[en] ²⁴¹Pu has the shortest half-life of the abundant plutonium isotopes present in reprocessed irradiated nuclear fuel with a value of approximately 14.3 years. It is important to know the half-life of ²⁴¹Pu with a higher fractional accuracy than that of the other plutonium isotopes because the half-life of ²⁴¹Pu and its associated uncertainty affects the estimation by decay calculation of both the total amount of separated plutonium in storage and the determination of the total plutonium mass by non-destructive assay. This paper addresses the determination of the ²⁴¹Pu half-life using nuclear calorimetry by the measurement of the thermal power as ²⁴¹Pu evolves in time from a sealed plutonium source, ideally initially rich in ²⁴¹Pu and chemically stripped of ²⁴¹Am. The absolute accuracy of nuclear calorimeters can be ensured over long periods of time (many years) using long-lived nuclear reference materials and/or traceable electrical heat standards. One can, therefore, expect nuclear calorimetry to offer an accurate way to determine the half-life of ²⁴1Pu, which is comparable in quality and independent, yet complementary, to other approaches. Temporal analysis of the power-versus-time data also yields an estimate of the specific power of ²⁴¹Pu, which other methods do not. After describing the principle of the method and developing the pertinent mathematical expressions, we outline the approach by drawing on some unpublished notes of Kenneth C. Jordan who carried out such experiments at the Mound Laboratory over 40 years ago. Today, Jordan’s work remains possibly the most significant experiment of its type to the ²⁴¹Pu nuclear data evaluator. However, objectively assigning confidence to his results is problematic because the details of the experiments and data reduction have never been adequately reported. This work goes some way to that end but, without the raw data and first-hand knowledge, cannot provide a complete record. We conclude that a new high-accuracy nuclear calorimetry campaign to re-measure the ²⁴¹Pu half-life and specific ²⁴¹Pu has the shortest half-life of the abundant plutonium isotopes present in reprocessed irradiated nuclear fuel with a value of approximately 14.3 years. It is important to know the half-life of ²⁴¹Pu with a higher fractional accuracy than that of the other plutonium isotopes because the half-life of ²⁴¹Pu and its associated uncertainty affects the estimation by decay calculation of both the total amount of separated plutonium in storage and the determination of the total plutonium mass by non-destructive assay. This paper addresses the determination of the ²⁴¹Pu half-life using nuclear calorimetry by the measurement of the thermal power as ²⁴¹Pu evolves in time from a sealed plutonium source, ideally initially rich in ²⁴¹Pu and chemically stripped of ²⁴¹Am. The absolute accuracy of nuclear calorimeters can be ensured over long periods of time (many years) using long-lived nuclear reference materials and/or traceable electrical heat standards. One can, therefore, expect nuclear calorimetry to offer an accurate way to determine the half-life of ²⁴¹Pu, which is comparable in quality and independent, yet complementary, to other approaches. Temporal analysis of the power-versus-time data also yields an estimate of the specific power of ²⁴¹Pu, which other methods do not. After describing the principle of the method and developing the pertinent mathematical expressions, we outline the approach by drawing on some unpublished notes of Kenneth C. Jordan who carried out such experiments at the Mound Laboratory over 40 years ago. Today, Jordan’s work remains possibly the most significant experiment of its type to the ²⁴¹Pu nuclear data evaluator. However, objectively assigning confidence to his results is problematic because the details of the experiments and data reduction have never been adequately reported. This work goes some way to that end but, without the raw data and first-hand knowledge, cannot provide a complete record. We conclude that a new high-accuracy nuclear calorimetry campaign to re-measure the ²⁴¹Pu half-life and specific