SNAP 8 Experimental Reactor (S8ER) Description

Contact: Isaac Naupa, iaguirre6.at.gatech.edu Contact: Stefano Terlizzi, sbt5572.at.psu.edu

note

For citing purposes, please cite (Garcia et al., 2022) and (Naupa et al., 2022).

Introduction

The S8ER was part of a fleet of reactors built during the Systems for Nuclear Auxilliary Power (SNAP) program. These reactors were space-based aiming to be used as auxiliary power for components such as satellites.

These systems were the first to explore novel microreactor technology and share many similar characteristics to modern designs that include comparable power output, compact core design, representative reactor-physics phenomena, alkali metal working fluids and high temperature solid moderators prone to hydrogen migration.

Reactor Assembly View, from (AID, 1973)

This work is part of an ongoing joint effort between Georgia Tech, University of Wisconsin-Madison, BWXT, and INL that leverages extensive experimental data from the Systems for Nuclear Auxiliary Power (SNAP) Program to validate the performance of several NEAMS tools in modeling effects that are unique to microreactor technology.

System Characterstics

The S8ER was designed to operate for a total of 10,000 hrs and operate at a power level of 600 kWth. In the interest of reducing size, weight, and performance, the system uses HEU in the form of Uranium-ZirconiumHydride (UZrH), with eutetic Sodium-Potassium Alloy (NaK) coolant in a tight hexagonal lattice arrangement.

Table 1: S8ER System Characteristics

Parameter	Value
Power (kWth)	600
Fuel	UZrH
Coolant	NaK
Inlet Temp ( $var element = document.getElementById("moose-equation-229ddb0f-7f4c-44e0-97fb-0c301f73734b");katex.render("\\degree", element, {displayMode:false,throwOnError:false});$ F)	1100
Outlet Temp ( $var element = document.getElementById("moose-equation-6974f685-ad68-4397-99a0-dc71b128e001");katex.render("\\degree", element, {displayMode:false,throwOnError:false});$ F)	1300
Heavy Metal Loading (kg of U 93.15 Wt%	6.56
Outlet Temp ( $var element = document.getElementById("moose-equation-0721ce56-a1d1-4c07-801f-59a207c2c6f1");katex.render("\\degree", element, {displayMode:false,throwOnError:false});$ F)	1300

Core Description

As described earlier, the S8ER is a compact nuclear reactor using homogenous combined HEU fuel with Zirconium-Hydride as the fuel-moderator mix. The system uses a mix of burnable poisons aswell as stationary and moveable reflectors for reactivity control.

S8ER Core and Reflector Assembly View, from (AID, 1973)

Table 2: S8ER Core Characteristics

Parameter	Value
Upper grid plate material	SS 316
Upper grid plate material	Hastelloy-C
Internal Reflector Material	BeO
External Reflector Material	Be
External Reflector Nominal Thickness	0.0762 m
Core Vessel Outer Diameter	0.237236 m
Core Vessel Height	0.237236 m
Hex Lattice Pitch	0.014478 m

Fuel Element

The core contains 211 elements arranged in a hexagonal lattice. Each rod contains the homogenous UZrH mix as the fuel base, a hydrogen diffusion barrier consisting of the ceramic AI-8763D infused with burnable poison Sm2O3, an internal atmosphere consisting of Helium as a gap, and a layer of Hastelloy N cladding. The fuel pins contain upper and lower end caps for containment as well as indexing.

S8ER Fuelpin Diagram, from (AID, 1973)

Table 3: S8ER Fuel pin Characteristics

Parameter	Value
Fuel	Zr-10 Wt% U-Hydrided to 6E+22 #/cm^3 of H
Fissile Enrichment	U-235 93.15 Wt%
Ceramic Material	AI-8763D
Burnable Poison	Sm2O3 (3.34 mg/in of clad)
Internal Atmosphere	He 0.1 atm
Cladding	Hastelloy-N
Fuel Rod Length	0.3556 m
Fuel Rod Outer Diameter	00.0135128 m

note

More information about the SNAP Reactors may be found here.

References

AID. Snap 8 summary report. 9 1973. URL: https://www.osti.gov/biblio/4393793, doi:10.2172/4393793.

@article{SNAP8Summary,
    author = "AID",
    title = "SNAP 8 summary report",
    institution = "Atomic Internation Division",
    doi = "10.2172/4393793",
    url = "https://www.osti.gov/biblio/4393793",
    journal = "",
    place = "United States",
    year = "1973",
    month = "9"
}

Samuel Garcia, Isaac Naupa, Dan Kotlyar, and Ben Lindley. Validation of snap8 criticality configuration experiments using serpent. In Proceedings of ANS Winter Conference. 1 2022.

@inproceedings{s8er_garcia2022,
    author = "Garcia, Samuel and Naupa, Isaac and Kotlyar, Dan and Lindley, Ben",
    title = "Validation of SNAP8 Criticality Configuration Experiments using SERPENT.",
    booktitle = "Proceedings of ANS Winter Conference",
    place = "United States",
    year = "2022",
    month = "1"
}

Isaac Naupa, Samuel Garcia, Stefano Terlizzi, Dan Kotlyar, and Ben Lindley. Validation of snap8 criticality configuration experiments using neams tools. In Submitted to Proceedings of M&C. 1 2022.

@inproceedings{s8er_naupa2022,
    author = "Naupa, Isaac and Garcia, Samuel and Terlizzi, Stefano and Kotlyar, Dan and Lindley., Ben",
    title = "Validation of SNAP8 Criticality Configuration Experiments using NEAMS Tools.",
    booktitle = "Submitted to Proceedings of M\&C",
    place = "United States",
    year = "2022",
    month = "1"
}

Introduction
System Characterstics
Core Description
Fuel Element
References