Chilled Water System

DOE-HDBK-1129-99

4.3 Chilled Water System

The chilled water system that is used to cool the tritium-related activities in a facility must be

carefully designed to minimize the volume and tritium concentration of the contaminated water

generated. The use of single-wall, water-to-gas heat exchangers in tritium removal systems and

vacuum furnaces for example, will result in tritium contamination of the chilled water system. In

some facilities, the same chilled water system is used to cool non-tritium activities in the same

building, and, at some sites, the same chilled water system is also used in non-tritium related

activities in adjacent buildings. As a result, tritium-contaminated wastewater is generated, and

tritium contamination is spread from one piece of equipment to another, from one room to another,

and from one building to another through the chilled water supply.

The chilled water system should be designed to minimize the volume of water that can be

contaminated with tritium. One technique is to use water-to-water heat exchangers or double-

walled, gas-flushed water-to-gas heat exchangers to isolate the high volume central system from

the tritium-related activities. The volume of water in the secondary loop is much smaller than that

in the primary loop.

The primary reason for using chilled water for cooling equipment is cost. The systems are reliable,

low in cost, small in size, readily available in many different sizes from many different

manufacturers, and easy to maintain. Air-to-air heat exchangers can, in some cases, be

substituted for chilled water cooling, but are larger in size and will not work in some applications.

Refrigerated cooling systems are more expensive, but operationally eliminate the need for

disposing of tritium-contaminated water generated by the chilled water systems.

4.4 Seismic and Wind Design and Evaluation of Structures and Facilities

Savannah River Site (SRS) has been the lead site for interfaces with the DNFSB and DOE EH

concerning NPH design issues associated with tritium. A summary of DOE Natural Phenomena

Hazards Policy is included in Section 5.7.1. This policy is also applicable to structures and the

complete facility. Section 5.7.2 and its references should be reviewed as part of the overall

seismic and wind design for evaluation of a tritium facility.

For wind loading provisions, American Society of Civil Engineers (ASCE) 7-95, "Minimum Design

Loads for Buildings and Other Structures," has recently been completed and issued and is

changed greatly from past versions. A "3-second peak wind gust" is used rather than "fastest mile

wind speed" as a design measure. Change Notice of DOE-STD-1020, "Natural Phenomena

Hazards Design and Evaluation Criteria for Department of Energy Facilities," is in error in

referencing ASCE 7-95, but keeping "fastest mile wind speed" as a measure. Wind speeds must

be converted to "3-second peak wind gust" for ASCE 7-95 to be correctly used.

An understanding of the types of loading produced by earthquakes and windstorms is useful in

planning mitigating approaches. An earthquake produces shaking, which will affect the entire

facility and its contents. Attention to anchorage and connection details to all structures, systems,

and components is essential. Earthquakes may also cause ground rupture if the facility is near a

fault. Loss of ground stability may also occur due to settlement or liquefaction and will depend on

soil types and location of the ground water table.

Windstorms generally affect the structural shell and systems and components outside of the

structure. Windstorms will produce direct pressure and suction on walls and roofs with increased