NOC-AE-13003010, Multi-Unit Dose Assessment Capability

Multi-Unit Dose Assessment Capability

ML13189A139
Person / Time
Site:	South Texas
Issue date:	06/25/2013
From:	Hildebrandt G South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-13003010
Download: ML13189A139 (4)

Text

ý ITN Nuclear Operating Company South Texas Pro/ed Electric GeneratngStaton P.. Box 289 Wadsworth. Texas 77483 */*A*

June 25, 2013 NOC-AE-1 3003010 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Multi-Unit Dose Assessment Capability

Reference:

NEI Letter, Commitment for Implementation of Multi-Unit Dose Assessment Capability; Pollock to Wiggins; dated March 14, 2013 (ML13073A522)

In the referenced letter, the nuclear industry agreed to provide a letter to the NRC staff from each licensee that addresses the following subjects:

• A summary of the current capability to perform multi-unit/multi-source dose assessment.

" For those who do not have this capability, the anticipated schedule to establish it on an interim and/or permanent basis. It is expected that interim measures will be available to perform this function prior to implementation of a permanent solution.

• Due dates associated with each key schedule action or milestone.

• A description of how the implementation schedule will be tracked and the associated tracking identifiers (e.g., a commitment tracking or corrective action system number).

In accordance with the referenced letter, STP Nuclear Operating Company (STPNOC) provides the attached information concerning our capability to perform offsite dose assessment during an event involving multiple release sources.

There are no commitments in this letter.

If there are any questions regarding this letter, please contact Robyn Savage at (361) 972-7438 or Joseph D. Enoch at (361) 972-8767.

Manager, Plant Protection

Attachment:

STP Multi-Unit / Multi-Source Dose Assessment Capability rds A STI 33705602

NOC-AE-1 3003010 Page 2 of 2 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 1600 East Lamar Boulevard Arlington, TX 76011-4511 Balwant K. Singal U. S. Nuclear Regulatory Commission Balwant K. Singal John Ragan Senior Project Manager Chris O'Hara U.S. Nuclear Regulatory Commission Jim von Suskil One White Flint North (MS 8 B1) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 Kevin Polio NRC Resident Inspector Richard Pena U. S. Nuclear Regulatory Commission City Public Service P. O. Box 289, Mail Code: MN116 Wadsworth, TX 77483 C. M. Canady Peter Nemeth City of Austin Crain Caton & James, P.C.

Electric Utility Department 721 Barton Springs Road C. Mele Austin, TX 78704 City of Austin Richard A. Ratliff Texas Department of State Health Services Robert Free Texas Department of State Health Services Sue Perkins- Grew Nuclear Energy Institute (NEI)

RMS

Attachment NOC-AE-1 3003010 Page 1 of 2 STP Multi-Unit I Multi-Source Dose Assessment Capability

1. Summary of current capability to perform multi-source dose assessment:

South Texas Project (STP) Units 1 and 2 uses the South Texas Assessment Model Projecting Estimated Dose Evaluation (STAMPEDE) computer program described below to perform dose assessment calculations under emergency conditions. STAMPEDE is a Windows-based, menu driven program which has the capability to provide near real time estimates of potential doses to individuals from releases of radioactive materials via the atmospheric pathway and to back-calculate release rates from field measurements.

STAMPEDE uses a straight-line Gaussian plume model for initial dose projections within the Plume Exposure Pathway Emergency Planning Zone (EPZ). It uses a segmented-plume model for tracking wind shifts and plume deposition over portions of the Ingestion Exposure Pathway EPZ. STAMPEDE can use system parameters and radiation monitor readings from plant monitoring systems, or the results of in-plant sampling, to estimate the source term and release rate. It then uses these values with meteorological data, which are input manually, to estimate plume location and to calculate projected doses. STAMPEDE can also use default data in the absence of plant-specific data. Plume transport and diffusion are normally based on meteorological data measured on the site meteorological tower. In the event that the meteorological data from the tower is unavailable, data is obtained from the National Weather Service or Impact Weather Service.

STAMPEDE currently models a release from a single pathway for one unit. Release pathways include, monitored unit vent release, unmonitored containment release, monitored steam generator tube rupture release, and an unmonitored steam generator tube rupture release.

Source terms for five pre-defined source terms are used to manually input data taken from plant monitors. The five source term options are: noble gas; noble gas and iodine; coolant inventory; gap activity; and core melt inventory. STAMPEDE also provides an option to manually enter a radionuclide mix inventory.

In order to perform multi-unit and/or multiple release pathway dose assessment, STP would perform individual computations for each unit and/or each release path. The results of these runs would be manually added together to provide a dose estimate from all release sources.

2. Schedule to establish multi-unit/multi-source dose assessment capability STP will implement interim measures for multi-unit/multi-source dose assessment capabilities by October 30, 2013. Permanent capabilities will be implemented no later than December 31, 2014.

Attachment NOC-AE-13003010 Page 2 of 2 STP Multi-Unit / Multi-Source Dose Assessment Capability Due dates associated with each key schedule action or milestone Action/Milestone Estimated CR Action Completion Date No.

1 Develop procedure for interim compensatory August 22, 2013 13-3735-6 measures for multi-unit/multi-source dose assessment capabilities.

2 Develop and conduct training to implement October 30, 2013 13-3735-7 interim compensatory measures for multi-unit/multi-source dose assessment.

3 Implement procedures for interim compensatory October 30, 2013 13-3735-8 measures for multi-unit/multi-source dose assess capabilities.

4 Upgrade STAMPEDE software for multi- July 31, 2014 13-3735-10 unit/multi-source dose assessment capability.

5 Develop user manual and procedures for August 31, 2014 13-3735-11 upgraded STAMPEDE.

6 Develop and conduct training for implementing December 31, 2014 13-3735-12 upgraded STAMPEDE.

7 Implement upgraded STAMPEDE program and December 31, 2014 13-3735-13 procedures.

3. A description of how the implementation will be tracked and the associated tracking identifiers The implementation and progress of the actions described above will be tracked using STP's corrective action program under condition report CR 13-3735 to ensure the milestones and actions discussed above are implemented under the schedule provided.