Information Notice 1990-65, Recent Orifice Plant Problems

Recent Orifice Plant Problems
	ML031130240
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	10/05/1990
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	IN-90-065, NUDOCS 9009280166
	Download: ML031130240 (10)
	v • d • e

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 October 5, 1990

NRC INFORMATION NOTICE NO. 90-65: RECENT ORIFICE PLATE PROBLEMS

Addressees

nuclear power

All holders of operating licenses or construction permits for

reactors.

Purpose

This information notice is intended to alert addressees to that recent problems that

recipients will

have been identified with orifice plates. It is expected and consider

review the information for applicability to their facilities suggestions

actions, as appropriate, to avoid similar problems. However, contained in this information notice do not constitute NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

associated

Recent licensee and NRC inspections have identified two problems in the reverse

with orifice plates. Namely, the installation of orifice plates

direction and the deformation of orifices in the direction of flow.

operators at

With respect to the first of the two problems, on August 8, 1988, error in

the San Onofre Nuclear Generating Station, Unit 1, discovered-an revealed

several daily calorimetric power calibrations. Further investigation

indication

that one of the three feedwater flow indicators was providing flow in the

that was lower than the actual feedwater flow. This error resulted as much as

indicated power on the nuclear instrumentation system being adjusted determined

four percent lower than the actual reactor power. The licensee

backwards, that the orifice plate for the deficient flow indicator was installed evaluation

causing the indicated flow to be less than the actual flow. Subsequent

showed that all accident scenarios described in the Final Safety Analysis

Unit

Report produced acceptable results despite the error. In 1985, San Onofre

1 reported a similar event (LER 50-206/85-014).

Nuclear

During an NRC walkdown of the containment spray system at the Farley element

Plant in April 1989, inspectors found that an orifice plate in a flow

spray additive tank

had been installed backwards. The flow element provided

found four

flow indication in the control room. The licensee subsequently feedwater

other orifice plates, used in the charging system, the auxiliarySimilarly, in

system, and the containment spray system, that were reversed.

July 1989 the Shearon Harris Nuclear Power Plant found a reversed orifice

the

plate. This orifice plate also was used to determine the flow rate for

containment spray system spray additive tank.

(< O 92 8 1 66 v 7C

IN 90-65 October 5, 1990 Reversed orifice plates have also been found at the Salem Nuclear Generat- ing Station, Brunswick Steam Electric Plant, Waterford Steam Electric Plant, Surry Power Station, and North Anna Power Station. At the Salem plant, in

May 1989, the flow metering orifices for the high-head cold leg safety injection

line were found installed backwards. After the orifices were correctly

installed, the indicated flow rate was 15 percent greater. At Brunswick, in

February 1989, the licensee discovered a flow restricting orifice installed

backwards in the high-pressure core injection minimum flow line, and in two

other systems. Waterford experienced problems with low indicated flow in the

recirculation line of a high pressure safety injection pump. The problem was

traced to a reversed flow orifice in May 1989. At Surry in August 1989, an NRC

inspector discovered a reversed flow orifice after the completion of a corrective

action program aimed at flow orifices. Further walkdowns by the licensee

identified two additional flow orifices installed backwards. At North Anna in

September 1989, a total of nine flow orifices were determined to be installed

backwards. Only orifices which are accessible during power operation were

inspected. The root cause of these events has generally been determined to be

inadequate procedures for and inspection of installations.

In February 1989, a second problem with orifice plates was identified at

Brunswick, i.e., several flow restricting orifices were deformed in the direc- tion of flow. The orifices were located in the residual heat removal system, the core spray injection and minimum flow line, and the high-pressure coolant

injection system. Each of the orifice plates was manufactured from A240-316

- statless-steel-arnd-was 8-inch-thik- _ltisth-icknes-Swas based on standard

orifice design that did not consider the thickness needed to prevent deforma- tion caused by flow and the differential pressure across the orifice plate.

In one instance, the orifice bore had increased from 1.021 inches to 1.088 inches, and the plate had ballooned outward approximately 0.5 inch. Subse- quently, the licensee evaluated the design of the orifice plates using allow- able material stresses, orifice plate geometric configurations, and system flow

rates. The results of this evaluation indicated that the applied stress

exceeded several times the allowable material yield stress. The licensee

determined that the root cause of the deformation was an inadequate design

thickness specification.

Discussion:

An orifice plate is commonly used as a primary flow element, and produces a

differential pressure from which a flow rate can be determined., Orifice plates

have a handle on which pertinent data is permanently marked, such as orifice

diameter, flange size, pressure rating, and, as appropriate, the word "In- let." The two most common types of orifice plates are squared edge and beveled

edge. On a beveled edge orifice plate that is properly installed, the word

Inlet" faces the inlet direction and the beveled edge faces the outlet direc- tion. A square edged orifice plate is not dependent upon orientation to

perform its function. However, Installation procedures for both types of

orifice plates should be consistent. A beveled orifice plate that is installed

backwards would provide a lower differential pressure across the flow element, resulting in a flow rate measurement that is lower than the actual flow rate.

IN 90-65 October 5, 1990 Orifice plates are also used as flow restrictors, to provide a specific

hydraulic resistance in a piping system to limit flow rate. A failure of

the orifice plate could cause excessive recirculation or bypass flow, which may

decrease the flow being delivered to the main flow path during an accident.

The failure of the orifice plate could also reduce the hydraulic resistance in

the system, increasing the total pump flow rate and the probability of centrif- ugal pump runout. Runout could damage the internal components of the pump, lead to inadequate net positive suction head, and overload the pump motor.

Increased flow rates in the orificed line could also lead to increased pipe

vibration and erosion. In addition, permanently deformed orifice plates could

provide inaccurate flow measurements.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact one

of the technical contacts listed below or the appropriate NRR project manager.

A Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Scott Sparks, Region II

(404) 331-4187 Andrew Kugler, NRR

(301) 492-0834 Attachment: List of Recently Issued NRC Information Notices

I

I

Attachment 1 IN 90-51 October 5, 1990

Page I of I

LIST OFRECENTLY ISSUED

NRCINFORMATION NOTICES

Intormation cat. or

Notice no. SubJect Issuance Issued to

90-64 Potential for Comma-Mode 10/4/90 All holders of

Failure of High Pressure OLs or CPs for

Safaty Injectlon Pumps or pressurized-water

Release of Reactor Coolant reactors.

Outside Containment During

A Loss-Of-Coolant Accident

90-43 Management Attention to the 10/3/90 All fuel cycle

Establishment and Main. licensees possess- tenance of A Nuclear Ing more than

Criticality Safety Program crtrcal mss

quantities of

special nuclear

material.

90-42 Requirements for Import 9/25/90 All irradiated

and Distribution of gemstone importers

Neutron-Irradiated Goes end distributors.

and all non-power

licensees.

90-41 Potential for Residual 9/20/90 All holders of

Heat Removal Pump OLs or CPs for

Pump Damage Caused By nuclear power

Parallel Pump interaction reactors.

90-60 Availability of Failure 9/20/90 All holders of

Data In the Government. OLs or CPs for

Industry Data Exchange nuclear power

Program reactors.

90-59 Errors In the Use of 9/17/90 All medical

Radioactive todine-131 licensees.

90-58 Improper Handling of 9/11/90 All NRCmedical

- Opttaft&Strontiua.9L . _ iceasees.

Beta Radiation Applicators

90-S7 Substandard, Refurbished 9/5/90 All holders of OLs

Potter S Brumfield Relays or CPs for nuclear

Misrepresented As Nw power reactors.

OL

Operating License

CP* Construction Permit

UNITED STATES FIRST CLAS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE & FEES PAID

WASHINGTON, D.C. 2055 USNAC:

PERMIT@ No a9 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $300