFEs will be moved to the southwest corner of the BST.

2. The area around the southwest corner of the BST on the Reactor Bay floor will be roped off and identified as a Hioh Radiation Area.

3. The LOPRA Assembly will be moved back from the BST Thermal Column a s

far as practical.

4. A 1" sheet of lead which measures 2' by 3' will be suspended from the Overhead Crane and positioned between the BST Thermal Column and the LOPRA.

5. The diver will use an air tank and reoulator from Midwest Scuba in Champaign and he shall be certified by tne National Association of Underwater Instructors (NAUI).

2

6. The diver will verify that the air reculator is operable and that there is sufficient air in the tank to accomplish the removal of t h e CIC and its cuide tube and the re-installation of the CIC quide tube.

Time of the dive will be monitored by a third party.

i

7. The diver shall have a safety line appropriately attacned during t h e dive. This line will be attended during the time the diver is in the BST.

8. The H and I rows of the LOPRA Assembly will be empty except for t h e blue topped graphite dummy elements in the H-3 and H-10 positions.

9. The diver shall wear film badoes, finger rings and pocket dosimeters so that the diver's radiation dose can be adequately determined.

10. Efforts to characterize the radiation fields around the LOPRA will continue up to and including the time that the 1" lead sheet between the BST Thermal Column and the LOPRA Assembly is installed.

The diver will enter the BST, remove the four bolts which hold the CIC cuide tube in place, ensure that the CIC and its cuide tube are free of the LOPRA grid plate and exit the BST. If the bolts cannot be removed, attempts will be made to free the CIC from the cuide tube by loosening the clamp around the top of the guide tube and pulling the CIC out of the guide tube.

After the LOPRA CIC has been removed from the guide tube and the guide tube has been refurbished, the diver will re-enter the BST, re-install the guide tube and exit the BST.

Measurements made around the LOPRA indicate that most of the radiation field at the point where the diver will work is due to gamma radiation from the TRIGA Core streaming through the BST Thermal Column. The installation of the 1" thick sheet of lead should reduce the dose from the TRIGA Core by about 70%. Removal of the LOPRA fuel elements is considered unwise as these elements are relatively " cold" and thus removing them would reduce the shielding more than the source term.

Crude calculations based on the measured doses from the LOPRA fuel elements suqqest that about 30% of the measured radiation field existing at the point where the CIC and guide tube will be unbolted is due to the LOPRA fuel. With the 1" lead sheet installed the expected radiation field should be 200-400 mR/ hour.

A dose equivalent of 200 mrem is acceptable to the diver.

The Health Physicist's evaluation of this evolution is attached.

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