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 E
| author name = Rossi C
| author affiliation = NRC/NRR
| author affiliation = NRC/NRR
| addressee name =  
| addressee name =  
Line 14: Line 14:
| page count = 5
| page count = 5
}}
}}
{{#Wiki_filter:UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:UNITED STATES


COMMISSION
NUCLEAR REGULATORY COMMISSION


===OFFICE OF NUCLEAR REACTOR REGULATION===
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 December 18, 1991 NRC INFORMATION


NOTICE 91-18, SUPPLEMENT
WASHINGTON, D.C. 20555 December 18, 1991 NRC INFORMATION NOTICE 91-18, SUPPLEMENT 1:  HIGH-ENERGY PIPING FAILURES CAUSED


1: HIGH-ENERGY
BY WALL THINNING
 
PIPING FAILURES CAUSED BY WALL THINNING


==Addressees==
==Addressees==
All holders of operating
All holders of operating licenses or construction permits for nuclear power


licenses or construction
reactors.
 
permits for nuclear power reactors.


==Purpose==
==Purpose==
The U. S. Nuclear Regulatory
The U. S. Nuclear Regulatory Commission (NRC) is issuing this information


Commission (NRC) is issuing this information
notice to alert addressees to continuing erosion/corrosion problems affecting


notice to alert addressees
the integrity of high energy piping systems and to alert addressees to


to continuing
apparently inadequate erosion/corrosion monitoring programs. It is expected


erosion/corrosion
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.


problems affecting the integrity
Background


of high energy piping systems and to alert addressees
On March 12, 1991, the NRC issued Information Notice (IN)91-18, "High Energy


to apparently
Piping Failures Caused by Wall Thinning," to describe ruptures and leaks in


inadequate
secondary systems carrying high energy fluids at the Millstone Nuclear Power


erosion/corrosion
Station, Unit 3, the San Onofre Nuclear Generating Station, Unit 2, and a


monitoring
foreign plant.


programs.
Following the pipe rupture at the Surry Power Station in 1986, the NRC issued


It is expected that recipients
Bulletin 87-01, "Thinning of Pipe Walls in Nuclear Power Plants," July 9, 1987.


will review the information
In this bulletin, the staff requested licensees and applicants to inform the


for applicability
NRC about their programs for monitoring the wall thickness of carbon steel


to their facili-ties and consider actions, as appropriate, to avoid similar problems.
piping in both safety-related and nonsafety-related high energy fluid systems.


However, suggestions
IN 91-18 included references related to this bulletin. IN 82-22, "Failures of


contained
Turbine Exhaust Lines," July 9, 1982, also provides relevant information


in this information
regarding pipe wall thinning in steam lines.


notice are not NRC requirements;
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
therefore, no specific action or written response is required.Background


On March 12, 1991, the NRC issued Information
Thinning," May 2, 1989. In this generic letter, the staff requested licensees


Notice (IN) 91-18, "High Energy Piping Failures Caused by Wall Thinning," to describe ruptures and leaks in secondary
and applicants to implement long term erosion/corrosion monitoring programs.


systems carrying high energy fluids at the Millstone
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


Nuclear Power Station, Unit 3, the San Onofre Nuclear Generating
steel systems carrying high energy fluids.


Station, Unit 2, and a foreign plant.Following
9121720218 ATTACHMENT 14


the pipe rupture at the Surry Power Station in 1986, the NRC issued Bulletin 87-01, "Thinning
IN 91-18, Supplement 1 December 18, 1991 The Electric Power Research Institute (EPRI) released computer codes CHEC and


of Pipe Walls in Nuclear Power Plants," July 9, 1987.In this bulletin, the staff requested
CHECMATE in June 1987 and April 1989, respectively, to assist in selecting for


licensees
testing those areas of the piping systems with highest probabilities for wall


and applicants
thinning. The CHEC calculation applies to pipes containing a single liquid


to inform the NRC about their programs for monitoring
phase and the CHECMATE calculation applies to pipes containing both liquid and


the wall thickness
vapor phases.


of carbon steel piping in both safety-related
On June 11, 1987, the Technical Subcommittee Working Group on Piping


and nonsafety-related
Erosion/Corrosion of the Nuclear Management and Resources Council (NUMARC)
issued a summary report describing a method using the CHECMATE computer code for


high energy fluid systems.IN 91-18 included references
monitoring carbon steel components exposed to the conditions conducive to


related to this bulletin.
erosion/corrosion.


IN 82-22, "Failures
==Description of Circumstances==
At Millstone Unit 2, on November 6, 1991, while the licensee, the Northeast


of Turbine Exhaust Lines," July 9, 1982, also provides relevant information
Nuclear Energy Company (NNECO), was operating the plant at 100 percent of full


regarding
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


pipe wall thinning in steam lines.In 1989, following
the feedwater heater, ruptured at its extrados (Figure 1). The elbow was


an audit of the erosion/corrosion
located downstream from a 4-inch flow control valve and a 4- to 8-inch


programs at ten plants, the NRC issued Generic Letter (GL) 89-08, "Erosion/Corrosion-Induced
expander. The high energy water in the pipe (approximately 463 F, 470 psig)
flashed to steam, actuating portions of the turbine fire protection deluge


Pipe Wall Thinning," May 2, 1989. In this generic letter, the staff requested
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


licensees and applicants
erosion/corrosion monitoring program.


to implement
The ruptured elbow was made of carbon steel with nominal wall thickness of


long term erosion/corrosion
0.322 inch. Wall thickness at the failed area was eroded to 95 percent of the


monitoring
initial nominal value. Other areas, away from the failed area, showed a loss


programs.The staff made this request to obtain assurances
of 22 percent of the wall thickness. The identical elbow in the A train had a


that procedures
maximum wall loss of 34 percent of the initial nominal value.


or administra- tive controls were in place to maintain the structural
Discussion


integrity
The licensee has had a program for monitoring high energy fluid piping since


of all carbon steel systems carrying high energy fluids.9121720218 ATTACHMENT
1981. The criteria for choosing components to be inspected include component


14 IN 91-18, Supplement
location and service conditions as determined by the engineering judgement of


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
the plant personnel. In contrast, more relevant parameters that could indicate


for testing those areas of the piping systems with highest probabilities
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).


for wall thinning.
In its response to GL 89-08, NNECo indicated that its Engineering Procedure


The CHEC calculation
EN-21153, "Thickness Testing of Secondary Piping," describes its monitoring


applies to pipes containing
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


a single liquid phase and the CHECMATE calculation
plant experience. However, although the pipe wall thickness testing program


applies to pipes containing
vlas included in the licensee's procedures, the licensee had not implemented the


both liquid and vapor phases.On June 11, 1987, the Technical
methodology using the EPRI computer codes at Unit 2. This omission may account


Subcommittee
for the licensee not having tested previously the piping that ruptured on


Working Group on Piping Erosion/Corrosion
November 6, 1991.


of the Nuclear Management
Li I st


and Resources
.i~5X*-13, Supp


Council (NUMARC)issued a summary report describing
December 18, 1991 The licensee did use an earlier version of the CHEC computer code in limited


a method using the CHECMATE computer code for monitoring
analyses at its other nuclear units. The licensee's program did not reflect


carbon steel components
the use of current versions of EPRI codes (either CHEC or CHECMATE). .The


exposed to the conditions
Unit 3 rupture described in the March 12, 1991, issuance of this information


conducive
notice prompted NNECo to commit to perform CHEC or CHECMATE analyses at all its


to erosion/corrosion.
units by December 31, 1991. However, at the time of the second rupture on


Description
November 6, 1991, the licensee was implementing this program at its corporate


of Circumstances
engineering office and not at Unit 2. The Unit 2 personnel were consequently


At Millstone
relying on inspection procedures that did not possess the benefit of the EPRI's


Unit 2, on November 6, 1991, while the licensee, the Northeast Nuclear Energy Company (NNECO), was operating
methodology for selecting areas of piping for UT inspection. After


the plant at 100 percent of full power, a rupture occurred in train B of the moisture separator
November 6, 1991, NNECo performed a CHECMATE analysis that did identify this


reheater (MSR)system. An 8-inch elbow, located between the first stage MSR drain tank and the feedwater
portion of the MSR system as highly susceptible to erosion or corrosion and


heater, ruptured at its extrados (Figure 1). The elbow was located downstream
thus as a candidate for UT inspection.


from a 4-inch flow control valve and a 4- to 8-inch expander.
This information notice requires  no specific action or written response. If


The high energy water in the pipe (approximately
you have any questions about the  information in this notice, please contact one


463 F, 470 psig)flashed to steam, actuating
of .the technical contacts listed below or the appropriate Office of Nuclear


portions of the turbine fire protection
Reactor Regulation (NRR) project  manager.


deluge system. The water level in the steam generator
(
                                    Charles E. Rossi, Director


decreased
Division of Operational Events Assessment


slightly.
Office of Nuclear Reactor Regulation


The licen-see had not selected the ruptured elbow for ultrasonic
Technical contacts:  K. 1. Parczewski, NRR


testing (UT) in its erosion/corrosion
(301) 504-2705 Vern Hodge, NRR


monitoring
(301) 504-1861 Attachments:
1. Figure 1, "Rupture of Elbow in Secondary System at


program.The ruptured elbow was made of carbon steel with nominal wall thickness
Millstone Unit 2 on November 6, 1991"
2. List of Recently Issued NRC Information Notices


of 0.322 inch. Wall thickness
6"xl2" FISH-ItIOUTH
 
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
BREAK AT EXTRADOS


Procedure EN-21153, "Thickness
FLOW


Testing of Secondary
4 in. dia.        4 in. dia.


Piping," describes
8 in. dia.


its monitoring
Motes:
  Vo. 1 B First Stage Moisture Separator


program, established
Reheater Drain Tank Drain Line


in accordance
Pipe: Carbon Steel


with EPRI guidelines
No Chromium Content


and using the CHEC pro-gram to select for testing those areas of the pipi ng systems with highest prob-abilities
Fluid: H2O @ 470 psig, 4630F


for wall thinning.
pH: 8.2-*8.7
          02: <2ppb


The licensee also selects areas on the basis of plant experience.
a' (Dr i.r '
                                                                                        CD


However, although the pipe wall thickness
Figure 1. Rupture of Elbow in Secondary System at Millstone Unit 2 on November 6, 199,      CD


testing program vlas included in the licensee's
-


procedures, the licensee had not implemented
A-ttzac~:.^,
                                                        IN 91-18, Supplem~nt 1 December 18, 3991 Page 1 of i


the methodology
LIST OF RECENTLY ISSUED


using the EPRI computer codes at Unit 2. This omission may account for the licensee not having tested previously
NRC INFORMATiON NOTICES


the piping that ruptured on November 6, 1991.
===Information                                  Date of===
Notice No.         Subject                  Issuance Issued to


.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
91-82          Problems with Diaphragms      12/18/91  All holders of OLs or CPs


program did not reflect the use of current versions of EPRI codes (either CHEC or CHECMATE). .The Unit 3 rupture described
in Safety-Related Tanks                for nuclear power reactors.


in the March 12, 1991, issuance of this information
91-81          Switchyard Problems that      12/16/91  All holders of OLs or CPs


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
Contribute to Loss of                  for nuclear power reactors.


this program at its corporate engineering
Offsite Power


office and not at Unit 2. The Unit 2 personnel
91-80          Failure of Anchor            12/11/91  All holders of OLs or CPs


were consequently
Head Threads on Post-                  for nuclear power reactors.


relying on inspection
Tensioning System During
 
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
Surveillance Inspection


System at Millstone
91-79          Deficiencies in the          12/06/91  All holders of OLs or CPs


Unit 2 on November 6, 199, CD-  
Procedures for Instal-                 for nuclear power reactors.
A-ttzac~:.^, IN 91-18, Supplem~nt


1 December 18, 3991 Page 1 of i LIST OF RECENTLY ISSUED NRC INFORMATiON
ling Thermo-Lag Fire


NOTICES Information
Barrier Materials


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
88-92,         Potential for Spent          11/29/91 All holders of OLs or CPs


in Safety-Related
Supp. 1        Fuel Pool Draindown                    for nuclear power reactors.


Tanks Switchyard
91-78          Status Indication of          11/28/91  All holders of OLs or CPs


Problems that Contribute
Control Power for                      for nuclear power reactors.


to Loss of Offsite Power Failure of Anchor Head Threads on Post-Tensioning
Circuit Breakers Used


System During Surveillance
in Safety-Related Appli- cations


Inspection
90-57,        Substandard, Refur-          11/27/91  All holders of OLs or CPs


Deficiencies
Supp. 1        bished Potter & Brum-                  for nuclear power reactors.


in the Procedures
field Relays Repre- sented as New


for Instal-ling Thermo-Lag
91-77          Shift Staffing at            11/26/91  All holders of OLs or CPs


Fire Barrier Materials Potential
Nuclear Power Plants                    for nuclear power reactors.


for Spent Fuel Pool Draindown Status Indication
91-76          10 CFR Parts 21 and          11/26/91  All holders of OLs or CPs


of Control Power for Circuit Breakers Used in Safety-Related
50.55(e) Final Rules                    and vendors for nuclear


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
f1                                        power reactors.


License CP = Construction
OL = Operating License


Permit}}
CP = Construction Permit}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Latest revision as of 01:57, 24 November 2019

High-Energy Piping Failures Caused by Wall Thinning
ML042380261
Person / Time
Issue date: 12/18/1991
From: Rossi C
Office of Nuclear Reactor Regulation
To:
References
IN-91-018, Suppl 1
Download: ML042380261 (5)
v • d • e


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.

Li I st

.i~5X*-13, Supp

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 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 Office of Nuclear

Reactor Regulation (NRR) project 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

a' (Dr i.r '

CD

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 Problems with Diaphragms 12/18/91 All holders of OLs or CPs

in Safety-Related Tanks for nuclear power reactors.

91-81 Switchyard Problems that 12/16/91 All holders of OLs or CPs

Contribute to Loss of for nuclear power reactors.

Offsite Power

91-80 Failure of Anchor 12/11/91 All holders of OLs or CPs

Head Threads on Post- for nuclear power reactors.

Tensioning System During

Surveillance Inspection

91-79 Deficiencies in the 12/06/91 All holders of OLs or CPs

Procedures for Instal- for nuclear power reactors.

ling Thermo-Lag Fire

Barrier Materials

88-92, Potential for Spent 11/29/91 All holders of OLs or CPs

Supp. 1 Fuel Pool Draindown for nuclear power reactors.

91-78 Status Indication of 11/28/91 All holders of OLs or CPs

Control Power for for nuclear power reactors.

Circuit Breakers Used

in Safety-Related Appli- cations

90-57, Substandard, Refur- 11/27/91 All holders of OLs or CPs

Supp. 1 bished Potter & Brum- for nuclear power reactors.

field Relays Repre- sented as New

91-77 Shift Staffing at 11/26/91 All holders of OLs or CPs

Nuclear Power Plants for nuclear power reactors.

91-76 10 CFR Parts 21 and 11/26/91 All holders of OLs or CPs

50.55(e) Final Rules and vendors for nuclear

f1 power reactors.

OL = Operating License

CP = Construction Permit


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