05000390/LER-2008-005, Inoperability of Radiation Monitor Due to Non-Conservative Setpoint
| ML083650062 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 12/29/2008 |
| From: | Brandon M Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 08-005-00 | |
| Download: ML083650062 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3902008005R00 - NRC Website | |
text
10 CFR 50.73 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Gentlemen:
In the Matter of
)
Docket No. 50-390 Tennessee Valley Authority
)
WATTS BAR NUCLEAR PLANT (WBN) UNIT 1 - LICENSEE EVENT REPORT (LER) 390/2008-005, REVISION 0 - REPORT OF INOPERABILITY OF RADIATION MONITOR DUE TO NON-CONSERVATIVE SETPOINT This submittal provides LER 390/2008-005. This LER documents an event where the plant was operated in a condition prohibited by Technical Specifications due to an inoperability of the radiation monitors used to comply with TS 3.4.15. The condition is reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).
There are no regulatory commitments associated with this submittal. If you have any questions concerning this matter, please contact me at (423) 365-1824.
Sincerely, M. K. Brandon Manager, Site Licensing and Industry Affairs Enclosure cc: See Page 2 December 29, 2008 Original signed by C. J. Riedl for
U.S. Nuclear Regulatory Commission Page 2 Enclosure cc (Enclosure):
NRC Resident Inspector Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 John G. Lamb, Project Manager U.S. Nuclear Regulatory Commission Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation MS O-8 H4 Washington, DC 20555-0001 U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Institute of Nuclear Power Operations 700 Galleria Parkway, NW Atlanta, Georgia 30339-5957 December 29, 2008
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
(See reverse for required number of digits/characters for each block)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010
, 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
- 2. DOCKET NUMBER 05000390
- 3. PAGE 1 OF 5
- 4. TITLE Inoperability of Radiation Monitor Due to Non-Conservative Setpoint
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME N/A DOCKET NUMBER N/A 10 29 2008 2008 - 005 -
0 12 29 2008 FACILITY NAME N/A DOCKET NUMBER N/A
- 9. OPERATING MODE 1
- 10. POWER LEVEL 100%
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in Abstract below or in II.
DESCRIPTION OF EVENT (continued):
C.
Dates and Approximate Times of Major Occurrences
Date Event June 20, 2008 DCN 52631 was issued to change the setpoint on radiation monitors 1-RE 106, and on 1-RE-90-112. Impact sheets did not identify all of the documents changes for radiation monitor 1-RE-90-112.
October 14, 2008 Radiation Monitor 1-RE-90-112, which was configured to lower containment, had its setpoint recalibrated to 13,000 cpm according to the SI and the Plant SSD.
October 29, 2008 LCO 3.4.15 Condition B was entered when it was determined that the particulate channel of radiation monitor 1-RE-90-112 had been calibrated to a non-conservative setpoint.
October 30, 2008 Radiation monitor 1-RE-90-112 was recalibrated to the proper setpoint.
D.
Other Systems or Secondary Functions Affected
No other systems were affected by the event.
E.
Method of Discovery
Evaluation of PER 154635 regarding the discrepancy between the as-found setpoint and the expected value led to the discovery of the non-conservative value for radiation monitor 1-RE-90-112.
F.
Operator Actions
The Operations staff (licensed personnel) entered the appropriate LCO once the condition was discovered.
Appropriate actions were taken while in the LCO. The setpoint was changed to the appropriate value to allow the particulate channel to become operable.
G.
Safety System Responses There were no safety system responses as a result of this condition.
III.
CAUSE OF EVENT
The cause of the event was determined to be a human performance issue stemming from an inadequate Question, Validate, and Verify (QV&V) review of the DCN. Radiation monitor 1-RE-90-112 was inadvertently left off the impact sheets during the DCN implementation process. Self checking was identified as a flawed defense. The cause was human error, and no process deficiencies were identified.
IV.
ANALYSIS OF THE EVENT
This event was a noncompliance with the WBN TS of very minor safety significance. When the particulate channel was unavailable, the containment pocket sump level monitor was still operable for leakage detection.
For periods of time when the particulate channels ability to detect one gpm within one hour was compromised, the radiation monitor did provide the ability to detect changes in RCS leakage, although low RCS activity could have delayed response time. Action B of TS 3.4.15 allows continued operation for up to 30 days provided containment atmosphere grab samples are taken every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, or when an RCS mass balance is performed every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The RCS mass balance was performed every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in accordance with Surveillance Requirement 3.4.13.1 from October 14-29, 2008. Other leakage detection methods such as humidity monitoring and containment air temperature indication, as well as the containment pocket sump level monitor were available to support RCS leak detection.
V.
ASSESSMENT OF SAFETY CONSEQUENCES
The event was determined to be of low safety significance because no significant leakage events occurred during the time of noncompliance. The Final Safety Analysis Report (FSAR) states that an RCS mass balance will be performed if the radiation monitor aligned to lower containment alarms concurrent with an increase rate of rise on the containment pocket sump monitor, or on a direct alarm from the containment pocket sump level monitor. RCS leakage detection was not challenged by the wrong setpoint on radiation monitor 1-RE-90-112. At all times, several diverse means for detecting abnormal leakage existed as discussed above.
VI.
CORRECTIVE ACTIONS-The corrective actions for this condition are being managed within TVAs Corrective Action Program (PERs 154635, 155844, and 155879) and therefore are not considered to be regulatory commitments. An overview of the corrective action plan is provided below:
A.
Immediate Corrective Actions
- 1.
TS 3.4.15 Condition B was entered and the required actions were taken.
- 2.
The particulate channel setpoint for 1-RE-90-112 was recalibrated to the appropriate value.
B.
Other Corrective Actions Taken
- 1.
The Plant SSD was updated to specify the correct particulate setpoint for radiation monitor 1-RE-90-112.
VII.
ADDITIONAL INFORMATION
A.
Failed Components None.
B.
Previous LERs on Similar Events There are no previous LERs from WBN that are similar to this event.
VII.
C.
Additional Information
During the course of resolving the particulate channel setpoint issue, the basis for the operability of the gaseous channel of the radiation monitors used for compliance with TS 3.4.15 was challenged by the NRC.
Due to sensitivity limitations of the gaseous channel, its ability to detect an RCS leak of one gpm within one hour based on actual WBN source terms could not be assured. TVA had previously recognized this limitation and had revised the WBN Updated Final Safety Analysis Report (UFSAR) per the 10 CFR 50.59 process.
This change identified that the gaseous channel may not detect an RCS leak of one gpm within one hour when RCS activity is lower than source terms specified in WBN FSAR Table 11.1-7. This change was submitted to NRC in UFSAR Amendment 2 on April 6, 2001. The revised UFSAR section was referenced in the TS Bases. It was TVAs position that the realistic source terms used to meet Regulatory Guide (RG) 1.45 requirements could be based on ANSI 18.1 source terms (specified in FSAR Table 11.1-7) vice the actual source term, which can vary significantly with fuel cladding performance. NRC notified TVA on October 29, 2008 that it disagreed with the acceptability of TVAs position and the change made to the UFSAR. While this concern was being resolved, TVA agreed to not declare the monitor operable, and to continue taking the TS required actions. To facilitate resolution of this concern, TVA chose to pursue a license amendment, in accordance with current NRC guidance provided in RG 1.45 Revision 1, to eliminate the TS requirement for the gaseous channel. This License Amendment Request was approved by NRC on November 25, 2008 and was issued as WBN License Amendment 71. The monitor was then declared operable and TS 3.4.15 was exited.
With respect to the differing professional opinion regarding the UFSAR change to the licensing basis for the gaseous channel of these radiation monitors, TVA has initiated PER 160075 to evaluate this aspect and is working toward resolving this issue. The TS compliance aspects of this differing opinion were resolved by License Amendment 71 as discussed above.
D.
Safety System Functional Failure This event did not involve a safety system functional failure as defined in NEI 99-02, Revision 5.
E.
Loss of Normal Heat Removal Consideration There was no loss of normal heat removal due to this condition.
VIII.
COMMITMENTS
None.