05000395/LER-2016-003-01, Regarding Steam Propagation Door Discovered Propped Open

Regarding Steam Propagation Door Discovered Propped Open

ML17040A533
Person / Time
Site:	Summer
Issue date:	02/09/2017
From:	Lippard G South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RC-17-0015 LER 16-003-01
Download: ML17040A533 (6)

LER-2016-003, Regarding Steam Propagation Door Discovered Propped Open

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 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) 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3952016003R01 - NRC Website

text

A SCANA COMPANY Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Sir I Madam:

George A. Lippard Vice President, Nuclear Operations 803.345.4810 February 9, 2017 RC-17-0015

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS), UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 LICENSEE EVENT REPORT (LER 2016-003-01)

STEAM PROPAGATION DOOR DISCOVERED PROPPED OPEN

Reference:

G. A. Lippard, SCE&G, letter to NRC, "Licensee Event Report (LER 2016-003-00), Steam Propagation Door Discovered Propped Open," dated November 14, 2016.

ADAMS Accession ML16319A400 Attached is a supplemental Licensee Event Report (LER) 2016-003-01, for the Virgil C.

Summer Nuclear Station (VCSNS), for LER 2016-003-00, as referenced. This report describes a condition and results from an event, discovered during routine operator rounds, where a steam propagation door to the Safety Related Chiller Room C (DRIB/107) was discovered propped open without all required compensatory actions.

The propped open door could have rendered both trains of Chilled Water nonfunctional if a High Energy Line Break (HELB) event occurred. This event had the potential to render both trains of High Head Safety Injection inoperable due to the loss of Chilled Water cooling to safety related room coolers. This report is submitted in accordance with 1 OCFR50.72(b)(3)(v) and 1 OCFR50.73(a)(2)(v)(D).

V. C. Summer Nuclear Station* P. 0. Box 88

• Jenkinsville, SC* 29065. F (803) 941-9776

Document Control Desk RC-17-0003 Page 2 of 2 Should you have any questions, please call Mr. Bruce Thompson at (803) 931-5042.

WHK/GAL/wm cc:

K. B. Marsh S. A. Byrne J.B. Archie N. S.Carns J. H. Hamilton S.M. Shealy W. M. Cherry C. Haney Very truly yours,..

George A. Lippard S. A. Williams NRG Resident Inspector L. W. Harris Paulette Ledbetter J. C. Mellette ICES Coordinator K. M. Sutton INPO Records Center Maintenance Rule Engineer Marsh USA, Inc.

NSRC PRSF (RC-17-0015)

RTS (CR-16-04703)

File (818.07) r

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3160-0104 EXPIRES: 10/31/2018 (06-2016)

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

l~~-

Reported lessons learned are incorporated into the licensing process and fed back to industry.

i LICENSEE EVENT REPORT (LER)

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

\\~ ':Ii Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail (See Page 2 for required number of digits/characters for each block) to lnfocollects.Resource@nrc.gov, and to the Desk Offioer. Offioe of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Offioe of Management and Budget, Washington, DC 20503. If a (See NUREG-1022, R.3 for instruction and guidance for completing this form means used to impose an information collection does not display a currently valid OMB control btl1rllwww on; gQ'lfrnadiog-[mldQC-CQllectiQDslnuregslstaffls[10221[3D number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE VC SUMMER - UNIT I 05000 I OF 4

4. TITLE STEAM PROPAGATION DOOR DISCOVERED PROPPED OPEN

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NO.

05000 FACILITY NAME DOCKET NUMBER JO 13 2016 2016 -

003 -

01 02 09 2017 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

D 20.2201 (b}

D 20.2203(a)(3)(i)

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A) 1 D 20.2201(d)

D 20.22a3(a)(3)(ii)

D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B)

D 20.2203(a)(1)

D 20.2203(a)(4)

D so.73(a)(2)(iii)

D 50.73(a)(2)(ix}(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1)(i)(A)

D 50.73(a)(2}(iv)(A)

D 50.73(a)(2)(x)

10. POWER LEVEL D 20.2203(a)(2)(ii)

D 50.36(c)(1)(ii)(A)

D 50.73(a)(2)(v)(A)

D 73.71(a)(4)

D 20.2203(a)(2)(iii)

D so.36(c)(2)

D 50.73(a)(2)(v)(B)

D 73.71(a)(5)

D 20.2203(a)(2)(iv)

D so.46(a)(3)(ii)

D 50.73(a)(2)(v)(C)

D 73.77(a)(1) 100 D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

[{] 50.73(a)(2)(v)(D)

D 73.77(a)(2)(i)

D 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii)

D so.73(a)(2)(i)(C)

[{]OTHER Specify In Abstract below or in TS 3/4.7.9, "Area Temperature Monitoring", and associated Table 3.7-7 describe the area temperature limits during normal operation due to cooling provided by the VU System. If the chiller cooling a Chilled Water loop is not running, room temperatures will rise over time. If the temperature in a given area exceeds the limit shown in TS Table 3.7-7 for eight hours, a Special Report detailing the basis for continued operability must be submitted to the NRC within 30 days.

Additionally, if the Technical Specification limit for a given area is exceeded by thirty degrees for four hours, the equipment in the associated area must be declared inoperable.

TS 3/4.8.2 "D.C. SOURCES", the D.C power sources and associated distribution systems during operation ensures that sufficient power will be available to supply the safety related equipment required for 1) the safe shutdown of the facility and 2) the mitigation and control of accident conditions within the facility. The minimum specified independent and redundant D.C. power sources and distribution systems satisfy the requirements of General Design Criterion 17 of Appendix "A" to 10 CFR 50.

VCSNS contracted an engineering firm to conduct an assessment of the impact on equipment affected by this condition.

Specifically, this evaluation considers DRIB/107 being propped open while the associated room's ventilation system HELB dampers remained open. HELB dampers are installed to prevent steam propagation from the Intermediate Building (18)

Harsh Area into the Chiller Rooms, Chilled Water Pump Room, Battery Rooms, and the Battery Charger Rooms (Mild Areas) during postulated HELB events when the affected chiller room door is propped open. The evaluation also considers the nonconforming condition of the Chiller Room and Chilled Water Pump Room drain system that was discovered under the extent of condition review. Specifically, steam propagation barriers (orifices) in the floor drainage system were installed incorrectly between the Chiller Rooms and the Chilled Water Pump Room. While this condition existed, Chiller Rooms B and C were connected by an 8-inch drain line, as were Chiller Room A and the Chilled Water Pump Room. The drainage system nonconformance condition will be reported in LER-2016-004.

A thermal hydraulic model was developed using the GOTHIC computer code (version 8.1) to calculate the environmental conditions that could have existed at the Intermediate Building (IS) 412 foot elevation during a postulated HELB event.

The GOTHIC computer program is a general purpose analysis tool that solves the conservation equations for mass, energy, and momentum for multi-component, multi-phase flow, and it has been used extensively for compartment transient analysis in nuclear power plants. The initial analysis indicated that during a postulated HELB event, the environmental result for the additional rooms connected by the drain line were not expected to significantly rise in temperature and humidity. And as a result, there would have been reasonable assurance that the risk significant equipment in the Mild Area (i.e., Chiller, Chiller Pump, Battery and Battery Charger rooms) would have been able to perform their required functions had such an event occurred.

However, further analyses were initiated to ensure smaller break sizes (<4" Nominal Pipe Size (NPS)) would not potentially lead to more steam propagation than the EQ design basis cases. The station performed analyses which postulated these types of breaks. For small breaks, the mass and energy release rates are low and the IB rooftop blowout panels do not actuate. Although temperatures within the 18 rise, IB pressure remains low, so that propagation of air/steam from the IB is small. As a result, entry of air/steam from the IB into Chiller Room C does not lead to significant changes in the Battery, Battery Charger, Chiller, and Chilled Water Pump room conditions.

For intermediate breaks, the mass and energy release rates could be high enough to result in degraded conditions at an open Chiller Room door, but low enough to not actuate the IB rooftop blowout panels. As a result, intermediate breaks have the potential to produce the largest changes in Battery/Battery Charger and Chiller Area room environmental conditions. However, for this worst case, the Battery/Battery Charger Area room temperatures remain in their normal operational band and relative humidity remains at normal values. Chiller Room A temperature remains in the normal operational band and relative humidity remains at normal values. The Chiller Pump Room temperature remains in the normal operational band and relative humidity remains at normal values because it is not connected via floor drains to the Chiller Room with the propped open door. The environmental conditions in Chiller Room B, however, would degrade to the point where Chiller B would fail due to high temperature resulting in one of the two trains of Chilled Water being inoperable during the time the door to Chiller Room C was propped open. Chiller Room A and the Chilled Water Pump Rooms would not have been affected by the postulated event.

3.0 SAFETY SIGNIFICANCE

A HELB event postulated to occur during the times when the non-conforming HELB barrier configuration existed would not have impacted the functionality of equipment in the Battery/Battery Charger Rooms (which would have remained within Technical Specification 3.7.9 limits) or the functionality of equipment in Chiller Room A and the Chilled Water Pump Rooms. There is no change to the result in the PRA model, and the condition is determined to be not risk significant.

4.0 PREVIOUS OCCURRENCE No previous occurrence within the last three years.

5.0 CORRECTIVE ACTIONS

To mitigate the events and preclude reoccurrence VCSNS conducted the following activities:

1. The door was closed as the immediate action and VCSNS issued Special Order 16-05 as an interim action to suspend propping open chiller room doors. This Special Order has since been cancelled as the proper plant configuration (drain orifices) has been restored to its normal configuration.

2. The station conducted a walkdown of the steam barriers associated with the event. Based on the walkdown the station evaluated the extent of condition of identified nonconformances addressed in LER 2016-004-00 (orifice) and LER 2016-005-00 (ductwork). A detailed analysis was completed to address safety significance.

3. Procedures have been reviewed and updated to minimize reoccurrence under the Corrective Action Program.

4. The station initiated an assessment of the potential impacts due to steam propagation. The resulting technical report documents the evaluation of the potential impact on equipment functionality of recently identified non-conforming HELB barrier configurations at VCSNS. Page 4

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