About

About & methods

Chimney Top Calculators is a small collection of technical calculators published by Chimney Top Digital Services. Each one implements a published formula, lists its constants and their sources, and shows a worked example so you can check the arithmetic yourself.

How the calculators work

• Everything runs in your browser. Nothing you type is sent to a server; there are no accounts.
• Results are encoded in the page address, so a copied link reproduces your inputs exactly.
• Calculations are covered by automated tests with known-answer checks and a pinned reference table.

What they are not for

The radiation calculators are educational estimates for idealized point sources. They are not for medical or clinical dosimetry, regulatory dose assessment or shielding design sign-off. The profitability and cost calculators are planning estimates, not financial, tax or accounting advice.

All sources

1. Unger, L. M. & Trubey, D. K. (1982). Specific Gamma-Ray Dose Constants for Nuclides Important to Dosimetry and Radiological Assessment. ORNL/RSIC-45/R1, Oak Ridge National Laboratory.
2. U.S. Department of Health, Education, and Welfare (1970). Radiological Health Handbook, revised edition. Public Health Service, Bureau of Radiological Health.
3. Cember, H. & Johnson, T. E. (2009). Introduction to Health Physics, 4th edition. McGraw-Hill. (Chapters on external radiation safety and shielding.)
4. NCRP Report No. 49 (1976). Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies up to 10 MeV. National Council on Radiation Protection and Measurements. (Broad-beam half-value and tenth-value layers for gamma sources.)
5. NCRP Report No. 151 (2005). Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-Ray Radiotherapy Facilities.
6. National Nuclear Data Center, Brookhaven National Laboratory. NuDat 3 (ENSDF evaluated half-lives and photon emission data).
7. Hubbell, J. H. & Seltzer, S. M. (2004). Tables of X-Ray Mass Attenuation Coefficients and Mass Energy-Absorption Coefficients (version 1.4). NIST Standard Reference Database 126.
8. ICRU Report 85 (2011). Fundamental Quantities and Units for Ionizing Radiation. (Mean energy per ion pair in dry air, W/e = 33.97 J/C.)
9. ICRP (2007). The 2007 Recommendations of the International Commission on Radiological Protection. ICRP Publication 103, Annals of the ICRP 37(2–4). (Table 2 and Eq. 4.3: radiation weighting factors.)
10. Thompson, A. & Taylor, B. N. (2008). Guide for the Use of the International System of Units (SI). NIST Special Publication 811.
11. U.S. Nuclear Regulatory Commission. 10 CFR 20.1004, Units of radiation dose.
12. U.S. Energy Information Administration. Electric Power Monthly, Table 5.6.A — Average Price of Electricity to Ultimate Customers by End-Use Sector.
13. Uptime Institute. Global Data Center Survey (annual). Industry-average power usage effectiveness (PUE).
14. The Green Grid (2012). WP#49 — PUE: A Comprehensive Examination of the Metric.
15. NVIDIA, AMD and Intel product specification pages (total graphics power / board power, TDP / default TDP, core counts).
16. Caterpillar Inc. Caterpillar Performance Handbook, "Owning & Operating Costs" section (hourly owning and operating cost method).
17. U.S. Army Corps of Engineers. EP 1110-1-8, Construction Equipment Ownership and Operating Expense Schedule.

Corrections

Spotted a wrong constant or a better reference? We correct errors promptly — the sources above show exactly what each number is based on.