ML20012D809

LER 90-003-00:on 900220,instrument Fluctuation Noted During Surveillance of Chilled Water Pump.Caused by Location of Flow Element within Chilled Water Sys.Relief Request Submitted & Field Problem Rept generated.W/900322 Ltr

ML20012D809
Person / Time
Site:	Crystal River
Issue date:	03/22/1990
From:	Boldt G, Moffatt L FLORIDA POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
3F0390-18, 3F390-18, LER-90-003, LER-90-3, NUDOCS 9003280394
Download: ML20012D809 (5)

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1 Power

' C OR P O R AT t O N i

March 22, 1990- '4 -

.3F0390-18 U. S., Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555

Subject:

Crystal: River Unit -3

,  : Docket No. 50-302 . ,

~0perating License No. DPR-72

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Licensee Event Report No. 90-03 -

Dear Sir:

Enclosed is Licensee Event Report' (LER) 90-03 which is submitted 'in -

- accordance with 10 CFR 50.73.

Should- there be any questions, please' contact this- office.

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Sincerely,.-

e

G.. L Boldt

-Vice President,-Nuclear Production m

.WLR:magl s  ;

' Enclosure

-xc: Regional Administrator, Region II

-Senior Resident Inspector I j

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• Present Plant Design Leads to Instrument Fluctuation Exceeding Required Range and Subsequent Technical Specification Violation EVENT DATE 151 LER NUMBER (St REPORT DATE (7) OTHER F ACILITIES INVOLVED (8)

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$USMes$10N YE$ III res, compiere EXPECTIO SUCMr$$ TON DA Til NO l l l A..TXACT WWF to f M wues t e , appreservieret f4ea we sue typeweerma hes/ 061 On February 20, 1990 Crystal River Unit 3 was in Mode 3, HOI' STANDBY, following a plant heatup fr m a forced outage. The Reactor coolant System was at a pressure of 2155 psig and a temperature of 5320F.

A surveillance was perfonned on a chilled water pump to denonstrate its acceptability in accordance with ASME Section XI. 'Ihe code requires that instrument fluctuations be within 2% of the nherved reading prior to the performance of the surseillan . 'Ihe 2% requirement could not be achieved.

However, when the averace flow reading was obtained the data was satisfactory.

A likely cause of the fluctuations is the location of the flow element within the chilled water system. 'Ihe element is located seven feet frm a 90 degree elbow where turbulent flow could exist. Also, the flow measurement device is an annubar which inherently will indicate hydraulic fluctuations when installed in a low flow system.

A relief request was submitted to the NRC proposing alternate acceptance criteria frun the requirements of IWP-4150 which restricts the instrument fluctuations to within 2% of the observed reading. 'Ihe proposed method is based in criterion of ANSI /ASME CHa-1988 which eliminates the 2% restriction and focuses on repeatable steady state results. An evaluation will be performed to investigate redesigning the chilled water system and/or provide a different type of flow element.

N/.C Form 36616-891 -

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[ rnxT tu on e w. .ma.w ome ram, sana un j- EVENT DESCRIFFION; On February 20, 1990 at 0800 Crystal River Unit 3 was in OPERATIONAL K)DE 3 (IUf STANDBY), following a plant heatup frun a - forced outage. Se Reactor Coolant System was at a pressure of 2155 psig and a tenperature of 5320F. As part of the In-Service Inspection (ISI) program, a surveillance was being performed on milled Water Punp 1A [1H,P] by Technical Support personnel. Se function of the surveillance is to demonstrate the acceptability of the chilled water punp in accordance with the criteria set forth by the ASME Boiler and Pressure Vessel Code Section XI, as outlined in Technical Specification 4.0.5(b). Sub-paragraph IWP-4150 of Section XI, methods of measurement, requires that instrument fluctuations be reduced to within 2% of the observed reading prior to the performance of the surveillance. Se chilled water system

[lH] flow measurement for this surveillance is obtained by connecting a portable differential pressure transmitter to a permanently installed annubar device.

! Se flow instrument fluctuations observed were greater than the 2% allowance.

In accordan with the surveillance pwceidre and sub-paragraph IWP-4150, if the fluctuations exceed the 2% range they may be dampened by using gauge snubbers or by throttling valves in the instrument lines. Both of these methods were attenpted to reduce the fluctuations. However, the fluctuations could not be reduced to less than 4%. February 21, 1990 was the last day of the administrative window to complete the surveillance. Utility personnel were instructed by management to continue with the surveillance to provide reasonable assurance that the punp was operating satisfactorily. With the exception of the instrument fluctuations the surveillance was performed satisfactorily. - A request for relief was informally subnitted to the NRC prior to the testing and the formal request followed prmptly.

EVENT ANALYSIS:

In accordance with the Schnical Specifications, two indeperrlent control room emergency ventilation systems must be operable. Willed water at sufficient flow, tenperature and pressure must be provided to each of the two control couplex emergency ventilation heat exchangers in order for the two trains of control roca emergency ventilation systems to be operable.

In addition to supplying chilled water to the control complex emergency ventilation heat exchangers, the chilled water system also supplies chilled water to the penetration cooling units and the roams containing the emergency feedwater initiation and control (EFIC) cabinets. Se EFIC cabinet rocas are equipped with an Appendix R backup cooling water system.

GC Form 386A (649)

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The design of the chilled water system has low flow conditions. The element used )

to measure flow is an annubar type element that, under low flow conditions, i typically will indicate hydraulic fluctuations in measurement. This, coupled with the physical location of the element downstream of an elbow, provides an indication of hydraulic fluctuation that cannot be reduced to be within 2% of the required reading.

The surveillance procedure was performed on both chilled water pumps as intended by ANSI /ASME OMa-1988, part 6, paragraph 4.6.1.5 to assure the intent of " steady-state" conditions and averaging the flow reading. When the desired averaaed flow reading was obtained, which was within 2% of the required reading, the data for both pumps was gathered in accordance with Section XI requirements and found L

satisfactory.

CAUSE:

Technical Specifications require in-service testing of ASME Code Class 1, 2 and 3 pumps in accordance with Section XI of the ASME Boiler and Pressure Vessel Code.

It is required that instrument fluctuation be within 2% of the observed reading, The instrument fluctuation (differential pressure) could not be dampened to within I the required 2%. Plant personnel have not yet determined the root cause of the greater than 2% instrument fluctuation. A likely cause of the fluctuation is the

. physical location of the differential pressure element within the chilled water I system. The-element is located approximately seven feet from a 90 degree elbow where turbulent flow could exist. Additionally, the element used to measure flow '

within the chilled water system is an annubar device. This type of flow element inherently will indicate hydraulic fluctuations when installed in a relatively low flow system.

I A relief request was submitted and approved by the NRC in March 1988. The flow element was replaced in 1989 and the relief request was withdrawn in October of 1989. The initial 1988 relief request and Florida Power Corporation's actions to resolve this relief request were based on the assumption that the root cause of the excess instrument fluctuation was a degraded flow element. Therefore, the post maintenance testing of the replaced flow element did not verify that the instrument fluctuations could be reduced within the 2% required range. Another relief request was submitted to identify the 2% instrument fluctuation as an impractical requirement. A more practical approach would be to obtain an averaaed flow reading which is within 2% of the required reading.

CORRECTIVE ACTIONS:

The surveillance was performed on both chilled water pumps satisfactorily as intended by ANSI /ASME OMa-1988, Part 6, paragraph 4.6.1.5, to assure that the intent of " steady-state" conditions were met.

NMC Form 306A (6491

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A relief request was written to identify the requirements of sub-paragraph IWP-4150, obtaining fluctuations in hydraulic instrument readings to be within 2% of the observed reading, as being impractical.

A field problem report was generated to evaluate redesigning the chilled water system and/or provide a different flow element to allow Code requirements to be met.

Florida Power Corporation has improved procedures and guidelines for performing root cause and failure analyses. These improvements should prevent recurrence of these types of errors and assumptions.

To preclude a similar event, Engineering is pursuing enhancing the existing.

instrumentation which will provide a digital averaging technique.

PREVIOUS SIMILAR EVENTS:

There have been six previous events associated with the in-service inspection program and Technical Specification 4.0.5. However, none of these events specifically involved instrument fluctuation criteria identified in ASME Section XI, 1983 Edition, IWP-4150.

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