ML20168A582

Final ASP Analysis - Oconee 3 (LER 287-75-007)

ML20168A582
Person / Time
Site:	Oconee
Issue date:	06/16/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1975-007-00
Download: ML20168A582 (4)

Text

PRECURSOR DESCRIPTION AND DATA NSIC Accession Number:

103392 Date:

June 27, 1975

Title:

Excessive Reactor Coolant Cooldown Rate at Oconee 3 The failure sequence was:

1. During a power reduction, an operator initiated a secondary side transient, which caused a primary side pressure/temperature transient and opened the pilot actuated pressurizer relief valve.

2. The relief valve failed to close (due to boric acid crystal buildup) and did not indicate open in the control room.

3. Reactor trip and high pressure injection occurred.

4. The operator closed the PORV block valve, re-opened it because of increasing pressurizer level, and finally closets it when RC pressure reached 800 psig, terminating the transient.

5. The relief valve quench tank rupture disk blew out, damagi~ig some pressurizer

.; "'ulat ion COT:

Ave action;

1. Procedures revised to prevent the initiation of a secondary side transient.

2. The unit 1 and unit 2 PORVs.were to, be examined for boric acid crystal buildup.

3. The PORV will be test cycled prior to each startup.

4. Operating personnel were advised that closure of the block valve was the cor-rective action for this occurrence.

Design purpose of failed system or component:

1. The valve provides pressure relief protection for the RCS.

Unavailability of system per WASH 1400: *N/A Unavailability of component:

PORV failure to close:10-2/D Unavailabilities are in units of per demand D-1.

Failure rates are in units of per hour HR-1.

Potential Severe Core Damage No No No No Yes No NSIC 103892 -Actual Occurrence I or Excessive -Cooldown Rate at Oconee 3

Auxiliary Feedwater and Secondary Heat Removal High Pressure Injection Low Pressure Recirculation and LPR/HPI Cros s-Connect Potential Severe Core Damage Sequence No.

2 3

4 5

6 7

NSIC 103892 -

Sequence of Interest for Excessive Cooldown Rate at Oconee 3

• failure requires operator error in failing to close the PORV isolation valve.

CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER:

103892 DATE OF LER:

June 27, 1975 DATE OF EVENT:

June 13, 1975 SYSTEM INVOLVED:

RCS COMPONENT INVOLVED:

Pilot operated relief valve CAUSE:

PORV stuck open, operator error SEQUENCE OF INTEREST; LOCA -

small break from stuck open PORV ACTUAL OCCURRENCE:

Stuck open PORV REACTOR NMAE:

Oconee 3 DOCKET NUMBER:

50-287 REACTOR TYPE:

PWR DESIGN ELECTRICAL RATING:

887 MWe REACTOR AGE:

2.5 yr VENDOR:

Babcock & Wilcox ARCHITECT-ENGINEERS:

Duke Power Co.

OPERATORS:

Duke Power Co.

LOCATION:

30.mtlje west of Greenville, SC DURATION:

N/A PLANT OPERATING CONDITION:

at 100% power SAFETY FEATURE TYPE OF FAILURE:

(a) inadequate performance; (b) failed to start; (c) made inoperable; 0-failed open DISCOVERY METHOD:

Transient while operating COMMENT:

-