ML062860428

Response to Request for Additional Information (RAI) Related to the Replacement of Trisodium Phosphate

ML062860428
Person / Time
Site:	Fort Calhoun
Issue date:	10/10/2006
From:	Reinhart J Omaha Public Power District
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LIC-06-0116
Download: ML062860428 (8)

Text

upHU Omaha Public Power District 444 South 16th Street Mall Omaha NE 68102-2247 October 10, 2006 LIC-06-0116 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

References:

1. Docket No. 50-285

2. Letter from OPPD (J. A. Reinhart) to NRC (Document Control Desk), "Fort Calhoun Station, Unit No. 1, License Amendment Request, Change of Containment Building Sump Buffering Agent from Trisodium Phosphate to Sodium Tetraborate," dated August 21, 2006 (LIC-06-0088)

3. Letter from NRC (A. B. Wang) to OPPD (R. T. Ridenoure), "Fort Calhoun Station, Unit No. 1 Request for Additional Information Related to the Replacement of Trisodium Phosphate" (TAC No. M02864) (NRC-06-0136)

SUBJECT:

Response to Request for Additional Information (RAI) Related to the Replacement of Trisodium Phosphate Attached please find the Omaha Public Power District (OPPD) response to Reference 3, which requested additional information concerning OPPD's License Amendment Request (LAR)

(Reference 2) seeking to replace Trisodium Phosphate (TSP) with Sodium Tetraborate (NaTB).

Reference 2 included a revised Basis for Technical Specification 3.6. Attached is a correction to that Basis concerning the representative sample mass of NaTB tested to determine its solubility and buffering ability after exposure to the containment environment.

As a result of testing conducted in accordance with the revised surveillance test (Reference 2,, 3.6 -

Page 6) it was determined that the calculation that determined the representative sample mass of NaTB was incorrect. The correct representative sample mass of NaTB is 1.24 to 1.27 grams. Revised markup and clean pages of 3.6 - Page 6 are provided in Attachments 2 and 3 respectively to supersede the pages submitted with Reference 2.

No commitments to the NRC are made in this letter. I declare under penalty of perjury that the foregoing is true and correct. (Executed October 10, 2006)

Ejnhlovment wvith, Eaual flnnnrtunntv i

en w ithI

.l '..........

U. S. Nuclear Regulatory Commission LIC-06-0116 Page 2 If you have any questions or require additional information, please contact Mr. Thomas C.

Matthews at 402-533-6938.

"J4/k.

Reinhart 8te Director Fort Calhoun Station JAR/mle Attachments: 1) Response to Request for Additional Information

2) Technical Specification 3.6 - Page 6 (Markup)

3) Technical Specification 3.6 - Page 6 (Clean)

Enclosure:

1) OPPD Chemical Model Spreadsheets c:

B. S. Mallett, NRC Regional Administrator, Region IV (w/o enclosure)

A. B. Wang, NRC Project Manager (w/o enclosure)

J. D. Hanna, NRC Senior Resident Inspector (w/o enclosure)

Director of Consumer Health Services, Department of Regulation and Licensure, Nebraska Health and Human Services, State of Nebraska (w/o enclosure)

LIC-06-0116 Page 1 Response to Request for Additional Information (RAI)

Related to the Replacement of Trisodium Phosphate NRC Question 1:

Provide an electronic copy of the PWR Owners Group (PWROG) chemical model spreadsheet for Fort Calhoun that shows the precipitates formed with trisodium phosphate (TSP) buffer and sodium tetraborate buffer.

OPPD Response to Question 1:

The requested spreadsheets are enclosed.

NRC Question 2:

The summary report for Testing ofAlternate Buffering Agents frr Fort Calhoun Station (Page 3 of 8) indicates the corrosion rate of aluminum in solution buffered with sodium tetraborate is significantly higher than the corrosion rate in solution buffered with TSP. Table I in the summary report provides the PWROG chemical model predictions that show an equal amount of NaAISi3O8 precipitate is predicted at Fort Calhoun with sodium tetraborate and TSP buffered environments. Discuss why the predicted amount of ahlminum based precipitate is equal in these environments when the amount of dissolved aluminum in the containment pool would presumably be much greater with sodium tetraborate.

OPPD Response to Question 2:

The predicted amount of aluminum based precipitate is equal in both environments because the chemical model does not take into account phosphate inhibition of aluminum corrosion. This effect is not included in the model because the broad conditions for this inhibition have not been well characterized. Therefore, the model predicts the same quantity of aluminum corrosion for both TSP buffer environments and NaTB buffer environments.

The testing results reflect the fact that the phosphate from the TSP buffer inhibits the amount of aluminum corrosion. This reduction in the amount of aluminum corrosion occurs due to the formation of a phosphate conversion coating which protects the aluminum metal.

LIC-06-0116 Page 1 Technical Specification 3.6 - Page 6 Markup

TECHNICAL SPECIFICATIONS 3.0 SURVEILLANCE REQUIREMENTS 3.6 Safety injection and Containment Cooling Systems Tests (Continued)

Operation of the system for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> every month will demonstrate operability of the filters and adsorbers system and remove excessive moisture build-up on the adsorbers.

Demonstration of the automatic initiation capability will assure system availability.

Determfination o6f th volume of buffeingn aget In cotainment mutb efo~rmeddue to th posslilty of leaking valves and componeosi0i*the containment buildln 'that could caus d1issolutionof the bufferingagent durngT:ior'alOWe onj

[

Arfeing, fequency sall be-tlzdt isual determine that~tiimobluffi6b~bf~ind

'agent contained fiaotbage.ii ikt iswthttb* reaiof acceptable roperatioj based on the bofd nt]

• b'**V i 3,

bAeasurad value or th rechnical -DalBc of q***Q b-sed0 ilobtit!n a hot zero powe4 (HZP) critical boron concentration`(CBC.

8 The kas fiiid'* o~t~rre,6f buffering agent must6 within.the area of acceptable operation of Figure 2-3 using this HZP CBC.value. Prior t1 eitYijng tje rfueling outage, visual buffering.agent volume determination is performed tc brisure,'hatt:the*,as1eft',

volUme of buffering agent bntaned inthebaskets is 2!72.5 f.Th.

requirement ensures that there is an adequate quantity of buffering agent toadjust the_ Ho thepost-LOCA sump solutionj to.a value t 7.0 for HZP CBC_ upto 1f800 inp..F Tesng must be performed to ensureuthe solubihty and buffenng ability of the'NaTB aftei exposure to the containment enviroinment A reprepsenotave* sample of,,1.24 to 1. 27. grams~o NaTB from one of the baskets in ctAirnen*t-I$

hSbme q0 in 099

O-01 liters of water at boron concentr'ation of 2436 -2456 ppm (equivalent to aIRCS boron concentration o 1800 ppm.- Figure 2,,3'using bohric acid. 'ta:stat,

• rrd temperatureof 115 - 125 0F; withou agitationt the solution must'be left to stand for. h*urs. Theliqutd 1i.ten decanted an_

mnixed,ý the temperature is iadjusted to 75 79-F and the p-measured. At this point, the must be > 7.0. The representative sampleweight is based ont the minimumi required NaT _T weight of 4301; pounds, less the quantity required to account for a-I.;dic radiolysis prQdjct (758 pounds), and maxirmum possible post-LOCA sump volume I

398e5,gallons.

normaized 1t a 1.0 liter sample. At a manufactured dendsi,6f bý.b

430 lp n

_.rresi:ondst0 the.mini, umvo1umeViof625*-

r1 ".1U06f-thei tibo6n nentrýa~tion"o the-tswa srepreent ative ofiiih m

u-Jflp

,ip~-1ble boron.cono ration correspondng to the maximumnps*ible 'pOst-tOC_

• um*V0IWi 1 The post:-LOC*A'

~v~o

• lume Originates from the Reactoro01ant Syste (RCS)kthe d

Safety'Injecton*R efu6ling WaterTank (SIRWT)heSafety Injecton Tank (SITs) and the Boric Acid Storage Tanks (BASTs) Theýmaxirmum post-LOCA sump boro o0nCentration is based on a curmulativeboroonconcentraUton in the RCSi;SIRWT, SITs an BASTs of.2446ppm. The cumiulativeab-or0i*' cncentration is based on a maximuR HZC w tho Xe on atBeglnnng 130f

,of Qycl ndiUones SiRWT and SITboro concebtrations at maximum ailed v.af c o50 ppmrand tnaxmpBAST ic0o

% wt. ~gtationeo ah rf qwiado r fr th~

containment sump.,.apid mibdn9,would :eo' 8g~~* l~ms*a

amount..g tm berethe required pHis achimai7.0 b tclh nset of1 recirculation after a LOCA

TECHNICAL SPECIFICATIONS Periodic detcrmnination of the volume of T-SP in containment must be fpeormc~nd duc to thc possibility of leaking valves and components in the co~ntain~ment bu ildlin thtcolause dissolution of the T-SP dUring norm~a! operation.

A refueling frqe~

shall be utilized to visually determine that the volume of TSP-cn-eta;ined in the TSP baskets is within the area of acceptable operation based on the T-SP v.olume required by Figure 2 3. A measured value or the Technical Data Book (T-DB)4I, "Reac-tivity C urves" mnay be used to-obta-;in a; hot zero power (HZP) cFritial boFro Goncentration (GBG). The "as found" volume of TSP must be within the area of ac.eptable another visual T-SP volume determnination is pe~formed to ensure that the "as left" volume ot T-SP contained in the baskets is >-I2-8.2-ft. This requirement ensures that there is an adequate quantity of TSP to ad*just the pH of the post L A

.ump solution to a value 7.0 for HZP CBC up to 1800 ppmn.

The periodic pH verification is also required on a refueling frequency. Operating eprec has shown this suR'eillance frequency acceptable due to margin in the volume of T-SP placed in the-conptainment building.

An "as left" representative sample of 1.78 1.81 grams of T-SP fromn one of the baskets in containment is submnerged in 0.00 1.01 liters of water at a boron concentration of 2439 2159 ppm (equiv.alent to a RCS boFro concentration of 1800 ppm Fi;gure 2 3).,At a-standard temnperature of 11 5 1 250Fm, without agitation, the solution should be left to stand for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The liquid is then decanted and mixed, the temperature adjusted to 75 792F and the pH mneasured. At this point the pH must be >- 70Threesnative sample weight is based on the minimum required T-SP w..eight at the beginning Of cycle of 6,800 Ibs H I,,Ih i -h, at a manufactured density of at least 53.0 Ib,/torspnst h miimumIr vonlume oe 128.3 3t, and maximum possible post-LOCA supvoue of 397,183 gallons, normalized to buffer a 1.0 liter s-ample.

3.6 - Page 6 Amendment No. 121,179,201,232 TSBC 03 010 0

LIC-06-0116 Page 1 Technical Specification 3.6 - Page 6 Clean

TECHNICAL SPECIFICATIONS 3.0 SURVEILLANCE REQUIREMENTS 3.6 Safety iniection and Containment Cooling Systems Tests (Continued)

Operation of the system for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> every month will demonstrate operability of the filters and adsorbers system and remove excessive moisture build-up on the adsorbers.

Demonstration of the automatic initiation capability will assure system availability.

Determination of the volume of buffering agent in containment must be performed due to the possibility of leaking valves and components in the containment building that could cause dissolution of the buffering agent during normal operation.

A refueling frequency shall be utilized to visually determine that the volume of buffering agent contained in the buffering agent baskets is within the area of acceptable operation based on the buffering agent volume required by Figure 2-3. A measured value or the Technical Data Book (TDB) II, "Reactivity Curves" may be used to obtain a hot zero power (HZP) critical boron concentration (CBC). The "as found" volume of buffering agent must be within the area of acceptable operation of Figure 2-3 using this HZP CBC value. Prior to exiting the refueling outage, visual buffering agent volume determination is performed to ensure that the "as-left" volume of buffering agent contained in the baskets is >72.5 ft3. This requirement ensures that there is an adequate quantity of buffering agent to adjust the pH of the post-LOCA sump solution to a value;> 7.0 for HZP CBC up to 1800 ppm.

Testing must be performed to ensure the solubility and buffering ability of the NaTB after exposure to the containment environment. A representative sample of 1.24 to 1.27 grams of NaTB from one of the baskets in containment is submerged in 0.99 - 1.01 liters of water at a boron concentration of 2436 - 2456 ppm (equivalent to a RCS boron concentration of 1800 ppm - Figure 2-3) using boric acid. At a standard temperature of 115 - 1250F, without agitation, the solution must be left to stand for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The liquid is then decanted and mixed, the temperature is adjusted to 75 - 790F and the pH measured. At this point, the pH must be >

7.0. The representative sample weight is based on the minimum required NaTB weight of 4301 pounds, less the quantity required to account for acidic radiolysis products (758 pounds), and maximum possible post-LOCA sump volume of 398,445 gallons, normalized to a 1.0 liter sample. At a manufactured density of 59.3 lbm/ft3, 4301 pounds corresponds to the minimum volume of 72.5 ft3.

For dissolution testing, the boron concentration of the test water is representative of the maximum possible boron concentration corresponding to the maximum possible post-LOCA sump volume. The post-LOCA sump volume originates from the Reactor Coolant System (RCS), the Safety Injection Refueling Water Tank (SIRWT), the Safety Injection Tanks (SITs) and the Boric Acid Storage Tanks (BASTs). The maximum post-LOCA sump boron concentration is based on a cumulative boron concentration in the RCS, SIRWT, SITs and BASTs of 2446 ppm. The cumulative boron concentration is based on a maximum RCS HZP CBC with no Xenon at Beginning of Cycle conditions, SIRWT and SIT boron concentrations at maximum allowed values of 2,350 ppm and maximum BAST concentration of 4.5 % wt.

Agitation of the test solution is prohibited since an adequate standard for the agitation intensity cannot be specified. The test time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> is necessary to allow time for the dissolved NaTB to naturally diffuse through the sample solution. In the post-LOCA containment sump, rapid mixing would occur, significantly decreasing the actual amount of time before the required pH is achieved. This would ensure achieving a pH ; 7.0 by the onset of recirculation after a LOCA.

3.6 - Page 6 Amendment No. 121,179,201,232 TSBC 03 010 0