Accountancy and Safeguards
Every gram of tritium is measured, tracked, and reconciled against decay, so that inventory records match physical reality within tight limits.
Measuring a moving target
Material accountancy for tritium is complicated by decay: the book quantity changes continuously even when nothing is withdrawn. Sound accountancy therefore reconciles measured inventory against a decay-corrected expectation, so that a genuine discrepancy can be told apart from expected decay.
What accountancy protects
- Continuity of knowledge: the location and quantity of material are always known.
- Discrepancy detection: real losses are separated from expected decay.
- Audit trail: transfers and processing steps are logged end to end.
For a strategic isotope, accountancy is also a chain-of-custody function. It provides confidence that material is where records say it is, which matters for both safety and security. This page describes the principle at a public level only; it contains no facility-specific procedures.
Decay as a built-in check
Paradoxically, decay helps accountancy: because the loss rate is precisely known, the expected inventory can be predicted with high confidence. A measured value that departs from the decay curve is a signal worth investigating. Well-designed systems use this to keep records tight.
Confidence from a known decay law
The precision of the decay constant is what makes tight accountancy possible. Because the expected inventory can be predicted with confidence from the last measurement and the elapsed time, any measured value that departs from that prediction is a meaningful signal rather than noise. Good systems exploit this to keep book-versus-physical differences small and to flag genuine discrepancies quickly. The same discipline provides continuity of knowledge about where material is and in what quantity, which is the foundation of both safety and security for a strategic isotope, described here only at a general public level.
For the breeder, accountancy requirements are specified as design and operational criteria; measured reconciliation performance is a post-commissioning result.