Information Notice 1991-18, High-Energy Piping Failures Caused by Wall Thinning: Difference between revisions
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| issue date = 12/18/1991 | | issue date = 12/18/1991 | ||
| title = High-Energy Piping Failures Caused by Wall Thinning | | title = High-Energy Piping Failures Caused by Wall Thinning | ||
| author name = Rossi C | | author name = Rossi C | ||
| author affiliation = NRC/NRR | | author affiliation = NRC/NRR | ||
| addressee name = | | addressee name = |
Revision as of 04:18, 14 July 2019
ML042380261 | |
Person / Time | |
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Issue date: | 12/18/1991 |
From: | Rossi C Office of Nuclear Reactor Regulation |
To: | |
References | |
IN-91-018, Suppl 1 | |
Download: ML042380261 (5) | |
UNITED STATES NUCLEAR REGULATORY
COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 December 18, 1991 NRC INFORMATION
NOTICE 91-18, SUPPLEMENT
1: HIGH-ENERGY
PIPING FAILURES CAUSED BY WALL THINNING
Addressees
All holders of operating
licenses or construction
permits for nuclear power reactors.
Purpose
The U. S. Nuclear Regulatory
Commission (NRC) is issuing this information
notice to alert addressees
to continuing
erosion/corrosion
problems affecting the integrity
of high energy piping systems and to alert addressees
to apparently
inadequate
erosion/corrosion
monitoring
programs.
It is expected that recipients
will review the information
for applicability
to their facili-ties and consider actions, as appropriate, to avoid similar problems.
However, suggestions
contained
in this information
notice are not NRC requirements;
therefore, no specific action or written response is required.Background
On March 12, 1991, the NRC issued Information
Notice (IN) 91-18, "High Energy Piping Failures Caused by Wall Thinning," to describe ruptures and leaks in secondary
systems carrying high energy fluids at the Millstone
Nuclear Power Station, Unit 3, the San Onofre Nuclear Generating
Station, Unit 2, and a foreign plant.Following
the pipe rupture at the Surry Power Station in 1986, the NRC issued Bulletin 87-01, "Thinning
of Pipe Walls in Nuclear Power Plants," July 9, 1987.In this bulletin, the staff requested
licensees
and applicants
to inform the NRC about their programs for monitoring
the wall thickness
of carbon steel piping in both safety-related
and nonsafety-related
high energy fluid systems.IN 91-18 included references
related to this bulletin.
IN 82-22, "Failures
of Turbine Exhaust Lines," July 9, 1982, also provides relevant information
regarding
pipe wall thinning in steam lines.In 1989, following
an audit of the erosion/corrosion
programs at ten plants, the NRC issued Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced
Pipe Wall Thinning," May 2, 1989. In this generic letter, the staff requested
licensees and applicants
to implement
long term erosion/corrosion
monitoring
programs.The staff made this request to obtain assurances
that procedures
or administra- tive controls were in place to maintain the structural
integrity
of all carbon steel systems carrying high energy fluids.9121720218 ATTACHMENT
14 IN 91-18, Supplement
1 December 18, 1991 The Electric Power Research Institute (EPRI) released computer codes CHEC and CHECMATE in June 1987 and April 1989, respectively, to assist in selecting
for testing those areas of the piping systems with highest probabilities
for wall thinning.
The CHEC calculation
applies to pipes containing
a single liquid phase and the CHECMATE calculation
applies to pipes containing
both liquid and vapor phases.On June 11, 1987, the Technical
Subcommittee
Working Group on Piping Erosion/Corrosion
of the Nuclear Management
and Resources
Council (NUMARC)issued a summary report describing
a method using the CHECMATE computer code for monitoring
carbon steel components
exposed to the conditions
conducive
to erosion/corrosion.
Description
of Circumstances
At Millstone
Unit 2, on November 6, 1991, while the licensee, the Northeast Nuclear Energy Company (NNECO), was operating
the plant at 100 percent of full power, a rupture occurred in train B of the moisture separator
reheater (MSR)system. An 8-inch elbow, located between the first stage MSR drain tank and the feedwater
heater, ruptured at its extrados (Figure 1). The elbow was located downstream
from a 4-inch flow control valve and a 4- to 8-inch expander.
The high energy water in the pipe (approximately
463 F, 470 psig)flashed to steam, actuating
portions of the turbine fire protection
deluge system. The water level in the steam generator
decreased
slightly.
The licen-see had not selected the ruptured elbow for ultrasonic
testing (UT) in its erosion/corrosion
monitoring
program.The ruptured elbow was made of carbon steel with nominal wall thickness
of 0.322 inch. Wall thickness
at the failed area was eroded to 95 percent of the initial nominal value. Other areas, away from the failed area, showed a loss of 22 percent of the wall thickness.
The identical
elbow in the A train had a maximum wall loss of 34 percent of the initial nominal value.Discussion
The licensee has had a program for monitoring
high energy fluid piping since 1981. The criteria for choosing components
to be inspected
include component location and service conditions
as determined
by the engineering
judgement
of the plant personnel.
In contrast, more relevant parameters
that could indicate erosion or corrosion
wastage include piping material and geometry,'fluid
prop-erties (flow, temperature, and acidity), and fluid contents (the acidity-controlling
agent and the concentration
of dissolved
oxygen).In its response to GL 89-08, NNECo indicated
that its Engineering
Procedure EN-21153, "Thickness
Testing of Secondary
Piping," describes
its monitoring
program, established
in accordance
with EPRI guidelines
and using the CHEC pro-gram to select for testing those areas of the pipi ng systems with highest prob-abilities
for wall thinning.
The licensee also selects areas on the basis of plant experience.
However, although the pipe wall thickness
testing program vlas included in the licensee's
procedures, the licensee had not implemented
the methodology
using the EPRI computer codes at Unit 2. This omission may account for the licensee not having tested previously
the piping that ruptured on November 6, 1991.
.i~ 5X*-13, Supp Li st I December 18, 1991 The licensee did use an earlier version of the CHEC computer code in limited analyses at its other nuclear units. The licensee's
program did not reflect the use of current versions of EPRI codes (either CHEC or CHECMATE). .The Unit 3 rupture described
in the March 12, 1991, issuance of this information
notice prompted NNECo to commit to perform CHEC or CHECMATE analyses at all its units by December 31, 1991. However, at the time of the second rupture on November 6, 1991, the licensee was implementing
this program at its corporate engineering
office and not at Unit 2. The Unit 2 personnel
were consequently
relying on inspection
procedures
that did not possess the benefit of the EPRI's methodology
for selecting
areas of piping for UT inspection.
After November 6, 1991, NNECo performed
a CHECMATE analysis that did identify this portion of the MSR system as highly susceptible
to erosion or corrosion
and thus as a candidate
for UT inspection.
This information
notice requires you have any questions
about the of .the technical
contacts listed Reactor Regulation (NRR) project no specific action or written response.
If information
in this notice, please contact one below or the appropriate
Office of Nuclear manager.(Charles E. Rossi, Director Division of Operational
Events Assessment
Office of Nuclear Reactor Regulation
Technical
contacts: K. 1. Parczewski, NRR (301) 504-2705 Vern Hodge, NRR (301) 504-1861 Attachments:
1. Figure 1, "Rupture of Elbow in Secondary
System at Millstone
Unit 2 on November 6, 1991" 2. List of Recently Issued NRC Information
Notices
6"xl2" FISH-ItIOUTH
BREAK AT EXTRADOS FLOW 4 in. dia.4 in. dia.8 in. dia.Motes: Vo. 1 B First Stage Moisture Separator Reheater Drain Tank Drain Line Pipe: Carbon Steel No Chromium Content Fluid: H2O @ 470 psig, 4630F pH: 8.2-*8.7 02: <2ppb CD (D .r a' r i 'Figure 1. Rupture of Elbow in Secondary
System at Millstone
Unit 2 on November 6, 199, CD-
A-ttzac~:.^, IN 91-18, Supplem~nt
1 December 18, 3991 Page 1 of i LIST OF RECENTLY ISSUED NRC INFORMATiON
NOTICES Information
Date of Notice No. Subject Issuance Issued to 91-82 91-81 91-80 91-79 88-92, Supp. 1 91-78 90-57, Supp. 1 91-77 91-76 Problems with Diaphragms
in Safety-Related
Tanks Switchyard
Problems that Contribute
to Loss of Offsite Power Failure of Anchor Head Threads on Post-Tensioning
System During Surveillance
Inspection
Deficiencies
in the Procedures
for Instal-ling Thermo-Lag
Fire Barrier Materials Potential
for Spent Fuel Pool Draindown Status Indication
of Control Power for Circuit Breakers Used in Safety-Related
Appli-cations Substandard, Refur-bished Potter & Brum-field Relays Repre-sented as New Shift Staffing at Nuclear Power Plants 10 CFR Parts 21 and 50.55(e) Final Rules 12/18/91 12/16/91 All holders of OLs or CPs for nuclear power reactors.12/11/91 All holders of OLs or CPs for nuclear power reactors.12/06/91 All holders of OLs or CPs for nuclear power reactors.11/29/91 All holders of OLs or CPs for nuclear power reactors.11/28/91 All holders of OLs or CPs for nuclear power reactors.11/27/91 All holders of OLs or CPs for nuclear power reactors.11/26/91 All holders of OLs or CPs for nuclear power reactors.11/26/91 All holders of OLs or CPs and vendors for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.f1 OL = Operating
License CP = Construction
Permit