physics

Godiva device

Godiva device is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Godiva device rather than just read about it. In short: The Lady Godiva device was an unshielded pulsed nuclear reactor originally situated at the Los Alamos National Laboratory (LANL), near Santa Fe, New Mexico. It was one of a number of criticality devices within Technical Area 18 (TA-18).

Key takeaways

Godiva device belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Godiva device to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Godiva device from memory before moving on to harder problems.

Reference excerpt

The Lady Godiva device was an unshielded pulsed nuclear reactor originally situated at the Los Alamos National Laboratory (LANL), near Santa Fe, New Mexico. It was one of a number of criticality devices within Technical Area 18 (TA-18). Specifically, it was used to produce bursts of neutrons and gamma rays for irradiating test samples, and inspired development of Godiva-like reactors. The radiation source within the Godiva device was a fissile metallic mass (usually highly enriched 235U), about 11.8 inches (30 cm) in diameter. This was located at the top of a 6.5-foot (2 m) high metal tower. The burst of radiation was produced when a piston of fissile material was quickly inserted into and extracted from a cavity within the larger fissile mass. During the time these two masses were combined, they formed a critical mass and a nuclear chain reaction was briefly sustained. Godiva's design was inspired by a self terminating property discovered when incorrectly experimenting with the Jemima device in 1952. Jemima operated by remotely lifting one stack of enriched uranium-235 disks up towards another, fixed, stack. On 18 April 1952, due to a miscalculation, Jemima was assembled with too many disks; this caused an excursion of 1.5 × 1016 fissions—an automatic scram—but no damage. On 3 February 1954 and 12 February 1957, accidental criticality excursions occurred, causing damage to the device but only insignificant exposures to personnel. This original Godiva device, known as Lady Godiva, was irreparable after the second accident and was replaced by the Godiva II.

Godiva II

Godiva II was constructed inside a concrete building with 20-inch-thick (51 cm) walls and 8-inch-thick (20 cm) roof in a canyon a quarter-mile (400 m) away from the control room. In 1959, Los Alamos agreed to make Godiva II available to DOD contractors free of charge for two days each month, acknowledging its unique facility for radiation tests. Godiva's success in creating intense bursts spurred development of similar pulsed reactors, which also suffered accidental excursions, for example: 28 May 1965 at the White Sands Missile Range (parts were thrown 15 feet (4.6 m)); and 6 September 1968 at the Aberdeen Proving Ground (middle melted, disks warped and bolts stretched). In December 2002, the U.S. Department of Energy announced it was to move its TA-18 testing equipment including the Godiva burst machine from the LANL to the Device Assembly Facility (DAF) at the Nevada Test Site (NTS).

Illustrations

Godiva device: A cylindrical wire cage encloses the spherical uranium mass at the top of this image of Godiva II. — A cylindrical wire cage encloses the spherical uranium mass at the top of this image of Godiva II.

Worked examples

Example 1 — a first encounter with Godiva device

Start with the simplest possible case. Write down what Godiva device claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Godiva device before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Godiva device ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Godiva device

In research: Godiva device appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Godiva device in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Godiva device is common in secondary-school and first-year university syllabi. It links to neighbouring topics Los Alamos National Laboratory, Nevada Test Site, Nuclear accidents and incidents in the United States, so understanding it makes those chapters shorter.
In everyday life: Look for Godiva device outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Godiva device in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Godiva device means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Godiva device out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Godiva device in simple terms?

Why does Godiva device matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Godiva device?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Godiva device.