ML20086P161
| ML20086P161 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/18/1991 |
| From: | Joshua Wilson TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9112260228 | |
| Download: ML20086P161 (6) | |
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n,m n, e December 18, 1991 U.S. Nuclear Regulatory Commission ATTN Docun ent Control Desk Washington, D.C.
20555 Gentlemen In the Matter of
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Docket Nos. 50-327 5
Tennessee Valley Authority
)50-32B SEQUOYAli Nt'CLF.AR ? L.C.*T f FlN) - NRC #NSPECTION REPORT $0-32 7. 3:'S/ 91 RESPONSE TO NOTICE )F V!OLnTION (NOV f 50-327/91-23-01 Euclosed is TVA's response to 3ru:e A. Wilson's letter to Dan A. Nauman dated November IB,1MI. which transmitted the subject NOV concerning an inadvertent loss of residual heat remeval cooling during the Unit 1 Cycle 5 refueling outage, r provides TVA's response to the SOV.
Summary statements of commitments contained in this submittal are provided in Enclosure 2.
If you have any questions concerning this submittal, please telephone M. A. Cooper at (615) S43-S924 Sincerely, 5 st4, L. Wilson Enclosure ces See page 2
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U.S. Nuclear Regulatory Commission Page 2 December 18, 1991 cc (Enclosure):
Mr. D. E.L LaBarge, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville. Maryland 20852 NRC Resident Inspector Sequoyah Nuclear Plaut=
2600 Igou Ferry Road-Soddy-Daisy. Tennessee 37379 Mr.
B.' A. Wilson, Project Chief U.S.. Nuclear Regulatory Commission Region !!
'!01 MWrletta-Street. NW. Suite 2900 Atlanta. Georgia 30323 I
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ENCLOSURE 1 RESPONSE TO NRC INSPECTION REPORT NOS. 50-327/91-23 AND 20-328/91-23 BRUCE A. WILSON'S LETTER IJ DAN A. NAUMAN DATED NOVEMBER 18, 1991 Violation 50-327/91-23-0.
" Technical Specificatiou 3.9.3.1 requires at least one residual heat removal loop to be in operation when in Mode 6.
" Contrary to the above, on October 15, 1991 the operating residual heat removal loop became inoperable for approximately one minute with Unit 1 in a Mode 6 (refueling) condition.
"This is a Severity Level IV violation (Supplement V)."
deason for the Violation The event was initiated by the inadvertent closure of the "A" train residual neat removal (RHR) rump suction Valve 1-FCV-7t-3.
The valve closed because of the inadvertent actuation of an interlock. during performance of preventive r
p maintenance (PM) nn the RHR pump suction valve from the Containment S umt ' -TCV-6 3-7 2.
3 The broader :auses of this event are associated with two inappropriate acticns.
The first is considered to te the failure to adequately address the implications of revising the schedule for the PM on the suction valve from the containment sump.
The work was originally scheduled to be performed in the core empty periad.
i.e.,
when RHR operability is not required.
When the work was rescheduled because of resource considerations with a predecessor activity, reviews did not adequately consider potential risie or otherwise detect the potential for ad'rerse impacts on the RHR system operation.
The second inappropriate action is associated with the approval to perform the PM on the valve. Operations' review determined that it was acceptable to perform the work based on familiarity with previous successful performances, their understanding of the scope of work to be performed (inspection only),
and their awareness of a hold order on the valve operator (MV0P-63-72).
The review, however, did not consider or recognize that the contacts for the 74-3 interlock were still energized with the :4V0P-63-72 hold order in place and that the finger base assembly removal and replacement presented a potential to inadvertently short the energized contacts.
Inadequate communications between the Operations and Maintenance personnel regarding the scope of work to be performed were evidenced by this event.
The understanding of the Operations personnel was that the activity was inspection caly.
It was evident that the discussion did not reveal the details of the activity associated with manipulation of the limit switches and/or the vs1ve operator handwheel. The Operations and Maintenance personnel agreed that no valve operation was to be performed.
Operations considered this to mean that
-2 only an lospection would be performed with no manipulat'ons cf equipment (other than cover removal and replacement).
It was evident that Operations was not aware of the manipulation of the finger plate assemt'.y with the energized interlock contacts.
The Maintenance crew underste:d that removal and replaceacnt of the finger plate assembly were part of the procedure, but was unaware that some of the energized contacts on the finger plate might impact other plant equipment.
Conversations with the personnel who wrote the clearance revealed that, although the exisience of the interlock with 1-FCV-74-3 was vall known, it was not considered in the c'.earance to disable the interlock, or to place an additional clearance on 1-FCV-74-3, because of the understood secpc of work (i.e., inspecticn only).
Corrective Steps That Have Been Taken and Results Achieved During the time the pump suction valve was closing, the operator received an annunciator in the main control room.
The operator atserved both the red end green lights illuminated for 1-FCV-74-3, indicating the valve was la mid-travel. When the valvo ccepleted its closure cycle, the operator immediately took manual control and reopened the va've, reestablishing REP.
flow.
'Jpon observing that the valve ss traveling to the open positien and that flow and pump amperage indicat
..a were returning to ncrmal, the operator determined that tripping the pumps r.a realigning to the opposite train were not required.
As innediate corrective action. Operations personnel were brief ed on the need to be extremely protective of the RHR system and its power sources.
A training letter to all licensed operaters was subsequently issued, detailing this event and the need to be well aware of the p)tential ier interlocked equipment actuation during maintenance on this type of equipment, discussing the work to be performed in full with a questioning attitude, and ensuring that terminology is clearly understood was stressed.
The baseline outage schedule was reviewed to ensure no other work had been moved from the core empty period.
Schedule logic changes following this event are suhlseted to a review and approval process to ensure the risk-analyzed outage schedule is not adversely affected.
Additionally, a site dispatch has been distributed throughout tne site discussing how inadequate communications can lead to significant events.
Corrective Steps That Will Be Taken to Avoid Further Violations s
Simple guidelines to prompt better communications in the work authorization process will be developed by working teams consisting of Operations and Maintenance personnel and the Site Human Performance Enhancement System Coordinator.
The guidelines develop-will be incorporated into a site standard practice.
, q.
cess evaluation team will review the process in wt.lch clearance requests 4
and will implement changes to site procedures, as appropriate.
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.e i activities scheduled during the core empty period will have a L
u i scheduling comments identifying that they are required to be
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ing the core empty period, and they are signit'icant activities in
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t.vn to the risk managemer-based schedule. The outage management
<"; e adard will be revised to proceduralize the requirements that have been
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- or review of logic chanBes that could affe(
the risk-analyzed 7
- = dele befata changing the schedule.
s instruction p.
.; the work for 1-MV0P-63-72 will be revised to add c
.on that the
.s interlocked with 1-FCV-74-3. that performance of f
' witheit the u
..ock :ircuit deenergized may result it inadvertent
_.ure of.-FCV-74-3, and to recuire the signature of Operations personnel
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' acing knowledge or the interlock. Analogous revisions of PM instructions
't
.her valies interlocked v'.th the RHR system will be issued.
PM in.
uctions for Unit ? alsus will be revised before the Unit 2 Cycle 5 g,
refayling cutage.
Ado..lonall:', the maintenance instruction invoked in the subject FM will be revised, as appropriate, to alert the Operatious and Maintenanca personnel of the potential for this type cf event and to recommend that Fo'.d orders include deenergizing the interlocked equipment.
2; Electrica'. saintenance and Industrial Safety will review the current practice for work an energized equipment against industry good practices and revise current standards as approp-iate-Date When F;111 Come11ance '4ill Be achie red Full compliance wa+ acnieved October 15, 1991, et 0215 Eastern standard time when-1-FCV-74-3 was reopened.
1
En ysa...
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r ENCLOSURE 2 List of Commitments 1.
The. outage management standard will be revised by March 15, 1992, to procedura11re the requirements that have been implemented for review of logic charges that could affect the risk-analyzed outage schedule before changing,the schedule.
2.
The preventive maintenatee (PM) instruction governing the work for 1-NV0P-63-72 will be revised by July 31, 1992, to add a caution that the valve is interlocked with 1-FCV-74-3, that performance of the PM without the interlock circuit deenergized may result in inadvertent closure of 1-FCV-74-3, and to requira the signature of Operations personnel 1
indicating knowledge of the interlock.
3.
Analogous revisions of PM instructions for other Unit i valves interlocked with the-residual heat removal system will be issued by July 31, 1992.
4.
PM instructions for Unit 2 valves will be revised before the Unit 2 Cycle 5 refueling
. age.
5.
The maintenance instruction invoked in the subject PM will be revised as
' appropriate to aler'. 3perations and Maintenance of the potential for this type.of event and to recommend that any hold order include deenergizing the: interlocked equipment by. February 15, 1992.
- 6. -Electrical Maintenance-and Industrial Safety will review the current practice for vark on energized equipment against industry good pract. ices and revise current standards as appropriate by February 15, 1992.
7.
Simple guidelines to prompt better communications in the work
= authorization process will be developed by a working team consisting of Operations and Maintenance personnel and the Site Human Performance Enhancement System Coordinator.
The guidel'ines developed will be provided i.. a site standard practice by February 24, 1992.
- 8. :A process.evaluacion team vill review the process by which clearance requests are developed and implement ch
.es to site procedures, as appropriate, by February 15, 1992.
PLO90204'/1560.
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