# Presentation: 707740

## New Types of Unattended Systems for Enrichment Plant Safeguards

## The Challenge

- There is no _***physical ***_difference between LEU and HEU detection: same equipment running the same way.  This is a declared facility.
- An HEU line could operate inside the larger LEU cascade.
- Some plants are configurable from the control room.
- Earlier systems used collimated gamma detectors, but the size of the plant makes this prohibitive.
- Like “hiding a diamond in a glass of water.”

## And... Enrichment Cascades are Big

- Enrichment Cascades are big!!
- If monitored locally  many, many                	detectors
- Typically, gamma-ray detectors are used  expensive
- Requires intimate engagement with equipment.

## Return on Investment 

- Issue is not size, consider ROI calculation:
- Figure of Merit is:

## Conceptual History of Unattended

- Inspections

- MiniGrand

- Rokkasho

- New Enrichment?

## The Beginning: Distributed Source TermAnalysis

- Make a grid of neutron counts
- Model entire cascade in MCNP.
- Adjust _**input**_ so that output matches, iteratively

## Next Step in DSTA: Near Real Time

- Linear response to neutron emission.
- No parametric dependence.
- Can be modeled as a simple linear system.

## An Observation: The Source of Neutrons in GasCentrifuge Plants

- The dominant source of neutrons in a UF6 system are produced by 234U alpha decay on fluorine.

## Vision

- An array of simple, totals neutron detectors suspended above a gas centrifuge enrichment cascade.
- The neutron emission rate is directly proportional to the gas pressure and the enrichment (because 234U follows 235U).
- Calculate the matrix of detector response to neutron emission from voxels in the cascade.
- Invert this matrix to find local neutron emission “hot spots” corresponding to enrichment.
- Nominally 100 – 1,000 second counts. Immediate results

## Conceptual View

## Possible Emission Profiles Corresponding to HEU

- Segment of cascade used continuously

- Entire cascade used for HEU.  Modified in time.

## Summary of Technical Challenges

| Issue | Difficulty | Status |
| --- | --- | --- |
| Cosmic ray background limits sensitivity | Medium  Hard | Acceptable, done |
| Holdup | Medium  Medium | Acceptable, done. |
| Calculating matrix elements | Hard  Easy | Demonstrated, done |
| Designing detectors that are easy to install | Medium  Medium  | Demonstrated, done. |
| Interference from storage containers | Unknown  Modest | Acceptable, done. |

## UF6 handling & Cascade hall

- Feed purification cold and chemical traps

- Product cold
- and chemical traps

- Solid feed and product
-  low T take off stations

- Feed purification and Tails
- low T takeoff station

## Cold trap (schematic)

- Purifies UF6 of light gases (e.g., HF).
- tank is cooled,
- UF6  sublimes,
- HF remains in vapor phase.
- HF (+ UF6) vented to chemical traps
- Kg’s UF6 accumulate in cold trap
- cold trap full: determined by weight (20 kg UF6 for product cold traps, 40 kg for feed cold traps)
- UF6 in trap is transferred to product cylinder when trap is full

## Coincidence Counting Basics

**Notes:**
T= totals coincidence
R= real coincidence rate
Epsilon = efficiency
Nu -1 first factorial moment
f = gate fraction
m=mass
M= multiplicity
F=
Alpha= alpha,n neutrons divided by spontaneous fission neutrons

## Coincidence Counting & Enrichment

## Coincidence Counting & Enrichment (con’t)

**Coincidence Counting & Enrichment (con’t)**

**Notes:**
approximation

## Problem Statement

**Problem Statement**

## Sample Results

- After lots of algebra:

- 1,000 sec count
- Initial mass = 1 kg
- Initial enrichment = 3%