dance) can be transmutated to tritium, but because of low abundand it presents a minor problem. The Experimental Gas Cooled Reacto which is under construction, will use helium for cooling purposes.

In Great Britain carbon dioxide is used in the closed-cycle gas-coole Calder Hall reactors. As the carbon dioxide passes through th reactor, small amounts of O19, N16, and C14 are produced.

2-4.2 Water Coolants

Water can be used for cooling in a single-pass system or in th closed-cycle type of operation. Large volumes of water must b available to cool a reactor in the single-pass system. At Hanford Columbia River water, pretreated to a high degree of purification, i used for cooling. After the water has passed through the reactor it is held for a short period (approximately 4 hr) in special basin before being returned to the river.

The more significant nuclides and their concentrations in the rive 4 and 24 hr after irradiation are listed in Table 2.5. Two other

TABLE 2.5-FIFTEEN SIGNIFICANT RADIONUCLIDES RELEASED TO THE COLUMBIA RIVER BY THE REACTOR EFFLUENT STREAMS* 1 (HANFORD OPERATIONS)

nuclides are formed from the neutron activation of oxygen-N16 and N17. These have short half-lives of 7.3 and 4.1 sec, respectively, and are not included in Table 2.5. When compared with the 168-hr week occupational MPC values reduced by a factor of 30, As" is the

Reactors with recirculating coolant systems are the Materials Tes Reactor (MTR) at the National Reactor Testing Station (NRTS near Idaho Falls, Idaho, and the Pressurized Water Reactor (PWR Shippingport, Pa. In the closed system the water used for coolin is filtered and demineralized before and during use to minimize forma tion of neutron-activation products. However, in passing throug the reactor, pipes, pumps, heat-exchange facilities, etc., the coolan picks up some contamination as a result of corrosion or abrasion Furthermore, fission products released from ruptured fuel element or from uranium contamination on the cladding of these fuel element may appear in the coolant. In most closed cooling systems, a sma percentage of the total flow is continuously demineralized and re turned to the main stream, thus maintaining its quality. In othe systems a portion of the coolant is bled off and discharged to waste and fresh demineralized water is added as makeup water.

Radionuclides formed from corrosion products and other source in various reactor coolant systems 13 are summarized in Table 2.6

TABLE 2.6-TYPICAL RADIONUCLIDES IN COOLANT IN A PRESSUR IZED-WATER NUCLEAR POWER PLANT**

*From I. H. Welinsky, P. Cohen, and J. M. Seamon, Proc. Am. Power Con., 18: 567 (1956).

†The four groups of nuclides in the table are arbitrarily defined as very short-lived, short-lived, interme diate, and long-lived activity.

*Neutrons per second per milliliter.

The compositions will vary with the nature of the reactor structura materials, fuel cladding, chemicals added for corrosion control, water purity, type of reactor, and neutron flux. Expected maximum steady state activity levels for nonvolatile fission products in the Shipping port PWR wastes have been published.14

In addition to the nuclides shown in Table 2.6, experimental boiling water reactors, similar to the types found at Argonne National Lab oratory (ANL), Dresden, and Vallecitos, produce some gaseous wastes Normal daily discharge rates for the Argonne facility 15 operating at 2 Mw power are 0.2 to 0.4 curies of Xe138 and 0.005 to 0.01 curies o Kr 88 It is also reported 15 that each time the EBWR reactor vessel i opened the system is filled with water and given a hydrostatic tes after which the excess water is bled off. This procedure has produce about 30,000 gal of liquid wastes (with a specific activity of abou 5 X 10-5 μc/ml) per year.

Operating at 20 Mw(t) for one year, the EBWR produced 127 cu f of solid waste, averaging 90 mc/cu ft, and 200,000 gal of water, with an average specific activity of 2 × 10-4 mc/gal, for a total of 11.4 curie and 40 mc, respectively. Radioactive gases are also released.

8

Where heavy water is used as moderator and/or coolant, e.g., the CP-5 at ANL, the NRX at Chalk River (Canada), and the Savannal River reactors, tritium is formed in the coolant by neutron irradiation of deuterium [H2(n,y)H3] in addition to the formation of N16, N17, and O19 from the oxygen.

2-4.3 Liquid-metal Coolants

Liquid metals such as sodium and NaK are used as coolants in several reactors, e.g., the Experimental Breeder Reactor (EBR), the land-based prototype of the Submarine Intermediate Reactor (S1G), and the sodium-cooled graphite-moderated Sodium Reactor Experiment (SRE). 15 The principal activities found in liquid-metal coolants are shown in Table 2.7.

TABLE 2.7-PRINCIPAL ACTIVITIES IN LIQUID-METAL COOLANTS 1

Organic-moderated reactors usually use polyphenyls as moderator and coolant. The wastes are primarily decomposition products from the irradiation of the organic material and contain negligible quantities of radioactivity.

If operated at 100 Mw(t), the Organic Moderated Reactor Experiment (OMRE) might produce 8 standard cu ft/Mwd (t) of nonradioactive gas and 27 lb/Mwd (t) of essentially nonradioactive solid sludge.8

Waste-disposal problems associated with homogeneous reactors & considered analogous to those of a chemical reprocessing plant a therefore are not treated as low-level problems.

2-4.6 Specific Reactor Operations

Information on waste discharges from reactor operations at NR and at Shippingport is included in the subsections that follow.

(a) National Reactor Testing Station, Idaho Falls. The amount radioactive materials and the quantity of solid wastes released to t environment at NRTS are summarized in Table 2.8.

TABLE 2.8 AMOUNT OF RADIOACTIVE WASTE RELEASED TO TH ENVIRONMENT 16

*Half-life of activity: 85% less than 10 days, 10% from 10 to 100 days, and 5% more than 100 days. †Over 75% of the radionuclides had a half-life of less than 2 hr. Approximate.

(b) Shippingport Atomic Power Station. At Shippingport liqu wastes are separated into four categories according to their expecte activity and ionic content: reactor-plant effluents, chemical-was liquids, special-waste liquids, and nonactive-waste liquids. T sources and estimated average volumes of these wastes are given Table 2.9. The composition of an estimated typical chemical-was solution is given in Table 2.10. From data reported," estimated an observed waste volumes and activity levels have been compared Table 2.11. The total quantity of activity released during the perio covered by the data amounts to 35,555 uc, which is less than the pe missible monthly release of 47,700 μc per month.

The fission gases are principally 5.3-day Xe133 and, to a less extent, 10-year Kr85. These gases are stored for 60 days to perm decay of the Xe133, after which the residual activity is released throug

*From J. R. LaPointe, W. J. Hahn, and E. D. Harward, Jr., Proc. Am. Soc. Civil Engrs., 131, 142-143 (May 1960).

TABLE 2.10-COMPOSITION OF AN ESTIMATED TYPICAL CHEN

WASTE SOLUTION*

(SHIPPINGPORT ATOMIC POWER STATION)

(May 1960).

*From J. R. LaPointe, W. J. Hahn, and E. D. Harward, Jr., Proc. Am. Soc. Civil Engrs., 86