05000206/LER-1989-001, :on 890108,reactor Vessel Thermal Shield Support Block Bolts Out of Tolerance.Caused by Support Sys Degradation.Monitoring Program Is Being Developed to Detect Changes in Thermal Vibration

:on 890108,reactor Vessel Thermal Shield Support Block Bolts Out of Tolerance.Caused by Support Sys Degradation.Monitoring Program Is Being Developed to Detect Changes in Thermal Vibration

ML13331A308
Person / Time
Site:	San Onofre
Issue date:	01/23/1989
From:	Morgan H Southern California Edison Co
To:	NRC Office of Administration & Resources Management (ARM)
References
LER-89-001, LER-89-1, NUDOCS 8901300342
Download: ML13331A308 (2)

LER-1989-001, on 890108,reactor Vessel Thermal Shield Support Block Bolts Out of Tolerance.Caused by Support Sys Degradation.Monitoring Program Is Being Developed to Detect Changes in Thermal Vibration

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(ii) 10 CFR 50.73(a)(2)(iii)
2061989001R00 - NRC Website

text

LICENSEE EVENT REPORT (LER) 7e C

e:

erc-NUCLEAR GENERATING STAT ON

!UI 1

01 ;1 01

'01 01 2i

.-:CTOR VESSEL THERMAL SHIELD SUPPORT BLOCK BOLTS OUT OF TOLERANCE DATE (5)

LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVCLVEO !5)

///

Sequent ial

///

Revision Month Day Year Facility Name Docket

/ay Year Year

/

Number

/ Number Month D

NONE 0151 0i 'DI 018 819 819 0

i 0

1 0

0 Ol 213 Fcs 81s1o19ol THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10CFR (9)

(Check one or more of the followina) (11) 0 20.402(b) 2 0.405(c) 50.73(a)(2)(iv) 73.71(b)

_R 20.405(a)(1)(i) 50.36(c)(1)

5) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)2(vi Other (Specify 01 01 0

20.405(a)(1)(iii) 5.73(a)(2)(i) 2viiiA Abstract bew and 20.405(a)(1)(iv)

X 50.73(a)(2)(ii)

SO.73(a)(2)(viii)(B) in text) 20.405(a)(1)(v) 50.73(a)(2)(iii) 5O.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER (12)

ne TELEPHONE NUMBER AREA CODE E. Morgan, Station Manager 7 1 1 1 4 31 61 81 -I 6 21 41 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

'255c SYSTEM COMPONENT MANUFAC-REPORTABLE ",CAUSE SYSTEM COMPONENT MANUFAC-REPORTABLE TURER TO NPRDS

////TURER TO NPROS I//

SUPPLEMENTAL REPORT EXPECTED (14)

Ex d

Month Day Year inptext)

I Submiss ion Yes T(If yes, comNlete EXPECTED SUBMISSION DATE)

HNO Date (15) 03 2 4 89

- TJRACT (Limit to 1400 spaces, i.e., approximately fifteen single-space typewritten lines) (16)

On 1/8/89, with Unit 1 in Mode 6 for the Cycle 10 refueling outage, after performing a remote video camera inspection of the reactor vessel thermal shield support system, it was revealed that three thermal shield support bolts were out-of tolerance.

This inspection was conducted in response to degraded thermal shield supports observed in August, 1987, at a similarly designed facility. The thermal shield, located between the core barrel and the reactor vessel (Component Code RV, System Code AB), reduces neutron induced, reactor vessel embrittlement.

The bottom of the thermal shield is fastened to the core barrel, in the lower core support region of the reactor, by six supports (Component Code SPT).

Each support consists of a support block, five bolts and 4 dowel pins.

Three bolts, one on one support and two on another support, were found protruding from the inner surface of the core barrel by an amount that exceeds normal, original assembly, tolerance.

This report is being submitted since these observations constitute a deviation from the original design, therefore, creating a potential for being outside the design basis of the plant.

The conditions observed during this inspection are currently being evaluated for

safety significance

The evaluation conservatively assumes that the bolts which are protruding from the surface of the core barrel have failed resulting in support system degradation. The evaluation also considers the safety impact of loose parts resulting from bolt failures. Preliminary results of the evaluation have indicated that the thermal shield continues to be adequately supported to permit safe operation during Cycle 10.

A monitoring program is being developed in order to detect changes in thermal shield vibration indicative of support system degradation. This progrm will be implemented for the duration of Cycle 10.

During the next refueling outage, in conjunction with the 10-year inservice inspection of the reactor vessel, further inspections will be performed and repairs will be made as necessary.

resui from bot0alues0reiinryrutse0eo:

Southern California Edison Company SAN ONOFRE NUCLEAR GENERATING STATION P

0 BOX 128 SAN CLEMENTE. CALIFORNIA 92672 H

E MORGAN ELEPHONE STATION MANAGER (7t4) 368 6241 January 23, 1989 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.

20555

Subject:

- Docket No. 50-206 30-Day Report Licensee Event Report No.89-001 San Onofre Nuclear Generating Station, Unit 1 Pursuant to 10 CFR 50.73(a)(2)(ii), this submittal provides the required 30-day written Licensee Event Report (LER) for an occurrence involving the Reactor Vessel Thermal Shield Support System. Neither the health and safety of plant personnel or the public was affected by this occurrence.

If you require any additional information, please so advise.

Sincerely, cc:

F. R. Huey (USNRC Senior Resident Inspector, Units 1, 2 and 3)

J. B. Martin (Regional Administrator, USNRC Region V)

Institute of Nuclear Power Operations (INPO)