05000266/LER-2006-001

LER-2006-001,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2662006001R00 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3)

Event Description:

On May 2, 2006, testing was conducted on the F-16, Control Room Charcoal/HEPA/Roughing Filter [FLT], in accordance with Technical Specification (TS) 5.5.10.c, "Ventilation Filter Testing Program." A sample of charcoal was sent to NUCON for methyl iodide penetration testing. On May 30, 2006, at 0923 the Control Room Emergency Filtration System (CREFS) [VI] was declared inoperable based on failure of the charcoal to meet the methyl iodide penetration acceptance criterion of "Control Room Emergency Filtration System (CREFS)," Condition A, "CREFS Inoperable" with a Required Action of "Restore CREFS to OPERABLE status" in a completion time of seven (7) days. Both units were in Mode 1 at 100% rated thermal power.

Operations replaced the F-16 charcoal filter trays on May 30, 2006. On May 31, 2006, freon leak testing of the F-16 control room charcoal adsorber [ADV] failed based on 98.6% filtration efficiency results. The acceptance criterion is z 99.00%. An inspection of the F-16 filter frame, housing and trays was performed.

This inspection identified degraded Sealant (RTV) on the north and south vertical seams of the downstream side of the charcoal adsorber (CAP 01033448). This degradation allowed upstream air to bypass the could lead to bypass air flow.

The charcoal filter trays were replaced again on June 3, 2006 (Work Order 286726). The trays were verified to be full prior to installation. The charcoal also passed a laboratory methyl iodide penetration test prior to shipment to Point Beach Nuclear Plant (PBNP).

The degraded RTV condition was resolved by applying new RN on the downstream side of the north and south vertical seams. In addition, new RN was applied to the upstream side of the north and south vertical seams (Work Order 286788). GE Silicone RTV 102 was used in accordance with the component instruction manual.

Testing was completed on June 3, 2006, that demonstrated compliance with TS 5.5.10.b, TS 5.5.10.c, and TS 5.5.10.d. Operations exited the CREFS TSAC June 4, 2006, at 2030.

During replacement of filters and repair of RN on the filter frame/housing, the tightness of the control room envelope (CRE) was not affected. The outside/pressurization airflow rate in control room ventilation system Mode 4 remained above the minimum of 4455 cfm. Therefore, the CRE to all adjacent spaces Differential Pressure (DP) measurements remained greater than 1/8" with significant margin to spare.

Component and system Description:

The CREFS provides a protected environment from which operators can control the unit following an uncontrolled release of radioactivity.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) POINT BEACH NUCLEAR PLANT UNIT 1 05000266 l REVISION The CREFS consists of one emergency makeup air filtration unit, two emergency makeup fans, two recirculation fans, and the required ducts and dampers necessary to establish the required flow paths and isolation boundaries. The CREFS is an emergency system, parts of which operate during normal operations.

The air entering the control room is continuously monitored by a noble gas radiation monitor and the control room itself is continuously monitored by an area radiation monitor. One detector output above its setpoint will actuate the emergency makeup mode of operation for the CREFS.

The limiting design bases accident for the control room dose analysis is the large break Loss of Coolant Accident (LOCA).

The CREFS will pressurize the control and computer rooms to at least 0.125 inches water gauge in the emergency makeup mode of operation. The CREFS role in maintaining control room habitability is discussed in the Final Safety Analysis Report (FSAR), Section 9.8.

The CREFS provides airborne radiological protection for control room personnel, as demonstrated by the limiting control room dose analysis for the design basis LOCA. Control room dose analysis assumptions are presented in the FSAR, Section 14.3.5.

Event Analysis and Safety Significance:

The F-16 filter is part of the control room ventilation system that is used for emergency operation and is used to maintain control room personnel radiation dose within regulatory requirements.

Prior to the test, there were no known significant conditions adverse to quality present. There were no conditions where nuclear safety or personnel safety were significantly threatened or had been compromised.

The condition was identified as part of routine testing that is performed to ensure system operation meets technical specification requirements.

This event was of low safety significance because this event would not have prevented CREFS from performing its safety function since the last successful completion of the Technical Specification surveillance. The methyl iodide penetration test result of the charcoal sample, 98.905% filter efficiency was well above the safety analysis (FSAR Section 14.3.5) stated 95% required filter efficiency for organic (methyl) and elemental material. In addition, a qualitative assessment of the impact of the extra out of service time was performed and concluded that there was no direct effect on Core Damage Assessment due to the CREFS being out of service.

FACILITY NAME (1) _ DOCKET NUMBER (2) _ LER NUMBER (6) _ PAGE (3)

Cause:

The exact cause for failure of the methyl iodide penetration test of the sample of the charcoal adsorber has not yet been determined. However, the subsequent test failure due to excessive bypass flow was attributed to a combination of:

• aging of the RN used to seal the seams between the filter frame and the filter housing, and

• possible bypass airflow due to an underfill condition in 7 of the 14 filter trays.

Corrective Action:

The F-16 charcoal filter trays were replaced with new trays that were verified to be properly filled before installation. The degraded RN condition was repaired by applying new RN over the degraded RN.

Proper gasket crush was verified when installing the new filter trays.

Previous Similar Events:

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