CNL-18-043, Clinch River - Submittal of Revised Site Safety Analysis Report Subsection 2.4.3.2, Probable Maximum Precipitation, in Support of Early Site Permit Application

Clinch River - Submittal of Revised Site Safety Analysis Report Subsection 2.4.3.2, Probable Maximum Precipitation, in Support of Early Site Permit Application

ML18075A314
Person / Time
Site:	Clinch River
Issue date:	03/16/2018
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of New Reactors
References
CNL-18-043
Download: ML18075A314 (5)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, TN 37402 CNL-18-043 March 16, 2018 10 CFR 52, Subpart A ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Clinch River Nuclear Site NRC Docket No.52-047

Subject:

Submittal of Revised Site Safety Analysis Report Subsection 2.4.3.2, Probable Maximum Precipitation, in Support of Early Site Permit Application for Clinch River Nuclear Site

Reference:

Letter from TVA to NRC, CNL-17-151, Revision 1 of Application for Early Site Permit for Clinch River Nuclear Site, dated December 15, 2017 By letter dated December 15, 2017 (Reference), Tennessee Valley Authority (TVA) submitted Revision 1 of the application for an early site permit (ESP) for Clinch River Nuclear Site. During a February 22, 2018 telephone call, the Nuclear Regulatory Commission (NRC) requested clarification to ESP application, Part 2, Site Safety Analysis Report (SSAR),

Subsection 2.4.3.2, Probable Maximum Precipitation, and SSAR Figure 2.4.3-2, Rainfall Time Distribution - Typical Mass Curve, regarding reference to the 3382, 2912, and 469 square mile probable maximum precipitation (PMP) storms and the 7980 square mile PMP storm.

The purpose of this letter is to provide a revision to SSAR Subsection 2.4.3.2 and Figure 2.4.3-2 clarifying reference to the PMP storms. An editorial change is being made to SSAR Subsection 2.4.3.2 as indicated in the third paragraph on page 1 of the enclosure and a note is being inserted on SSAR Figure 2.4.3-2 as indicated on page 2 of the enclosure to clarify reference to the 3382, 2912, and 469 square mile PMP storms. An editorial change is also being made to correct the 3382 square mile PMP storm as indicated in the first paragraph on page 1 of the enclosure. The revised SSAR subsection and figure will be incorporated in a future revision of the ESP application.

There are no new regulatory commitments associated with this submittal. If any additional information is needed, please contact Dan Stout at (423) 751-7642.

U.S. Nuclear Regulatory Commission CNL-18-043 Page 2 March 16, 2018 I declare under penalty of perjury that the foregoing is true and correct. Executed on this 16th day of March 2018.

Respectfully, Digitally signed by J. W. Shea J. W. Shea DN: cn=J. W. Shea, o=Tennessee Valley Authority, ou=Nuclear Licensing, email=jwshea@tva.gov, c=US Date: 2018.03.16 11:10:44 -04'00' J. W. Shea Vice President, Nuclear Regulatory Affairs and Support Services Enclosure Clinch River Nuclear Site Safety Analysis Report Revised Subsection 2.4.3.2 and Figure 2.4.3-2 cc (Enclosure):

A. Fetter, Project Manager, Division of New Reactor Licensing, USNRC M. Sutton, Project Manager, Division of New Reactor Licensing, USNRC cc (without enclosure):

C. Haney, Regional Administrator, Region II, USNRC F. Akstulewicz, Director, Division of New Reactor Licensing, USNRC J. Colaccino, Branch Chief, Division of New Reactor Licensing, USNRC P. Vokoun, Project Manager, Division of New Reactor Licensing, USNRC M. M. McIntosh, Regulatory Specialist, Eastern Regulatory Field Office, Nashville District, USACE

U.S. Nuclear Regulatory Commission CNL-18-043 Page 3 March 16, 2018 bcc (without enclosure):

M. A. Balduzzi G. A. Boerschig S. M. Bono C. C. Chandler D. M. Czufin R. E. Detwiler S. M. Douglas R. L. Gambone J. P. Grimes E. K. Henderson J. M. Holcomb D. L. Hughes J. N. Perry J. T. Polickoski R. J. Schiele E. D. Schrull J. W. Shea P. R. Simmons D. P. Stout K. T. Walsh B. A. Wetzel A. L. Williams Clinch River Project ECM

ENCLOSURE CLINCH RIVER NUCLEAR SITE SAFETY ANALYSIS REPORT REVISED SUBSECTION 2.4.3.2 AND FIGURE 2.4.3-2 The following paragraphs of SSAR Subsection 2.4.3.2 are being revised as indicated.

Strikethroughs indicate text to be deleted. Underlines indicate text to be added.

2.4.3.2 Probable Maximum Precipitation The 33803382, 2912, and 469 sq mi PMP storms are modeled as nine-day events. A three-day antecedent storm was postulated to occur three days prior to the three-day PMP storm in each PMF determination. Rainfall depths equivalent to 30 percent of the main storm were used for the antecedent storms for the 33803382, 2912, and 469 sq mi storms uniform areal distribution.

These conditions are as recommended in HMR-56 report (Reference 2.4.3-4).

The 7980 sq mi PMP event is also modeled as a nine-day event with a similar three-day antecedent storm, three-day dry period, and three-day main storm pattern. Antecedent storm rainfall depths applied were equivalent to 40 percent of the main storm with a uniform areal distribution. The HMR-41 report (Reference 2.4.3-1) states that a subsequent rainfall is applicable for this storm. However, the peak elevation at the CRN Site during this PMF event occurs about 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> before the beginning of any subsequent rainfall, during a period when any subsequent rainfall induced increased flows could not compensate for the rate at which the upstream dams failure discharges are decreasing.

Temporal distribution patterns were adopted for all events based upon major observed storms transposable to the Tennessee Valley and distributions used by Federal agencies. The adopted distributions were within the limits stipulated in Chapter VII of HMR-41 (Reference 2.4.3-1) or Section 2.2.14 of HMR-56 (Reference 2.4.3-4) as applicable. These distributions placed the heaviest precipitation approximately in the middle of the antecedent and main storms. The twelve 6-hour rainfall increments of each 72-hour storm were ordered from D1 (maximum depth) to D12 (smallest depth). In the 3382, 2912, and 469 sq mi PMP storms, the rainfall increments were and applied in each 72-hour duration in the following sequence: D12, D11, D10, D9 (first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />), D2, D1, D3, D4 (middle 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) and D5, D6, D7, D8 (last 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />). The adopted sequence closely conforms to the method used by the U.S. Army Corps of Engineers (USACE)

(Reference 2.4.3-3). A typical distribution mass curve resulting from this approach is shown in Figure 2.4.3-2. The and the controlling 7980 sq mi Bulls Gap centered storm temporal distribution is shown in Table 2.4.3-3.

As shown in Table 2.4.3-1, the PMP event producing the highest PMF water surface elevation at the CRN Site was determined to result from the 7980 sq mi Bulls Gap centered storm producing PMP on the watershed as defined in HMR-41 (Reference 2.4.3-1). The PMP storm having the largest seasonal precipitation occurs in March and would produce 17.02 inches of rainfall in three days on the watershed above Watts Bar Dam (Reference 2.4.3-1). The storm producing the PMP would be preceded by a three-day antecedent storm producing 6.00 inches of rainfall, which would end three days prior to the start of the PMP storm.

CNL-18-043 E-1

SSAR Figure 2.4.3-2 is being revised (inserted applicable PMP storms box) and will be replaced with the following figure.

Figure 2.4.3-2. Rainfall Time Distribution - Typical Mass Curve CNL-18-043 E-2