Information Notice 1993-67, Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel: Difference between revisions
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| issue date = 08/16/1993 | | issue date = 08/16/1993 | ||
| title = Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel | | title = Bursting of High Pressure Coolant Injection Steam Line Rupture Discs Injures Plant Personnel | ||
| author name = Grimes B | | author name = Grimes B | ||
| author affiliation = NRC/NRR | | author affiliation = NRC/NRR | ||
| addressee name = | | addressee name = | ||
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| page count = 14 | | page count = 14 | ||
}} | }} | ||
{{#Wiki_filter:U - | {{#Wiki_filter:U -AU | ||
UNITED STATES | |||
NUCLEAR REGULATORY COMMISSION | |||
OFFICE OF NUCLEAR REACTOR REGULATION | |||
WASHINGTON, D.C. 20555 August 16, 1993 NRC INFORMATION NOTICE 93-67: BURSTING OF HIGH PRESSURE COOLANT INJECTION | |||
STEAM LINE RUPTURE DISCS INJURES PLANT | |||
PERSONNEL | |||
==Addressees== | ==Addressees== | ||
All holders of operating licenses or construction permits for | nuclear power | ||
All holders of operating licenses or construction permits for | |||
reactors. | |||
==Purpose== | ==Purpose== | ||
The U.S. Nuclear Regulatory Commission (NRC) is issuing | information | ||
The U.S. Nuclear Regulatory Commission (NRC) is issuing thissteam driven | |||
notice to remind addressees of the hazards associated with | |||
injection (HPCI) | |||
coolant injection systems such as the high pressure coolant at BWRs and the | |||
system and the reactor core isolation cooling (RCIC) system will | |||
auxiliary feedwater system at PWRs. It is expected that recipients and consider | |||
review the information for applicability to their facilities X | |||
actions, as appropriate, to avoid similar problems. However, suggestions therefore, no | |||
contained in this information notice are not NRC requirements; | |||
specific action or written response is required. | |||
Background | |||
the HPCI turbine | |||
The purpose of HPCI steam exhaust rupture discs is to protect event if the normal | |||
casing and associated exhaust piping from an overpressure Quad Cities Station, exhaust path to the suppression pool becomes blocked. At | |||
in series with a | |||
two 40.6-cm [16-inch] stainless steel discs are installed sensor | |||
6.4-cm [2.5-inch] spacer between them to allow for a pressure | |||
while serving no control function, instrumentation line. The pressure sensor, to alert the | |||
actuates an alarm in the control room at 68.9 kPa [10 psig] | |||
of the HPCI | |||
operators that the inner disc is leaking. The normal range The HPCI high | |||
exhaust steam pressure is 172 to 207 kPa [25 to 30 psig].- | |||
and is sensed by | |||
exhaust pressure turbine trip setpoint is 689 kPa [100 psig] piping | |||
the section of | |||
pressure sensors located downstream from where piping. The | |||
containing the rupture discs branches off from the exhaust vertically over the | |||
section of piping containing the rupture discs is mounted | |||
greater than | |||
turbine exhaust and vents directly to the HPCI room. Pressure inner disc to rupture | |||
1034 kPa [150 psig] in the exhaust line will cause the | |||
steam into the HPCI room. | |||
and impact the outer disc, releasing | |||
==Description of Circumstances== | ==Description of Circumstances== | ||
During a quarterly inservice test of the HPCI pump at the Commonwealth | Edison | ||
During a quarterly inservice test of the HPCI pump at the Commonwealth line rupture | |||
9, 1993, the exhaust steam | |||
Quad Cities Station, Unit 1, on June | |||
9308100248 F QrRi | |||
IN 93-67 August 16, 1993 discs burst, releasing steam into the HPCI room, burning, and slightly | |||
contaminating, five workers. The rupture discs burst within one second after | |||
the turbine was started. Fire doors between the Unit 1 and Unit 2 HPCI rooms | |||
were blown off their hinges into the Unit 2 HPCI room. Both sets of double | |||
doors that are part of the secondary containment boundary were also blown | |||
open. The floor latch on the inner containment door was bent; the outer doors | |||
were also slightly damaged, but were repaired, closed and sealed approximately | |||
35 minutes after the event. The steam release was terminated by automatic | |||
isolation of the steam supply line on high HPCI turbine area temperature about | |||
20 seconds into the event. | |||
Discussion | |||
Upon investigating the event, the licensee determined that water had | |||
accumulated in the turbine casing because the drain system level switches for | |||
the Unit 1 HPCI system had failed. In April 1992, the licensee performed a | |||
reliability-centered maintenance study which recommended the level switches be | |||
included in the preventive maintenance program but the recommendation had not | |||
been acted on at the time of the event. The Unit 2 HPCI drain system level | |||
switches were also found to be inoperable. | |||
The slug of water created during the HPCI turbine roll passed from the turbine | |||
casing to the vertical exhaust line and compressed the air in the 40.6 cm | |||
[16 inch] line containing the rupture discs. The resulting pressure pulse | |||
caused the inner rupture disc to burst, which impacted the outer disc as | |||
designed and caused it to burst as well. The exhaust line pressure sensors, located in the horizontal 61 cm [24 inch] exhaust line that tees off from the | |||
vertical 40.6 cm [16 inch] rupture disc line, did not detect a high pressure | |||
(see Figure 1). The pressure switches were within tolerance and should have | |||
immediately isolated the steam supply upon sensing a high exhaust pressure | |||
before the rupture discs burst. The fact that a high exhaust line pressure | |||
was not detected indicates two possible causes for the disc rupture. Either | |||
the inner rupture disc was degraded and burst at lower-than-design pressure, or the pressure pulse actually exceeded the design pressure and caused the | |||
disc to burst, relieving the exhaust line pressure before the downstream | |||
pressure sensors detected a high pressure condition. | |||
While inspection of the rupture discs did not reveal any degradation from | |||
corrosion or aging, the vendor, Black Sivalls & Bryson, Inc, stated that the | |||
discs are warranted for one year of service under normal conditions. The HPCI | |||
and RCIC rupture discs at Quad Cities Station had been in service for 20 years | |||
and were not part of any scheduled inspection or preventive maintenance | |||
program. When consulted about the event, the vendor advised against using the | |||
spare discs in the plant storeroom because they were purchased at the same | |||
time as the failed discs. The licensee later replaced the failed discs with | |||
new units. Before this event, the licensee recently replaced a HPCI rupture | |||
disc during a refueling outage at the Dresden Station, a plant similar to Quad | |||
Cities, after finding a crack in the disc during an inspection. The rupture | |||
discs were inspected at the Dresden station as part of an enhancement to the | |||
preventive maintenance program that was recommended by a reliability-centered | |||
analysis. | |||
I I | |||
IN 93-67 August 16, 1993 The steam injured five workers, four of whom were participating in the HPCI | |||
pump surveillance test. The fifth, and m6st severely. injured worker was a | |||
health physics technician in the room on routine rounds, who was not aware of | |||
the danger posed by the surveillance test. The test procedure contained no | |||
specific guidance on room occupancy. Interviews with the workers revealed | |||
that they had performed the surveillance in the past and were familiar with | |||
the process. This familiarity may have led to a relaxed attitude toward | |||
personal safety. The workers stated that during previous surveillances they | |||
sometimes evacuated the room before rolling the turbine, or stood near the | |||
doors to be ready to escape. The licensee made no routine announcement over | |||
the plant paging system to alert plant personnel before the HPCI-turbine | |||
start, and the workers were not prepared for the turbine to start. | |||
A lack of constant communication between the workersand the control room may | |||
have contributed to the personnel injuries. If a control room operator had | |||
been in contact with the workers in the HPCI room during the turbine roll, the | |||
workers would have been aware of the impending turbine start and, after start, the steam supply might have been manually-isolated or the turbine manually | |||
tripped before the automatic isolation caused by the high area temperatureoin | |||
the HPCI room. | |||
When the Unit 1 HPCI rupture disc failure caused the fire doors to be blown | |||
off their hinges and into the Unit 2 HPCI room, one of the doors impacted a | |||
pipe hanger in the room and moved it 5.1 centimeters [2 inches]. If the steam | |||
release had resulted from a high energy line break from the inlet side of the | |||
HPCI steam line instead of the exhaust line, the damage to the Unit 2 HPCI | |||
system could have been more severe. While high energy line breaks have been | |||
analyzed for safety systems at all plants, the doors to rooms containing high | |||
energy steam lines may not have been included in the analysis. For example, at Duane Arnold Energy Center, the licensee discovered that while the HPCI and | |||
RCIC rooms were qualified for pressures of 26.2 kPa [3.8 psig], the doors | |||
between these rooms and the reactor building would yield at 6.9 kPa [1 psig]. | |||
The licensee for the Quad Cities Station will implement a preventive | |||
maintenance schedule for both the HPCI and RCIC rupture discs and the level | |||
switches. The licensee will review the surveillance test procedure and | |||
evaluate the missile hazard created by the fire doors. The licensee replaced | |||
the rupture discs for the Unit 2 HPCI and RCIC systems with new ones after the | |||
event at Unit 1 and is considering burst testing the removed discs to | |||
determine if they are degraded. | |||
IN 93-67 August 16, 1993 This information notice requires no specific action | |||
you have any questions about the information in this or written response. If | |||
the technical contact listed below or the appropriate notice, please contact | |||
Reactor Regulation (NRR) project manager. Office of Nuclear | |||
Brian K. Grim s, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Clark Vanderniet, RIII | |||
(708) 790-5594 David Skeen, NRR | |||
(301) 504-1174 Attachments: | |||
1. Figure 1, "Simplified Layout of Quad Cities | |||
Station HPCI Turbine Exhaust Steam Line" | |||
2. List of Recently Issued NRC Information Notices | |||
Cq~ | |||
0cr 1 cO | |||
Cd)h r- | |||
4 | |||
0 OUTER RUPTURE DISC _____ | |||
\TO VENT TO | |||
HPCI ROOM | |||
INNER RUPTURE DISC | |||
[1 In] | |||
2 40.6 cm | |||
[16 in] | |||
CLOSABLE CHECK | |||
CHECK VALVE VALVE I | |||
SUPPRESSION | |||
50.8 cm | |||
LOCKED I [20 In] STEAM INLET LINE | |||
OPEN I FROM "B" MAIN | |||
I 61 cm STEAM LINE | |||
I [24 In] | |||
I | |||
25 cm | |||
RX BLDG HPCI ROOM [10 In] | |||
I | |||
I | |||
POOL I | |||
I | |||
D NOTES: | |||
1. PRESSURE SWITCH ACTUATES ALARM IN CONTROL ROOM WHEN PRESSURE BETWEEN THE INNER RUPTURE DISC AND OUTER | |||
RUPTURE DISC IS GREATER THAN 68.9 kPa [10 psig]. ALARM IS FOR INNER RUPTURE DISC LEAK DETECTION. | |||
2. REDUNDANT PRESSURE SWITCHES IN EXHAUST STEAM LINE TRIP THE HPCI TURBINE IF PRESSURE IS GREATER THAN 689 kPa [100 psig]. | |||
3. RUPTURE DISC MAXIMUM DESIGN BURST PRESSURE IS 1034 kPa [150 psig]. | |||
Figure 1 - Simplified Layout of Quad Cities Station HPCI Turbine Exhaust Steam Line | |||
Attachment 2 IN 93-67 August 16, 1993 LIST OF RECENTLY ISSUED | |||
NRC INFORMATION NOTICES | |||
Information Date of | |||
Notice No. Subject Issuance Issued to | |||
93-66 Switchover to Hot-Leg 08/16/93 All holders of OLs or CPs | |||
Injection Following for pressurized water | |||
A Loss-of-Coolant reactors. | |||
Accident in Pres- surized Water Reactors | |||
93-65 Reactor Trips Caused 08/13/93- All holders of OLs or CPs | |||
by Breaker Testing for nuclear power reactors. | |||
with Fault Protection | |||
Bypassed | |||
93-64 Periodic Testing and 08/12/93 All holders of OLs or CPs | |||
Preventive Maintenance for nuclear power reactors. | |||
of Molded Case Circuit | |||
Breakers | |||
93-63 Improper Use of Soluble 08/11/93 All holders of OLs or CPs | |||
Weld Purge Dam Material for nuclear power reactors. | |||
93-62 Thermal Stratification 08/10/93 All holders of OLs or CPs | |||
of Water in BWR Reactor for boiling water reactors. | |||
Vessels | |||
93-61 Excessive Reactor Coolant 08/09/93 All holders of OLs or CPs | |||
Leakage Following A Seal for nuclear power reactors. | |||
Failure in A Reactor | |||
Coolant Pump or Reactor | |||
Recirculation Pump | |||
93-60 Reporting Fuel Cycle and 08/04/93 All fuel cycle and materials | |||
Materials Events to the licensees. | |||
NRC Operations Center | |||
93-59 Unexpected Opening of 07/26/93 All holders of OLs or CPs | |||
Both Doors in An for nuclear power reactors. | |||
Airlock | |||
93-58 Nonconservatism in Low- 07/26/93 All holders of OLs or CPs | |||
Temperature Overpressure for pressurized-water | |||
Protection for Pressurized- reactors. | |||
Water Reactors | |||
OL = Operating License | |||
CP = Construction Permit | |||
l | |||
IN 93-67 August 16, 1993 This information notice requires no specific action or written response. If | |||
you have any questions about the information in this notice, please contact | |||
the technical contact listed below or the appropriate Office of Nuclear | |||
Reactor Regulation (NRR) project manager. | |||
orig /s/'d by CIGrimes/for | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Clark Vanderniet, RIII | |||
(708) 790-5594 David Skeen, NRR | |||
(301) 504-1174 Attachments: | |||
1. Figure 1, "Simplified Layout of Quad Cities | |||
Station HPCI Turbine Exhaust Steam Line" | |||
2. List of Recently Issued NRC Information Notices | |||
*SEE PREVIOUS CONCURRENCE. | |||
OFC *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III | |||
NAME DSkeen JMain PWen CVanderniet | |||
DATE 07/08/93 , 07/08/93 07/14/93 07/14/93 OFC | |||
NAME | |||
DATE | |||
*C:DRS:R-III | |||
GWright | |||
[ 07/14/93 I *SC:OEAB:DORS | |||
RDennig | |||
107/15/93 | |||
*C/OEAB/DORS | |||
AEChaffee | |||
07/15/93 | |||
*C:SPLB:DSSA | |||
CEMcCracken | |||
]07/16/93 | |||
_ I__ i | |||
OFC *D:DSSA *C/OGCB:DORS D/DORS A^r | |||
NAME AThadani GMarcus BGrimes t | |||
DATE 07/24/93 07/29/93 0,S/\o/93 V | |||
[OFFICIAL RECORD COPY] | |||
DOCUMENT NAME: 93-67.IN | |||
\- IN 93-XX | |||
July XX, 1993 This information notice requires no specific action or written response. If | |||
you have any questions about the information in this notice, please contact | |||
the technical contact listed below or the appropriate Office of Nuclear | |||
Reactor Regulation (NRR) project manager. | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Clark Vanderniet, RIII | |||
(708) 790-5594 David Skeen, NRR | |||
(301) 504-1174 Attachment: | |||
===List of Recently Issued NRC Information Notices=== | |||
*SEE PREVIOUS CONCURRENCE. | |||
*D:DSSA | |||
AThadani | |||
07/24/93 OFC *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III | |||
NAME DSkeen JMain PWen CVanderniet | |||
DATE J07/08/93 07/08/93 07/14/93 07/14/93 OFC *C:DRS:R-III *SC:OEAB:DORS *C/OEAB/DORS *C:SPLB:DSSA | |||
NAME GWright RDennig AEChaffee CEMcCracken | |||
DATE J07/14/93 | |||
.Y. | |||
07/15/93 107/15/93 J07/16/93 OFC C/OGCB:DORS D/DORS | |||
NAME GMarcus ifM BGrimes T | |||
DATE 07/.9/93 07/ /93 | |||
[OFFICIAL RECORD COPY] | |||
DOCUMENT NAME: IN93 XX.QC1 | |||
IN 93-XX | |||
July xx, 1993 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. | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Clark Vanderniet, R-III | |||
(708) 790-5594 David Skeen, NRR | |||
(301) 504-1174 Attachment: List of Recently Issued NRC Information Notices | |||
*SEE PREVIOUS CONCURRENCE | |||
OFFICE *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III | |||
NAME DSkeen JMain l PWen CVanderniet | |||
1'I | |||
DATE 07/08/93 07/08/93 07/14/93 07/14/93 | |||
*C:DRS:RIII *SC:OEAB:DORS *C:OEAB:DORS C:SPLBAS* D: DSS 3q % | |||
GWright RDenning AChaffee CEMcCracken ACThadani | |||
07/14/93 [07/15/93 07/15/93 -07/2/f93 07/2A/93 C:OGCB:DORS D: DORS | |||
GHMarcus BKGrimes | |||
07/ /93 07/ /93 DOCUMENT NAME: QCHPCIIN.WEN C 5 G-4J -z--l - 2'J 43-- | |||
- k k- 9 CJ- | |||
IN 93-XX | |||
July xx, 1993 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. | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Clark Vanderniet, R-III | |||
(708) 790-5594 David Skeen, NRR | |||
(301) 504-1174 Attachment: List of Recently Issued NRC Information Notices | |||
*SEE PREVIOUS CONCURRENCE | |||
OFFICE *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III | |||
NAME DSkeen JMain PWen CVanderniet | |||
DATE 07/08/93 L, 07/08/93 I_,__. . _, | |||
07 114/93 | |||
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07/14/93 | |||
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GWright R enn afee | |||
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07/14/93 [ 3 07/j</93 07/ /93 07/ /93 C:OGCB:DORS D:DORS | |||
GHMarcus BKGrimes | |||
0 | |||
07/ /93 07/ /93 DOCUMENT NAME: QCHPCIIN.WEN | |||
- E7/14/93 12:53 787905538417463837 | |||
?03 P. 0', | |||
IN 93-XX | |||
July xx. 1993 This infiIrmation notice requires no specific action noticet please contact | |||
or written response. It | |||
you have any questions about the information inthis | |||
the tech lcal contmct listed below or the appropriate Office of Nuclear | |||
Roactor r.gulmtion (NRR) project manager. | |||
Brian K. Grimes, Director | |||
Division of sOrating RGOM Support | |||
Office of Nuclear Reactor Regulation | |||
Technic~l contacts Clark Vanderniet, R-II1 | |||
(708) 790-5594 Oavid Skeen NRR | |||
(301) 604-1174 Attach 4 nt: List of Recently Issued NRC Information Notices | |||
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J \1 IN 93-XX | |||
July xx, 1993 This information notice requires no specific action or written response. If | |||
you have any questions about the information in this notice, please contact | |||
the technical contact listed below or the appropriate Office of Nuclear | |||
Reactor Regulation (NRR) project manager. | |||
Brian K. Grimes, Director | |||
Division of Operating Reactor Support | |||
Office of Nuclear Reactor Regulation | |||
Technical contacts: Clark Vanderniet, R-III | |||
(708) 790-5594 David Skeen, NRR | |||
(301) 504-1174 Attachment: List of Recently Issued NRC Information Notices | |||
*SEE PREVIOUS CONCURRENCE I | |||
OFFICE *OEAB:DORS *TECH:ED _ i'O | |||
_GC W DRS:R-III | |||
NAME DSkeen JMain PWen CVanderniet | |||
DATE 07/08/93 07/08/93 07/ W/93 07/ /93 C:DRS:RIII SC:OEAB:DORS C:OEAB:DORS C:SPLB:DSSA D:DSSA | |||
GWright RDenning AChaffee CEMcCracken ACThadani | |||
07/ /93 J07/ . | |||
/93 | |||
.I | |||
07/ /93 07/ /93 07/ /93 C:OGCB:DORS D:DORS | |||
GHMarcus BKGrimes | |||
07/ /93 07/ /93 DOCUMENT NAME: QCHPCIIN.WEN | |||
I | |||
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OFC OEAB:DORS SC/OEAB:DORS PUB:ADM C/OEAB:DORS | |||
NAME DSkeen o RDennig Tech Ed T7avLY AChaffee | |||
[DATE 17 /g/93 / /93 7/P /93 / /93 OFC OGCB:DORS C/DRS/R-III DRS/R-III | |||
NAME PWen GWright CVanderniet | |||
DATE / /93 / /93 / /93 OFC TECH BRANCH CHF TECH BR C/OGCB:DORS D/DORS | |||
NAME l GMarcus l BGrimes | |||
DATE / /93 / /93 / /93 1 / /93 l | |||
[OFFICIAL RECORD COPY] | |||
DOCUMENT NAME: IN93 XX.QC1}} | |||
{{Information notice-Nav}} | {{Information notice-Nav}} |
Latest revision as of 04:24, 24 November 2019
U -AU
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 August 16, 1993 NRC INFORMATION NOTICE 93-67: BURSTING OF HIGH PRESSURE COOLANT INJECTION
STEAM LINE RUPTURE DISCS INJURES PLANT
PERSONNEL
Addressees
nuclear power
All holders of operating licenses or construction permits for
reactors.
Purpose
information
The U.S. Nuclear Regulatory Commission (NRC) is issuing thissteam driven
notice to remind addressees of the hazards associated with
injection (HPCI)
coolant injection systems such as the high pressure coolant at BWRs and the
system and the reactor core isolation cooling (RCIC) system will
auxiliary feedwater system at PWRs. It is expected that recipients and consider
review the information for applicability to their facilities X
actions, as appropriate, to avoid similar problems. However, suggestions therefore, no
contained in this information notice are not NRC requirements;
specific action or written response is required.
Background
the HPCI turbine
The purpose of HPCI steam exhaust rupture discs is to protect event if the normal
casing and associated exhaust piping from an overpressure Quad Cities Station, exhaust path to the suppression pool becomes blocked. At
in series with a
two 40.6-cm [16-inch] stainless steel discs are installed sensor
6.4-cm [2.5-inch] spacer between them to allow for a pressure
while serving no control function, instrumentation line. The pressure sensor, to alert the
actuates an alarm in the control room at 68.9 kPa [10 psig]
of the HPCI
operators that the inner disc is leaking. The normal range The HPCI high
exhaust steam pressure is 172 to 207 kPa [25 to 30 psig].-
and is sensed by
exhaust pressure turbine trip setpoint is 689 kPa [100 psig] piping
the section of
pressure sensors located downstream from where piping. The
containing the rupture discs branches off from the exhaust vertically over the
section of piping containing the rupture discs is mounted
greater than
turbine exhaust and vents directly to the HPCI room. Pressure inner disc to rupture
1034 kPa [150 psig] in the exhaust line will cause the
steam into the HPCI room.
and impact the outer disc, releasing
Description of Circumstances
Edison
During a quarterly inservice test of the HPCI pump at the Commonwealth line rupture
9, 1993, the exhaust steam
Quad Cities Station, Unit 1, on June
9308100248 F QrRi
IN 93-67 August 16, 1993 discs burst, releasing steam into the HPCI room, burning, and slightly
contaminating, five workers. The rupture discs burst within one second after
the turbine was started. Fire doors between the Unit 1 and Unit 2 HPCI rooms
were blown off their hinges into the Unit 2 HPCI room. Both sets of double
doors that are part of the secondary containment boundary were also blown
open. The floor latch on the inner containment door was bent; the outer doors
were also slightly damaged, but were repaired, closed and sealed approximately
35 minutes after the event. The steam release was terminated by automatic
isolation of the steam supply line on high HPCI turbine area temperature about
20 seconds into the event.
Discussion
Upon investigating the event, the licensee determined that water had
accumulated in the turbine casing because the drain system level switches for
the Unit 1 HPCI system had failed. In April 1992, the licensee performed a
reliability-centered maintenance study which recommended the level switches be
included in the preventive maintenance program but the recommendation had not
been acted on at the time of the event. The Unit 2 HPCI drain system level
switches were also found to be inoperable.
The slug of water created during the HPCI turbine roll passed from the turbine
casing to the vertical exhaust line and compressed the air in the 40.6 cm
[16 inch] line containing the rupture discs. The resulting pressure pulse
caused the inner rupture disc to burst, which impacted the outer disc as
designed and caused it to burst as well. The exhaust line pressure sensors, located in the horizontal 61 cm [24 inch] exhaust line that tees off from the
vertical 40.6 cm [16 inch] rupture disc line, did not detect a high pressure
(see Figure 1). The pressure switches were within tolerance and should have
immediately isolated the steam supply upon sensing a high exhaust pressure
before the rupture discs burst. The fact that a high exhaust line pressure
was not detected indicates two possible causes for the disc rupture. Either
the inner rupture disc was degraded and burst at lower-than-design pressure, or the pressure pulse actually exceeded the design pressure and caused the
disc to burst, relieving the exhaust line pressure before the downstream
pressure sensors detected a high pressure condition.
While inspection of the rupture discs did not reveal any degradation from
corrosion or aging, the vendor, Black Sivalls & Bryson, Inc, stated that the
discs are warranted for one year of service under normal conditions. The HPCI
and RCIC rupture discs at Quad Cities Station had been in service for 20 years
and were not part of any scheduled inspection or preventive maintenance
program. When consulted about the event, the vendor advised against using the
spare discs in the plant storeroom because they were purchased at the same
time as the failed discs. The licensee later replaced the failed discs with
new units. Before this event, the licensee recently replaced a HPCI rupture
disc during a refueling outage at the Dresden Station, a plant similar to Quad
Cities, after finding a crack in the disc during an inspection. The rupture
discs were inspected at the Dresden station as part of an enhancement to the
preventive maintenance program that was recommended by a reliability-centered
analysis.
I I
IN 93-67 August 16, 1993 The steam injured five workers, four of whom were participating in the HPCI
pump surveillance test. The fifth, and m6st severely. injured worker was a
health physics technician in the room on routine rounds, who was not aware of
the danger posed by the surveillance test. The test procedure contained no
specific guidance on room occupancy. Interviews with the workers revealed
that they had performed the surveillance in the past and were familiar with
the process. This familiarity may have led to a relaxed attitude toward
personal safety. The workers stated that during previous surveillances they
sometimes evacuated the room before rolling the turbine, or stood near the
doors to be ready to escape. The licensee made no routine announcement over
the plant paging system to alert plant personnel before the HPCI-turbine
start, and the workers were not prepared for the turbine to start.
A lack of constant communication between the workersand the control room may
have contributed to the personnel injuries. If a control room operator had
been in contact with the workers in the HPCI room during the turbine roll, the
workers would have been aware of the impending turbine start and, after start, the steam supply might have been manually-isolated or the turbine manually
tripped before the automatic isolation caused by the high area temperatureoin
the HPCI room.
When the Unit 1 HPCI rupture disc failure caused the fire doors to be blown
off their hinges and into the Unit 2 HPCI room, one of the doors impacted a
pipe hanger in the room and moved it 5.1 centimeters [2 inches]. If the steam
release had resulted from a high energy line break from the inlet side of the
HPCI steam line instead of the exhaust line, the damage to the Unit 2 HPCI
system could have been more severe. While high energy line breaks have been
analyzed for safety systems at all plants, the doors to rooms containing high
energy steam lines may not have been included in the analysis. For example, at Duane Arnold Energy Center, the licensee discovered that while the HPCI and
RCIC rooms were qualified for pressures of 26.2 kPa [3.8 psig], the doors
between these rooms and the reactor building would yield at 6.9 kPa [1 psig].
The licensee for the Quad Cities Station will implement a preventive
maintenance schedule for both the HPCI and RCIC rupture discs and the level
switches. The licensee will review the surveillance test procedure and
evaluate the missile hazard created by the fire doors. The licensee replaced
the rupture discs for the Unit 2 HPCI and RCIC systems with new ones after the
event at Unit 1 and is considering burst testing the removed discs to
determine if they are degraded.
IN 93-67 August 16, 1993 This information notice requires no specific action
you have any questions about the information in this or written response. If
the technical contact listed below or the appropriate notice, please contact
Reactor Regulation (NRR) project manager. Office of Nuclear
Brian K. Grim s, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Clark Vanderniet, RIII
(708) 790-5594 David Skeen, NRR
(301) 504-1174 Attachments:
1. Figure 1, "Simplified Layout of Quad Cities
Station HPCI Turbine Exhaust Steam Line"
2. List of Recently Issued NRC Information Notices
Cq~
0cr 1 cO
Cd)h r-
4
0 OUTER RUPTURE DISC _____
\TO VENT TO
HPCI ROOM
INNER RUPTURE DISC
[1 In]
2 40.6 cm
[16 in]
CLOSABLE CHECK
CHECK VALVE VALVE I
SUPPRESSION
50.8 cm
LOCKED I [20 In] STEAM INLET LINE
OPEN I FROM "B" MAIN
I 61 cm STEAM LINE
I [24 In]
I
25 cm
RX BLDG HPCI ROOM [10 In]
I
I
POOL I
I
D NOTES:
1. PRESSURE SWITCH ACTUATES ALARM IN CONTROL ROOM WHEN PRESSURE BETWEEN THE INNER RUPTURE DISC AND OUTER
RUPTURE DISC IS GREATER THAN 68.9 kPa [10 psig]. ALARM IS FOR INNER RUPTURE DISC LEAK DETECTION.
2. REDUNDANT PRESSURE SWITCHES IN EXHAUST STEAM LINE TRIP THE HPCI TURBINE IF PRESSURE IS GREATER THAN 689 kPa [100 psig].
3. RUPTURE DISC MAXIMUM DESIGN BURST PRESSURE IS 1034 kPa [150 psig].
Figure 1 - Simplified Layout of Quad Cities Station HPCI Turbine Exhaust Steam Line
Attachment 2 IN 93-67 August 16, 1993 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information Date of
Notice No. Subject Issuance Issued to
93-66 Switchover to Hot-Leg 08/16/93 All holders of OLs or CPs
Injection Following for pressurized water
A Loss-of-Coolant reactors.
Accident in Pres- surized Water Reactors
93-65 Reactor Trips Caused 08/13/93- All holders of OLs or CPs
by Breaker Testing for nuclear power reactors.
with Fault Protection
Bypassed
93-64 Periodic Testing and 08/12/93 All holders of OLs or CPs
Preventive Maintenance for nuclear power reactors.
of Molded Case Circuit
Breakers
93-63 Improper Use of Soluble 08/11/93 All holders of OLs or CPs
Weld Purge Dam Material for nuclear power reactors.
93-62 Thermal Stratification 08/10/93 All holders of OLs or CPs
of Water in BWR Reactor for boiling water reactors.
Vessels
93-61 Excessive Reactor Coolant 08/09/93 All holders of OLs or CPs
Leakage Following A Seal for nuclear power reactors.
Failure in A Reactor
Coolant Pump or Reactor
Recirculation Pump
93-60 Reporting Fuel Cycle and 08/04/93 All fuel cycle and materials
Materials Events to the licensees.
NRC Operations Center
93-59 Unexpected Opening of 07/26/93 All holders of OLs or CPs
Both Doors in An for nuclear power reactors.
Airlock
93-58 Nonconservatism in Low- 07/26/93 All holders of OLs or CPs
Temperature Overpressure for pressurized-water
Protection for Pressurized- reactors.
Water Reactors
OL = Operating License
CP = Construction Permit
l
IN 93-67 August 16, 1993 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.
orig /s/'d by CIGrimes/for
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Clark Vanderniet, RIII
(708) 790-5594 David Skeen, NRR
(301) 504-1174 Attachments:
1. Figure 1, "Simplified Layout of Quad Cities
Station HPCI Turbine Exhaust Steam Line"
2. List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE.
OFC *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III
NAME DSkeen JMain PWen CVanderniet
DATE 07/08/93 , 07/08/93 07/14/93 07/14/93 OFC
NAME
DATE
- C:DRS:R-III
GWright
[ 07/14/93 I *SC:OEAB:DORS
RDennig
107/15/93
- C/OEAB/DORS
AEChaffee
07/15/93
- C:SPLB:DSSA
CEMcCracken
]07/16/93
_ I__ i
OFC *D:DSSA *C/OGCB:DORS D/DORS A^r
NAME AThadani GMarcus BGrimes t
DATE 07/24/93 07/29/93 0,S/\o/93 V
[OFFICIAL RECORD COPY]
DOCUMENT NAME: 93-67.IN
\- IN 93-XX
July XX, 1993 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Clark Vanderniet, RIII
(708) 790-5594 David Skeen, NRR
(301) 504-1174 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE.
- D:DSSA
AThadani
07/24/93 OFC *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III
NAME DSkeen JMain PWen CVanderniet
DATE J07/08/93 07/08/93 07/14/93 07/14/93 OFC *C:DRS:R-III *SC:OEAB:DORS *C/OEAB/DORS *C:SPLB:DSSA
NAME GWright RDennig AEChaffee CEMcCracken
DATE J07/14/93
.Y.
07/15/93 107/15/93 J07/16/93 OFC C/OGCB:DORS D/DORS
NAME GMarcus ifM BGrimes T
DATE 07/.9/93 07/ /93
[OFFICIAL RECORD COPY]
DOCUMENT NAME: IN93 XX.QC1
IN 93-XX
July xx, 1993 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.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Clark Vanderniet, R-III
(708) 790-5594 David Skeen, NRR
(301) 504-1174 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III
NAME DSkeen JMain l PWen CVanderniet
1'I
DATE 07/08/93 07/08/93 07/14/93 07/14/93
- C:DRS:RIII *SC:OEAB:DORS *C:OEAB:DORS C:SPLBAS* D: DSS 3q %
GWright RDenning AChaffee CEMcCracken ACThadani
07/14/93 [07/15/93 07/15/93 -07/2/f93 07/2A/93 C:OGCB:DORS D: DORS
GHMarcus BKGrimes
07/ /93 07/ /93 DOCUMENT NAME: QCHPCIIN.WEN C 5 G-4J -z--l - 2'J 43--
- k k- 9 CJ-
IN 93-XX
July xx, 1993 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.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Clark Vanderniet, R-III
(708) 790-5594 David Skeen, NRR
(301) 504-1174 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE
OFFICE *OEAB:DORS *TECH:ED *OGCB:DORS *DRS:R-III
NAME DSkeen JMain PWen CVanderniet
DATE 07/08/93 L, 07/08/93 I_,__. . _,
07 114/93
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07/14/93
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07/14/93 [ 3 07/j</93 07/ /93 07/ /93 C:OGCB:DORS D:DORS
GHMarcus BKGrimes
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07/ /93 07/ /93 DOCUMENT NAME: QCHPCIIN.WEN
- E7/14/93 12:53 787905538417463837
?03 P. 0',
IN 93-XX
July xx. 1993 This infiIrmation notice requires no specific action noticet please contact
or written response. It
you have any questions about the information inthis
the tech lcal contmct listed below or the appropriate Office of Nuclear
Roactor r.gulmtion (NRR) project manager.
Brian K. Grimes, Director
Division of sOrating RGOM Support
Office of Nuclear Reactor Regulation
Technic~l contacts Clark Vanderniet, R-II1
(708) 790-5594 Oavid Skeen NRR
(301) 604-1174 Attach 4 nt: List of Recently Issued NRC Information Notices
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J \1 IN 93-XX
July xx, 1993 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate Office of Nuclear
Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical contacts: Clark Vanderniet, R-III
(708) 790-5594 David Skeen, NRR
(301) 504-1174 Attachment: List of Recently Issued NRC Information Notices
- SEE PREVIOUS CONCURRENCE I
OFFICE *OEAB:DORS *TECH:ED _ i'O
_GC W DRS:R-III
NAME DSkeen JMain PWen CVanderniet
DATE 07/08/93 07/08/93 07/ W/93 07/ /93 C:DRS:RIII SC:OEAB:DORS C:OEAB:DORS C:SPLB:DSSA D:DSSA
GWright RDenning AChaffee CEMcCracken ACThadani
07/ /93 J07/ .
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07/ /93 07/ /93 07/ /93 C:OGCB:DORS D:DORS
GHMarcus BKGrimes
07/ /93 07/ /93 DOCUMENT NAME: QCHPCIIN.WEN
I
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OFC OEAB:DORS SC/OEAB:DORS PUB:ADM C/OEAB:DORS
NAME DSkeen o RDennig Tech Ed T7avLY AChaffee
[DATE 17 /g/93 / /93 7/P /93 / /93 OFC OGCB:DORS C/DRS/R-III DRS/R-III
NAME PWen GWright CVanderniet
DATE / /93 / /93 / /93 OFC TECH BRANCH CHF TECH BR C/OGCB:DORS D/DORS
NAME l GMarcus l BGrimes
DATE / /93 / /93 / /93 1 / /93 l
[OFFICIAL RECORD COPY]
DOCUMENT NAME: IN93 XX.QC1