U-602184, Provides Results of Continued Investigation Into 930701 Inoperability of SGTS Exhaust Stack High Range Radioactivity Monitor ORIX-PR008,as Committed to in

Provides Results of Continued Investigation Into 930701 Inoperability of SGTS Exhaust Stack High Range Radioactivity Monitor ORIX-PR008,as Committed to in

ML20057A168
Person / Time
Site:	Clinton
Issue date:	09/03/1993
From:	Phares R ILLINOIS POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
U-602184, NUDOCS 9309130134
Download: ML20057A168 (2)

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Illinois Power Company Clinton Power Station

. P.O. Box 678 Clinton. IL 61727 Tel217 935-88B1 P@WER U-602184 L30-93(09-03)LP IE.100c September 3,1993 Docket No. 50-461 10CFR50.36 -

Document Control Desk Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Follow-Up Repon for the Extended Inoperability of the SGTS Exhaust Stack High Range Radioactivity Monitor at Clinton Power Station (CPS)

Dear Sir:

As committed in Illinois Power (IP) letter dated July 19,1993 (U-602155), IP now provides the results of the continued investigation into the July 1,1993 inoperability of the Standby Gas Treatment System (SGTS) Exhaust Stack High Range Radioactivity Monitor (ORIX-PR008). As previously reponed, the cause of the inoperability was due to a degraded pump which did not provide adequate sample air flow. The root cause of the pump failure has been determined and is discussed in this report. Additionally, the two replacement pumps which were installed and tested in the system with unsatisfactory results have been evaluated and are also discussed in this repon.

Root Cause of the July 1.1993 Failure of ORIX-PROOS The initial pump, which failed in-service, was inspected and tested by IP personnel.

The testing verified that the pump delivered inadequate flow. The pump was therefore returned to Parker Metal Bellows (PMB), the pump manufacturer, for further testing.

Initial testing verified the results oflow flow, but the root cause was not yet established at the time the July 19,1993 Speciil Report was submitted.

PMB continued their investigation into the failure by disassembling and inspecting the internals of the failed pump. PMB discovered that the viton gasket, which provides a seal between the inlet and outlet valve reeds, was contacting the outlet reed. This contact was enough to reduce flow below the required value. PMB indicated that this condition could be the result of many factors, including the possibility for the gasket to be' overly -

compressed and/or slightly mispositioned during pump assembly, reducing the normal

_ clearance between the valve reed and gasket. In addition, the gasket may ' creep' (due to heat and mechanical stress) over time and contact the valve reed. Based on the fmdings 9309130134 930903 3 .c @\' ' D' PDR ADOCK 05000461 Q S PDR. b.

. Page 2 of 2 to U-602184 reported by PMB, it has been concluded that the root cause of the failure on July 1,1993 is the result of a slight shifling of the gasket due to one or a combination of the above factors. As a slight change in pump erformance can occur over time due to this shifting, a contributor to the failure may be due to the small margin allowed for pump degradation as discussed below.

Results from Investigation of the Two Replacement Pump In-Service Failures As noted in IP's previous report, two replacement pumps were installed and [

operated but did not meet the system flow requirements. The pumps were then inspected and tested by IP personnelf As the system sample pumps are designed to provide a minimum flow of 5 liters per minute (Ipm), the results of the on-site testing determined ,

that each pump (out of the system) produced over 101pm. The two replacement pumps -

were subsequently sent to PMB for further evaluation and were found to be within the manufacturer's specifications. This suggests that, given pressure and flow losses with the -

pumps installed and operated in the system, there is little margin between the current manufacturer's pump flow specifications and the current system design flow requirements.

The required system flow as specified per CPS procedure 6948.02 "SGTS Stack ,

EfIluent-AXM Iodine and Particulates" is currently 61pm

• 1 Ipm in accordance with recommendations from Eberline, the system vendor. The design flows for the isokinetic flow nozzles within the monitoring system (s) at CPS are 51pm for the SGTS system and i

5.331pm for the Heating, Ventilation and Air Conditioning (HVAC) system. On this basis, IP is re-evaluating the flow criteria specified in the above procedure against the flow requirements of the system to determine if additional margin can be provided. Completion of this re-evaluation does not, in the mean time, preclude IP from obtaining replacement pumps that meet currently specified flow requirements.

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Sincerely yours, V, ,

Richard F. Phares l Director-Licensing CLIE/smd ,

cc: NRC Clinton Licensing Project Manager l NRC Resident Office, V-690 Regional Administrator, Region III, USNRC Illinois Department of Nuclear Safety 1

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