ML20002B003
| ML20002B003 | |
| Person / Time | |
|---|---|
| Site: | University of Illinois |
| Issue date: | 12/05/1980 |
| From: | Beck G, Milavickas L ILLINOIS, UNIV. OF, URBANA, IL |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8012090303 | |
| Download: ML20002B003 (4) | |
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Nuclear Engineering Program fN."[2$$i[.ifi"7$'
December 5,1980 (217) ?33 2295 Director Division of Reactor Licensing
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U. S. Nuclear Regulatory Commission Washington, D. C.
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Dear Sir:
SUBJECT:
Abnormal occurrence at the University of Illinois Advanced -
TRIGA Reactor, License No R-115.
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On toy.- 26, 1980, the reactor was operated for about 20 minutes in 6
violation of a Limiting Condition of Operation with respect to the required instrumentation in Section 3.4 of the Technical Specifications. The instruments that were not operable were the measuring channels that indicate the fuel temperature. The loss of this system also caused a malfunction of a required safety system component given in Section 3.5 of the Technical Specifications, namely the fuel element temperature scram system.
DISCUSSION At about 4:30 pm on Nov. 26, 1980, the licensed operator in charge of the operation noted that he had no fuel temperature indications on the fuel temperature meters. The reactor gower was at 1.2 MW, at which time the normal fuel temperature is about 360-370 C.
The operator glanced at a pilot strip receptacle that gives power to the fuel temperature circuit and noted that the switch was in the off-position. This was turned on and a scram occurred from the fuel temperature meters. Turning on the switch resulted in an over-shoot of the fuel temperature indicator pens, allowing the pens to reach the scram set point at 600 C.
When the abnormality was noted, the operator looked at the pilot strip receptacle because a digital voltmeter had been unplugged from the same 4
receptacle by a student previous to the occurrence. The student apparently turned off the switch when removing the digital voltmeter.
Normally the digital voltmeter is removed by the operator. !!owever, at the time of the occurrence the operator was occupied with other duties.
A report to Region III, Division of Inspection and Enforcement was made on November 28, 1980. Unfortunately this was not done within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> since Nov. 27 was Thanksgiving Day and the laboratory was closed. After a short analysis on Nov. 28, a decision was made that an abnormal occurrence did happen and hence licensing was notified.
CORRECTIVE ACTION:
The major corrective action stems from the fact that the pilot strip receptacle was used to power other systems and was accessible in the control room. As a first step, the power for the fuel temperature instrumentation was moved to the back of the console where only licensed individuals are allowed to make changes.
Plans are new to use the single receptacle that 6 yl 5
sono 90 sos
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powers the control console. A plug with an add-a-line feature will be 3
utilized. These plugs will be fixed so that if the cable is inadvertently
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pulled, power to the console will be lost and a reactor shutdown would occur.
i On the positive side, this system will allow a planned removal of the fuel i
. temperature system for maintenance without removing power to the control j.
console.
Ihe change will be completed by December 5,1980.
j NOTE:
The fuel temperature circuit is unique to the Advanced TRIGA Reactor 1
at the University of Illinois. A change was made in 1974 because of
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difficulties in determing accurate readings with a new instrumented fuel element. 'Ihe thermocouples of this element had higher resistance readings j
that previous instrumented fuel elements which were not compatible with j
the original circuit. A complete discussion and review of this change can be found in the 1974 Annual Report.
A copy of the pertinent section of this Annual Report is attached.
J Signed:
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Gerald P. Beck, Reactor Supervisor C
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L. R. Milavickas, Chairman I
Nuclear Reactor Committee s
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CC: Region III, Office of Inspection and Enforcement 4
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i From: Annual Report, Illinois Advanced TRIGA Reactor - Feb. 28, 1975 License No. R-115 Docket No.
50-151 page S V.
CONDITIONS UNDER SECTION 50.59 _of _10 CFR _50 A.
Changes to_ System 1.
Emergency Core Spray - Float Switch Circuitry Following the Regulatory Inspection in 1973 and the changes that were initiated to. clarify portions of the Technical Specifications (Change No. 3 - December 21, 1973), a review of the systems revealed that the float switch was not initially wired to perform one of its required functions - initiation of the core spr./.
As a result, the circuitry was 3
changed so that this switch will initiate 3 gpm emergency spray in addition to causing a reactor scram and isolating the reactor tank.
2.
Fuel Temperature Circuit When the additional instrument fuel element (Reference to p. 2 of this report) was obtained, it was found that the resistances of the thermocouples were considerably higher than the original elements.
This came from a design 4
change that was made by the manufacturer to possible improve the use of these elements before the thermocouple output is lost. Unfortunately, this increase in the resistance caused a slight mismatch with the original design of the 4
fuel temperature circuit.
When these thermocouples were connected into the circuit, the output indicated by the meter was about 10% less than the actual output.
Thus before using these thermocouples in the safety circuit (fuel temperature scrams), it was necessary to make changes to correct the differences.
A buffer was placed between the thermoenuple leads and the output indication so that a calibration of the meters would be independent of the thermocouple resistance.
The buffer allows an operator to check the actual millivolt output of a thermocouple without by-passing the reading on the meter.
(Reference is made to Item VII on Change No. 3, Decemb er 21, 1973 that gave permission to by-pass one of the temperature scram circuits while making a channel check on-the other temperature indication.
With the above change, this is not longer required.)
During checks on the fuel temperature scram function, the temperature switch is placed in another position to obtain a signal to the meter. As a result it is possible for the operator to leave the switch in this position rather than returning it to the operate position.
'To lessen the possibility of this occurring, a red light was placed on the face plate of the switch and is on when the switch is not in the operate position. This added indication.
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page 9 was installed when the above change was made.
Evaluation This change was approved by the Nuclear Reactor Committee and was considered to be a change that would not require prior Commission authoritation (Section 50.59 of 10 CFR).
The addition of the buffer did not change the intende'd safety function of the circuit.
Although the scram set points might have been lowered when the new instrumented fuel element was connected to the original circuit, this procedural change is not necessary with the present circuit.
The ability to check the millivolt output without disengaging the scram function and the addition of the red light indicator were both considered to be improvements on the original design.
B.
Changes in, Procedures 1.
Rules and Regulations The Rules 'and Regulations for the Operation of the Nuclear Reactor Laboratory were reviewed by the Nuclear Reactor Committee and a Revised Edition No. 10 was approved.
The changes that were made included:
(1) A correction of Reactor Operation criteria as per Change No. 3 to the Technical Specifications; (2) A statement that two licensed operators are required for concurrent operation of the TRIGA and LOPRA.
(Although this policy had been followed since the initial start-up of LOPRA, a statement to this effect had not been included in the Rules and Regulations.); and (3) A requirement that any experiment using the LOPRA for operations above 1.0 kW or in the pulsing mode should be approved by the Committee.
Evaluation: An evaluation of these changes clearly indicates that there would be no requirement to obtain prior Commission authorization.
2.
Isolation Valves Following the difficulties with the isolation valves (page 5 of this report), a Temporary Procedure was approved for operations without these valves.
This was done since it was at first thought that completing the repairs might involve a considerable time. Although a procedure had been approved in 1973 (Reference to page 5 of 1973 Annual Report), a more comprehensive cet was evaluated and approved by the Nuclear Reactor Committee.
Evaluation: The basic procedure and the evaluation of same is contained in the 'Information Letter to DRL - September 1974 It was concluded that prior i
Commission authori:ation was not warranted since the operation of the valves
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