ML102250466

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NRC Staff Exhibit 63 - Boric Acid Corrosion Guidebook, Revision 1: Managing Boric Acid Corrosion Issues at PWR Power Stations EPRI, Palo Alto, CA (2001) 1000975 Pages 4-25 & 4-26
ML102250466
Person / Time
Site: Prairie Island  Xcel Energy icon.png
Issue date: 08/13/2010
From:
NRC/OGC
To:
Atomic Safety and Licensing Board Panel
SECY RAS
Shared Package
ML102250464 List:
References
50-282-LR, 50-306-LR, ASLBP 08-871-01-LR-BD01, RAS 18398
Download: ML102250466 (4)


Text

PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 Docket Nos. 50-282-LR and 50-306-LR NRC STAFF EXHIBIT 63 Boric Acid Corrosion Guidebook, Revision 1: Managing Boric Acid Corrosion Issues at PWR Power Stations, EPRI, Palo Alto, CA (2001) 1000975 Pages 4-25 & 4-26

Boric Acid Corrosion Guidebook, Revision 1 Managing Boric Acid Corrosion Issues at PWR Power Stations Effective December 6. 2006. this report has been made publicly available in accordance with Section 734.3(b)(3) and published in accordance with Section 734.7 the U.S. Export Administration Regulations. As a result of this publication, this is subject to only copyright protection and does not require any license WARNING: from EPRI. This notice supersedes the export control restrictions and any Please read the License Agreement proprietary licensed material notices embedded in the document prior to publication.

on the back cover before removing the Wrapping Material.

Technical Report

EPRI Licensed Material Boric Acid Corrosion Tests Test Ref.: A Test Type: Immersion Aerated and Deaerated Boric Acid Org/Date: Westinghouse (1967)

References:

"Materials Behavior Related Issues for Bolting Applications in the Nuclear Industry." Conference: Improved Technology for Critical Bolting Applications, Chicago, Ill., July 20-24, 1986. MPC-Vol. 26 [22].

Absorption o/Corrosion Hydrogen by 302B Steel at 70F to 500F.

Westinghouse Electric Corporation, 1967, WCAP-7099 [23].

Test Configuration, Procedure, and Results Westinghouse conducted a series of tests on electrically isolated coupons of A-302 Grade B low-alloy steel in both aerated and deaerated environments. Some experiments involved cases where the low-alloy steel test coupons were coupled to 304 stainless steel. Tests were conducted at 2500 ppm boron at several different temperatures.

Table 4-3 gives the average corrosion rate for long periods of time (40-160 days) for each of the test conditions. The test results plotted in Figure 4-8 show the effect of test duration.

Table 4-3 Average Corrosion Rates in Aerated and Oeaerated Water - Westinghouse Tests Temperature in Corrosion Rate Oeaerated in Corrosion Rate Aerated in OF eC) IncheslYear (mm/yr) IncheslYear (mm/yr)

Isolated Coupled to 304 Isolated Coupled to 304 70 (21) 0.0002 (0.005) --- 0.002 (0.05) 0.002 (0.05) 100 (38) 0.00005 (0.0013) 0.00005 (0.0013) 0.007 (0.18) 0.007 (0.18) 140 (60) 0.00007 (0.0018) 0.00011 (0.0028) 0.015 (0.38) 0.015 (0.38) 500* (260) --- --- 0.24 (6.1) --

  • Provided at meeting with Westinghouse.

Key observations from these tests are:

  • In deaerated water at temperatures less than 140°F (60°C), the corrosion rates are very low.
  • In aerated water, the corrosion rates increase with temperature from 70°F to 140°F (21°C to 60°C) with the long-term corrosion rate at 140°F (60°C) being about 0.0 IS in/yr (0.38 mrnlyr).
  • The galvanic couple between low-alloy steel and stainless steel has little effect on the corrosion rates of low-alloy steel in borated water.

4-25

EPRI Licensed Material Boric Acid Corrosion Tests

  • Initial corrosion rates can be much higher than long-term corrosion rates.
  • The corrosion rate in aerated borated water at 500 0 P (260°C) is 0.24 inlyr (6.1 mrnlyr).

Conclusions Corrosion rates in low-temperature de aerated water are very low. Corrosion rates in aerated water at temperatures less than 140 0 P (60°C) are acceptably low to not pose a serious problem with leakage of borated water.

18000 200 o A302B Isolated Coupons ACO A3028 Isolated Coupons 16000

  • A302B Coupled to 30488 180 .... A3028 Coupled to 30488 14000 160 12000 140 N

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U° U° 1-6000 80 4000 60 21 'C ~ 4.77 X 10" mm/yr (70'F ~ 0.002 In/yr)

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140 160 Test Time, Days Test Time. Days Corrosion as measured in wei~ht loss Corrosion as A3028 in deaerated of A302B in air-saturated bOriC acid boric acid solution containing solution containing 2500 ppm boron 2500 ppm boron Figure 4-8 Corrosion Rate in Aerated and Deaerated Water - Westinghouse Tests [22) 4-26