ML14071A519

Letter Regarding Staff Feedback on BWROG Material Dissolution Test Plan

ML14071A519
Person / Time
Site:	Boiling Water Reactor Owners Group
Issue date:	03/26/2014
From:	Anthony Mendiola Licensing Processes Branch (DPR)
To:	Leslie Hill BWR Owners Group, Southern Nuclear Operating Co
Golla J
References
Download: ML14071A519 (7)

Text

March 26, 2014 Ms. Lesa Hill, Chairman Boiling Water Reactor Owners Group Southern Nuclear Operating Company PO Box 1295 Bin B048 Birmingham, AL 35201-1295

SUBJECT:

NRC STAFF FEEDBACK ON BOILING WATER REACTOR OWNERS GROUP REPORT BWROG-ECCS-TP-4-1, REVISION 4, BWR MATERIAL DISSOLUTION TEST PLAN

Dear Ms. Hill:

With regard to the ongoing Boiling Water Reactor (BWR) Emergency Core Cooling Suction Strainer Resolution effort, the U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the BWR Owners Group (BWROG) report BWROG-ECCS-TP-4-1, BWR Material Dissolution Test Plan enclosed with your letter, identified as BWROG-14003, dated January 23, 2014, and offers the following feedback. The NRC staff would like to discuss this feedback with your staff by teleconference, as soon as practical, in order to clarify any questions you may have with it and to discuss the best method for responding to it:

1. Although the staff agrees that early communication is very helpful to both the NRC and BWROG, it is important for the NRC staff to more fully understand current BWR plant materials to make informed comments concerning test materials, environments, and other test plan features. Therefore, consistent with the staffs previous comments on the BWROG ECCS Suction Strainers Chemical Effects Strategy document, the staff is interested in obtaining a summary of BWR plant materials survey. It would be acceptable to the staff if this information was provided with individual plants identified by letter or number instead of the specific plant name. While the summary provided by the BWROG (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML12093A141) in response to our previous request was useful, it does not provide enough detail for the staff to judge the appropriateness of the test plan.

2. The stated test objective is to quantify the amount and characteristics of species released to the coolant when BWR containment materials are exposed to simulated suppression pool/torus water from a bounding post-loss-of-coolant accident (LOCA) temperature excursion at a BWR. The ratio of coolant mass to the area or mass of each material during testing will simulate the ratio at a typical BWR. In this context, is the typical amount of material intended to represent: (i) a median or mean for the fleet, (ii) a median or mean for only plants containing that particular material, or (iii) some other value?

3. In general, the Material Dissolution Test Plan does not yet have sufficient details to provide comments. Sections 2.2 and 2.3 identify the test materials and ratios of materials to coolant. These sections state that these values will be finalized following completion of the BWROG site survey of materials. Therefore, the staff is not able to

L. Hill comment on the adequacy of these test parameters until the completed BWROG materials survey results are available.

4. Section 2.4 states that the release rate tests will be performed in BWROG suppression pool chemistries representative of un-buffered and buffered (Standby Liquid Control injection) environments. Information previously provided by the BWROG (Accession No. ML12093A141) indicates the amount of sodium pentaborate injected can vary by more than a factor of 20 between the minimum and maximum plant values. In order to provide feedback on the test plan, the staff will need to understand the range in concentrations of boron produced by the different amounts of sodium pentaborate addition and the boron concentrations planned for the test matrix.

5. Defining the appropriate chemical environment for testing may not be straightforward due to: (1) variability in the amount, if any, of sodium pentaborate injection, (2) pH transients resulting from the types and quantities of insulation materials that may dissolve, (3) differences in environment or flow conditions in locations where debris could collect, and (4) the potential for formation of acids following a LOCA.

Therefore, the staff is interested in understanding the assumptions and other supporting information that is being used to determine the test matrix.

6. Section 2.5.1 indicates that the precipitate formation tests will be held at approximately 200 0F for approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. Please provide the basis for the test duration. In addition, this section states that filters will be weighed to quantify the amount of precipitate. Are the filters going to be dried prior to weighing? Staff notes that drying some precipitates from pressurized water reactor related testing (NUREG/CR-6915, p20) resulted in a roughly 90 percent weight loss.

7. The material release tests will be conducted using a bounding BWR suppression pool temperature profile. Release rate estimates as a function of temperature from 140 0F to 210 0F will be developed from the data. Please describe how the release rates will be determined from tests with continual changes in temperature?

8. Please discuss how the precipitation samples will be the cooled from 200 0F to either 140 0F or 110 0F. The staff notes that the cooling rate can affect the characteristics of a precipitate.

9. According to the test plan, the post-LOCA test apparatus exposure vessel volume is approximately 5 liters. The staff questions if the resulting material sample sizes will be so small that inhomogeneous materials, such as insulation materials, will be prone to significant differences in dissolution tests due to sampling issues. For instance, if a test called for a very small mass of fiberglass to properly scale to the solution volume, that sample may contain only fibers that were exposed to the hot plate temperature during the baking process or conversely only fibers that were not adjacent to the hot plate depending on how the sample was taken. Small samples could also contain a non-representative amount of binder.

10. Page 7 of the Dissolution Test Plan states that a Nukon cake will be loaded onto a stainless steel screen prior to testing. Please provide additional details concerning how this cake will be formed, including any thermal or mechanical processing of the

L. Hill fibers prior to cake formation, the amount of material, and whether these materials are intended to represent a strainer debris bed. The staff notes that previous vertical loop testing has shown fiber preparation techniques can significantly impact the filtering characteristics of a fiber bed. Please provide the flow area for the face of the cake. If the purpose of the cake is to detect chemical precipitates, please describe how it will be verified that the fiberglass cake is an adequate detector of precipitation?

11. Preliminary results from the BWROG site materials survey indicated that significant areas of uncoated concrete are not generally present in the BWR containment.

Therefore, concrete is not currently included in the test plan. Did the survey consider amounts of degraded coatings on concrete that could fail in a post-LOCA environment? Did the survey consider the potential area of concrete exposed within the zone of influence by a jet?

12. Please confirm that all in-stream filters used to pre-filter solution samples will be visually examined after each test to check for precipitates. Will filter time be recorded as a potential diagnostic tool?

13. Section 3.5.3.2 indicates that Nukon and calcium silicate samples removed from tests will be photographed, dried in an oven prior to weighing, and then stored for possible post-test analysis. Will a visual exam be performed prior to drying?

14. Section 3.5.3.3 discusses inorganic zinc (IOZ) samples but the test matrices do not include IOZ.

15. Tables 4-1 and 4-2 show the preliminary test matrices for post-LOCA Simulation Testing and Precipitate Formation Testing, respectively. There does not appear to be any repeat testing shown in either table. The staff is interested in how repeatability will be assessed.

16. Since Table 4-2 shows the preliminary types of materials but does not provide quantities, it is not clear if the quantity of each material is constant or changes throughout the test matrix. Use of a typical amount in each test may not evaluate the range of conditions that could exist following a LOCA. For example, testing with large quantities of Nukon may seem conservative from a material quantity perspective, however, the presence of silica in sufficient concentrations will inhibit aluminum corrosion possibly resulting in a non-conservative result for plants/pipe breaks with less Nukon. Please discuss if the precipitate formation assessment tests include an evaluation of threshold quantities of species that would result in precipitate formation in the representative environments.

17. Based on the information provided, the staff is not able to determine the velocity of the fluid past the materials in the exposure vessel. The effects of fluid velocity should be evaluated for the projected plant conditions. For example, corrosion product on galvanized steel coupons may remain on the test sample in quiescent or low flow conditions. In tests performed in Germany, water falling over galvanized steel grating produced zinc based corrosion products that transported to a fibrous debris bed and resulted in significant head loss.

L. Hill

18. Page 7 of the Dissolution Test Plan states that the flow rate will be controlled between 1 and 5 gallons per minute. This will yield a velocity through the column of about 0.1 feet per second. Please provide the basis for the 0.1 feet per second column velocity and clarify if the flow rate is constant during the test or varies by a factor of 5.

If the flow rate varies as discussed above, please discuss how a constant column velocity is maintained.

19. The staff has several questions related to the test apparatus schematic shown on page 7 of the Dissolution Test Plan.

a. Please describe the purpose of the chamber labeled Nukon.

b. What is the unlabeled chamber shown to the left of the Exposure Vessel?

c. How are materials such as fiberglass and calcium silicate (cal-sil) restricted from transporting around the test loop? The staff notes that efforts to contain these types of materials in mesh bags need to strike a balance between preventing transport to the filter cake and permitting representative exchange between the test fluid and the test materials.

d. Please discuss how it will be ensured that precipitates, if formed, will transport to the filter cake instead of settle in various areas of the test loop.

20. Sections 3.4.2 and 3.4.3 describe the preparation of Cal-Sil and Nukon test materials. Please discuss if these materials are intended to be part of the filter cake or are test materials being evaluated solely for their contribution to the chemical source term. Please clarify whether the Nukon is baked or shredded first. Please discuss if there are any differences between the processing for Nukon prepared for the filter cake as compared to Nukon exposed elsewhere in the test loop.

L. Hill Please contact Joseph Golla at 301-415-1002 or via e-mail at Joe.Golla@nrc.gov as soon as you are ready to arrange for the teleconference.

Sincerely,

/RA/

Anthony J. Mendiola, Chief Licensing Processes Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Project No. 691 cc: See next page

ML14071A519 NRR-106 OFFICE PLPB/PM PLPB/LA ESGB/BC SSIB/BC (A)

PLPB/BC NAME JGolla DBaxley GKulesa JStang AMendiola DATE 03/12/2014 03/18/2014 03/19/2014 03/21/2014 03/26/2014 Boiling Water Reactor Owners Group Project No. 691 cc:

BWROG Chairman Lesa Hill Southern Nuclear Operating Company PO Box 1295 Bin B048 Birmingham, AL 35201-1295 lphill@southernco.com BWROG Project Manager Michael Iannantuono GE-Hitachi Nuclear Energy PO Box 780 M/C A-70 3901 Castle Hayne Road Wilmington, NC 28402 Michael.iannantuono@ge.com BWROG Program Manager Kenneth McCall GE-Hitachi Nuclear Energy PO Box 780 M/C A-70 3901 Castle Hayne Road Wilmington, NC 28402 Kenneth.mccall@ge.com BWROG ECCS Suction Strainers Committee Chairman Steve Scammon slscammon@energy-northwest.com