ML20086S382

SR-S1-74-06:damage Discovered on Pipe Restraint Anchors on Safety Injection Accumulator Discharge Lines.Caused by Flashing & Water Hammer Shock Experiences During Early Operation

ML20086S382
Person / Time
Site:	Surry
Issue date:	01/24/1975
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
SR-S1-74-06, SR-S1-74-6, NUDOCS 8403010541
Download: ML20086S382 (5)

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. O O VIRGINIA ELECTMIC AND POWER COMI*ANY ~,

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.y Mr. Norman C. Moseley, Director Scrial No. 412 Directorate of Regulatory Operations P0&M/JTB:clw United States Nuclear Regulatory Commission Region II - Suite 818 Docket No. 50-280 230 Peachtree Streat, Northwest License No. DPR-32 Atlanta, Georgia 30303

Dear Mr. Moseley:

The Virginia Electric and Power Company hereby submits forty (40) copies of Special Report No. SR-SI-74-06.

The substance of this report has been reviewed by the Station Nuclear Safety and Operating Committee and will be placed on the agenda for the next meeting of the System Nuclear Safety and Operating Committee.

Very truly yours,

. . dll Col C. M. Stallings Vice President-Power Supply and Production Operations Enclosure cc: Mr. K. R. Coller (39 copies SR-SI-74-06) 8403010541 750124 PDR ADOCK 05000290 S PDR 3g{J

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-SPECIAL REPORT i SR-SI-74-06 i

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'i- SAFETY-INJECTION PIPE SUPPORTS i

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e I. INTRODUCTION As a result of the recent discovery of damaged pipe restraint anchors on the Unit No. 2 safety injection (SI) accumulator discharge lines, an inspection of Unit No. I pipe restraints was conducted. The inspection revealed damaged anchors similar to those found on Unit No. 2, as described in Special Report 1 umber SR-S2-74-01. The results of the investigation are centained herein.

II. DISCUSSION Pipe restraints H-4, H-10 and H-16 rigidly support SI accumulator discharge lines SI-45, SI-46 and SI-47, respectively. These pipe restraints, identical to those of Unit No. 2, are designed to withstand loads (in-cluding seismic) during normal system operation. Each restraint is con-structed of three built-up stainless steel beams, joined to a stainless steel ring reinforcement which is welded to the pipeline it supports. The restraint legs are arranged in a " Tee" configuration, with two (2) of the beams joined diametrically opposite each other on the ring reinforcement, and the third beam situated at right angles to each beam. Each beam is welded to its stainless steel baseplate which is anchored to a two-foot thick conrete floor. Rigid attachment of the baseplate to the concrete floor.is accomplished by the insertion of bolt anchor fasteners in the concrete and the insertion of six (6) inch long bolts into the anchor fasteners to' hold the baseplate to the concrete. A bed of grouting, one (1) inch thick (as per the original specification), is placed between the baseplates and the concrete floor.

The SI piping anchors on Unit No. I were subject to similar load transients as described in SR-S2-74-01 for Unit No. 2 anchors. As a

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- 1 result, they sustained similar damage, as detailed below. Damage to Loop A anchors consisted of very minor cracking of the grout with no physical evidence of damage to the concrete or the concrete fasteners. . Damage to the Loop B anchor consisted of a semicircular crack around the base of one of three anchor baseplates, propagating down to the concrete fasteners with some cracking and spalling of the grout. Loop C damage consisted of some cracking and spalling of the grout, with some of the concrete fasteners pulled out approximately !c inch. There was no evidence of damage to the concrete. Some pipe supports and hangers adjacent to the damaged pipe restraints were also found to have received minor damage. This was an-ticipated, however, considering water hammer and flashing vibrations exerted-similar forces on adjacent hangers.

The safety injection piping in Unit Nos. I and 2 is similar; therefore, since Loop B is the same in both units the analysis performed for Unit No. 2 restraints -is applicable te Unit No. 1. The physical evidence in Unit No. I revealed that the movement of the pipe was much less than that of Unit No. 2; therefore, the stresses were lower.

Since Loops A and C of Unit No. 1 received relatively minor damage, an attempt was made to re-tighten each fastener that showed evidence.of

. pulling out.. If the bolt fail # ta tighten,_.then_that bolt was replaced.

by a 3/4 in x 10 in. Hile'@ _t alt. The-loo'se and cracked grout was J :'

removed and repoured. A cov3, , , the . damaged concrete was found to have shallow surface cracks penetrating in ' depth to-approximately four 1(4)-

- inches, i.e. to the bottom of'the fasteners.- This. concrete was'chippedi i  :,

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/ out to. expose good concrete and.Hilti-Kwik bolts ( 3/4 in. x.10 in.).were installed to permit anchoring into unaffected' concrete. An epoxy bonding.

agent was applied to.the exposed' concrete 7and new concrete poured to the n.-

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original level. The baseplate was then re-grouted to complete the anchor. The adjacent damaged pipe supports and hangers were fixed by re-tightening existing 3/4 in. fasteners where possible or by installing the next larger size (7/8 in. diameter) fasteners.

Non-destructive tests were conducted to determine if damage had occurred to adjacent piping and welds. Ultrasonic testing of welds on the three (3) SI loops, from the weld downstream of the second check valve in the accumulator discharge line up to and including the weld into the reactor cold leg piping, was performed. The test results revealed no significant indica tions.

III. CONCLUSIONS The damaged restraints were the result of flashing and water hammer shock experienced during the early operation of the unit (Special Report SR-S2-74-01). As a result of modifications made to the safety injection system operating procedure, the water hammer and flashing have not recurred.

The corrective action performed assures the ability of the restraints to function as originally intended.

The events described herein did not affect the safe operation of the station or the health and/or safety of the general public.

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