ML13113A233

Technical Letter Report, PNNL Evaluation of Licensees Alternative for Volumetric Inspection of Dissimilar Metal Butt Welds at the Calvert Cliffs Plant

ML13113A233
Person / Time
Site:	Calvert Cliffs
Issue date:	04/23/2013
From:	Jay Collins Piping and NDE Branch
To:
Collins J
References
TAC ME8871
Download: ML13113A233 (21)

Text

TECHNICAL LETTER REPORT EVALUATION OF LICENSEES ALTERNATIVE TO 10 CFR 50.55A(G)(6)(II)(F) FOR LIMITATIONS TO VOLUMETRIC EXAMINATIONS OF DISSIMILAR METAL WELDS CONSTELLATION ENERGY CALVERT CLIFFS NUCLEAR POWER PLANT - DOCKET NUMBER: 50-318 BACKGROUND By letter dated June 7, 2012, and with subsequent information in a letter dated January 10, 2013, the licensee, Constellation Energy, submitted an alternative to the examination requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(6)(ii)(F) which, in part, requires licensees implement American Society of Mechanical Engineers Boiler and Pressure Vessel (ASME) Code Case N-770-1, Alternative Examination Requirements and Acceptance Standards for Class 1 PWR Piping and Vessel Nozzle Butt Welds Fabricated With UNS N06082 or UNS W86182 Weld Filler Material With or Without Application of Listed Mitigation Activities. The CFR requirements include a baseline ultrasonic examination to be performed on each full penetration piping butt weld in the reactor coolant pressure boundary welded with Alloy 82/182 materials. Ultrasonic examination requirements are listed in ASME Code Section XI and ASME Code Case N-770-1, as modified by CFR.

The licensee submitted an alternative to volumetric examination coverage requirements for several dissimilar metal welds (DMWs) at Calvert Cliffs Nuclear Power Plant (Calvert Cliffs).

The alternative applies to limited coverage obtained on circumferential scans (for detection of axially-oriented cracking), as well as for limited coverage on axial scans (for detection of circumferential cracking) on select DMWs. The NRC requested that Pacific Northwest National Laboratory (PNNL) evaluate the licensees alternative with respect to claimed coverage and ultrasonic technique capabilities as applied to two reactor coolant pump (RCP)-to-primary loop piping welds identified as Weld 30-RC-21A-10 and Weld 30-RC-21B-10. The evaluation included theoretical modeling of the sound beams based on actual phased-array design parameters and component geometrical information provided by the licensee. Additionally, based on NRC request, PNNL performed limited backscattered acoustic energy response modeling from a simulated circumferential flaw. It should be noted that currently modeled sound field extents and densities, and reflected energy from the simulated flaw, represent only isotropic material, i.e., actual grain sizes and structures, velocity ranges, and other material variables that will affect sound beam attenuation, re-direction, specular reflections from flaws, and signal-to-noise values have not been applied, and in some cases, are presently unknown.

Another consideration is the potential for inconsistent transducer coupling. This variable is not addressed in the current modeling software, as CIVA1 tends to set perfect contact between the probe and the examined component. However, the actual component outside diameter (OD) weld surfaces, from where the manual phased-array examinations were performed, would typically possess varied waviness around the circumference of the pipe, as the weld crowns 1

CIVA is a trademarked acoustic modeling software package developed by CEA.

would have been manually ground or blended smooth prior to examination. Depending on the extent of surface irregularities that exist, intermittent and unpredictable losses of ultrasonic transducer coupling may affect transmitted sound beam coherence. This can be more pronounced with phased-array probes, as the array is generally required to be adequately coupled over the entire primary axis in order for wave-fronts emitted from individual elements to constructively interfere to produce proper beam steering and focusing. In addition, the licensee stated that probe wedges with flat contact surfaces were used for these examinations, which could also contribute to coupling inconsistencies in wavy regions, or if the probe were to rock during circumferential scans on the component.

Based on the physical limitations described above, the models should be viewed as a best-case representation only.

As requested, PNNL performed individual assessments for each of the subject welds. These are provided in the following sections of this report.

EVALUATION Weld 30-RC-21B-10 Weld 30-RC-21B-10 is a full penetration DMW on a discharge nozzle joining the reactor coolant pump outlet to a cast austenitic stainless steel (CASS) safe end. The carbon steel primary piping is clad with stainless steel on the inside diameter (ID), and the CASS safe end is welded directly to the RCP housing. An idealized cross-sectional depiction of Weld 30-RC-21B-10 is shown as Figure 1. Note that this scaled drawing shows the OD surface to have some irregularity. Because OD surface features of a ground weld crown can vary circumferentially, and no information was obtained from the licensee to depict actual field conditions, PNNL modeled Weld 30-RC-21B-10 with essentially flat surfaces and only accounted for OD dimensional changes such as the slight axial taper noted across the weld. Figure 1 also provides the ASME examination volume required as a red dashed area.

Figure 1. Idealized Cross Section of RCP Weld 30-RC-21B-10 The axial examination (for detecting circumferentially-oriented flaws) of this weld is physically limited by a welded structural steel insulation support that extends on a circumferential arc of approximately101.6 mm (4 in.) in length. Further limiting the axial examination is a spray nozzle branch connection that impacts axial scanning access for approximately 254 mm (10 in.) around the piping circumference, and is located just downstream of the insulation support. These physical limitations are illustrated in Figures 1 and 2. Due to these limitations, the licensee has postulated the maximum circumferential PWSCC flaw size that, due to scanning limitations, could go undetected in this weld. The semi-elliptical flaw is shown to have dimensions of 254 mm (10 in.) in length and a maximum of 30.5 mm (1.2 in.) in through-wall extent; highlighted as red in Figure 2.

Figure 2. End View of RCP Weld 30-RC-21B-10 Detailing Access Limitations and Potentially Circumferential Flaw in this Area The licensee also submitted a volumetric examination sketch, showing theoretical beam plots for axial scan coverage obtained; this sketch includes the postulated semi-elliptical planar flaw that could go undetected. The sketch is reproduced as Figure 3, and indicates that a flaw developing in the susceptible material region could grow to a maximum through-wall extent of 30.5 mm (1.2 in.) before detection (via flaw tip specular or diffracted responses) in the examination region containing the insulation support plate and spray nozzle. Without these limitations, axial scans can be initiated at a sufficient distance away from the weld on the carbon steel primary piping to ensure 100% volumetric coverage of the susceptible material, as full volumetric scans were completed for the remaining circumferential sections of the weld. Due to the scanning limitations described, the licensee estimated volumetric coverage for axial scans at approximately 93% of the required circumference of the weld, which includes the full inner one-third of the susceptible weld material, as examined from the ID-clad carbon steel piping. No coverage credit was taken for the CASS safe end material.

Figure 3. Licensee Calculated Volumetric Coverage and Largest Undetected Flaw for Weld 30-RC-21B-10 PNNL modeled theoretical ultrasonic beam intensities for the applied phased array examination on this weld in 10 degree increments from 0 to 80 degrees, using the licensees stated half path focusing method of 113 mm (4.4 in.). The focal law values, actual probe physical matrix parameters, and the idealized drawing submitted by the licensee were used as inputs to this model. Figure 4 shows examples of UT beams for 10 and 30 degrees, respectively, as simulated by CIVA. The models were generated using a 6 dB filter applied to the sound beam.

Although the licensee has not taken credit for angles below 30 degrees, beam coverage for 10 degrees is shown to demonstrate that ID coverage may potentially be improved by using lower refracted angles (between 10 and 30 degrees). As modeled, the 30 degree beam simulation correlates with the lower angle volumetric coverage provided by the licensees description of beams from 30 to about 70 degrees (as illustrated in Figure 3).

The licen beams fr (4.4 in.) o steered b beams fr degrees focused a The mod dB beam intensity reduction a best-c grain stru coupling real flaws significan Postulat PNNL ev flaw origi simulatio the weld Figure 4.

nsees phase rom 0 to 85 d of metal path beams less t rom approxim will not prod at too short del predicts t m intensities is diminishe n; for examp case scenar ucture of the issues desc s, resulting i ntly more ch ted Flaw De valuated theo inating in the ons focused with a scan PNNL Mode ed array pro degrees, at o h after exitin than about 4 mately 0 to 3 duce useful b a metal path that all sound near the ID ed by 50% of ple, 12 dB is rio; that is, n e weld is incl cribed above n decreased allenging ou etection in W oretical dete e susceptible on assessin region that eled -6 dB B be was oper one-degree ng the probe 40 degrees, 30 degrees.

beam profile h length.

d beams abo of the weld.

f the initial m s 4 times low o material a uded in the e, will typical d signal-to-n utside the the Weld 30-RC ection of the e material re ng the detect was physica Beams for 10 rated with fo increments,

. This focal and only pro Similarly, s es for detecti ove approxim The 6 dB maximum; ev wer than init ttenuation o model. The ly lower the oise ratio (S eoretical 6d

-21B-10 licensee-po egion, using tion of a plan ally limited b and 30 Degr ocal laws def each focus length is be oduces 6 d teered beam ing flaws nea mately 30 de value repres very 6 dB is ial sound en or sound bac ese factors, a amplitudes S/N), and ma dB region.

stulated ID-c modeled de nar type, sem y the insulat rees Respec fined to prod ed at approx eyond the ID B field dens ms above ab ar the ID be egrees to ha sents a poin s an addition nergy. The m ckscattered f as well as ot of signal res aking flaw de connected c efect respons mi-elliptical f tion support tively duce steered ximately 113 surface for sities at the I bout 65-70 cause they a ave less than nt where field nal 50%

model repres from the coa ther potentia sponses from etection circumferent ses. These flaw located and spray d

3 mm D for are n 6 d

sents arse al m

ial in

nozzle bo have an at the cro of the co Figu Theoretic weld, orig back as p from 0 to oss as previ arc length o own of the fl mponent an ure 5. Top: P cal flaw dete ginating with possible in r o 60 degrees ously depict f 254 mm (1 aw, as illustr nd was conne Perspective V ection was fir h the phased relation to th s in 5 degree ted in Figure 0 in.) and a rated in Figu ected to the View of Semi rst assessed d array probe e scan regio e increments e 3. The sem maximum th ure 5. The fl ID surface.

i-elliptical Pla d by simulati e positioned on), as show s were selec mi-elliptical p hrough-wall law was plac anar Flaw; B ing a linear a d against the wn in Figure 6 cted for this s planar defec extent of 30 ced in the bu Bottom: End V axial pipe sc e insulation s

6. Insonifica simulation.

ct was define 0.5 mm (1.2 utter/weld re View of Flaw can over the support (as f ation angles ed to in.)

egion w

far set

Figure 7 upper lef the weld is the cen the resul on the bl display s simulated the right) on the s simulated not resul are proje position t observed could pos However considere trap regio that a low modest a the start simulatio from weld Fig shows resu ft image sho in relation to ntral ray for ts displayed ack cursor b showing all a d flaw respo

), as generat hot number d time-ampli t in a strong ected to be h to insonify th d in the figur ssibly be de r, the 30 deg ed as ID-con on. The view wer inspectio amplitude re position tow on. Thus, it is d centerline gure 6. Persp lts of the def ws that the p o the insulat the L-wave, correlate w bar. The low angles simula onses for ang ted from the r correspond itude A-Scan ID corner-tr higher than th he ID connec re indicating tected at 30 gree angle b nnected bec w of the flaw on angle, su sponse from ward the weld s imperative as possible pective View fect respons probe is in th tion support) 30 degree r with the initial wer left imag ated versus gles 0 to 60 initial scan ding to 30 de n image. Th rap response he ID conne ction region) that a postu degrees giv eam would b cause this an from the init ch as appro m the ID corn d region, the that the sca

) for the grea w of Flaw with se simulation he initial sca

). The ray tr refracted an l scan positio e is an unpr time at a pa degrees (0 d position. Th egrees. The he A-scan im e from the fl ected region

). A low am ulated flaw o ven the axia be unable to ngle does no tial scan pos oximately 20 ner-trap of th e postulated an begin at t atest amoun h Linear Line n from the 30 an position (a race line exit gle. The up on indicated rocessed no articular scan degrees on he black curs lower right q mage shows aw, as angle (a lower ang plitude top-of 30.5 mm (

l scanning li o assess whe ot adequatel sition (lower degrees, co his flaw. As flaw disappe he simulated nt of volumet e Scan Path 0 degree sca as far back a ting the cent pper right ima d by the num n-volume co n position. S the left and sor in this im quadrant dis that a 30 de es of 30 deg gle is require

-of-flaw resp 1.2 in.) throu mitation.

ether the fla y insonify th left of the fig ould possibly the scan pro eared from v d starting po tric coverage an angle. T as possible f ter of the pro age shows t meric 0 labe orrected sect Shown are 60 degrees mage is cent plays the egree angle gree and abo ed from this ponse is ugh wall exte w could be he ID flaw co gure) indicat y result in a ogressed fro view in the oint (as far b

e.

he from obe that ling torial on ered does ove scan ent orner-tes om ack

At the req elliptical a 30 deg position w normalize this angle good com Figure 8 through w Figure 7 quest of NR planar flaw t ree inspecti was selected e the variab e and positio mmon respo shows the A wall extent fl

7. Defect Re C, a second to determine on angle. T d as a const le height top on for all flaw onse for norm A-Scan view law.

esponse at 3 d evaluation e the effect o The ID corne tant referenc p-of-flaw res ws evaluated malizing amp w of the corne 0 Degrees fr was conduc of through-w r-trap respo ce signal at 0 ponses. Th d (regardles plitudes of th er response rom the Initia cted using th wall depth on nse at 20 de 0 dB (maxim e corner trap s of through he top-of-flaw at 0 dB give al Scan Posit he previously n the top-of-f egrees from mum screen p response i h wall depth) w responses en by the 30 tion y defined se flaw respons the initial sc height) to is unchangin and so mak

s. For refere

.5 mm (1.2 i mi-se at can ng at kes a

ence, in.)

Continuin (1.2 in.) w response flaw dept beyond t the best highlighti through w that a flaw theoretic Table 1).

Fi ng to locate was made d e was record th; the peake he center of top-of-flaw r ing response wall extent fl w with a ma al top-of-flaw igure 8. Corn the probe ag eeper in inc ded at each ed flaw resp f the 30-degr response co es from the 3 laws, respec aximum throu w response ner Trap 0 dB gainst the in rements of 2 increment to ponse was a ree beam. I uld be deter 30.5, 35.6, 4 ctively, and i ugh-wall exte (lowest delta B Reference nsulation sup 2.5 mm (0.1 o define the llowed to su n this mann rmined. Figu 40.6, and 43 nsonified at ent of 35.6 m a amplitude) e A-Scan at 2 pport, the ini in.). The th response of bside as the er, the maxi ure 9 shows 3.2 mm (1.2, the 30 degr mm (1.4 in.)

) when using 20 Degrees tial flaw dep eoretical top f the flaw wit e flaw depth mum flaw d a series of A 1.4, 1.6, an ree angle. It results in th g a 30 degre pth of 30.5 m p-of-flaw th increasing increased epth to prod A-Scans d 1.7 in.)

t was observ he highest ee beam (see mm g

duce ved e

Figure In additio evaluated nozzle pr

9. Variable H Table 1 on, flaw dete d just outsid recluded a fu Height Defec

- 30 Degree Flaw Heig mm (in.

30.5 (1.2 33.0 (1.3 35.6 (1.4 38.1 (1.5 40.6 (1.6 43.2 (1.7

• 0 dB set to ID ection of the de of the reg ull scan path ct Signal Res Top of Flaw ght

.)

To

2)

3)

4)

5)

6)

7)

D corner trap original sem ion impacted

h. In this reg sponses at 3 w Response a op of Flaw Degre p response at mi-elliptical 3 d by the insu gion, the pro 0 Degrees fr as a Function

Response

ees (dB)*

15.3 11.9 10.8 11.2 14.6 19.6 20 degrees 0.5 mm (1.2 ulation suppo obe was ena rom the Initia n of Flaw He at 30 2 in.) through ort, where o abled to mov al Scan Posit ight h-wall flaw w only the spra ve an additio tion was y

nal

8.9 mm (

material.

both the 30 degre this figure Figure 1 Finally, a same axi support),

allowed t Figure 11 end) of th scan leng are most could be is not dis (0.35 in.) aw At this loca ID corner tra ee insonificat

e.

10. Top: Side B

as shown in ial scan limit

, where the n to move the 1 indicates t his flaw can gth is allowe t likely super accurately d splayed in Fi way from the ation the flaw ap and top-o tion angle, a e and End Vi Bottom: Defe Figure 11, th tation as des nozzle boss additional 8 hat a strong also be see ed. At this ex rimposed; th depth-sized gure 11.

weld, permi w has a nom of-flaw respo as shown in iews Respec ect Signal Re he far edge o scribed abov is the only p

.9 mm (0.35 ID corner-tr en with a 30 d xtremity, spe hus it would n using stand tting greater minal through onses are cle Figure 10. N ctively of Sca esponse from of the flaw w ve (for the a physically lim 5 in.) away fr rapped resp degree inso ecular respo not be expec ard tip diffra r inspection h-wall extent early seen in Note the noz an without In m Flaw at 30 was evaluate rea immedia miting factor, rom the weld onse from th nification an onses from t cted that a s action techniq coverage of of 24.2 mm n the simulat zle boss is n nsulation Sup Degrees ed for detect ately outside

, and the pro

d. The simu he extremity ngle, when th he ID corner shallow throu ques. Note f the suscep m (0.95 in.) a tion result fo not displayed pport Limitat tion under th e the insulati obe is theref ulation shown y (near to the he additiona r and top-of-ugh-wall flaw the nozzle b tible nd or the d in tion; he on fore n in e

l

-flaw w

boss

Figure 11

1. Top: Side Flaw Edg and End Vie e; Bottom: D ews Respect Defect Signa tively of Scan l Response f n without Ins from Flaw Ed sulation Sup dge at 30 De port Limitati grees on at

Weld 30-RC-22A-10 Weld 30-RC-22A-10 is a full penetration DMW on the RCP suction nozzle joining carbon steel, ID clad, primary piping to a CASS safe end. The safe end is welded directly to the RCP housing. An idealized cross-sectional depiction of Weld 30-RC-22A-10 is shown as Figure 12.

This weld varies from the outlet Weld 30-RC-21B-10 by an OD taper between the ferritic elbow to the CASS safe end, as depicted.

Figure 12. Idealized Cross Section for Weld 30-RC-22A-10 As with the previous weld, the licensee submitted sketches showing areas where no volumetric coverage was obtained for Weld 30-RC-22A-10. One such sketch is provided as Figure 13. The licensee estimated combined circumferential scan coverage (for axially-oriented flaws) to be approximately 91% of the required volume. The area of no coverage is shown to be an ID region of the weld nearest the carbon steel in the susceptible Alloy 82/182 weld/buttering material that has a potential to contain an undetected PWSCC flaw that is 5.1 mm (0.2 in.)

through-wall and 10.2 mm (0.4 in.) long (shown in red in the figure). Note that the licensee did not take credit for electronically skewing the UT beam a maximum of 10 degrees down into the weld ID region. As shown in the figure, the primary reason for limited coverage is the OD taper.

Figure 13. Licensee Calculated Volumetric Coverage for Weld 30-RC-22A-10 Optimized ID Impingement Flaw detection in austenitic weld materials is complicated, but is generally believed to require a corner-trapped, or crack-face, specular response to be back-scattered to the detecting probe with sufficient energy to yield a minimum 2:1 S/N. This amplitude is affected by several factors, including material acoustic properties, and impedance mismatching and orientation of the flaw, with respect to the impinging sound beam. When attempting to detect axially-oriented, ID surfacing-breaking planar flaws, there is a theoretical optimum range of ID impingement angles that should be designed into the transducer/wedge combination. The desired impingement angle should be within a critical range (above or below which sound would not optimally impact the ID surface to produce a corner-trapped flaw response) and can be calculated by the following:

( )

( )

OD sin sin ID

=

(1) where:

is the ID impingement angle, is the initial refracted angle from the probe on the OD surface, and OD/ID is the ratio of the outside-to-inside pipe diameters.

A graphical depiction of this relationship is shown as Figure 14. According to the industrys Performance Demonstration Initiative (PDI) generic DMW ultrasonic procedure 10 (PDI-UT-10),

the optimum ID impingement angle () for detecting PWSCC on the subject welds is in the range of 55-60 degrees, vis--vis, the transmitted refracted angle () should be in the range of 42-46 degrees.

Figure 14. Representation of Solution for ID Impingement Angle PNNL also modeled Weld 30-RC-22A-10 for beam coverage results for +/-10 degree lateral skews at steered angles of 42 and 46 degrees. Sound fields with a 6 dB filter were again used as shown in Figure 15 for the refracted L-wave beams. Here, due to the OD taper and slightly increased wall thickness as compared to Weld 30-RC-21B-10, an area of less than 6 dB coverage is shown to exist on the ID region of the weld; this appears to contradict the licensees stated coverage. Given the phased array parameters employed, the models show that full coverage (using 6 dB field intensities) is not obtained with beam steered angle ranges of between 42 to 46 degrees (optimized for ID impingement) even with electronic lateral skewing of +/-10 degrees. Figures 16 and 17 depict side views of the sound fields at 42 and 46 degrees positioned over carbon steel. The beam computation models show that a flaw height of approximately 12.69 mm (.49 in) could exist before the 6dB sound field at 42 degrees would be able to detect the tip of the flaw.

Figure 15 End View: PNNL Modeled 6 dB Coverage (42 Degrees) Positioned over Carbon & Weld (Weld 30-RC-22A-10)

Figure 16 Side View: Sound Field Intensity Profile at 42 Degrees on Weld 30-RC-22A-10

Figure 17 Side View: Sound Field Intensity Profile at 46 degrees on Weld 30-RC-22A-10

Shown below in Figures 18, 19, 20 and 21 are the 12dB (4 times less) theoretical sound intensity fields for the same +/-10 degree lateral skews at steered angles of 42 and 46 degrees, at locations adjacent to and over the weld. As can be seen, the lower intensity sound fields appear to insonify the entire ID region.

Figure 18 Skewed sound fields on Weld 30-RC-22A-10 for 12dB envelope at 42 degrees adjacent to weld over carbon steel; top left is top view, bottom left is pipe axial view, right is cross-section perspective Figure 19 Skewed sound fields on Weld 30-RC-22A-10 for 12dB envelope at 46 degrees adjacent to weld over carbon steel; top left is top view, bottom left is pipe axial view, right is cross-section perspective

Figure 20 Skewed sound fields on Weld 30-RC-22A-10 for 12dB envelope at 42 degrees over weld; top left is top view, bottom left is pipe axial view, right is cross-section perspective Figure 21 Skewed sound fields on Weld 30-RC-22A-10 for 12dB envelope at 46 degrees over weld; top left is top view, bottom left is pipe axial view, right is cross-section perspective

CONCLUSIONS Modeling of Weld 30-RC-21B-10 has shown 6 dB beam coverage at the ID region of the weld at a refracted angle of approximately 30 degrees, or less. The simulations are in agreement with the licensees prediction of coverage for the 30 degree angle only, as this is the lower value claimed to have been qualified. The simulated 6 dB coverage at 30 degrees results in a similar beam trajectory over the weld region as shown by the licensees sketch, and PNNL agrees that a flaw must grow to a minimum of 30.5 mm (1.2 in.) in through wall extent before a top-of-flaw response could theoretically be observed. Defect response simulations complement the beam coverage plots, indicating that a top-of-flaw response is observed from a flaw of this size. It should be noted that simulations were conducted without material noise or attenuation which could significantly reduce signal strength and quality.

Further defect response simulations indicate that as the flaw grows in through-wall depth, response(s) from the top of flaw increase with a maximum response from a flaw that is approximately 35.6 mm (1.4 in.) through wall, based on a 30 degree inspection angle. Thus, if volumetric coverage claims only begin using a 30 degree angle, it is more likely that a 35.6 mm (1.4 in.) through-wall flaw will be detected than the shallower flaw proposed by the licensee.

Defect response simulations, when scans are not limited by the insulation support, indicate that a 30 degree beam produces higher amplitude ID corner-trap responses, rather than significantly reduced top-of-flaw responses, which should result in improved flaw detection.

Ultrasonic beam computation models of Weld 30-RC-22A-10 partially agree with coverage maps provided by the licensee (see Figure 13), but potential flaws of the size provided by the licensee may go undetected during an inspection due to the lack of sufficient beam intensity at the ID surface region. Models using optimized impingement angles for detecting axially oriented flaws (L-wave refracted angles of 42-46 degrees) do not project 6 dB sound beams generally desired for flaw corner-trap detection at the ID region. In addition, based on the models, a roughly 17% through-wall, or approximately 12.69 mm (0.49 in.), deep flaw is the minimum depth needed to place the upper region of the flaw just into the 6dB sound field. It is important to note that, as in models of Weld 30-RC-21B-10, simulations on Weld 30-RC-22A-10 also do not account for material attenuation and/or noise.