Source: https://guthlabs.ai/docs/instruments/radioactive-decay-half-life-calculator/implementation/

instrument implementation / implementation-contract

# Radioactive Decay / Half-Life Calculator implementation

A source-bound implementation contract for Radioactive Decay / Half-Life Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-003

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero half-life causes division by zero and must be rejected. The probe also exposes a convention hazard: negative elapsed time yields an apparent quantity greater than the initial quantity unless the instrument rejects or explicitly labels backward-time extrapolation.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "isotope": "C-14",
    "half_life": 5730,
    "half_life_unit": "years",
    "initial_parent_atoms": 1000000,
    "elapsed_time": 5730,
    "elapsed_time_unit": "years"
  },
  "expected_outputs": {
    "decay_constant_per_year": 0.000120968094,
    "remaining_parent_atoms": 500000,
    "activity_per_year": 60.484047
  },
  "working": "1. λ=ln(2)/t½=0.69314718056/5730=0.000120968094 year^-1. 2. λt=0.000120968094×5730=0.69314718056. 3. N=N0e^(-λt)=1,000,000×e^(-0.69314718056)=1,000,000×0.5=500,000 atoms. 4. A=λN=0.000120968094×500,000=60.484047 decays/year. This is not Bq because λ is per year."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/radioactive-decay-half-life-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/radioactive-decay-half-life-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/radioactive-decay-half-life-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`