ML19332A648

Interim Deficiency Rept Re Possibility of Inflective Insulation in Annular Space Between Reactor Vessel & Shield Dislodging During LOCA & Shearing Reactor Pressure Vessel Level Sensing Lines.Final Rept Will Be Forwarded on 810515

ML19332A648
Person / Time
Site:	Grand Gulf
Issue date:	09/08/1980
From:	Mcgaughy J MISSISSIPPI POWER & LIGHT CO.
To:
References
AECM-80-209, NUDOCS 8009160591
Download: ML19332A648 (3)

Text

so MISSISSIPPI POWER & LIGHT COMPANY

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Helping Build Mississippi P. O. B O X 16 4 0, J A C K S O N. MIS SISSIP PI 39205

=coucrio~ o rn arw rur September 8, 1980 Office of Inspection & Enforcement U. S. Nuclaar Regulatory Commission Region II 101 Marietta Street, N. W.

Suite 3100 Atlanta, Georgia 30303 Attention: Mr. J. P. O'Reilly, Director

SUBJECT:

Grand Gulf Nuclear Station Units I and II Docket Nos. 50-416/417 File 0272/15525/15526 PRD-80/48, RPV Sensing Lines, Interim Report AECM-80/209 On August 8, 1980, Mississippi Power & Light Co., notified Mr. M. Hunt, of your office, of a Potentially Reportable Condition (PRD) regarding the possibility of reflective insulat. ion in the annular space between the reactor vessel and shield dislodging during a loss of ccolant accident (LOCA) and .; hearing RPV vessel level sensing lines.

We are continuing to investigate the safety implications and reportability of this matter. Our interim report is attached. We expect to provide our final determination of reportability and proposed corrective actions by May 15, 1981.

Yours truly, 5/ 1 f

[/ " J . P. McGaughy, Jr.

Assistant Vice President Nuclear Production NDi!:rh Attachment hN

.5 cc: (.over) ll/

8009160 59/_. [ ,

Member Middle South Utilities System

MISSISSIPPI POWER & LIGHT COMPANY Office of Inspection & Enforcement USNRC, Region II Page 2 AECM-80/209 Attention: Mr. J. P. O'Reilly, Director cc: Mr. N. L. Stamploy Mr. R. B. McGehee Mr. T. B.' Conner Division of Inspection & Enforcement

. U. S. Nuclear Regulatory Commission Washington, D. C. 20555 l

1 i

m Page 1 of 1 Attachment, AECM-80/209 INTERIM REPORT FOR PRD-80/48 DESCRIPTION-OF THE DEFICIENCY If a-Loss of Coolant. Accident (LOCA) were to occur at the Grand Gulf Nuclear Station (GGNS), the reflective insulation in

=the annular space between the reactor vessel and shield wall could dislodge and produce missiles sufficient to shear any of the one-inch vessel' level _ sensing 1~ines. The potential for this condition exists in the LOCA case where a slot break occurs in one of the twelve

' reactor recirculation pump discharge lines. The force of the escaping steam and water could create pressure waves spreading around the reactor vessel and shield wall. These pressure waves.could cause pieces of the reflective insulation to break off and become missiles.

This event is known as annulus pressurization (AP).

The potential exists, therefore, that this deficiency, were it to have remained uncorrected, could have adversely affected the safety of operation of the GGNS.

APPROACH TO RESOLUTION OF THE DEFICIENCY .-

The Constructor and NSSS vendor are performing engineering analyses to determine whether this deficiency could adversely affect safe operation of GGNS.

Ihe approach for corrective action will be determined on the basis of these analyses.

STATUS OF PROPOSED RESOLUTION Analysis-to date has shown that the most massive insulation block nay be accelerated sufficiently to shear any one-inch vessel level sensing line it impacts. The analysis is continuing and is being tracked under MCAR 497.

REASON FOR DELAYING FINAL REPORT Engineering analysis is incomplete.

-PROJECTED FINAL REPORT SUBMITTAL DATE May 15, 1981

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