Development of Components for an In-situ Analysis System for the Exploration of Manganese Nodules
Authors: Lange Joachim P. , Biemarm Wilfried G. 
Published: October 2008

Gesellschaft fur Kernforschung mbH develops the comprehensive manganese nodule exploration system MANKA II. The system includes an in-situ analysis by prompt (n, y) spectroscopy with 252cf source, a hydraulic sampling system, Helium Cryostat, and data transmission by coaxial cable. The system is designed for 6,500 m maximum water depth. Components of the intermediate deep sea sled MANKA I are presented, together with the concept of the in-situ analysis and results of component tests.

INTRODUCTION

The discovery of marine deposits of oil and minerals has opened vast new reservoirs to satisfy the rising demand for energy and raw materials in the world. One of the most prominent among these potential new sources are the vast fields of manganese nodules with their potential as suppliers of copper and nickel. 1

Before an economical exploitation of thenodule fields can be attempted, detailed knowledge on water depth and bottom topography, shape and size and metal contents of the nodules, as well as their surface concentration are required as a function of' location. At the Nuclear Research Center of Karlsruhe, Germany, work was started some time ago to design a comprehensive manganese nodule exploration system - code-named MANKA II - that would yield most of these data in one pass over a location. Significant time and money savings are expected from this system, which will incorporate several methods of surveying and an in-situ analysis to eliminate the time-consuming sampling in water depths of, for instance, 6,000 m. Fig. 1 gives a schematic picture of this system. It will be ready in 1978. 2

For the development and testing of the in-situ analysis itself, a high performance deep sea sled - code-named MANKA I - was designed and built, which will be towed over the sea floor taking samples, analyzing, and transmitting the data to a research vessel via cable. The deep sea test of MANKA I is scheduled for early 1976 and will have as its main objective the confirmation of the performance of the components of the analysis system under deep sea conditions.

All components of the sled were designed for a water depth of 6,500 m. Most of them are at present in the test phase before final assembly; some subsystems were already tried out in shallow water.

THE METHOD OF ANALYSI§

The in-situ analysis makes use of the neutron-induced prompt gamma radiation. Fig. 2 gives a schematic view of the necessary components. A neutron source of 1 mg of Cf-252 is placed in the center of the nodule filled circaloy analysis chamber. The neutrons induce characteristic prompt gamma radiation in the nuclei of the interesting elements Mn, Fe, Co, Cu and Ni, and a high resolution Ge(Li) detector records this radiation. An impulse height spectrum is generated by proper electronics, the characteristic lines of each element are identified, and the peak contents is measured. With additional parameters measured at the same time and the spectral data a small computer calculates the concentration of the metals in the nodules.