Table 2.5. Allotropic Forms of Plutonium Metal(a)

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

Table 2.5. Allotropic Forms of Plutonium Metal(a)

Density, g/cm3(b)

Phase

Stability Range, C

Stable below 115

19.86

~115 to 200

17.70

(

~200 to 310

17.14

310 to 452

15.92

452 to 480

480 to 640

16.51

(a)

Wick, 1967, p. 34.

(b)

Theoretical X-ray density. The actual density is slightly lower due to crystal

lattice imperfection.

Plutonium is an active metal. In moist air or moist argon, the metal oxidizes rapidly,

producing a mixture of oxides and hydrides (Haschke, 1992). If the metal is exposed

long enough, an olive-green powdery surface coating of PuO2 is formed. With this

coating, the metal is pyrophoric, so plutonium metal is usually handled in an inert, dry

atmosphere of nitrogen or argon. Oxygen retards the effects of moisture and acts as a

passivating agent (Raynor and Sackman, 1963). For a description of the storage hazards

that the oxidation of plutonium metal creates, see Section 2.6.3.1, "Oxidation of

Plutonium." A comprehensive treatment of the oxidation of plutonium, the properties of

its oxides, oxide growth, and oxidation kinetics was reviewed by Colmenares (1975).

Plutonium metal also reacts with most common gases at elevated temperatures.

Plutonium metal is rapidly dissolved by HCl, HBr, 72% HCl04, 85% H3PO4, concentrated

CCl3COOH (trichloroacetic acid), sulfamic acid, and boiling concentrated HNO3 in the

presence of 0.005M HF. The metal reacts slowly with water, dilute sulfuric acid, and

dilute acetic acid. There is no reaction with the metal in pure HNO3 at any concentration,

with concentrated acetic acid, nor with dilute sodium hydroxide.

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