.123a

.123b

Preparation and shipment

of four
four Fricke
Fricke dosimeters, two as
controls and two for irradiation, and evaluation of the ferric-
ion content in terms of absorbed dose in the phantom. A report
of the test results will be furnished.

For an additional fee an additional Fricke dosimeter may
supplied and
ferric-ion

its

content

be

evaluated after

irradiation.

Standard reference materials of certified radioactivity are ilable from the National Bureau of Standards, Washington, DC 20234. For racteristics and prices see the latest edition of NBS Misc. Pub. 260 and supplements.

231.211 Calibration of gamma-emitting radioactive samples.

Calibration of gamma-emitting radioactive samples that conform to physical, chemical, and activity level specifications for measurement the Bureau's 4πy-ionization chamber:

(2)

Chemically stable solutions of the following radio-nuclides in the specified activity ranges can be measured.

i.

50-100 microcuries of sodium-22, sodium-24, scandium-46, cobalt-60, yttrium-88.

ii. 150-300 microcuries of manganese-54, iron-59, zinc-65, strontium-85, niobium-95, iodine-131, cesium-137,

iii.

tantalum-182, gold-198, mercury-203.

300-600 microcuries of potassium-42, cobalt-57, cerium139, cerium-141, mercury-197.

thickness

Solutions should be 5 ml in volume and flame-sealed in glass
vials or ampoules
O.D. 16.0 ± 0.5 mm, wall

of

approximately 0.5 mm.

231.211b

231.211z

Chemically stable solutions of the following
the specified activity ranges can be measured.

i.

ii.

iii.

radio-nuclides

in

10-20 microcuries of sodium-22, sodium-24, scandium-46, cobalt-60, yttrium-88.

30-60 microcuries of manganese-54, iron-59, zinc-65,
strontium-85, niobium-95, iodine-131, cesium-137,
tantalum-182, gold-198, mercury-203.

60-100 microcuries of potassium-42,
139, cerium-141, mercury-197.

Solutions should be
vials or ampoules of
approximately 0.5 mm.

cobalt-57, cerium

5 ml in volume and flame-sealed in glass O.D. 16.0 ± 0.5 mm, wall thickness

Special measurements not covered by the above schedule.

231.212 Calibration of alpha-emission rate of sources.

Calibration of alpha-emitting radioactive samples that conform to the physical and activity level specifications for measurement in the Bureau's 2α-proportional counter:

231.212a Chemically stable samples that conform to the physical and activity level specifications listed below can be measured.

i. Source diameter should not exceed 10 cm.

of

ii. Source thickness should be such that more than 99.5%
the emitted alpha particles have an energy greater than
400 keV.

iii.

Emission rate should not exceed 5 x 103a ps.

231.212z Special measurements not covered by this schedule.

231.213 Calibration of beta-emitting radioactive samples.

to

Calibration of beta-emitting radioactive samples that conform the physical, chemical, and activity level specifications for measurement in either the Bureau's 2TB-windowless proportional flow counter or in the Bureau's 2TB-ionization chamber:

6.7

1.213a Chemically stable solutions of the following following radio-nuclides in the specified activity ranges can be measured in the Bureau's 2TB-windowless proportional flow counter.

1.213b

1.213z

147.

iv. 10-100 microcuries/milliliter of sulfur-35.

Solutions should be approximately 5 ml in volume and flamesealed in glass vials or ampoules.

Chemically stable solutions of the following radio-nuclides in the specified activity ranges can be measured in the Bureau's 2TB-ionization chamber.

Solution

i. 2-20 microcuries/milliliter of phosphorus-32.
should be neutral
mg/ml total solids.

or weak acid with not more than 0.2

ii.

2-20 microcuries/milliliter of strontium-89, strontiumyttrium-90. Solution should be weak HC1 (1N or less)

with not more than 0.2 mg/ml total solids.

Solutions should be approximately 5 ml in volume and flamesealed in glass vials or ampoules.

Special measurements not covered by this schedule.

Neutron Physics

231.220 General.

B117,

National Bureau of Standards,

Direct inquiries to, and mark shipments for the attention of: utron Physics Section, RAD P shington, DC 20234. Telephone: 301-921-2234.

231.221 Neutron sources.

❤

(a) Calibration of the neutron emission rate from laboratory andard neutron sources should be of particular assistance to those ncerned with fundamental nuclear experiments, design, and control of clear reactors, problems of protection from neutron radiation, and dustrial applications of neutron sources.

Sources of strength greater than about 105 neutrons/second are librated against the NBS national standard radium beryllium (y,n) source

about 1.25 x 106 neutrons/second. The calibration is performed by measuring with a scintillation dip counter the gamma-activity resulting from the activation of manganese 55 by the thermalized neutrons. Weaker sources are calibrated against a standard source having a similar neutron spectrum in a 4 x 4 x 6-foot graphite column, using a boron-lined proportional counter to detect the thermalized neutrons.

(b) Advance arrangements must be made for the calibration of laboratory standards. The following information must be furnished:

(1) A diagram showing the source location in the shipping container and instructions for removal of the source, if necessary. (2) A description of any special markings on the source. (3) The dimensions of the source, including the relative

internal location of the active ingredients.

(4)

The nature and amount of radioactive ratio of neutron producing ingredients.

(5)

material and the

The kind of metal enclosing source and, if possible, the number of grams of each element.

(6) The date the source was sealed.

(c) Sources accepted for calibration must be sealed, packed, and shipped in such a way leakage and contamination will be avoided. From one to two months should be allowed for completion of the calibration. The uncertainty of the standard error in the emission rate of the source submitted usually will be reported within 3%.

(d) For further information on the NBS standard neutron sources and flux standards see: Absolute Calibration of the National Bureau of Standards Photoneutron Source-III: Absorption in a Heavy Water Solution of Manganous Sulphate, R. H. Noyce, E. R. Mosburg, Jr., S. B. Garfinkel, and R. S. Caswell, Reactor Sci. Technol. (J. Nucl. Energy Parts A/B) 17, 17, 313 (1963); Absolute Calibration of the NBS Photoneutron Standard: I, J. A. DeJuren, D. W. Padgett, and L. F. Curtiss, J. Research NBS 55, 63 (August 1955); Absolute Calibration of the NBS Photoneutron Standard-II: Absorption in Manganese Sulfate, J. A. DeJuren and J. Chin, J. Research NBS 55, 311 (December 1955); Absolute Calibration of the NBS Standard Thermal Neutron Density, J. A. DeJuren and H. Rosenwasser, J. Research NBS 52, 93 (February 1954); A Recalibration of the NBS Standard Thermal Neutron Flux, E. R. Mosburg, Jr. and W. M. Murphey, Reactor Science and Technology (J.N.E. Parts A/B), 14, pp 25-30 (1961).

231.221a Determination of ratio of neutron emission rate of unknown source to primary standard in MnSO4 bath or graphite column.