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Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND NO. 2015-XXXXP

Summary of the Nuclear Risk Assessment for the Mars 2020 Mission

Environmental Impact Statement NETS 2015 Conference

February 23-26, 2015

Team Members

Daniel J. Clayton, John Bignell, Christopher A. Jones, Daniel P. Rohe, Gregg J. Flores, Timothy J. Bartel, Fred Gelbard, San Le, Charles W. Morrow, Donald L. Potter, Larry W. Young, Nathan E. Bixler and Ronald J. Lipinski

Acknowledgements Department of Energy Office of Space and Defense Power Systems (NE-75) National Aeronautics and Space Administration (NASA) Reviewers - Ryan Bechtel, Steven Giannino, Scott Hopkins and Yale Chang

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LAUNCH • MSL Class/Capability LV • Period: July/Aug 2020

CRUISE/APPROACH • 7.5 month cruise • Arrive Feb 2021

ENTRY, DESCENT & LANDING • MSL EDL system: guided entry and

powered descent/Sky Crane • 25x20km landing ellipse • Access to landing sites ±30° latitude,

≤0.5 km elevation • ~950 kg rover

SURFACE MISSION • Prime mission of one Mars year • 20 km traverse distance capability • Seeking signs of past life • Returnable cache of samples • Prepare for human exploration of Mars

Mars 2020: Mission Concept

http://mars.jpl.nasa.gov/mars2020/

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NEPA Requires EIS for the Mission

MISSION & LAUNCH

VEHICLE DATA (NASA)

ACCIDENT DESCRIPTIONS

(NASA)

SYSTEM DESIGN & TEST DATA

(DOE)

Nuclear Risk Assessment

(DOE)

Environmental Impact

Statement (NASA)

NASA Record of Decision

Sandia writes the Nuclear Risk Assessment for DOE for the Environmental Impact Statement

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Scope of EIS

The Mars 2020 EIS considers both radiological and non-radiological environmental impacts from the proposed action and the alternatives.

The analysis in the EIS includes:

Preparation for a Launch

Impacts from a Normal Launch

Possible Launch Accidents

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Mars 2020 EIS Mission Alternatives

Alternative 1 (Proposed Action): A rover powered by a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG)

Full operability over one Mars year (687 Earth days) Complete access to desired landing site region (30˚ North to 30˚ South

latitudes around the planet) No restrictions on operations Highest science return of Alternatives

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Safety is built from the inside out and from the outside in. Analysis must quantify this for decision makers.

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Multi-Mission Radioisotope Thermoelectric Generator (MMRTG)

Launches Can Fail

Atlas Fallback

Delta 241 Jan 27, 1997

Titan 34D

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Launch Safety Analysis Approach Goal: Quantitative estimate of the risk for use by decision maker

Mean probability of release of PuO2 Amount of PuO2 released (“source term”) Health effects (dose, latent cancer fatalities over 50 years) Land contamination (e.g. square km of > 0.2 microCi/m2) All expressed as mean values, percentile values, and exceedance probability

graph (Complementary Cumulative Probability Distribution) Numerous phenomena need to be modeled

Blast and impact Fire and thermal Reentry Accident sequence options Atmospheric transport and consequences

Start with detailed understanding of the response of RPS to insults Perform detailed simulations and Monte Carlo sequence codes

used to develop the probabilistic risk analysis

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Launch Safety Code Suite

Databook Ch 5 Site

Ch 8 Accidents

Ch 3 Launch Vehicle Ch 6 Flight Safety

Ch 4 Spacecraft Ch 9 Explosive

Ch 9 Debris

Ch 3 Launch Vehicle Ch 9 Fire

Ch 7 Trajectory Ch 9 Reentry

Impact Sierra/SM Zapotec

CTH

Fire SFM

PEVACI SINDA

Reentry LAPS TAOS HANDI CMA

Data Tables

Accidents LASEP

Release Records

Consequence STORM

IAT HYSPLIT FDOSE

Meteorology Population Geography

Health Physics

Health Effects, Land Contamination

Risk Integration

CARS

Exceedance Probabilities &

Uncertainty

Legend Data Code

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Blast and Impact Modeling Blasts from launch destruct and

ground impact of propellant tanks or solid propellant fragments

Ground impact of MMRTG Impact of spacecraft and launch

vehicle debris on MMRTG and components

Impact of solid propellant fragments on MMRTG and components

SNL’s Sierra/SM used for analyses Hundreds of parallel processors,

days to weeks of run time for each configuration

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MMRTG 45° Impact at 75 m/s (terminal velocity is 60 m/s)

No fuel release

Solid Propellant Burn Modeling Solid propellant fire temperatures exceed iridium clad melt and PuO2

vaporization temperatures Modeling begins with extensive fire testing and data acquisition Uses Sandia’s Sierra/Fuego detailed fire model Export Fuego’s physics module into Fluent for scoping studies Feed results into Sandia’s PEVACI code for numerous accident simulations

Solid Propellant Burn Test Sierra/Fuego Simulation Fluent with physics module from Fuego

With sideward burn

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LAPS Reentry Code Description

Reentry Object Definition

Initial Reentry Conditions

Trajectory Definition (TAOS or user provided)

Nonablating Cold Wall Boundary Layer Heating

(BLUNTY, HANDI, or MAGIC)

Ablation & Heat Conduction (CMA)

MMRTG Breakup v-gamma Map (gamma is entry angle)

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LASEP Stochastically Simulates the Range of Potential Launch Accidents

Launch Accident Sequence Evaluation Program

• 100,000 lines of Fortran code

• Hundreds of subroutines

• Extensive QA

• Over a million accident scenarios run for FSAR

• LASEP Models:

– Rocket trajectory, accident time, liquid propellant explosion and fires, blast effects, fragment impact, component fallback, component ground impact, impact by debris, solid propellant fires, orbital reentry, and other phenomena

Land Impact Water Impact

Reentry

Blast

Fire

Impact by debris

Launch Accident Sequence Evaluation Program

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Release Locations and Amounts

LASEP models numerous potential scenarios, randomly choosing time of failure, explosion characteristics, etc.

Release location and amounts determined mechanistically

Probability distributions for release are determined Potential release locations from numerous LASEP launch simulations

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Consequence Modeling

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Sandia Transport Of Radionuclides Model (STORM) uses NOAA’s HYSPLIT code, leveraging NOAA’s extensive investment and readily accessing NOAA’s weather database

Calculate health effects from inhalation, resuspension, ingestion, cloudshine, and groundshine

Fireball Rise Height Particle Transport Land Usage

Mission Phases

Prelaunch – MMRTG installation to launch Early Launch – until no potential for land impact Late Launch – up to 100,000 ft Suborbital – end of first stage burn Orbital – until spacecraft separation Long Term – if spacecraft does not land on Mars and returns

to earth

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Source Term Results

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Overall accident probability – 2.5%

Conditional probability of release – 1.5%

Mean given a release 15.5 Ci

Consequences

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Overall mean given a release Maximum Individual Dose – 15.9 mrem Collective Dose – 126 person-rem Health Effects – 0.0759 Land Contamination – 1.94 km2

Cropland Intervention – 0.034 km2

Mission Risk

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Overall Mission Risk – 2.9E-05 (1/34,400) Main contribution to risk is from Early Launch accidents Uncertainty range, percentile confidence levels

5th – 1.2E-6 (1/833,000) 95th – 7.3E-4 (1/1,370)

Mars 2020 Record of Decision

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