What the document says
This November 1946 US Navy report sets the rules for cleaning radioactive contamination off ships that worked at Bikini Lagoon after the Crossroads atomic bomb tests. It covers non-target vessels, meaning the ships not used as targets in the tests. The report states that all of them picked up radioactive material from the lagoon water to some degree. It lists the parts most affected: the underwater hull, the fire and flushing systems, the salt water sides of condensers and heat exchangers, evaporators, anchors and anchor chain, and small boats.
The Navy writes that most of these areas no longer give off enough external radiation to be of concern. The danger it names instead is internal poisoning. A person is at risk if they eat or breathe the radioactive material, or get it into an open cut or a skin abrasion. Each ship had to be monitored first, meaning surveyed with a radiation meter, to find where the material sat and how much was present. Any suspect part counted as contaminated until a monitor cleared it. After cleaning, crews had to request remonitoring to check the work.
The main cleaning agent is a muriatic acid mix, which is hydrochloric acid, in one procedure one gallon of commercial acid to ten gallons of fresh water plus two ounces of inhibitor. Crews circulated it through salt water piping, condensers and evaporators, then flushed with salt water and neutralized with boiler compound. Scale, rust and marine growth had to be scraped off wet so no dust formed, then kept wet, placed in a closed container and sunk at sea. Used solutions went overboard at least 10 miles out or beyond the 100 fathom curve.
Key points
- 01All non-target vessels that entered Bikini Lagoon after the atomic bomb tests are described as more or less contaminated by radioactive material picked up from the lagoon water.
- 02The stated hazard is internal, not external: danger comes from eating, breathing, or getting the material into an open cut or skin abrasion.
- 03An underwater hull met final clearance if the average of readings at ten representative areas on each side was .020 roentgens/day or less, corrected to 1 October 1946.
- 04Hulls still above the limit after scraping and hosing had to be wet sandblasted in drydock, with the sand collected and prepared for sinking at sea.
- 05In evaporators, acid was recirculated for at least two hours and not over four, and all distilled fresh water made in the first twenty-four hours back in service was dumped overboard.
- 06Lines, fenders, brooms, swabs and similar fibrous equipment were not susceptible to any known method of decontamination at the time and had to be segregated and disposed of.
Source: U.S. Department of Energy, OpenNet declassified document archive, OSTI ID 16016570. The summary is written from the document’s own text. Old scans can be hard to read, so check the original for anything you plan to cite.