L-2019-107, License Amendment Request - Iodine Removal System Elimination

License Amendment Request - Iodine Removal System Elimination

ML19137A052
Person / Time
Site:	Saint Lucie
Issue date:	05/17/2019
From:	Deboer D Florida Power & Light Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-2019-107
Download: ML19137A052 (5)

Text

MAY 1 7 2019 L-2019-107 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 St. Lucie Plant Unit 2 Docket No. 50-389 Renewed Facility Operating License No. NPF-16 License Amendment Request - Iodine Removal System Elimination References

1. FPL Letter L-2018-182 dated November 9, 2018, "License Amendment Request Iodine Removal System Elimination." (ADAMS Accession No. ML18316A028)

2. NRC Email from Michael Wentzel to Ken Frehafer dated April 18, 2019, "St. Lucie Plant, Unit No. 2, Request for Additional Information Regarding the License Amendment Request Pertaining to the Iodine Removal System (EPID L-2018-LLA-0301)."

In Reference 1 above, Florida Power and Light Company (FPL) requested a license amendment to the St. Lucie Nuclear Plant Unit 2 Renewed Facility Operating License No. NPF-16. Specifically, the proposed change involved eliminating the Technical Specification (TS) for the Iodine Removal System as well as simplifying maintenance associated with trisodium phosphate dodecahydrate (TSP) basket TS Surveillance Requirements.

In Reference 2 above, the NRC staff identified areas where additional information is needed to support its review. The attachment to this letter provides FPL's response to this request for additional information. The supplemental information does not alter the conclusion in Reference 1 that the change does not involve a significant hazards consideration pursuant to 10 CFR 50.92, and that there are no significant environmental impacts associated with this change.

This letter contains no new or revised regulatory commitments.

Should you have any questions regarding this submittal, please contact Mr. l\!Iichael]. Snyder, Licensing Manager, at 772-467-7036.

Florida Power & Light Company 6501 S. Ocean Drive, Jensen Beach, FL 34957

L-2019-107 Page 2 I declare under penalty of perjury that the foregoing is true and correct.

Executed on MAY 1 7 2019 Sincerely, Daniel DeBoer Site Director St. Lucie Plant Enclosure cc: USNRC Regional Administrator, Region II USNRC Project Manager, St. Lucie Nuclear Plant, Units 1 and 2 USNRC Senior Resident Inspector, St. Lucie Nuclear Plant, Units 1 and 2

L-2019-107 Attachment Page 1 of 3 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST REGARDING THE IODINE REMOVAL SYSTEM EPID L-2018-LLA-0301 FLORIDA POWER & LIGHT COMPANY ST. LUCIE PLANT, UNIT NO. 2 DOCKET NO. 50-389 NRC RAI-MCCB-1:

Title 10 of the Code of Federal Regulations (10 CFR), Section 50.67, Accident source term, provides the requirements for postulated fission product releases during a postulated design basis accident (DBA), and General Design Criterion (GDC) 41 states that systems to control fission products shall be provided to reduce the concentration of fission products released following postulated accidents. NUREG-0800 Section 6.5.2, Containment Spray as a Fission Product Cleanup System, provides review guidance to the NRC staff regarding control of containment spray pH as it relates to fission product removal effectiveness. Additionally, Branch Technical Position 6-1, pH for Emergency Coolant Water for Pressurized Water Reactors, provides review guidance to the staff regarding stress-corrosion cracking due to exposure to containment spray during a postulated DBA.

In Section 3, Technical Evaluation, of the LAR, the licensee states that containment spray additives (i.e. hydrazine) in the containment spray system were not credited for radioiodine removal as part of the extended power uprate license amendment. However, the NRC staff has reviewed the reference provided by the licensee and could not determine whether spray additives are credited for radioiodine removal. In order to determine whether the Iodine Removal System, which injects hydrazine into the containment spray system, may be removed from TS, the NRC staff requires confirmation that hydrazine is not credited for radioiodine removal.

Provide the justification, or previously approved reference, to demonstrate that hydrazine is not required for radioiodine removal, or to reduce the probability of stress-corrosion cracking of austenitic stainless steel components during a postulated DBA.

FPL Response:

Calculation NAI-1421-208 Rev. 2, Post LOCA Containment Sump pH values for St. Lucie Unit 2, determines the time-dependent pH of the post-LOCA containment sump for post-Extended Power Uprate (EPU) conditions. The calculation considers the Trisodium Phosphate Dodecahydrate (TSP) baskets and borated water concentrations for the Refueling Water Tank, Safety Injection Tanks and Reactor Coolant System. Time histories from the minimum pH of containment sump from the calculation are shown on UFSAR figure 6.5-8a and 6.5-8b. A minimum pH of 7.0 is required prior to the recirculation actuation signal (RAS) mode. The pH is controlled with baskets of TSP in the containment sump which dissolves as the post-LOCA water level increases. The resulting sump pH value at recirculation is 6.971 with the minimum water level volume and minimum water level timing. The effect of hydrazine on the post-LOCA containment sump pH is not considered in calculation NAI-1421-208 Rev. 2.

L-2019-107 Attachment Page 2 of 3 Prior to the Extended Power Uprate (EPU), two calculations were performed to establish the Post-LOCA Containment Recirculation Spray and Sump pH Values for St. Lucie Unit 2.

Calculation NAI-1158-003 included the effects of hydrazine on pH buffering. The minimum recirculation sump pH was calculated to be 6.93. Calculation NAI-1158-002 did not consider hydrazine and also calculated the minimum recirculation sump pH to be 6.93. As the pH is slightly higher for EPU conditions, it is concluded that acceptable pH can be achieved prior to recirculation without the use of hydrazine.

Unit 2 UFSAR Section 6.1.1.2 states that within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> post-accident, the recirculating water mixture is stabilized at a neutral pH, in accordance with Branch Technical Position MTEB 6-1, pH for Emergency Coolant Water. MTEB 6-1 states that with a minimum pH value of 7.0 in ECCS solutions, no cracking should be observed at chloride concentrations up to 1000 ppm during the time of interest. It also states that for spray water recirculated from the containment sump, the higher the pH in the 7.0 to 9.5 range, the greater the assurance that no stress corrosion cracking will occur. UFSAR section 6.5.2.3.2 states The pH of liquid solutions that are recirculated within the containment following a design basis accident is stabilized at approximately 7.0 to 8.1. Calculation NAI-1421-208 Rev. 2 determined the maximum sump pH to be 8.102. Since the minimum sump pH during recirculation is approximately 7.0, and does not exceed 9.5, it is concluded no stress corrosion cracking will result.

The table below provides the Total Effective Dose Equivalent (TEDE) for EPU from calculation NAI-1421-202 which does not include the use of hydrazine. Calculation NAI-1421-202, St.

Lucie Unit 2 EPU LOCA Radiological Analysis with Alternative Source Term, was issued to analyze the radiological consequences of the LOCA event for the extended power uprate conditions. Within this calculation, there is no credit taken for hydrazine addition to remove radioiodines from the containment atmosphere following a LOCA. The calculation demonstrates that the results for Exclusion Area Boundary dose, Low Population Zone dose and Control Room dose are all within the appropriate regulatory acceptance criteria.

TEDE Dose (rem)

Exclusion Area Low Population Control Boundary Zone Room EPU total 1.26 2.74 4.64 Acceptance 25 25 5 Criteria NRC RAI-LLA0301-MCCB-2:

Section 50.67, Accident source term, of 10 CFR provides the requirements for postulated fission product releases during a postulated DBA, and GDC 41 states that systems to control fission products shall be provided to reduce the concentration of fission products released following postulated accidents. NUREG-0800 Section 6.5.2, Containment Spray as a Fission Product Cleanup System, provides review guidance to the NRC staff regarding pH control systems as they relate to fission product removal effectiveness. The St. Lucie 2 TSs credit the use of TSP to buffer the pH of the containment spray and emergency core cooling system solution during a postulated DBA.

L-2019-107 Attachment Page 3 of 3 In LAR Section 2.3, Description of Proposed Changes, the licensee proposes to change SR 4.5.2.e.4 to state that a sample of TSP will be submerged in a solution representative of the refueling water tank (RWT). However, the LAR doesnt describe how the solution will be representative of the water in the RWT. Explain how the solution representative of the RWT water will be prepared, including any chemical species added to reflect water chemistry conditions in the RWT, and the temperature at which the SR is conducted.

FPL Response:

The typical Unit 2 RWT chemistry parameters are as follows:

• Boron - >1900 PPM to <2200 PPM, as boric acid

• Fluoride - <150 PPB

• Chloride - <100 PPB

• Sulfate - <100 PPB

• Aluminum - <80 PPB

• Magnesium - <40 PPB

• Silica - <1 PPM

• Lithium - <0.05 PPM

• Various radionuclides Based on typical parameters, the only significant contributor to pH and buffering of the RWT is the boric acid. Therefore, no other chemical species other than boron are added when preparing approximately 40 liters (10.57 gallons) of a boric acid solution containing 2100-2150 PPM boron. Based on calculations, the water preparation procedure is as follows:

1. Collect approximately 550 grams from a new drum of boric acid granules.

2. Obtain two clean plastic containers capable of holding 20 liters.

3. Clean and rinse each container three times with demineralized water.

4. Fill each container with 20 +/- 0.1 liters of demineralized water.

5. Add 244 +/- 0.1 grams of boric acid granules to each of the two 20 liter plastic containers.

6. Stir/agitate mixture until boric acid fully dissolved.

7. Obtain 5 ML from each container for analysis.

8. Analyze each container for boron concentration.

a. Acceptance criteria is 2100-2150 PPM BORON.

9. Between 9.9 to 10.1 gallons (37.47 to 38.23 liters) of this solution is needed to perform the surveillance.

The surveillance is performed with the RWT representative sample temperature at 120 + 10oF as required by the Technical Specifications.