05000391/LER-2016-001, Regarding Loss of Automatic Containment Isolation for the Steam Generator Blowdown Sampling Lines
| ML16165A244 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 06/13/2016 |
| From: | Simmons P Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 16-001-00 | |
| Download: ML16165A244 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2) |
| 3912016001R00 - NRC Website | |
text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 June 1 3, 2016 10 cFR 50 73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unat 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391
Subject:
Licensee Event Report 391/2016-001-00, Loss of Automatic Containment lsolation for the Steam Generator Blowdown Sampling Lines This submittal provides Licensee Event Report (LER) 391/2016-001-00. This LER provides details concerning improper use of electricaljumpers that led to a loss of automatic containment isolation for the Steam Generator Blowdown Sampling Lines. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(i)(B) and 10 CFR 50.73(a)(2)(vii).
Please direct any questions concerning this matter to Gordon Arent, WBN Licensing Director, at (423) 365-2004.
Respectfully, Paul Simmons Site Vice President Watts Bar Nuclear Plant Enclosure cc: see Pag e 2
^/
U.S. Nuclear Regulatory Commission Page 2 June 13, 2016 cc (Enclosure):
NRC Regional Administrator - Region ll NRC Senior Resident lnspector - Watts Bar Nuclear Plant
NRC FORM 366 U.S. NL -JAR REGULATORY COMMISSION (1 1-201s)
..f'*o'?,
iBgi LT.ENSEE EVENr REP,RT (LER) e"Ir'it
't**a APPROVED BY...dB: NO.3150-0104 EXPIRES: 1013112018
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Watts Bar Nuclear Plant, Unit 2
- 2. DOCKET NUMBER 05000391
- 3. PAGE OF 6
1
'1. TITLE Loss of Automatic Containment lsolation for the Steam Generator Blowdown Sampling Lines
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FAGILITIES INVOLVED MONTHI DAY I YEAR YEAR I t=-t'r=Hft REV NO.
MONTH I DAY YEAR FAcIuw NAME I
oocTET NUMBER N/A lun 04 14 I 2016 2016 - 001 00 06 13 2016 FACTLTTY NAME I
DOCKET NUMBER N/A lN/A
- 9. OPERATING MODE It. THIS REPORT lS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR $: (Check all that appty) 3 tr 2o.zzo1(b) n 2o.22os(aX3Xi) tr 50.73(a)(2xiixA) tr 50.73(aX2XviiiXA) tr 2o.22ot(d) tr 20.2203(aX3)(ii) tr s0.73(aX2X.iXB) tr s0.73(a)(2)(viii)(B) tr zo.22o3(aX1) tr 2o.22os(aX4) tr 50.73(ax2xiii) tr 50.73(a)(2)(ixXA) tr zo.2zos(aX2)(i) n 50.36(cx1x.xA) tr 50.73(aX2XivXA) tr 50.73(aX2Xx)
- 10. POWER LEVEL n 2o.2zo3(a)(2)(ii) n 50.36(cxl XiiXA) tr 50.73(aX2XvXA) tr rs.r1(aX4) tr 2o.2zos(aX2Xiii) tr 50.36(cX2) tr 50.73(aX2XvXB) tr rcl1(a)(s) tr zo.22o3(aX2Xiv) tr 50.46(ax3xii) tr 50.73(a)(2)(vXc) tr B.rt(a)(1) tr 2o.z2os(aX2Xv) tr s0.73(ax2)(i)(A) tr 50.73(aX2)(vXD) tr B.rr(ax2)(i) tr 2o.2zo3(aX2)(vi)
X 50.73(aX2XiXB)
X 50.73(aX2Xvii) tr B.r7(a)(2xii) tr 50.73(aX2X.Xc) tr OTHER Specify in Abstract betow or in
C. Dates and Approximate Times of Occurrences
Date Time (EDT) Event 03/18/16 1832 Entered Mode 4 with inoperable ClVs 03/30/16 1639 Entered Mode 3 with inoperable ClVs 04102116 0453 Re-entered Mode 4 with inoperable ClVs 04108116 0527 Re-entered Mode 3 with inoperable ClVs 04114116 1700 Maintenance discovered ClVs for the SGBD sampling lines inoperable with plant in Mode 3. Entered LCO 3.6.3, Condition C.
04114116 2234 Exited TS LCO 3.6.3, Condition C.
D. Manufacturer and Model Number of Components that Failed There were no component failures. The inoperable ClVs were due to human error.
E. Other Systems or Secondary Functions Affected
No other systems or functions were affected.
F. Method of discovery of each Component or System Failure or Procedural Error
The failure of the ClVs to close was discovered during attempts by maintenance to restore SGBD sample lineup.
G. Failure Mode and Effect of Each Failed Component The inability to close the ClVs for the SGBD sampling lines was due to improper installation of the electricaljumpers used in the valve control circuits. The misplaced jumpers not only bypassed the AFW pump auto/manualstart signal but also the Containment Phase A lsolation signaland the controlvalve seal-in circuit. Bypassing the controlvalve seal-in circuits caused the valves to immediately return to the open position when the hand switches were released from the closed position. Bypassing the seal-in circuits defeated the ability to manually close the ClVs from the main controlroom.
H. Operator Actions
Upon identifying the failure to close the ClVs for the SGBD sampling lines, (TS) Limiting Condition for Operation (LCO) 3.6.3, Condition C, "One or more penetration flow paths with one containment isolation valve inoperable," was entered.
l. Automatically and Manually lnitiated Safety System Responses The condition described in this report did not result in any automatic or manual safety systems activation.
ilt
CAUSE OF THE EVENT
A. The cause of each component or system failure or personnel error, if known.
The inability to automatically or manually close the SlVs and the ClVs for the SGBD sampling lines was due to improper installation of the jumpers used in the valve control circuits. The misplaced jumpers not only bypassed the AFW pump running contacts but also the Containment Phase A lsolation signals and the controlvalve seal-in circuits. Bypassing the controlvalve seal-in circuits is the reason why the valves immediately returned to the open position when the hand switches were released from the closed position.
B. The cause(s) and circumstances for each human performance related root cause.
Chemistry procedure 2-CM-6.60, Revision 5, specified the wrong terminal points for bypassing the AFW pump auto/start signals. This event was attributed to a lack of procedural compliance for safety related systems, along with a lack of peer checking, during the procedure revision process.
ln particular, Revision 5 was not coordinated with the Electrical Engineering Group prior to implementation. Lack of formal procedure preparer training and inadequate system knowledge contribute to procedure noncompliance.
ANALYSIS OF THE EVENT
During plant operation, SG samples for each steam generator are taken every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to verify primary to secondary leakage is within limits. When the AFW System is in service, flow paths that could result in a loss of SG inventory are isolated, including SG blowdown and SG sampling. To obtain a representative sample, 11 liters of sample must be purged through the sample line. The sample flowrate for each SG is approximately 8 gallons per hour (gph). ln Mode 1, with AFW secured, a SG sample can be taken without the use of jumpers. To allow a SG sample to be taken in Modes 24 when the AFW is in service, jumpers are installed around the open contacts for the AFW pumps using chemistry procedure 2-CM6.60. These jumpers allow the SlVs and the ClVs for the SGBD sampling lines to remain open with the AFW pumps running, but will not prevent the isolation of the sample flow path from a Phase A containment isolation signal. On March 14,2016, when attempting to restore the Unit 2 SGBD sampling lines to normal alignment, the hand switches for the SlVs and ClVs were placed in the closed position, the valves momentarily indicated closed (green) and then immediately returned to the open position (red) when released. At that time it was determined that the jumpers were not properly installed.
The ClVs for the SGBD sampling lines are required to be Operable per TS in Modes 14. With the jumpers improperly installed, the ClVs were disabled. The SGBD Sampling System for Unit 2 credits a closed system inside containment as the first containment boundary with automatic isolation valves located outside containment as the second containment boundary. While the ClVs in question were prevented from automatic closure, the closed system inside containment remained operable and manual flow control valves located downstream of the defeated outboard ClVs were available to provide redundant isolation if necessary. Accordingly, the containment isolation safety function was not lost. However, defeating the automatic and manual closure of the outboard ClVs represents a condition prohibited by TS.
The SlVs and the ClVs in the SGBD sampling lines also serve as redundant isolation valves to prevent potential loss of SG inventory that could impact the AFW function following an accident or plant IV.
V.
transient. As discussed above manual flow control valves located downstream of the defeated outboard ClVs were available to isolate the SGBD sampling lines if required. ln addition, SG inventory loss due to sampling, when in use, is small (8 gph). With the AFW in service and no decay heat on Unit 2, the ability to shut down the reactor and maintain a safe shutdown condition was not impacted. With no core decay heat, removal of residual heat is not an issue. With no irradiated fuel in the Unit 2 core, an uncontrolled release of radioactive material is not credible. The small loss of SG inventory would not have adversely impacted the ability to mitigate the consequences of an accident. However, the loss of both trained isolation valves represent a common cause inoperabilty of independent trains.
ASSESSMENT OF SAFETY CONSEQUENCES
A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event.
The WBN Unit 2 design credits a closed system inside containment as the first containment boundary with automatic isolation valves located outside containment as the second containment boundary. While the disabled ClVs prevented automatic and manual isolation of the SGBD sampling lines, a containment isolation boundary for the closed system inside containment remained operable for mitigating Design Bases Accidents. ln addition, flow control valves (FSV-430A, B, C, and D) downstream of the ClVs were available to manually isolate the SGBD sampling lines to maintain containment integrity and preserve SG inventory if necessary.
B. For events that occurred when the reactor was shut down, availability of systems or components needed to shutdown the reactor and maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident SG inventory loss due to sampling, when in use, is small (8 gph). With AFW in service and no decay heat on Unit 2, the ability to shut down the reactor and maintain a safe shutdown condition was not impacted. With no core decay heat, removalof residual heat is not an issue. With no irradiated fuel in the Unit 2 core, an uncontrolled release of radioactive material is not credible, The small loss of SG inventory would not have adversely impacted the ability to mitigate the consequences of an accident.
C. For failure that rendered a train of a safety system inoperable, an estimate of the elapsed time from the discovery of the failure until the train was returned to service.
The containment isolation valves for the SGBD sampling lines were discovered to be inoperable on April 14,20'16 at approximately 1700 EDT and were returned to service on April 14,20'16 al 2234 EDT, which was approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and 34 minutes.
CORRECTIVE ACTIONS
This event was entered into the Tennessee Valley Authority Corrective Action Program and is being tracked under condition report (CR) 1160910.
vt.
A. lmmediate Corrective Actions The electricaljumpers were removed and the SlVs and the ClVs were returned to service.
B. Corrective Actions to Prevent Recurrence Revised Procedure 2-CM-6.60, "Steam Generator Sampling in Hot Sample Room (Modes 2),'to incorporate revised jumper control and appropriate departmental procedure reviews. The effectiveness of this corrective action will be assessed at the conclusion of the Unit 2 Power Ascension Testing. This assessment will determined whether the procedure revisions correctly performed the intent of 2-CM.60.
VII. ADDITIONAL INFORMATION
A. Previous similar events at the same plant On March 21, 2008, with Watts Bar Unit 1 in Mode 3 it was discovered that jumpers installed to block the Safety lnjection (Sl) automatic actuation logic in the Sold State Protection System had not been removed. The jumpers were installed during Cycle 8 Refueling Outage in accordance with lnstrument Maintenance lnstruction ((lMl) 99.040. The Sl automatic actuation function is required in Modes 1, 2, 3, and 4 per TS 3.3.2, Table 3.3.2-1, Function 1.b. Upon discovery the plant entered TS LCO 3.0.3.
With the plant in Modes 3 and 4, both trains of the Sl automatic actuation logic were rendered inoperable for approximately 33 hours3.819444e-4 days <br />0.00917 hours <br />5.456349e-5 weeks <br />1.25565e-5 months <br /> and 38 minutes. The event was reported under NRC Event Notification 44085. The event was attributed to a combination of both procedural inadequacy (i.e., the step removing the jumper did not required verification) and personnel error.
B. Additional lnformation None.
C. Safety System Functional Failure Consideration This condition did not result in a safety system functionalfailure because a containment isolation boundary for the closed system inside containment remained operable and was capable of mitigating a Design Bases Accident. Additionalflow controlvalves located downstream of the defeated ClVs were available to isolate the SGBD sampling lines to maintain containment integrity and to preserve SG inventory if the AFW pumps were required to mitigate a design bases event.
D. Scrams with Complications Consideration There was no scram associated with this event.
VIII. COMMITMENTS
None.