ML20077G644

Final Significant Deficiency Rept SDR 83-09 Re Yarway Hy-Drop Throttling Valves W/Cracked Seats.Initially Reported on 830617.Caused by Incomplete Braze Matls.Valves Will Be Replaced.Also Reportable Per Part 21

ML20077G644
Person / Time
Site:	Wolf Creek, Callaway, 05000000
Issue date:	07/18/1983
From:	Seiken S BECHTEL GROUP, INC., STANDARDIZED NUCLEAR UNIT POWER PLANT SYSTEM
To:	Jay Collins, James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
REF-PT21-83-006-000 10CFR-50.55E, PT21-83-006-000, PT21-83-6, SDR-83-09, SDR-83-9, SLNRC-83-037, SLNRC-83-37, NUDOCS 8308040368
Download: ML20077G644 (7)

Text

"

i,*

.8 MA SNUPPS Standardised Nuclear Unit -

July 18,1983 5 Choke Cherry Road

$7[jd,'Y'*"d****

o SLNRC 83- 037 FILE: 0491.10.2/M -231 B SUBJ: Significant Deficiency Report (SDR) 83-09 Yarway Hy-Drop Throttling Valves i Mr.~ James G.' Keppler?

Administrator, Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Mr. John T. Collins Administrator, Region IV U.S. Nuclear Regulatory Commission Suite 1000, Parkway Central Plaza Arlington, Texas 76012 Docket Nos. STN 50-482 and STN 50-483 Gentlemen:

The enclosed report is being furnished on behalf of the SNUPPS Utilities; i.e. Union Electric Company and Kansas Gas and Electric Company, as a final Significant Deficiency Report under 10CFR50.55(e) criteria. The deficiency involves cracks in the seats of 1-1/2 inch Yarway Hy-Drop stainless steel valves and was initially identified at Callaway plant.

On the basis of further investigation, these problems were judged to be generic in nature resulting from incomplete braze materials between the valve body and stellite seat. As indicated in the enclosed report, design modifications have been developed which will preclude cracking of the stellite seats in valves installed in either Callaway or Wolf Creek plants.

The deficiency described in the enclosure was originally reported to NRC Region III and IV via telecon of June 17, 1983. In view of the generic nature of the deficiency, the valve supplier was requested to file a report of the defect pursuant to 10CFR Part 21. A report under Part 21 regulation was subsequently issued to NRC Region I on June 21, 1983.

If you have any quedions regarding the enclosed report, please advise.

Very truly yours, S. Seiken Manager, Quality Assurance SJS/dck/18a2 3

Enclosure:

Final Report concerning Yarway Hy-Drop Throttling Valves cc: Page Two  %, g $N 8308040368 830710 PDR ADOCK 05000482 PDR Kg'g ; fl

1 SLNRC 83- 037 Page Two I cc: G. L. Koester, KGE w/ encl.

D. T. McPhee, KCPL D. F. Schnell, UE "

H. W. Roberds, NRC/WC J. H. Neisler, NRC/ Cal "

J. Konklin, NRC/ Reg. III "

R. C. DeYoung, Dir. OIE, NRC/ Wash. D.C. w/ enc 1.

I

.- j 1

)

SNUPPS PROJECT j 10 CFR 50.55(e) FINAL REPORT CONCERNING YARWAY HY-DROP THROTTLING VALVES WITH CRACKED SEATS BECHTEL POWER CORPORATION GAITHERSBURG, MARYLAND JULY 18,1983

SEE- M -4 ,

e-5 m. A ,.1m5L w4 m e-,a.*. G- B-JA e -

~s -e- ~J. L--aA4 A,1-" - u 2 ----- a, --G-1- .

i 1

.I 1

TABLE OF CONTENTS I. DESCRIPTION OF DEFICIENCY 1 i II. CAUSE OF DEFICIENCY l III. ANALYSIS OF SAFETY IMPLICATIONS 2 IV. CORRECTIVE ACTION 2 a

t i

t A

Z I

e

~

l I.

l 1

l

4 SNUPPS PROJECT 10 CFR 50.55(e) FINAL REPORT CONCERNING YARWAY HY-DROP THROTTLING VALVES WITH CRACKED SEATS I. Description of Deficiency Cracks were discovered in the seats of twelve 1 1/2" Yamay Hy-Drop stainless steel throttling valves installed at Callaway Plant.

Examination at the Yamay Plant revealed each damaged valve to have a lack of sufficient brazing material between the stellite seat ring and the stainless steel valve body. The lack of braze materials re-sults in a gap between the seat ring and valve body and makes the seat susceptible to cracking when subjected to closing forces. Subsequent to this examination, two valves with cracks were also discovered at the Wolf Creek Plant site.

Only 1 1/2" diameter valves which utilize stainless steel bodies are affected by the problem. Thirty-five such valves were originally shipped to each of the SNUPPS sites (Callaway and Wolf Creek). The manufacture by Yarway of 1 1/2" diameter stainless steel valves of this design has been limited to SNUPPS (Callaway/ Wolf Creek) orders. The valves for sizes other than 1 1/2" contain thicker valve seats. The force required to crack valves with thicker scats is sig-nificantly greater than the yield strength of the stem.

II. Cause of Deficiency Yarway's investigation indicates that the incomplete braze is due to the much greater differential thermal expansion of the 316 stain-less steel body than the F-22 (chrom-moly) body material previously used and qualified. The resulting clearance between the seat and valve body at braze temperature was too great to permit the required flow by capillary action. Yarway has had no difficulty in makino brazes in valve assemblies of this size and design containing F-22 valve bodies and stellite seats.

l L

Yarway's manufacturing sequence calls for the visual inspection of each valve following brazing to confirm the presence of a reservoir of braze at the top of the seat. Due to the valve size and configura-tion, it is difficult to visually confirm that braze mater,ial is pres-ent. Even on the valves with cracked seats, Yarway's inspectors thought that braze was present, until sectioning and detailed inspection dis-closed otherwise.

The combination of greater thermal expansion of the stainless steel body and the difficulty in confirming the presence of brazing material behind the seats by visual inspection contributed to the failures ex-perienced at Callaway.

III. Analysis of Safety Implications The function of the valves in the SNUPPS design is to provide a predetermined flow rate as opposed to isolation or shutoff service.

The valves are flow limiting devices to prevent run-out of the safety injection and centrifugal charging pumps and to limit flow to an affected loop following a LOCA. If the valve seat is damaged to the extent that the valve could no longer naintain the pre-set flow within design limits, then accident mitigation could be affected.

Further, pieces of the seat material could break loose and enter the reactor coolant system.

IV. Corrective Action The valve seats for all 1 1/2" diameter Yarway throttling valves in-stalled at Callaway and Wolf Creek sites have been re-inspected.

Valves found to have cracked seats will be replaced. The twelve Callaway valves with cracked seats have since been cut out and re-placed. The two Wolf Creek valves with cracked seats are in the process of being replaced.

I

. .. . i I

i l

l It has been concluded that cracks in the stellite seats can only occur from the process of torquing shut the valves. To eliminate any possibility of such damage, the valves will be modified in the field and a permanent stop bushing installed to prevent valve closure. The bushings will be installed on all affected Yarway valves installed at Callaway and Wolf Creek in accordance with Yarway's instructions and a Field Change Work Plan prepared by Bechtel. The field modifications will be completed prior to fuel load at each plant.

l