Regulatory Guide 3.31

Emergency Water Supply Systems for Fuel Reprocessing Plants

ML12220A061
Person / Time
Issue date:	09/30/1975
From:	Office of Nuclear Regulatory Research, NRC/OSD
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References
RG-3.031
Download: ML12220A061 (4)

U,R. NUCLEAR REGULATORY COMMISSION September 1975 REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 3.31 EMERGENCY WATER SUPPLY SYSTEMS FOR FUEL

REPROCESSING PLANTS .

B. DISCUSSION

Paragraph 50.34(a)(3)(i) of 10 CFR Part 50 requires The emergency water supply system (EWSS) for the that an application for a construction permit for a fuel cooling water system, the fire protection system, and reprocessing plant include the principal design criteria other safety-related systems includes th ater sources, for the proposed facility. The principal design criteria the retaining structures (e.g., pond im), pumps, establish the design, fabrication, construction, testing, and connecting conduits up to, not uding, the and performance requirements for structures, systems, main headers of the fuel s e' ol,0 e storage and components important to safety, that is, structures, tanks, and process ves 1 tems; the loop systems, and components that provide reasonable assur- distribution system .P e 1 rorK tion system; or ance that the facility can be operated without undue risk intake structures of- be-related satt systems or to the health and safety of the public. equipment tha Lpy i of water. If surge storage tanks, re s, . rtions thereof are required to acco i.ng, fire protection, or other The emergency water supply system (EWSS) for a safet6fun t demand a supply of water, it is fuel reprocessing plant is considered a system important imp tt t too satisfy the requirements of the to safety. Therefore, it should be designed to meet the e wa r source.

safety demands under normal and abnormal conditions and should include redundancy to the extent necess mergency water supply system performs the to maintain, with adequate capacity, the ability t er- wing safety functions:

form safety functions assuming a single failure. In di- tion, the emergency water supply system b 1. Provides water to meet the heat rejection require- signed to permit testing of the functional rabilit an ments for the fuel storage pool, waste storage tanks, and capacity, including the full operational seq ce, o ach certain process vessels in the event the normal operating system for transfer between normal an ency source is disrupted, supply sources and of the operation of associated safety systems. , 2. Provides water to the loop distribution system of the fire protection system in the event the normal ath RC wsupply is disrupted, and This guide ns of emergency water acceptable tPt ff and presents bases for the 3. Provides water for the operation of any safety- design of e t nish emergency water to the related equipment or system in the event the normal fuel stora -l,evel radioactive waste storage, design source is disrupted.

fire protect system, certain process vessels, and any other safety- ted equipment or system requiring a It is important that the emergency water supply system supply of water to perform the design safety function, be capable of providing sufficient water to permit all of directly or indirectly. these safety functions to be accomplished.

USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commission. U.S. Nuclear Regulatory Commission. Washington. D.C. 20566. Attention: Docketing and Regulatory Guides re issued to describe and make available to the publicice Section.

methods acceptable to the NRC staff of implementing specific parts of the Commissions regulations, to delineate techniques used by the staff in evalu- The guides are issued in the following ten broad divisions:

ating specific problems or postulated accidents, or to provide guidance to appli.

cants. Regulatory Guides are not substitutes for regulations, and compliance 1. Power Reactors 6. Products with them is not required. Methods and solutions different from those set Out in 2. Research and Test Reactors 7. Transportation the guides will be acceptable if they provide a basis for the findings requisite to 3. Fuelsand Materials Facilities 8. Occupational Health the issuance or continuance of a permit or license by the Commission. 4. Environmental and Siting 9. Antitrust Review Comments and suggestions for improvements in these guides are encouraged 5. Materials and Plant Protection 10. General at all times, and guides will be revised, as appropriate, to accommodate com- ments and to reflect new information or experience. However, comments on Copies of published guides may be obtained by written request indicating the this guide, if received within about two months after its issuance, will be par- divisions desired to the U.S. Nuclear Regulatory Commission. Washington, D.C.

ticularly useful in evaluating the need for an early revision. 20555. Attention: Director, Office of Standards Development.

An acceptable emergency water source is capable of and (4) a single failure of man-made structural features.

providing adequate water for an indefinite period of In applying the "single failure," various mechanistic time or for that period of time needed to evaluate the failure modes can be postulated. One can be ultraconser- situation and to take the corrective action necessary to vative and choose to assume a complete functional loss, provide an adequate supply. Some finite capacity may but this is not necessarily required. For example, it is be acceptable if it can be demonstrated that replenish- desirable to consider the consequences of a postulated ment can be effected to ensure the continuous capability major rupture of a dam (including the time-related of the EWSS to perform its safety functions (particularly effects of forces imposed at the time of rupture);

the cooling functions), taking into account the avail- however, it is not necessarily required that one assume ability of replenishment equipment and the limitations the dam disintegrates instantaneously with total loss of that may be imposed on the mobility of such equipment function.

as a result of an accident.

Where conduits and pumps are required as part of the The emergency water supply system safety functions EWSS, it is desirable to have at least two complete de- may incorporate natural or man-made features or a com- livery systems. However, a single delivery system (con- bination of the two. More than one water source may be duit, pump, and valves) may be acceptable if it-canbe involved to provide the safety function under different demonstrated that the capability will exist, following a conditions. Because of the importance of the EWSS to natural phenomenon, to repair the damage or to install a safety, it is necessary to design the system to ensure its reliable emergency line within a time period that is small operation during and following the design-basis natural in comparison with the time required to develop a haz- phenomena postulated for the site. In addition, it is also ard.

necessary that the safety function of the EWSS be en- sured during other applicable site-related events that Where the EWSS includes more than one source of may be caused by natural phenomena such as stream water, the individual water sources may have different blockage or diversion or reservoir depletion or, if appli- design requirements. It is important that multiple water cable, events caused by acts of industrial sabotage or sources (including their associated retaining structures, events caused by accidents from processing irregularities required conduits, and pumps) be separated and pro- or equipment malfunction. tected so that failure of any one will not induce failure in any other so as to preclude accomplishing the safety Combinations of less severe natural and accidental function of EWSS. It is desirable that the complex (but phenomena or conditions may also be considered to the not necessarily all its individual features) be capable of extent needed for a consistent level of conservatism; for withstanding each of the most severe natural phenomena example, such combinations could be evaluated in cases expected, other site-related events, reasonable com- where the probability of their existing at the same time binations of natural phenomena and/or site-related is comparable to the probability associated with the events, and a single failure of man-made structural fea- occurrence of the most severer phenomena. tures without loss of capability of the EWSS to accom- plish its safety functions. The most severe phenomena It is most important to have a high level of assurance may be considered to occur independently and not that the water supply for the EWSS will be available simultaneously. In addition, the single failure of man- when the need arises. In the case of natural supply made structural features need not be considered to occur sources, historical experience indicates that severe simultaneously with severe natural phenomena or site- natural events may result in blockage or diversion of related events.

streams as well as changes in levels of bodies of water.

Furthermore, failures of man-made portions of an EWSS It would be acceptable if Water Source No. 1 (say a are not uncommon. Because of these factors, it is desir- man-made pond with a dam), connecting conduits and able to give consideration to an EWSS composed of at pumps were capable of withstanding only the safe least two water sources, each capable of performing the shutdown earthquake,tornado, and drought, and Water specified safety functions, unless it can be demonstrated Source No. 2 (say a stream with an existing dam) and its that there is an extremely low probability of losing the conduits and pumps were capable of withstanding only capability of a single source. For those cases in which an the probable maximum flood. It would be necessary, applicant believes that a single water source is adequate however, that the complex as a whole be capable of to meet the needs of the safety function, the applicant withstanding any reasonably probable combination of should demonstrate that the source can withstand natural or accidental phenomena without loss of the individually, without loss of the design safety function, safety functions. It is important that the EWSS, as a each of the following events: (1) The most severe natural complex, be shown to be highly reliable by indicating phenomena expected at the site with appropriate that certain conditions are satisfied. For example, ambient conditions, but with no two or more such consider Water Source .No. 2, above. Such conditions phenomena occurring simultaueously, (2) the site-related would include: (1) the stream cannot be diverted or events that have occurred or that may occur during the blocked sufficiently to affect the availability of water at plant lifetime, (3) reasonably probable combinations of the connecting conduits; (2) no serious transportation less severe natural phenomena and site-related events accidents have occurrecd or can be reasonably expected;

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and (3) the dam was designed to appropriately conserva- Sufficient conservatism should be provided to ensure tive requirements, has functioned properly over its that the water supply is available and that design-basis lifetime, and (based on projection of the best available temperatures of safety-related equipment are not ex- data) will function properly for the lifetime of the fuel ceeded so as to lead to an unacceptableloss of function.

reprocessing plant it serves. Compliance with these For EWSS where the supply may be limited and/or the conditions would not, however, remove the need for temperature of plant intake water from the source may another source of cooling water if a single failure of the eventually become crucial (e.g., ponds, lakes, or cooling dam could result in losing the safety function of this towers, where recirculation between plant cooling water source of water. discharges and intake can occur), transient analyses of supply and/or temperature should be performed and An acceptable EWSS would be designed to permit adequate safety margins verified.

testing of its capacity and functional operability for transfer between normal and emergency water supply These analyses should include suffi~cient information with subsequent testing of each associated safety system. to substantiate the assumptions and analytical methods It is important that the transfer from normal to emer- used. Where possible, this information should include gency water supply be accomplished by a method which actual performance data for a similar cooling method ensures that the facility can be operated without undue operating under load near the' specified design con- risk to the health and safety of the public. In general, a ditions, or justification that conservative values (e.g.,

method involving automatic transfer would be preferred. heat transfer) have been used.

However, where it can be demonstrated that the design safety function of the associated systems is not impaired 2. The EWSS complex, whether composed of single by delays inherent in a manual transfer method, such a or multiple water sources, should be capable of with- method could be acceptable. standing individually, without loss of safety functions specified in regulatory position C.1, each of the follow- It would expedite the licensing process to include in ing events:

the technical specifications a description of and schedule for tests to be performed and to include a statement of a. The most severe design-basis natural phe- actions to be taken in the event the above tests indicate nomena expected, but with no two or more such that the required capability of the EWSS is inadequate phenomena occurring simultaneously, to perform its designed safety functions. b. The site-related events (e.g., transportation accident, stream diversion, or blockage) that historically

C. REGULATORY POSITION

have occurred,

1. The emergency water supply system (EWSS) c. Combinations of less severe natural phenomena should be capable of providing a suficient quantity of and site-related events, water to satisfy (1) the safety needs of the fire pro- tection system; (2) the safety needs of the cooling sys- d. A single failure of man-made structural tems for the fuel storage pools, the waste storage tanks,

2 features.

1 and certain process vessels; and (3) the safety needs of any other equipment or system requiring a supply of water to perform its design- safety function, directly or 3. The EWSS should consist of at least two sources of indirectly. This adequate supply of water should be pro- water, including their retaining structures, each with the vided for an indefinite period or for some finite number capability to perform the safety functions specified in of days if it can be demonstrated that replenishment or regulatory position C.l above, unless it can be demon- use of an alternative water supply can be effected to strated that there is an extremely low probability of ensure the continuous capability of the EWSS to per- losing the capability of a single source.

form its safety functions, taking into account the avail- ability of replenishment equipment and limitationts that 4. There should be at least two conduits, each with a may be imposed on "freedom of action" 3 following an pump (if a pumping head is required), connecting the accident or the occurrence of severe natural phenomena. source(s) with the intake structures of the plant, unless it can be demonstrated that the capability will exist, IThese are process vessels that might self-concentrate as a result following a natural or accidental phenomenon, to repair of heat generated by the fission products. Vessels in this cate- damage or to install an emergency conduit within a time gory could include (1) dissolvers, (2) input accountability and period that is small in comparison with the time required feed adjustment tanks, (3) solvent, extraction feed tanks, for a hazard to develop. The conduits and pumps should

(4) high-level waste evaporators, and (5) waste accountability tanks. be separated and protected so that failure of any one

2An example of such a need would be the water necessary to will not induce failure of any other.

operate an emergency boiler supplying steam to sump and transfer jets in the high-level liquid waste storage complex. 5. The EWSS should be designed to permit testing of

3

"Freedom of action" includes mobility of equipment as well as its functional operability and capacity, including the full options available to the plant management. operational sequence of the system, for transfer between

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normal and emergency supply sources, and testing of the

D. IMPLEMENTATION

operation of associated safety systems.

The purpose of this section is to provide information

6. The EWSS should incorporate devices to detect to applicants and licensees regarding the staff's plans for and indicate low flow in the system or system com- utilizing this regulatory guide.

ponents. These devices can be provided as an integral part of a safety system (cooling, fire, etc.) if such devices are located downstream from the intake structure Except in those cases in which the applicant proposes (header, fire loop, etc.) for the particular system. an alternative method of complying with specified portions of the Commission's regulations, the method

7. The technical specifications for the plant should described herein will be used in the evaluation of include: submittals for construction permit applications docketed after May 31, 1976.

a. A description of and schedule for tests to be performed, If an applicant wishes to use this regulatory guide in b. Provisions for action to be taken in the event developing submittals for applications docketed on or that conditions threaten partial loss of capability of the before May 31, 1976, the pertinent portions of the EWSS. application will be evaluated on the basis of this guide.

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON. 0. C. 20555 POSTAGE AND FEES PAID

UNITEO STATES NUC..EAR

OFFICIAL BUSINESS REGULATORY COMMISSION

PENALTY FOR PRIVATE USE. $300

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