ML20099H157
| ML20099H157 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 08/13/1992 |
| From: | Cottle W ENTERGY OPERATIONS, INC. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9208180160 | |
| Download: ML20099H157 (11) | |
Text
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Entergy Operatior.s. Inc.
-=7 ENTERGY m
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1 August = 13, 1992
- w. T. cotti.
u U.S._ Nuclear Regulatory Commission l
Mail Station-P1-137
' Washington, D.C.
Attention:
Document Control Desk
Subject:
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPP-29 Response to Violation for Failure to Follow Procedure Report No. 50-416/92-16, dated 07/17/92 (GNRI-92/00152)
GNRO-92/00102 Gentlemen:
Entergy Operations, Inc. hereby submits the response to Notice of Violation 50-416/92-16-01.
l We recognize that the performance of Grand Gulf is not up to our or your expectations in the areas of self-verification and attention to detail.
Previous corrective. actions primarily aimed at the individual employees have resulted in a reduction of the overall level of_ significance of personnel error when compared to historical events and have - had otber positive-effects such as heightened awareness of shutdown risk. However, such actions have not been as effective as desired in lowering the rate of occurrence.
Consequently, in a letter to all site personnel I have communicated the-seriousness of this situation and have emphasized my expectations concerning personal responsibility and accountability associated with attention to detail and self-verification.
In addition, we have initiated actions intended to improve our level of supervisory,
'formance-and involvement in the oversight of safety-
. critical and cip-critical work.
1)_
We are placing additional controls on selected evolutions involving trip-critical and safety related systems which could impact plant reliability or result in undue safety system _ challenges.
These controls will require that detailed briefings be held between engineering, maintenance, and operations personnel, as appropriate, prior to being performed to ensure all parties understand the: activity, the expected results and the possible consequences.
9208180160 920813 s1( l DR ADOCK 0500 6
s GNRO-92/00102 Page 2 of 5 This same requirement will apply to scope changes on work in progress - the requesting individual will be required to brief control room personnel concerning the proposed changes and possible impacts.
A Shift SRO will oversee these briefirgs.
2)
To increase management oversight of attentien to detail, the first line discipline supervisors are required to be at the job location during performance of selected work on the trip critical and safety related system work as described above.
A Shii* SRO will perform this function if a first-line supervisor is not available for any reason..
Furthermore, GGNS management is concor..ed about our - continuing susceptibility to lightning induced transients.
We recognize that our previous corrective actions-have not been effective in eliminating - the cause of the condition, however, we have taken'a number of pc.sitive steps to mitigate its effects.
GGNE personnel are aggressively testing methods to eliminate the sensitivity of our neutron monitoring circuits to lightning strikes.
'.1 )
An integrated engineering group consisting of plant engineers, CHAR Engineering and General Electric personnel was - assembled -- as a result of the November 1991 scram.
This -group provided corrective actions that were implemented prior to or during MOS,. and were intended to perform the following functions:
a.
Reduce the susceptibility of the APRM signal cables to high frequency noise.
b.
Reduce the susceptibility of the APRM signal cables to. low ~ frequency-noise.
(i. e., -
filter chokes referenced in LER 92-010)*
c.
Reduce the susceptibility of the primary APRM power supply to. noise transients.
~
This recommendation could not be completed during RF05 because of problems identified ouring testing of this design. Subsequent bench usts.have identified a better approach to reducins the susceptibility of the APRM system to low frequency noise. We have identified a path for a noise voltage to couple onto the APRM circuit through
- set of diodes. The magnitude of this noise voltage is prop (rtional to the size of a jumper internal to the APRM panels. Increasins the size of this jumper, to reduce the jumper's -
resistance,-reduces the potential drop across this jumper and subsequently reduces the noise impressed on the APRM circuit, A desige to increase the sise of this jumper is scheduled to begin implementation during the week of August 8, 1992. Additionally, GGNS is currently evaluating the removal of these
'" coupling diodes" thus eliminating the path for this noise to couple onto the AFRM circuit.
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- GNRO-92/00102
- Page 3 of 5 d.
Reduce potential noise environment in the APRM panels.
e.
Reduce the potential for coupling of noise into the LPRM signal cables at the containment penetrations.
f.
Reduce the potential for lightning striking unit 2.
g.
Issued standing order to reduce power during lightning storms to reduce the potential for invalid safety system actuation during lightning storms.
i 2)
In an attempt to identify the root cause for GGNS' susceptibility to lightning induced transients, recorders have been installed in the plant to help identify noise-sources.
3)
GGNS has contracted with' Failure Prevention, Inc.
to support-our effort in identifying the root cause for the susceptibility of the APRM system to lightning induced scrams.
4)
A weather monitoring system was installed to g ve control room personnel the ability to track storm fronts as they come in close proximity to the plant, enabling operations personnel to decrease and increase reactor power in a more timely and efficient manner.
5)
Feasibility studies have been initiated on the possibility of installing a time delay in the APRM upscale neutron trip circuit.
There is a high potential for this type modification to reduce our ' susceptibility to lightning strike scrams due to the very short duration of circuitry spikes.
This modification would require regulatory approval prior to implementation.
Grand Gulf will-continue to aggressively pursue an acceptable solution to-lightning induced transients.
Addit'ionally, realizing that improvements are needed in management
. oversight _and philosophy at.GGNS, an extensive critical review of how problems are identified, corrected and trends established for-trigger - mechanisms has been initiated.
Two such areas being critically-reviewed are:
3-o
-Root-Cause Analysis o
Corrective Action Program e
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4 GNRO-92/00102 Page 4: of 5 A
Q
' Specific action items in these and other areas will be discussed
' during the. August 17, 1992 meeting with Region II staff.
Grand Gulf management will continue to closely monitor the success of _ these efforts and make adjustments as necessary to achieve expected improvements.
We are dedicated to making Grand Gulf a world class performer-and appreciate your candid feedback.
Yours truly, wy W
WTC/RR/cg attachment cc:
Mr.
D.
C.
Hintz
-Mr. J. L. Mathis-(w/a)
Mr. R. B. McGehae (w/a)
Mr. N.
S. Reynolds (w/a)
Mr. H 'L. Thomas (w/o)
Mr. Stewart D. Ebneter (w/a)
Regional Administrator U.S.
Nuclear Regulatory Commission Region II-101 Marietta St.,
N.W.,
Suite 2900 Atlanta,. Georgia 30323 Mr.
P. W. O'Connor, Project Manager (w/a)
Office of Nuclear Reactor Regulation
.U.S.
Nuclear Regulatory Commission Mail.Stop 13H3 Washington, D.C.-20555 m.._
,C Att6chment I to GNRO-92/00102 Page 1 of 7 Notice of Violation 92-16-01 Example 1 Technical Specification 6.8.1.a requires that written procedures be established, implemented and maintained covering the applicable procedures recommended in Appendix "A" of Regulatory Guide 1.33, Revision 2.. Regulatory Guide 1.33, Appendix A, recommends that procedures for performing maintenance which can affect the performance of-cafety-related equipment should be properly preplanned and performed in accordance with written procedures and documented instructions. Administrative Procedure 01-S-07-1,-Control of Work on Plant Equipment and Facilities, paragraph 6.1.2, requires, in part, that mainter.ance and repairs of safety-related equipment be performed in accordance with approved procedures or instructions. Work Order 57258 required the Division I-load shedding and sequencing panel to be deenergized-prior to maintenance.
Contrary to the above, on May 19,1992, during the performance of Work order 57258, a non-licensed operator mistakenly deenergized the Division II load shedding and sequencing (LSS) panel instead of the Division I panel.
I.
Admission or Denial of the Alleced Example 1 of Violation Entergy Operations, Inc. admits to this violation.
II.
The Reason for the Violatipn, if Admitted On May 19, 1992, a maintenance wcrk order required the Unit 1 Division I LSS panel to be deenergized in accordance with approved written instructions. The 15 and 24 VDC power supplies were'to be replaced during the maintenance. Plant maintenance personnel. proceeded to the control room, received authorization from the operations shift supervisor and requested that an operator assist in the down-powering evolution. Maintenance personnel proceeded to the Unit 2 Division I-LSS panel and waited for operations assistance.
The non-licensed operator entered the Unit 1 Division I LSS panel area and inquired about maintenance personnel performing the1 required maintenance on the LSS panel. The operator was informed that the maintenance technician was in the Unit 2 area. The operator talked to the technician and
-they proceeded to the Unit 1 area.
The operator and technician entered the Division II LSS area and reviewed the work order for instructions. The operator inquired about being at the proper panel and the technician responded in the affirmative. The operator also questioned Lthe technician on the authorization of the work to be performed and was allowed to review the control room authorization on the work order.
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Attachment I to GNRO-92/00102-Page 2 of 7 However, the operator did not review the componer.t number which was specified in the work order and in the work instructions._After reviewing the authorization, the operator proceeded to deenergize the Division II LSS panel.
The cause of the occurrence is inattention to the component number specified in the work order instructions and a lack of~self-verification.
III. Corrective Steps Which Have Been Taken anf. Results Achieved The Operations Superintendent discussed the event with the operator involved and the appropriate operations staff.
The maintenance technician was removed from safety-related activities pending' review of the incident-Maintenance management emphasized to department personnel the importance of equipment identification / tagging throughout the plant.
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Attachment I to GMRO-92/00102 Page 3 of 7 Notice of Violation 92-16-01 Example 2 Maintenance Procedure 07-S-14-368, Clean and Inspect Boll and Kirch Type 161 or 2.62 multimantle filter assemblies, step 7.1.2, required the maintenance staff to detention a top vent plug on the main turbine Electro-Hydraulic Control (EHC) System Filter flange to: verify _that the filter housing was isolated from EHC system pressure prior to removing the filter flange cover to replace.the filter.
Contrary to the above, on June 18, 1992, a maintenance worker did-not perform step 7.1.2 of procedure 07-S-14-368 to verify isolation from the EHC before detentioning the stud nuts on the filter flange. This resulted in a large EHC oil leak which depressurized the EHC system, causing a reactor scram.
IV.
Admission or Denial of the A11eced Example 2 of Violation Entergy_ Operations, Inc. admits to this violation.
V.
Th1 Reason for the Violation, if Admitted On-June 17, 1992 a maintenance work order (WO) was generated to change and clean EHC filter N32D009. The task was not attempted until the 2330 hour0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br /> mechanical shift reported to work.-
In preparation for the task, the mechanics went to the
' filter-assembly to familiarize themselves-with-the task. In their observation, they noticed that the vent plug for the filter was damaged and the corners of the hex head were severely; rounded off. The condition is assumed-to have been caused by-the use of improper wrenches on the hex head. The mechanics returned to the maintenance-_ shop and obtained-the required tools for the filter change-out.
The non-licensed Turbine' Building operator was requested to remove the north filter.from service and place.the south
' filter in service (this is accomplished by one manual actuator which operates two three-way valves simultaneously). The operator operated the valves'; then the mechanics ~ verified the appropriate filter had been isolated by placing their hands on the two filters'and comparing the temperature _ difference. The south filter was relatively hot and the north was warm, but not at ambient temperature.
The mechanics-proceeded to vent the filter-in order to relieve any. residual pressure. During the venting process, EHC fluid continuously drained out of-the filter prior to securing.the vent plug. It was concluded that the filter was still pressurized and additional efforts to isolate the I
' filter would be necessary to perform the task.
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Attachment Z to.GNRO-92/00102 page 4 of 7 9
The operator initiated a condition identification (CI) to document the three-way valve leaking by its seat. However, the operator did not inform control room personnel.
On June 18, 1992,. the mechanics informed the incoming maintenance specialist.of the status of task and difficulties experienced by operations in isolating the filter. The mechanics also informed the oncoming mechanical supervisor of difficulties in-isolating the filter. The uncompleted work package was turned over to the oncoming 0730 hour0.00845 days <br />0.203 hours <br />0.00121 weeks <br />2.77765e-4 months <br /> mechanical shift. A discussion of the filter cleaning was performed in the work control group morning meeting; however, the relationship between the WO for the filter and the CI for the leaking valve was not fully communicated.
j The maintenance specialist who accepted the turnover from the 2330 hour0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br /> mechanics informed the oncoming mechanical shift supervisor:of the urgency of the task performance and difficulties experienced during the first attempt to perform the task.
.The mechanics were informed of the difficulties and requested to identify possible alternative methods of
-isolating the~ north filter. Following a review of the system
~ diagrams, it was determined that there was no other way to
-isolate the filter other than the three-way valve.
The' mechanics proceeded to the filter. assembly and met a
-different non-licensed operator in the filter area. The mechanics inquired about difficulties with isolating the filter.on the previous shift. However, this operator did not
.know the details of the difficulties encountered during tta first attempt.-Mechanics also inquired about the need to 1
change-the filter. The control room was. called and conveyed that:the~ filter needed'to be changed. No further inquiries were made to identify: details surrounding the first filter
-change-attempt. The operator verified the filter was isolated'by local indications and informed the mechanics that the filter'was isolated.
Therefore, mechanics felt confident that the filter was isolated atd only residual pressure would exist in the filter. housing. Mechanics attempted to remove the vent plug,
?but were_ unsuccessful in loosening the plug. The procedure
. governing the-activity required the vent to be loosened
- prior ito--- the removal of the filter cover. Without consulting their supervisor, the mechanics decided to loosen
-theLeover outs to relieve any residual pressure in the filter housing._
l This was a1 violation of procedure. Upon loosening the cover, the filter 0-ring-blew out as a result of the internal pressure due'to the leaking three-way valve.
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l Attachment I to GNkO-92/00102 Page 5 of 7 Large quantities of EHC fluid were lost due to the displacement of the 0-ring. The loss of fluid caused a low reservoir level and subsequent control fluid pressure decrease. Following the control fluid pressure decrease, the main turbine stop and control valve partially closed causing vessel voids to collapse and neutron flux to increase which resulted in a high flux condition and subsequent signal to RPS.
Mechanics involved with the second attempt to change the filter did not have the procedure available at the filter assembly. The procedure required the vent plug to be
/
loosened and removed prior to loosening the filter cover. An attempt was made to remove the vent plug, however, it was unsuccessful due to the hex head corners being rounded.
7 This step would have verified that the filter was not properly isolated. This step was not performed before proceeding to the next procedural stop. This deviation from procedure was not authorized by maintenance management.
Following no negative responses on inquires of difficulties with the first filter change-out attempt, mechanics were confident that the filter was isolated and felt that no adverse consequences would result from loosening the filter cover. The mindset that the filter was isolated prompted the mechanic to bypass the step which would have verified the filter isolaced.
The non-licensed operator generated CIs on problems identified during the attempt to isolate and change the filter. Control room personnel and operation shift management were not made aware of the identified problems..
therefore, the control room had no knowledge of the actual conditions. This is identified as a causal factor to the event.
The operator logged the attempt and results of the attempt in the building log book. Also, the operator discussed the details of the condition with the oncoming Turbine Building operator. However, a different operator was assigned to assist the mechanics and did not have detailed knowledge of the problems encountered during the previous shift. This is identified as a contributing factor.
The mechanics involved during the previous shift performed a turnover to the oncoming maintenance specialist and mechanical supervisor. The details of problems with the filter were not discussed. This is identified as a causal factor.
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Attachment I to GNRO-92/00102 Page 6 of 7 Investigation of tne event revealed previous difficulties with isolating and cleaning EHC filters. During filter cleanings, the vent plug was used to verify positive isolation and the absence of pressure and fluid. In 1989, it was concluded that an easier method to verify positive filter isolation would be to install vent valves and lines on the top of the filters. An Engineering Evaluation Request was generated to implement this modification, but was considered an enhancement and had low priority for implementation. This is considered a contributing factor to the event.
VI.
ggrrective Steps Which Havo Begn_Taken_and_Sest.ts Achieved The mechanics involved were formally reprimanded for their failure to adhere to the procedural requirements. A series of discussions were performed with all mechanical personnel stressing the importance of procedural adherence by the mechanical maintenance superintendent. Additionally, discussions concerning procedural compliance were he'd with all maintenance department personnel by the discipli,e superintendents and the manager of the plant maintent ce section.
Plant management now requires direct supervisory attention to selected work being performed on trip critical systems which could impact plant reliability or result in undue safety system challenges.
The operations plant supervisor is now required to review the building operators' log books each shift.
The mechanical section turn-overs have been enhanced by requiring the 2330 hour0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br /> mechanical shift to come in thirty minutes earlier to receive a more detailed turn-over from the mechanical supervisor. They also will attend the operations shift briefing. Additionally, they will be required to remain thirty minutes after their shift to ensure a thorough turn-over to the oncoming mechanical supervisor.
A review of outstanding documents (i.e., nonconformance documents, WOs, EERs, etc.) for other potential problems which may be related to trip critical systems was performed.
The items identified during the review have been reviewed with appropriate management to ensure top priority is given to recolving these issues.
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Attachment I to GNRO-92/00102 Page'7 of 7 Corrective 0(9As to-be Taken to Preclude Further Violations VII.
The control of work process procedures will be revised to require detailed briefings to be held between engineering (as applicable), maintenance and operation personnel on-non-routine evolutions involving selected trip-critical and safety-related systems which could impact plant reliability or result in undue safety system challenges. Scope changes in the described activities would require the requesting individual to brief control room personnel concerning the proposed changes and possible impacts.
VIII.
Date When Full Compliance Will Be Achieved i
These actions will be completed by August 30, 1992.
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