05000390/LER-1917-013, Regarding Incorrectly Adjusted Auxiliary Building Gas Treatment System Damper Leads to a Condition Prohibited by Technical Specifications

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Regarding Incorrectly Adjusted Auxiliary Building Gas Treatment System Damper Leads to a Condition Prohibited by Technical Specifications
ML17310A254
Person / Time
Site: Watts Bar  Tennessee Valley Authority icon.png
Issue date: 11/06/2017
From: Simmons P
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 17-013-00
Download: ML17310A254 (7)


LER-1917-013, Regarding Incorrectly Adjusted Auxiliary Building Gas Treatment System Damper Leads to a Condition Prohibited by Technical Specifications
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
3901917013R00 - NRC Website

text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 November 6, 2A17 10 cFR 50.73 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391 Subject: Licensee Event Report 39012017-013-00, lncorrectly Adjusted Auxiliary Building Gas Treatment System Damper Leads to a Condition Prohibited by Technical Specifications This submittal provides Licensee Event Report (LER) 39012017-013-00. This LER provides details concerning a condition where a damper which would not fully close resulted in a condition prohibited by the Technical Specifications (TS). This condition is being reported as a condition prohibited by TS in accordance with 10 CFR 50.73(aX2Xi)(B).

There are no regulatory commitments contained in this letter. Please direct any questions concerning this matter to Kim Hulvey, wBN Licensing Manager, al (423) 3os-zrzo.

Respectfully,%

Paul Simmons Site Vice President Watts Bar Nuclear Plant Enclosure cc: See Page 2

U.S. Nuclear Regulatory Commission Page 2 November 6, 2017 cc (Enclosure):

NRC Regional Administrator - Region ll NRC Senior Resident Inspector - Watts Bar Nuclear Plant

NRC FORM 366 (04-2017\\

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o-IW, U.S. NUCLEAR REGULATORY COMMISSION LTCENSEE EVENT REPORT (LER)

APPROVED BY OMB: NO.3150-0104 ExptRES: oil31t2o2o

, 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 1
2. DOCKET NUMBER 05000390
3. PAGE OF 5

1

4. TITLE

_ lncorrectly Adjusted Auxiliary Building Gas Treatment System Damper Leads to a Condition Prohibited by Technical Specifications

5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED MONTHI ORy I Venn YEAR I t.-trt#s,-

REV NO.

MONTH I DAY YEAR FACILIry NAME Watts Bar Nuclear Plant, Unit 2 IOSOOOSg1 09 06 I 2017 2017 013 - 00 06 11 2017 FACILITY NAME I

oocxgr NLIITrtaER

9. OPERATING MODE 1 1. THIS REPORT lS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR g: (Check alt that appty) 1 tr 20 z2o1 (b) tr 2o.2zo3(a)(3Xr) tr 50.73(aX2)(iiXA) n 50 73(a)(2XviiiXA) n 20 2zo1(d) tr 20 z2o3(a)(3)(ii) t] 50 73(aX2XiiXB) tr 50.73(aX2Xviii)(B) tr zo 2zo3(aX1) n 20.2203(a)(4) n 50 73(ax2xiii) n 50 73(aX2Xix)(A) n 20 z2o3(aX2)(i) tr 50.36(cX1)(i)(A) tr 50.73(a)(2)(iv)(A) tr 50 73(aX2Xx)
10. POWER LEVEL 100 tr zo 22o3(a)(2Xii) tr 50 36(cX1X.iXA) tr 50.73(aX2XvXA) tr rc T1(aX4) tr 20 2203(aX2)(iii) n so s6(cX2) tl 50 73(a)(2)(v)(B) tr rcT1(a)(s) tr 2o.z2o3(aX2Xiv) n 50.46(ax3xii) tr 50 73(a)(2)(v)(c) tr rcrr(a)(1) tr zo zzo3(a)(2Xv) tr 50 73(aX2XiXA) n so 73(aX2)(vXD) tr fi 77(aX2Xi) tr 2o.zzo3(aX2)(vi)

X 50.73(aX2Xi)(B) tr 50 73(aX2Xvii) tr fi 77(ax2xii) tr 50 73(a)(2)(iXC) tr OTHER Specify in Abstract betow or in directly to the shield building exhaust vent. Following an accident, potential radioactivity releases within the AB are processed by the ABGTS units prior to release to the environment.

ABGTS performs the primary safety-related function of maintaining the AB at a minimum negative pressure of -0.25 inches water gauge (wg) to assure that the guidelines in 10 CFR 100 and General Design Criteria (GDC) 19 are not exceeded. Sufficient air is drawn from the ABSCE to establish and maintain the desired building negative pressure. The negative pressure chosen for post-accident operation is sufficiently low to ensure that airborne contamination in the AB is not released to the environment yltltgut being processed by the ABGTS units. Although the maximum permissible ABSCE leakage rate is 9900 cubic feet per minute (cfm) at -0.25 inches wg with respect to the outside environment, ABGTS will maintain a minimum fan capacity of 9300 cfm at all times. This will allow for adequate airflow for a maximum allowable ABSCE infiltration rate of 7930 cfm, and margin for a postulated one inch service air line break (1370cfm) due to a Safe Shutdown Earthquake (SSE), at a negative differential pressure of

- 0.25 inches wg.

The inability of ABGTS Train A to meet the required greater than or equal to 1370 cfin total vacuum relief line airflow required by the design does not necessarily render ABGTS Train A incapable of performing its specified safety function during a Loss of Coolant Accident (LOCA) (maintaining ABSCE at i negativJ pressure, -0.25 inches wg and -0.5 inches wg). The difference between the actual vacuum relief measured value (corrected for pressure) and 1370 cfrn (from a postulated one inch air line break) provides the margin foTABSCE breaching permits during plant operation. The ABSCE breach margin is calculated using ABGTS total flow, vacuum relief line flow, and AB pressures. Therefore, once either train of ABGT-S's breach margin is exceeded that unit of ABGTS becomes inoperable and unable to perform its specifi ed safety function.

Testing performed on September 6,2017 showed the failure of damper 2-FCO-30-108 to fully close impacted the ability to accommodate the postulated one inch service air line break when the calculated breaches through the ABSCE exceeded 63.9 square inches for Train A. This breach margin was exceeded between July 7, 2017 at2030 EDT and September 5,2017 at 1645 EDT. Following correction of damper 2-FCO-30-108, the ABSCE breach margin increased to over 170 square inches.

ASSESSMENT OF SAFETY CONSEQUENCES

As described in the previous section, the ABGTS Train A was not able to perform its safeg function for a design basis accident with a one inch service airline failure. The postulation of a seismic event and a Design Basis Event (DBE) are not assumed to occur concurrently, but are considered for the purposes of design and operability. The consequences of this event are judged to be low, and are not modeled in the plant Probabilistic Risk Assessment (PRA).

A. Availability of systems or components that could have performed the same function as the components and systems that failed during the event Train B of ABGTS remained operable during this time period.

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 residuai heat, control the release of radioactive material, or mitigate the consequences of an accident V.

Train B of ABGTS remained operable during this time period.

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 Train A of ABGTS was operable based on ABSCE breaches in effect when the condition of damper 2-FCO-30-108 was identified. The condition identified on September 6, 2017 was corrected on September 19,2017.

VI. CORRECTIVE ACTIONS

This event was entered into the Tennessee Valley Authority (TVA) Corrective Action Program and is being tracked under Condition Report (CR) 1335791.

A. lmmediate Corrective Actions The issue improperly adjusted damper was corrected after identification.

B. Corrective Actions to Prevent Recurrence or to Reduce Probability of Similar Events Occurring in the Future Corrective actions will be provided in a supplement to this report.

VII. PREVIOUS SIMILAR EVENTS AT THE SAME SITE

LER 390/2009-001 reported that Surveillance lnstructions used to test the ABGTS were ndt adequate in that the closure of non-safety ventilation dampers may have masked the performance of safety related dampers. ln addition, as part of this report, two failures of a temporary boundary door used to facilitate Unit 2 construction were reported. Corrective actions included revising procedures to ensure that non-safety dampers could not mask the performance of safety related dampers during testing. The event described in LER 390-2017-013 is different in that it is related to performance of post maintenance inspections, not surveillance procedures.

VIII. ADDITIONAL INFORMATION

None.

IX. COMMITMENTS None.Page 5 of,,, 5,,,