ML20168A720: Difference between revisions

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=Text=
=Text=
{{#Wiki_filter:uction Valves to Decay Heat Pumps Fail to Open at Rancho Seco re sequence was:
{{#Wiki_filter:PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:
g testing, neither sumnp isolation valve opened when an open signal pplied.
120995 Date: November 11, 1976
e action; alves were moved manually and then cycled electrically.. The bypass hes for the valve torque switches-was-adjusted to permit more motor before the bypass switches difopped. out.
rpose of failed system or component:
alves provide for fluid flow from the sump to the low pressure and pressure recirculation systems and the building spray system (while e recirculation mode) following a LOCA.
ility of system per WASH 1400:
* low pressure recirc:  1.3 x 10-2  /D high pressure recirc:  9  X 10-3/D ility of component per WASH 1400:
* motor operated valve,   failure to operate. 1 x 10-3 /D vailabilitieQ are in units of per demand D-1 . Failure rates are in per hour HR-T


core Damage No No No - No LOCA and unit in shutdown.
==Title:==
NSIC 120995 - Actual Occurrence for Failure of Both Suction Valves to Decay Heat Pumps from Emergency Sump at Rancho Seco
Suction Valves to Decay Heat Pumps Fail to Open at Rancho Seco The failure sequence was:
: 1. During testing, neither sumnp isolation was applied.
valve opened when an open signal
.Corrective action;
: 1. The valves were moved manually and then cycled electrically.. The bypass switches for the valve torque switches-was-adjusted to permit more motor turns before the bypass switches difopped. out.
Design purpose of failed system or component:
: 1. The valves provide for fluid flow from the sump to the low pressure and high pressure recirculation systems and the building spray system (while in the recirculation mode) following a LOCA.
Unavailability of system per WASH 1400:
* low pressure recirc:
1.3 x 10-2 /D high pressure recirc:
9 X 10-3/D Unavailability of component per WASH 1400:
* motor operated valve, failure to operate.
1 x 10-3/D UnavailabilitieQ are in units of per demand D-1.
Failure rates are in units of per hour HR-T


Small   Reactor   Auxiliary     ]High         Low Pressure   Potential  Sequence LOCA   Trip     Feedwater and Secondary Heat Removal jInjection Pressure,   Recirculation and LPR/HPI Cross-Connect Severe Core Damage No.
Potential Severe core Damage No No No -
No LOCA and unit in shutdown.
NSIC 120995 -
Actual Occurrence for Failure of Both Suction Valves to Decay Heat Pumps from Emergency Sump at Rancho Seco
 
Small Reactor Auxiliary  
]High Low Pressure LOCA Trip Feedwater and
: Pressure, Recirculation Secondary jInjection and LPR/HPI Heat Removal Cross-Connect Potential Severe Core Damage Sequence No.
2 3
2 3
4 5
4 5
6 7
6 7
NSIC 120995 - Sequence of Interest for Both Sump Suction Valves to Decay Heat Pumps Fail to Open at Rancho Seco
NSIC 120995 -
Sequence of Interest for Both Sump Suction Valves to Decay Heat Pumps Fail to Open at Rancho Seco


CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS CCESSION NUMBER-       120995 LER:   November 22, 1976 F EVENT:   November 11, '1976 INVOLVED:     Decay heat NT INVOLVED:     Pumps Switch setting incorrect.
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER-120995 DATE OF LER:
E OF INTEREST:           LOCA OCCURRENCE:             Valves fail to open for decay heat system.
November 22, 1976 DATE OF EVENT:
NAME:   Rancho Seco NUMBER:   50-312 TYPE:   PWR ELECTRICAL RATING:         918   MWe R AGE:     2.1   yr B&W CT- ENGINEERS:     Bechtel RS:   Sacramento Municipal Utility District N:   .25 mi1les SE..of. Sacramento, CA N:   360(a) hours OPERATING CONDITION:       Shut down.
November 11, '1976 SYSTEM INVOLVED:
FEATURE TYPE OF FAILURE:         (a) inadequate performance;     (b) failed to start; QDmade inoperable;     (d) ______
Decay heat COMPONENT INVOLVED:
ERY METHOD:     During test.
Pumps CAUSE:
T:   Bypass switches for torque switches were dropping out before valve disc cleared seat resulting in torque switch stopping valve movement.}}
Switch setting incorrect.
SEQUENCE OF INTEREST:
LOCA ACTUAL OCCURRENCE:
Valves fail to open for decay heat system.
REACTOR NAME: Rancho Seco DOCKET NUMBER:
50-312 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
918 MWe REACTOR AGE:
2.1 yr VENDOR:
B&W ARCHITECT-ENGINEERS:
Bechtel OPERATORS:
Sacramento Municipal Utility District LOCATION:  
.25 mi1les SE..of. Sacramento, CA DURATION:
360(a) hours PLANT OPERATING CONDITION:
Shut down.
SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; QDmade inoperable; (d)
DISCOVERY METHOD:
During test.
COMMENT:
Bypass switches for torque switches were dropping out before valve disc cleared seat resulting in torque switch stopping valve movement.}}

Latest revision as of 20:37, 10 December 2024

Final ASP Analysis - Rancho Seco (LER 312-76-015)
ML20168A720
Person / Time
Site: Rancho Seco
Issue date: 06/16/2020
From: Christopher Hunter
NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1976-015-00
Download: ML20168A720 (4)
v • d • e


Text

PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:

120995 Date: November 11, 1976

Title:

Suction Valves to Decay Heat Pumps Fail to Open at Rancho Seco The failure sequence was:

1. During testing, neither sumnp isolation was applied.

valve opened when an open signal

.Corrective action;

1. The valves were moved manually and then cycled electrically.. The bypass switches for the valve torque switches-was-adjusted to permit more motor turns before the bypass switches difopped. out.

Design purpose of failed system or component:

1. The valves provide for fluid flow from the sump to the low pressure and high pressure recirculation systems and the building spray system (while in the recirculation mode) following a LOCA.

Unavailability of system per WASH 1400:

  • low pressure recirc:

1.3 x 10-2 /D high pressure recirc:

9 X 10-3/D Unavailability of component per WASH 1400:

  • motor operated valve, failure to operate.

1 x 10-3/D UnavailabilitieQ are in units of per demand D-1.

Failure rates are in units of per hour HR-T

Potential Severe core Damage No No No -

No LOCA and unit in shutdown.

NSIC 120995 -

Actual Occurrence for Failure of Both Suction Valves to Decay Heat Pumps from Emergency Sump at Rancho Seco

Small Reactor Auxiliary

]High Low Pressure LOCA Trip Feedwater and

Pressure, Recirculation Secondary jInjection and LPR/HPI Heat Removal Cross-Connect Potential Severe Core Damage Sequence No.

2 3

4 5

6 7

NSIC 120995 -

Sequence of Interest for Both Sump Suction Valves to Decay Heat Pumps Fail to Open at Rancho Seco

CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER-120995 DATE OF LER:

November 22, 1976 DATE OF EVENT:

November 11, '1976 SYSTEM INVOLVED:

Decay heat COMPONENT INVOLVED:

Pumps CAUSE:

Switch setting incorrect.

SEQUENCE OF INTEREST:

LOCA ACTUAL OCCURRENCE:

Valves fail to open for decay heat system.

REACTOR NAME: Rancho Seco DOCKET NUMBER:

50-312 REACTOR TYPE:

PWR DESIGN ELECTRICAL RATING:

918 MWe REACTOR AGE:

2.1 yr VENDOR:

B&W ARCHITECT-ENGINEERS:

Bechtel OPERATORS:

Sacramento Municipal Utility District LOCATION:

.25 mi1les SE..of. Sacramento, CA DURATION:

360(a) hours PLANT OPERATING CONDITION:

Shut down.

SAFETY FEATURE TYPE OF FAILURE:

(a) inadequate performance; (b) failed to start; QDmade inoperable; (d)

DISCOVERY METHOD:

During test.

COMMENT:

Bypass switches for torque switches were dropping out before valve disc cleared seat resulting in torque switch stopping valve movement.

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