ML20215K383

Safety Evaluation Re Util 861229 Submittal Concerning Matl Properties for Fracture Toughness Requirements for Protection Against PTS Events,Per 10CFR50.61.Reported Values of Copper & Nickel Content Unacceptable

ML20215K383
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	05/07/1987
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML20215K351	List: ML20215K348 ML20215K383
References
NUDOCS 8705110178
Download: ML20215K383 (10)

Text

. - _ - _ _ _ _ _ _ _ _ - _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _

1. 1. N o,, UNITED STATES 2 o NUCLEAR REGULATORY COMMISSION

.- f .. ,I WASHINGTON, D. C. 20065 C

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO IIATERI AL PROPERTIES FOR FRACTURE TOUGHNESS REQUIREMENTS FOR PROTECTION AGAINST PRESSURIZED THERMAL SHOCK EVENTS - 10 CFR 50.61 COMMONWEALTH EDISON COMPANY ZION NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKETS N0s. 50-295/304

1.0 BACKGROUND

The PTS submittal for Zion 1 and 2 submitted by Commonwealth Edison on

_ January 17, 1986 was based on a report by Westinghouse Electric Corporation, WCAP-10962. The controlling reactor vessel material from the standpoint of pressurized thermal shock evaluations was identified as the circumferential beltline weld in the Zion I reactor vessel and the lower shell longitudinal welds in Zion 2. Both critical welds were made with weld wire heat number 72105 and weld flux 8669 and are desig-nated WF-70 by Babcock and Wilcox (B&W), the vessel manufacturer.

To arrive at the best estimate copper and nickel contents for these vessel welds, Westinghouse averaged 87 measurements that had been reported for several weldments made with wire 72105. The majority of these came from studies made by B&W and reported in BAW 1799. Weld wire 72105 also had been used with weld flux 8773 to make a number of surveillance welds for B&W vessels including Zion 1 and 2. All were designated WF-209-1. The unusually large number of measurements of copper and nickel was also the result of some special studies conducted by B&W to determine throughwall variability in a nozzle dropout that contained WF-70 weld material and other studies on pieces of WF-209-1 material from the archives.

8705110178 870507 PDR ADOCK 05000295 g PDR

. 2_

The chemical composition given in BAW 1799 was 0.35% Cu and 0.59% Ni. ,

However, in WCAP-10962, Westinghouse added about 30 data taken mainly from two surveillance reports by Southwest Research Institute (SWRI).

which gave the results of X-ray fluorescence measurements on irradiated broken Charpy bars. The measurements of copper content were signifi-cantly lower than the values given in BAW 1799. The average of 87 values was 0.32% Cu and 0.56% Ni. The differences in the averages seem small  !

i

--- when one considers that the standard deviations reported in BAW 1799 were about 0.05% Cu and about 0.01% Ni. However, the difference is crucial

with regard to meeting the screening criteria at the end of licensed life i for Zion 1.

1 I

In its review of the submittal for Zion 1, dated June 24, 1986, the PWR-B ,

L Engineering Branch concluded that many of the 30 measurements added to the

] list in WCAP-10962 were not credible, and the copper and nickel contents should be 0.35% and 0.59% as reported in BAW 1799. This finding was trans-mitted to Connonwealth Edison by letter of August 14, 1985. At a meeting on October 3, 1986, representatives of Commonwealth Edison and Westinghouse presented additional data and arguments in support of their j position. These arguments were rejected by the staff for reasons given below. The Commonwealth Edison position was put in writing in another 4

submittal dated December 29, 1986 which referenced WCAP-11350, a compila-

tion of the technical infcrmation presented at the meeting. This SER is

a review of the December 29, 1986 submittal. ,

i i

I i .

~ '

- _ . L . -,., . - - . .

1.1 Review of the December 29, 1986 Submittal and WCAP-11350 It is important to begin this review by restating the issue: to determine best estimate values for the copper and nickel contents of weld WF-70 in the Zion 1 circumferential beltline weld and the Zion 2 lower shell longitudinal welds. Having no measurements on those weldments per se, it is our practice to use measurements on

[ other weldments made with weld wire of the same heat number 72105.

Having no evidence that the weld flux lot affects either copper or nickel content, differences in flux have been ignored. Bec'ause most of the copper in the weld comes from the plating on the weld rod from which the wire is drawn, plating thickness variability con-tributes to the differences in copper content between weldments and within weldments as well. Nickel, on the other hand, is present as an alloying element, and in heat 72105 the variability of nickel l content is very small when measured by the emission spectrographic analytical method.

i The approach used in this SER for arriving at a best estimate of the chemistry is to first average the measurements made on each indi-vidual weldment as indicated in Table I, keeping separate the measure-ments made by different analytical techniques or at different times.

This approach is consistent with that used in Section III.2 in WCAP-11350. From the discussion and data tabulated in WCAP-11350

~

'a .

e.

l there appear to have been measurements made on nine weldments.

Three of the nine weldments were weld metal qualification welds WF-70, WF-209-1, and WF-113. Single measurements made on them in 1969 are not shown in Table I (although they were included in the listing in WCAP-11350) because retests made by B&W in 1983 of these and other wire / flux combinations showed the early measurements to be consistently lower than the retests, and in their judgment the modern measurements were more credible (see BAW 1799, p. 6-5). The retests were done on archive material in the form of weld chips, which were melted to form a " button" for analysis purposes, following'the method used for the original measurements.

One of the nine weldments was from a nozzle dropout from the fabri-1 cation of a Midland vessel nozzle shell course. The average of 15 measurements made by B&W to study through thickness variability is I shown in Table I. Copper content ranged from 0.35% to 0.49%. Nickel content ranged from 0.58% to 0.61%

The remaining five of the nine weldments were made to provide samples for surveillance tests of the effect of radiation on the material.

The averages of the copper and nickel measurements made by different techniques, different laboratories, or at different times are given

! in Table I.

l The measurerlents made on irradiated Charpy bars from the Zion 1 sur-veillance Capsule X and Zion 2 surveillance Capsule T are shown in Table I, but they are not sufficiently credible to be included in this analysis for the following reasons:

1. The author of the SWRI reports from which these values come questioned their validity for reasons given in the Zion 1, Capsule X surveillance report by Southwest Research Institute.

In brief, the small size and the gama activity of the samp'!e complicate the analytical procedures.

2. Measurements of nickel content by X-ray fluorescence on irradiated broken Charpy bars fall in the range from 0.47% to 0.57% Ni, whereas measurements by emission spectrographic analysis ranged from 0.57% to 0.62%, with 44 of 57 values being either 0.58% or 0.59% Ni. This is an indication that there were difficulties with the X-ray fluorescence technique when applied to irradiated broken Charpy bars.

3. For the Zion 1, Capsule X material, the copper measurement made by Westinghouse using X-ray fluorescence on unirradiated material was 0.35% compared to an average of 0.26% by SWRI and 0.22% by Westinghouse, using the X-ray fluorescence method on irradiated Charpy bars. The SWRI measurements on the Zion 2 Capsule T material also seemed low in comparison to the measurements made by Westinghouse (see Table I). l l

u_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _

g

~ ~ ~ -

t, . -

l 4., In an attempt to make an estimate of the copper and nickel con-tent of the Zion 1 and 2 surveillance weldments, WCAP-11350 con-tains a comparison of the Charpy 30 ft. Ib. shift data from the surveillance reports with predictions based on Revision 2 to Regulatory Guide 1.99. This analysis indicates a copper content of about 0.27% if the Zion data are assumed to fall on the mean curve. This is an estimate with considerable uncertainty because, e

for the correlation used in developing the basis for Revision 2, one standard deviation is 28'F and this corresponds to about 0.08% copper. Yet, it is an indication that the measurements of copper content made by SWRI may indeed be low.

The letter of December 29, 1986 from Comonwealth Edison which sub-mitted WCAP-11350 said that the staff's reservation about the credi-bility of X-ray fluorescence (XRF) measurements was inconsistent with staff's position in its review of Amendment 100 from Fort Calhoun.

The latter cited studies of the chemistry of welds in the vessel head that were made with weld wire from the same heat number as certain girth welds. In response, the staff notes that the Fort Calhoun  ;

l samples tested by XRF were also tested by emission spectrographic l means and were not pieces of irradiated Charpy bars, which suffer from their small size and the effort of gamma activity of the sample on the measurement of the fluorescent peak.

r _._ . - . . ,

4 a,,. .

l i

Finally, there was some new information provided by B&W in the form of emission spectrographic analysis results obtained from two test blocks taken from the Midland 1 Reactor Vessel Surveillance Weld. For Test Block BN 10 there were six measurements ranging from 0.35% to 0.38% Cu (average of 0.36% Cu) and 0.59% Ni, the same for all six measurements.

i For Test Block BN 6 there were six measurements ranging from 0.32% to 0.41% Cu (average of 0.56% Cu). Nickel content ranged from 0.58% to 0.59%. These averages are given at the bottom of Table I.

i The summary of data in Table I plus the new information given ab'ove provides data on three weld metal qualification weldments, one nozzle belt dropout (a full-thickness weld), and five surveillance weldments reported in WCAP-11350, plus two test blocks from another surveillance weldment. For the three weld metal qualification weldments there is only one measurement for each. For the Zion 1 and Zion 2 surveillance weldments there is only one measurement each on unirradiated material, the others being deemed not credible as described above. For the remaining six weldments the average j

copper and nickel values used in this analysis are the average of four or more measurements. The grand average of the 11 copper values is 0.348% Cu and for the nickel it is 0.585% Ni, Alternatively, if only the six weldments for which credible multiple (four  ;

or more) measurements are considered, the average copper contents are:

l l

)

1

--,.m -- = , - . . , , -

y .

0.419, 0.355, 0.357, 0.302, 0.362, and 0.360. The grand average of these six values is 0.359% Cu. For the nickel it is 0.589% Ni, Viewed another way, of these six values five are above 0.35% Cu and only one is below.

Even if it is conceded that the two Zion surveillance welds have copper contents below 0.35%, and there is some evidence that they do, there are only three weldments below 0.35% Cu and five above.

2.0 CONCLUSION

The staff concludes from this analysis that its evaluation given in the earlier SER and repeated below is supported by this evaluation. The licensee's estimated copper and nickel values are not acceptable because they averaged suspect data with the credible data. We believe the more credible data should be given greater weight.

For Zion 1, the controlling beltline material from the standpoint of PTS susceptibility was identified to be the intermediate shell circumferential I weld WF-70 (weld wire heat number 72105). For Zion 2, the controlling 1

material was identified to be the lower shell longitudinal welds which l

were also WF-70.

The material properties of the controlling material and the associated margin and chemistry factor were reported to be:

s. _ -. -

'5 x . . . :. au . . . -

s k

4 Utility Submittal Staff Evaluation Cu(coppercontent,%) 0.32 0.35 r Ni (nickel content, %) 0.56 0.59 I (Initial RTNDT, F) 0 0 M (Margin,'F) -- 59

CF (Chemistry Factor, 'F) -- 226.8 4

I l- Principal Contribution: P. N. Randall i Dated:

1 MAY 7 1997 i ,

4 h

t A

1 '

l l

1 i

i l

' I

^

D '

. a, . ~~~ X .T a l.: . ..- - ..

o. ,

TABLE I

SUMMARY

OF COPPER AND NICKF'. CONTENTS OF WELDMENTS MADE WITH WIRE HEAT 72105 Code Weld No. of No. Flux Source Technique  % Cu  % Ni Measurements 3 Weld Metal Qualification Weldments WF-70 8669 B&W ESA 0.340* 0.580* 1 WF-209-1 8773 B&W ESA 0.400* 0.590* 1 WF-113 8688 B&W ESA 0.300* 0.610* 1 1 Nozzle Belt Dropout (Midland Vessel)

WF-70 8669 B&W ESA 0.419* 0.593* 15 5 Surveillance Weldments, WF-209-1 Crystal 8773 B&W Sury. ESA 0.390 0.100** 1 River 3 8773 B&W Archive ESA 0.355* 0.605* 4 Oconee 2 8773 B&W Surv. ESA 0.350 0.590 2 0.357* 0.580* 6 8773 B&W Archive ESA Oconee 3 8773 B&W Surv. ESA 0.295 0.580 2 8773 B&W Archive ESA 0.302* 0.582* 26 Zion 1 8773 WSCLI XRF 0.350* 0.570* 1 8773 SWRI XRF(Irr.)*** 0.259 0.543 8 8773 WARD XRF(Irr.)*** 0.220 0.540 2 Zion 2 8773 WSCLI XRF 0.280* 0.550* 1 8773 SWRI XRF(Irr.)*** 0.229 0.521 10 8773 WARD XRF(Irr.)*** 0.283 0.533 3 Two Test Blocks From Midland I Surveillance Weldment Test Block 8773 B&W ESA 0.362* 0.590* 6 BN 10 Test Block 8773 B&W ESA 0.360* 0.583* 6 BN 6 ESA = Emission Spectrometry Analysis XRF = X-ray Fluorescence Spectrometry IRR = Irradiated Charpy Specimen B&W = Babcock and Wilcox WSCL1 = Westinghouse (Spectrochem Laboratory, Inc.)

SWR 1 = Southwest Research Institute WARD = Westinghouse Advance Reactor Divison

• The 11 weldments for which measurements were averaged.

• • A-typical weld (See BAW 10144A), not included in NRC averages.

• • • Not included in NRC averages.

.