ML20042B341

LER 82-014/03L-0:on 820219,during Normal Operation,A RHR Loop Declared Inoperable Due to Failed Snubber GBB-4-SS-211 & Hanger GBB-4-H10.Caused by Minor Damage & Pipe Movement on a Rhr.Snubber Replaced & Hanger Repaired

ML20042B341
Person / Time
Site:	Duane Arnold
Issue date:	03/19/1982
From:	Varner D IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20042B333	List: ML20042B332 ML20042B341
References
LER-82-014-03L, LER-82-14-3L, NUDOCS 8203250230
Download: ML20042B341 (2)

Text

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, o 13 # 1 ubber GBB-4-SS-211 and hanger GBB-4-H10. This made LPCI inop. requiring- I e I a 7-day LC0 per TS 3.5.A.S. RHR cross-tic line was promptly closed. Imme I lo # Si l d. and daily thereafter, the operability of contain. spray, both core sp i la is i i rays, and diesel generators was demonstrated. "A" RHR was made operable I l o 1711 after 6.5 days. Four similar occurrences of water hammer damace to RHR. I F5Ti'l I (R0 77-08, 77-29, 79-25, 82-08). I 1 . . ea OE oE Su C E CCMPONENT C008 SusC006 su e loist -l C l F l@ [XJ@ [Z,J @ l Z l Z l Z l Z l Z l ZI@. l Zl@ LZ,J @

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NAME OF PREPARER David M. Varner ,, g y , . 319_851_5611  ?

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, DUANE ARN0LD ENERGY CENTER Iowa Electric Light and Power Company Licensee Event Report - Supplemental Data Docket No. 050-0331 Licet 9e Event Report Date: 3/19/82 Reportable Occurrence No.: 82-014 Event

Description:

Duririg normal operation, the "A" loop of the residual heat removal (RHR) system was declared inoperable because of the discovery of failed snubber GBB-4-SS-211 and hanger GBB-4-H10 on the "A" RHR line. The inoperable "A" RHR made the low pressure coolant injection (LPCI) subsystem inoperable and a 7-day limiting condition for operation (LC0) was entered as' required by Technical Specification 3.5.A.5. The RHR crosstie line was promptly closed. Operability of both core spray subsystems, the containment spray subsystem, and the diesel generators required for operation of such components was demonstrated immediately and daily thereafter. The "A" RHR was made operable after 6.5 days, which ended the 7-day LC0 for an inoperable LPCI. There have been thrue previous similar occurrences of water hammer damage to a different section of 'the RHR piping system (see R0 77-8, 77-29, and 79-25) and one previous similar occurrence with the same contributing cause (see R0 82-8).

Cause

Description:

Upon inspection, additional minor damage and indications of pipe movenent were discovered on the "A" RHR line. An evaluation concluded that inadequate fill system performance coupled with inadequate venting of the "A" RHR loop permitted the accumulation of noncondensables in the loop piping. When an RHR pump was started, a significant water hammer transient was experienced by the "A" loop which resulted in the damage observed.

Corrective Action:

Snubber GBB-4-SS-211 was replaced with a tested spare and stiffening plates were added. The baseplate for hanger GBB-4-H10 was replaced and new anchor bolts were installed. All other minor damage was repaired and/or replaced as necessary.

The spring hangers supporting the "A" RHR loop were inspected and adjusted to the cold load setting where required. A hydrostatic test of the "A" RHR loop was performed with no indications of leakage. Dye-penetrant testing of selected high stress areas of the "A" RHR loop resulted in no indications of pipe cracks.

With the satisfactory completion of these tests and repairs, the "A" RHR loop and LPCI were declared operable. To preclude recurrence, system venting and filling procedures have been modified on a temporary basis to ensure that all high points are vented periodically and whenever there is a loss of RHR pressure.

Investigations are continuing to determine the adequacy of the RHR fill system and the effect of injection line valve leakage.

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