ML19340A637
| ML19340A637 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/01/1976 |
| From: | Bolger R COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML19340A635 | List: |
| References | |
| NUDOCS 8009020582 | |
| Download: ML19340A637 (10) | |
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Commonwealth Edison One First Nationat Plaza. Chicago. Illinois Address Reply to: Post Offico Box 767 Chicago. lilinois 60690 l
June 1, 1976 Mr. James G. Keppler Regional Director - Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137
Subject:
Dresden Station Units 1, 2, and 3 IE Inspection Reports 50-10/76-07, 50-237/76-07, and 50-249/76-06 NRC Dkts. 50-10, 5 0- 2 3 , and 50-249
Dear Mr. Keppler:
1 Enclosed is the response to the subject IE Inspection Reports transmitted by your letter dated April 28, 1976.
An i
additional week to prepare the response was requested from your office on May 21, 1976.
Please contact this office if you are in need of any additional information.
Very truly yours, 4
R.
L. ;3olge Assistant Vice President Enclosure I
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INFRACTION NO. 1 t
Refueling Interlock Surveillance - Drcsden Unit 2 I
~ l Discussion:
At 1330 houts on March 22, 1976, refueling operations were curtailed due to a broken wire on the refueling grapple thumb latch.
The thumb latch is utilized as a quick brake du ring upward and down -
ward grapple movements.
The broken wire caused a short in the circuitry which prohibited upward or downward movement. A non-safety related work request was issued (W.R. 2522) to repair the wire.
The electrician repaired the wire and found that a set of relay contacts for the fuel hoist overload trip were damaged as a result of the grounded broken wire.
The relay was replaced and the grapple was placed back in service without testing at 1525 hours0.0177 days <br />0.424 hours <br />0.00252 weeks <br />5.802625e-4 months <br /> on March 22, 1976.
At 0802 hours0.00928 days <br />0.223 hours <br />0.00133 weeks <br />3.05161e-4 months <br /> on March 23, 1976, the reactor mode switch was placed in shutdown and remained in shutdown until 0001 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> on March 28, 1976, l
whan tha -ada r" itch ass again switched to refuel. At 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on u
j the,same day,,the refueling prerequisites checklist was completed, which included the refueling interlock check (800-S-I).
l The maintenance and testing associated with Work Request 2522 were performed in accordance with procedure. Accotding to procedure, the determination of whether work is safety or non-safety related and the testing requirements is the responsibility of an Operating Engineer.
For Work Request 2522, the Operating Engineer determined that the work was not safety related and that no post maintenance testing was required.
The work was completed in accordance with these determinations.
In retrospect with knowledge of the exact nature of the repair performed, it appears that the repair was associated with interlocks e
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on the fuel hoist operation (raise and lower). These interlocks do not restrict refteling procedures such that there is assurance that I
inadvertent criticality does not occur as discussed in the Technical Specification Bases 3.10/4.10A; however, these interlocks do perform a prote.ctive function and are included in the Refueling Interlock Check, procedure 800-S-I.
Based on the information discussed in' previous paragraphs, we have concluded that Technical Specification 4.10.A does not require testing following the work performed under Work Reg test 2522.
It is i
reccgnized that due to the complex nature of many plant systems, Work Requests that initially appear to be non-safety related have the poten-tial for involving safety related work. For this reason, we considered the following corrective actions appropriate.
Corrective Action:
The repair was completed March 23, 1976. A satisfactory surveil-i lance of the refueling grapple interlocks was completed March 28, 1976.
Corrective Action to Avoid Recurrence:
This item of noncompliance will be reviewed with the Station Operating Er.gineers to p. ovide additional assurance that similar Work Requests will be thoroughly evaluated for possible indirect safety sigsificance and that appropriate tests will be required.
Date of Full Compliance:
The Technical Specification surveillance requirement was met by the surveillance testing completed March 28, 1976.
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INFRACTION NO. 2 Adherence to weekly control rod exercising procedure.
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Discussion:
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Unit 1 had been operating at 170 MWe for a number of days prior to the event. All operations had been performed normally, including i
surveillance testing.
The off gas activity had been between 8,000 i
and 10,000 microcuries/second at this power level.
On Monday, March 29, 1976, at approximately 3:30 a.m.,
the off gas activity exhibited an unexplained step increase. The off gas sample taken Monday morning showed an activity level'of approximately 45,000 microcuries/second.
Later on Monday, a second sample was taken and showed that the activity had dropped to about 35,000 micr: curies /
second. Off gas samples taken on subsequent days during the remainder of that week showed a steady decrease in off gas activity. Activity at the end of the week was approximately 16,000 to 20,000 microcuries/
second.
A review of the operations performed on the unit prior to the l
event was made. This review included investigating the surveillance testing performed on Sunday morning, March 28, 1976. The surveillance
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test performed at this time was the Control Rod Following Verification using procedure 300-S-II (Rev. 2, Feb. 1975). In reviewing the data sheet for this surveillance test, it was noted that the operator had moved 24 control rod tips past one another. These rod movements were made because he had selected the wrong level of incore monitors to verify control rod movement. The "D" level monitors were selected to monitor fully withdrawn control rods and the "A" level monitors were selected to monitor fully inserted control rods. By selecting the
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wrong level of incore chambers to monitor centrol rod following, the operator was required to move the control rods further than normal to
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obtain a response. Past experience with control rod movement had 7
indicated that fuel damage can result when control rod tips pass one another. The flux peak associated with the tips reinforce one another, 1
causing an extremely high peak at that point in the fuel.
A review of the procedure used for this surveillance test revealed that the operator had violated the Precautions section and the Limita-tions and Actions section of the procedure.
The Precaution section specifies that the operator inspect the control rod pattern to insure thac no diagonally adjacent control rods come within one notch of each 4
other.
The Limitations and Actions section specifies that if the operator cannot achieve a response on the incore system, he should consult the appropriate nuclear engineer. Apparently, neither one of these actions were taken at the time this test was performed. The procedure appears to be deficient in that it does not address the novement of face adja-cent control rods.
It only addresses the moveme:t cf diagonally adja-cent control rods. A number of the control rods moved during this sur-veillance test were face adjacent rods.
The prozedure also does not contain any statements as to which incore levels should be used to monitor control rods at various elevations in the core.
The operator who performed this surveillance test has been a Nuclear Station Operator (NS0) since May 24, 1973. During most of the time since his promotion, he had been assigned to a crew containing a Senior Control Operator. Since a Senior Contrcl Operator could not 9
I operate on Units 2 and 3, the NSO did net operate on Unit 1 except for infrequent periods during much of this time. On January 19, 1976, the NSO was reassigned to a crew consisting of all Nuclear Station Operators. This was the first time the NSO had performed this sur-veillanc e test since joining the new crew.
The NSO has been an active participant in Dresden Station's requalification program. The Dresden Station investigating committee met with the NSO and discussed this incident. During this discussion, the NSO could offer no reason for selecting the incorrect incore level during the control rod verifica-tion test.
The Assistant Superintendent and the Unit 1 Operating Engineer met with the Shift Engineer in charge of operations. and diserased the.
Unit 1 incident. It was determined that during the test the NSO's on this crew are expected to perform routine surveillances without specific instructions from supervisors. Since the Control Rod Following Verifi..
cation test is a routine surveillance, the Shift Engineer expected the the Nuclear Station Operator to perform it without specific instructions.
In discussions with the operator and the Shif t Engineer, it was
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e apparent that neither individual was aware of the problems associated with passing control rod tips. Both men have received training in 4
control rod movements and core physics. However, neither of them related that training to the movement of control rod tips past one another.
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Corrective Action:
At the conclusion of the control rod following verification, the control rods were returned to previous steady state operating positions.
In these positions, the adjacent control rod tips are not moved within one notch.
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Corrcctiva Action to Avoid Rzcurrcnce:
1.
The selector switch for incore levels located on the reactor console was labeled to indicate the relationship of incore levels to control rod positions in the core.
2.
The requalification program for licensed operators encompasses instructions concerning the movement of control rods.
This train-ing in the past has been included with the technical or theoretical aspects of core pl.; sics. To further reinforce the importance of this training, special training is in progress.
This training addresses the practical everyday movement of control rods and the do's and don'ts of control rod movement.
3.
Prior to January 1, 1977, a representative number of licensed operators will be quizzed to determine the effectiveness of the control rod movement training and determine further training needs.
4.
As discussed in Infraction No. 3, the procedure was revised to furthe; reduce the possibility of recurrence.
Date of Full Compliance:
On March 28, 1976, when the test was completed and the control rods returned to steady state operating position, full compliance with pro-cedural requirements was achieved.
The corrective actions to prevent recurrence will be completed on the following schedule:
1.
April 1, 1976 2.
August 1, 1976 3.
January 1, 1977 4.
Completed May 6, 1976
a INFRACTION No. 3 Lack of precaution concerning possible fuel damage if face s
adjacent control blade tips are within one notch. '
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riscussion:
To the extent reasonably achievable, procedures involving control l
rod manipulation have been thoroughly reviewed and revised to provide 1
appropriate instructions for maximizing fuel cladding integrity. These instructions cover not only factors evaluated in the Safety Analysis Report, but cover to the best of our current knowledge all factors affecting fuel cladding integrity.
It is our judgement that these procedures significantly improve fuel performance as evidenced by the i
current Dresden Unit 1 performance compared with recent fuel cycles.
Since during this particular event the existing precaution concerning diagonally adjacent control rod tips was not adhered with, it is our l
judgemant that the lack of a precaution concerning face adjacent control rod tips did not contribute to the event.
It is apparent that the operator was not familiar with the precautions of the procedure, and additional precautions would not have been considered. The lack of the precaution did not contribute to this particular event.
t As a result of our review of the event, it was determined that a
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precaution concerning face adjacent control rod tips could provide s
additional assurance that face adjacent control rods will be manipu-lated in a manner to preclude possible fuel cladding degradation. With-out this revision, the existing procedure will keep face adjacent control tips separated; however, this specific precaution should increase aware-ness of the concern. This additional precaution is intended to reduce 1
the possibility of procedural errors resulting in fuel degradation.
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l Corrective Action:
The current procedure on Control Rod Exercising has been revised
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as follows:
1.
An. additional precaution warning against the positioning of face '
4 adjacent control rod tips within one notch position of each other in high power areas has been added.
2.
The first step of the procedure has been revised to identify which I
incore level to observe for different control rod positions.
l 3.
Exercising of control rods will be limited to single notch cove-ment as required by Technical Specifications for withdrawn rods.
Incore instrumentation will be monitored for response, but incore i
response will not be required for successful completion of the 1
surveillance.
Corrective Action to Avoid Recurrence:
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It is expected that the above corrective action will significantly reduce the probabillij of a recurrence of this type of error. The over-all intent is to reduce control tad movement to the minimum amount j
necessary for operation,and surveillance.
Date of Full Compliance:
Full compliance was achieved May 6, 1976, with the approval of l
the revised procedure.
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DEFICIENCY NO. 1 Personnel in line of sight of reactor grid during a control rod movement.
's Discussion:
During reloading of the Unit 2 reactor, control rods were being
. notched to determine operability after each fuel cell was loaded.
Contrary to Master Refueling Procedure DFP 800-1, Section D.4,' all personnel did not evacuate all areas from which the grid of the reactor vessel may be viewed (leave the reactor line-of-sight) anytime a control rod is to be wi*.hdrawn.
Step F.6.f. (1) of the same procedure contains the following caution. Caution: Via communications, be aware that no one is over the reactor during any Control Rod movements.
In accordance with this procedure, this Caution is the responsibility of the unit reactor operator (NSO).
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Corrective Action:
Reactor reloading was completed.
Corrective Action to Avoid Recurrence:
Upon review c. this event, it was apparent that the responsibility for ensuring that no personnel are over the reactor prior to control rod movements was not well understood. To clarify this responsibility, the Master Refueling Procedure will be revised. The revision will require the unit reactor operator to obtain from the Fuel Handling Foreman notification that no personnel are in line of sight of the reactor grid prior to moving control rods.
t Date of Full Compliance:
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Refueling activities have been completed for Unit 2 and the pro-I l
cedure revision will be completed prior to the Unit 3 refueling outage l
which is scheduled to begin August 30, 1976.
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DEFICIENCY NO. 2 Lost Work Request.
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Corrective Action,:
s A search was made for Work Request No. 2841; however, the document was not located.
The Operating Engineer and Quality Control Engineer have evaluated the information in the Work Request Log and have con-cluded that the work was not safety related.
In accordance with Q.P. 3-52, page 3. Note, last sentence, "If maintenance is non-safety related and non-code, proceed with work in accordance with station practices." No retention requirements have been established for non-
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safety related work requests; therefore, completed'non-safety related"'-
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work requests are filed only on an informal bases by the Maintenance 3
Department. Since work was not safety related, no documentation was 1
required after completion of the work.
Corrective Action to Avoid Recurrence:
None.
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Date of Full Compliance:
The review by the Unit 2 Operating Engineer and Quality Control Engineer was completed May 26, 1976.
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