ML19331A198

Final Deficiency Rept Re Reactor Vessel Surveillance Specimen Holder Tube Failure.Caused by Design Error.New Assembly Designed by B&W.Drawing & Table Encl

ML19331A198
Person / Time
Site:	Midland
Issue date:	05/27/1977
From:	CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Shared Package
ML19331A196	List: ML19331A192 ML19331A198
References
NUDOCS 8006170921
Download: ML19331A198 (5)

Text

gual Rey *,rt on Re actor Vamnel_ Surveil _ lance Specimen 1!nider Tuhes

. l . . .

This report han heen written pursuant to 10CFR50.55(c) (3) to document the disposition of the significant deficiency determined to exist in regard to the surveillance specimen holdcr tube assembly (SSitTA) design for EMI 177

' fuel assembly plants.

Description of the Dcffriency Ac reported in the original report on this deficiency, in-service failures .

of the SSilTA design in operating ELU 177 FA plants have occurred. Tlicsc f ailures ucre attributed to flou-induced relative motion of the holder tube and t,urveillance capsule holder train, i.e. push rod and spacers. Of the six operating plants nf fected all have had the original SSitTA design removed.

Safety Inplications Although the SSP.TA does not perform a dircet safety function, the surveillance specimen capsules instal 3 cd in the tubes provide monitoring of the fracture toughness properties of reactor vessel beltline region materials.

Failure of Tile SSilTA's could cause loss of the surveillance specimen capsules, in addition to creating loose parts within the reactor vessel. This would not represent en imminent threat to public health and safety but could result in the irretrievable loss of necessary material data. It codld also result in damage to portions of the reactor vessel internal structure and cladding and potential flou blockage due to debric generated by the f ailure.

Corrective Action Following the in-scrvice failurcs of the original design of SS!!TA a new assembly was designed by B&W (see figure 1) . This design and the vibration assessment program (VAP) for qualifying the design was presented to the NRC Staf f in a mcoting on May 27, 1976. As a result of this meeting, and subsc- **

quent topical report submittals, the new design was installed on Davis-Besse, ~

Unit 1 for subsequent measurement of the deflections and strains of the assembly to comparc with predictions and allowable values.

800617'O 727

Cntrect_{ve Action cont'd '

'. . , ~

Of particular interest the VAP (uhich included twann sents of FIV responnen) was information to provide (1) annurance of ntructural integrity of the SSilTA design and (2)to assure once that potential wear acchanisms have been eliminated. This I;tN VAP provides conclusive proof that the new SSliT denign will perform its funetion without the adverse safety implications dcncribed-above.

The results of the measurement program indicate:

(1) Measured resonant frequencies for the SSilT comparc wc11 with predictions.

(Sce Table 1).

(2) 'Ec measured amplitude of response of the SS11TA's are very small. (See Table 2)

(3) Measured stresses on the SSliT brackets are lou ( 150 psi),1 css than predicted, and occt the acceptance critoria.

(4) Visual inspection following IIFT shows no evidence of ucar or structural degradation. (See Tabic 3).

The test program included SSHTA's traded with capsules in configurations which represent the three possible inservice configurations, (i.e., no capsules, sna11 capsules, and large capsules). Thus it is concluded that:

1. the structural adequacy of the new SSilTA design has been verified and

2. it will perform satisfactorily during its design life.

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tNew Desi0n SSHT a, l h $'N::.

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Closure Assembly w 1.fj j =#j

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Capsule

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M ~'NLower End Plus i

Fic.1 New desipuuiventanec ipecimen * ,

holder tube and capsules. ,

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' ' ' ' " T'able 1 '

. SSIIT *" cen.1,1y 1:aillal' Renonant Frc<1uen 'en In-Water Source Reconant Frc<luencies - 11,7 ARC Laboratory 160 273 357 461 D-B 1: SS!!TA, Location 1 160 -

34 0 500 SSilTA, Location 2 160 -

260 360 500 SSIITA, Location 3 160 - - 500

~ Calculated 219 245 337 430 Table 2 - Relativo Ikflectionn'of Tube to Cansula (Mils) 530F Center Tubc/ Capsules Frcquency 1 ,

2 3 30 llZ .45 .25 1.7 100 HZ .023 .014 .13 145 117. .012 -

.34 160 llZ -

.026 .

200 11Z , .024 .022 .11 265 112 - .014 -

295 11Z .0069 .010 .0091 335 llZ .013 .015 -

395 llZ .0051 .0088 .0044 495 11Z .0063 .014 .0095

. . - - . - - - -- - +

_, . s. .. :.... . .r -

Tabic 3 Post llot Functional Test Inspection Resulta Arcas Inspected Method Renultc/

Comm ntu

1. All welds (Clocuro, Tube, and Capsules) Visual-4X 1o Cracks

2. Bracket Legs Visual-4X Ho Cracks

3. Tube Ligaments Visual-4 X No Cracks

4. Bracket Incide Diameter Visual - Fiber No~ k'a ter Scope & Measured Bore Micrometers

5. Closure Finger Visual-Fib er No !! car or Plantic Latch Ledge Scope Deforma tion

6. All Closure Parts Visual-4X No Wear c:: cept minor Burnishing in Finger Latch Slots and on Split Ring.

No Structural degradation.

7. Closure Utdges, Visual-4X No Wear, Chrome Platin;;

Capsule end Fittings, and Fit-Up Inta c t . The Closurc Uedge and Lower End Plugs ,& Top Capsule for Ass'y No. 3.did not Mate well, due to ccatacting in the Radius,

- caused by out of tolerance i

condition.

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