Shielding device

In a boiling water nuclear reactor having an under-vessel area with control rod drives, each control rod drive having a flange assembly comprising a control rod drive housing flange and a mating control rod drive flange joined together by bolting means. A shielding device is described comprising: shielding members wherein (a) each shielding member is comprised of: (i) a cylindrical outer wall of a non-corrosive metallic substance, (ii) an annular outer bottom wall of a non-corrosive metallic substance, (iii) a first cylindrical inner wall of a non-corrosive metallic substance, (iv) an annular inner bottom wall of a non-corrosive metallic substance fixedly attached to the first inner wall, (v) an annular upper interior wall of a non-corrosive metallic substance fixedly attached to the interior surface of the outer wall and the upper perifery of the first inner wall, (vi) a second cylindrical inner wall of a non-corrosive metallic substance fixedly attached to the interior perifery of the outer bottom wall and the inner bottom wall, (vii) two radial walls of a non-corrosive metallic substance, (viii) an amount of shielding material disposed within the partial cylindrical chamber; (b) each shielding member is provided with attachment means comprising: (i) a first contact point; (ii) a second contact point; and (c) each shielding member has a suitable geometry such that, when the shielding members are assembled in mating continuous engagement, they surround and enclose the lower terminus of the control rod drive with an effective amount of shielding material