Information Notice 1990-65, Recent Orifice Plant Problems
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
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
This information notice is intended to alert addressees to recent problems that
have been identified with orifice plates. It is expected that recipients will
review the information for applicability to their facilities and consider
actions, as appropriate, to avoid similar problems. However, suggestions
contained in this information notice do not constitute NRC requirements;
therefore, no specific action or written response is required.
Description of Circumstances
Recent licensee and NRC inspections have identified two problems associated
with orifice plates. Namely, the installation of orifice plates in the reverse
direction and the deformation of orifices in the direction of flow.
With respect to the first of the two problems, on August 8, 1988, operators at
the San Onofre Nuclear Generating Station, Unit 1, discovered-an error in
several daily calorimetric power calibrations.
Further investigation revealed
that one of the three feedwater flow indicators was providing flow indication
that was lower than the actual feedwater flow.
This error resulted in the
indicated power on the nuclear instrumentation system being adjusted as much as
four percent lower than the actual reactor power.
The licensee determined
that the orifice plate for the deficient flow indicator was installed backwards, causing the indicated flow to be less than the actual flow.
Subsequent evaluation
showed that all accident scenarios described in the Final Safety Analysis
Report produced acceptable results despite the error. In 1985, San Onofre Unit
1 reported a similar event (LER 50-206/85-014).
During an NRC walkdown of the containment spray system at the Farley Nuclear
Plant in April 1989, inspectors found that an orifice plate in a flow element
had been installed backwards. The flow element provided spray additive tank
flow indication in the control room. The licensee subsequently found four
other orifice plates, used in the charging system, the auxiliary feedwater
system, and the containment spray system, that were reversed.
Similarly, in
July 1989 the Shearon Harris Nuclear Power Plant found a reversed orifice
plate. This orifice plate also was used to determine the flow rate for the
containment spray system spray additive tank.
( < O 9 2 8 1 6 6 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
October 5, 1990
Page I of I
LIST OF RECENTLY ISSUED
NRC INFORMATION 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 NRC
medical
- 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.
- Operating License
- Construction Permit
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 2055
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE. $300
FIRST CLAS
POSTAGE & FEES PAID
USNAC:
PERMIT@
No a9
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.
, n-
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
Document Name: ORIFICE
- SEE PREVIOUS CONCURRENCES
- SEE PREVIOUS FAX CONCURRENCE
- OGCB:DOEA:NRR
- RII
- RPB:ADM
C/OGCB:DOEA:NRR
D/DOEALI
_-
AJKugler
SSparks
TechEd
CHBerlinger
CERossir
09/06/90
09/10/90 09/12/90
09/26/90
W/, /90
IN 90-XX
September xx, 1990 Orifice plates are also used as flow restrictions, which provide a specific
hydraulic resistance in a piping system to limit the 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.
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
Document Name: ORIFICE
- SEE PREVIOUS CONCURRENCES
- SEE PREVIOUS FAX CONCURRENCE
- OGCB:DOEA:NRR
AJKugler
09/06/90
- RII
SSparks
09/10/90
- RPB:ADM
TechEd
09/12/90
CB:DOEA:NRR
CHBerlinger
094 /90
D/DOEA:NR?,,
CERoss I
09/
/90
IN 90-XX
September xx, 1990 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.
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
Document Name:
ORIF
OGCB:DOEANRR
AKugler 4t
09/06/90
RII #
SSparks
09/
/90
RPB:ADM
TechEd ,*
09/
/90
C/OGCB:DOEA:NRR
CHBerlinger
09/
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D/DOEA:NRR
CERossi
09/
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09/06/90
Okif
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39
IN 90-XX
September xx, 1990
I 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.
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
Document Name:
ORIF
OGCB:DOEA:NRR
AKugler
09/ /90
RII
SSparks
09/
/90
RPB:ADM
TechEd MYWr-
09/]i/0
C/OGCB:DOEA:NRR
CHBerlinger
09/
/90
D/DOEA:NRR
CERossi
09/
/90