TSTF-514

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1.0 Description

NUREG-1433 Specification 3.4.6, "RCS Leakage Detection Instrumentation," and

NUREG-1434 Specification 3.4.7 of the same title require instrumentation to detect

significant reactor coolant pressure boundary (RCPB) degradation as soon after

occurrence as practical to minimize the potential for propagation to a gross failure. The

Improved Standard Technical Specifications (ISTS) for BWR/4 plants (NUREG-1433)

requires one drywell floor drain sump monitoring system, one channel of either primary

containment atmospheric particulate or atmospheric gaseous monitoring system, and

(optionally) a primary containment air cooler condensate flow rate monitoring system.

The BWR/6 ISTS (NUREG-1434) requires one drywell floor drain sump monitoring

system, one channel of either drywell atmospheric particulate or atmospheric gaseous

monitoring system, and (optionally) a drywell air cooler condensate flow rate monitoring

system.

Questions have been raised regarding the Operability requirements for these instruments.

In particular, improvements in plant fuel integrity have resulted in a reduction of the

Reactor Coolant System (RCS) activity. As a result, the atmospheric radioactivity

monitors may not be capable of promptly detecting an increase in RCS leakage.

The proposed change revises the Bases to clearly define the RCS leakage detection

instrumentation Operability requirements and to modify the Actions to be taken when the

atmospheric gaseous radioactivity monitor is the only Operable monitor to require

additional, more frequent monitoring of other indications of RCS leakage and to shorten

the time allowed to restore another monitor to Operable status.

2.0 Proposed Change

The "RCS Leakage Detection Instrumentation," specification (BWR/4 LCO 3.4.6 and

BWR/6 LCO 3.4.7) is revised to add a new Condition. New Condition D is applicable

when the atmospheric gaseous radioactivity monitor is the only Operable monitor (i.e., all

other monitors are inoperable). The Required Actions require analyzing grab samples of

the primary containment (BWR/4) or drywell (BWR/6) atmosphere and monitoring RCS

leakage using administrative means every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and restoring another monitor to

Operable status within 7 days. The subsequent Conditions are renumbered to reflect in

addition of the new Condition.

The Bases are revised to clearly define the RCS leakage detection instrumentation

Operability requirements in the LCO Bases and to eliminate discussion from the Bases

that could be erroneously construed as Operability requirements. The Bases are also

revised to reflect the changes to the Technical Specifications and to more accurately

reflect the existing Technical Specifications.

Also, the primary containment and drywell air cooler condensate flow rate monitor is

plant-specific, and therefore bracketed in the NUREG. The specifications and Bases are

revised to consistently bracket references to this monitor.

3.0 Background

General Design Criterion (GDC) 30 of Appendix A to 10 CFR 50 requires means for

detecting and, to the extent practical, identifying the location of the source of RCS

Leakage. Regulatory Guide (RG) 1.45, Revision 0, "Reactor Coolant Pressure Boundary

Leakage Detection Systems," May 1973, describes acceptable methods for selecting

leakage detection systems. Revision 1 of RG 1.45 was issued in May 2008. However,

operating nuclear power plants are not committed to Revision 1 of RG 1.45.

NRC Information Notice (IN) 2005-24, "Non-conservatism in Leakage Detection

Sensitivity," (ADAMS Accession No. ML051780073) pointed out that the reactor

coolant activity assumptions used for designing the containment radiation gaseous

radiation monitor may be greater than the RCS radioactivity level present during normal

operation. As a result, the containment gas channel may not be able to detect a 1 gpm

leak within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at the current RCS radioactivity level.

RG 1.45, Rev. 0, Regulatory Position C.2 states that "Leakage to the primary reactor

containment from unidentified sources should be collected and the flow rate monitored

with an accuracy of one gallon per minute (gpm) or better." Regulatory Position C.3

states, "At least three separate detection methods should be employed and two of these

methods should be (1) sump level and flow monitoring and (2) airborne particulate

radioactivity monitoring. The third method may be selected from the following: a.

monitoring of condensate flow rate from air coolers, b. monitoring of airborne gaseous

radioactivity. Humidity, temperature, or pressure monitoring of the containment

atmosphere should be considered as alarms or indirect indication of leakage to the

containment." Regulatory Position C.5 states, "The sensitivity and response time of each

leakage detection system in regulatory position [C.]3. above employed for unidentified

leakage should be adequate to detect a leakage rate, or its equivalent, of one gpm in less

than one hour." RG 1.45, Rev. 0, states, "In analyzing the sensitivity of leak detection

systems using airborne particulate or gaseous radioactivity, a realistic primary coolant

radioactivity concentration assumption should be used. The expected values used in the

plant environmental report would be acceptable." Many plants pre-date the issuance of

RG 1.45 and their plant-specific licensing basis is described in their UFSAR. In either

case, the appropriate sensitivity of the atmospheric radiation monitors is dependent on the

design assumptions and the plant licensing basis of each licensee.

The ISTS "RCS Leakage Detection Instrumentation" Bases do not clearly define the basis

for Operability for the RCS leakage detection instrumentation. Operability requirements

should be defined in the LCO section of the Bases. However, the current Bases contain

information that could be construed as Operability requirements in the Background,

Applicable Safety Analysis, and LCO sections. In addition, the current Bases do not

accurately describe the Operability of a detector as being based on the design

assumptions and licensing basis for the plant.

Because the atmospheric gaseous radiation monitor cannot always detect an RCS leak at

a rate of 1 gpm within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, some plants have removed the monitor from the Technical

Specification list of required monitors. However, experience has shown that the

containment atmosphere gaseous radiation monitor is useful to detect an increase in RCS

leak rate and provides a diverse means to confirm an RCS leak exists when other

monitors detect an increase in RCS leak rate. Therefore, the preferred solution is to retain

the atmospheric gaseous radiation monitor in the LCO list of required equipment, and to

revise the Actions to require additional monitoring and to provide less time before a plant

shutdown is required when the atmospheric gaseous radiation monitor is the only

Operable monitor.

4.0 Technical Analysis

This change will reduce the number of unnecessary MODE changes and requests for

enforcement discretion by clarifying the Operability requirements for the RCS leakage

detection instrumentation and by allowing a limited time to repair one or more of the

inoperable monitors. A plant shut down solely as a result of the loss of the preferred TS

monitoring capability could be avoided. The use of alternate leakage detection

monitoring for a limited time is an appropriate response to this condition.

The proposed Bases changes will clarify the Operability requirements of the RCS leakage

detection instrumentation. All references to RG 1.45 are revised to reference Revision 0

of the RG. Information in the Background and Applicable Safety Analysis sections of

the Bases that could be construed as Operability requirements is deleted. The LCO

section of the Bases is expanded to provide a detailed discussion of the Operability

requirements for each of the required instruments. For the atmospheric radioactivity

monitors, the Bases clearly relate Operability to the design assumptions and licensing

basis for the plant and a reference to the Final Safety Analysis Report description of the

design basis of the monitors is included.

As described in 10 CFR 50.36(c)(2)(i), the Limiting Condition for Operation and

associated Operability requirements represent the lowest functional capability or

performance levels of equipment required for safe operation of the facility. In practice,

the leakage monitoring instrumentation is typically set to provide the most sensitive

response without distracting the reactor operators with unnecessary alarms.

When the atmospheric gaseous radiation monitor is the only Operable monitor, the

current Technical Specifications require grab samples of the primary containment or

drywell atmosphere once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and restoration of the inoperable monitors within

30 days. The proposed change requires analyzing grab samples from the primary

containment or drywell atmosphere and monitoring RCS leakage by administrative

means once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and restoration of at least one additional monitor within 7 days.

Administrative means of monitoring RCS leakage include monitoring and trending

parameters that may indicate an increase in RCS leakage. There are diverse alternative

mechanisms from which appropriate indicators may be selected based on plant conditions.

It is not necessary to utilize all of these methods, but a method or methods should be

selected considering the current plant conditions and historical or expected sources of

unidentified leakage. The Bases list the plant-specific administrative methods, such as

primary containment and drywell pressure, temperature, and humidity, Component

Cooling Water System outlet temperatures and makeup, Reactor Recirculation System

pump seal pressure and temperature and motor cooler temperature indications, Drywell

cooling fan outlet temperatures, Reactor Building Chiller amperage, Control Rod Drive

System flange temperatures, and Safety Relief Valves tailpipe temperature, flow, or

pressure. These indications, coupled with the atmospheric grab samples, are sufficient to

alert the operating staff to an unexpected increase in unidentified LEAKAGE.

A primary containment or drywell grab sample is comparable to the atmospheric

particulate radiation monitor with respect to the ability to detect RCS leakage. Due to the

time to take and analyze the grab sample, this is not a continuous monitoring method.

However, the frequent performance of the grab samples ensures there is no significant

loss of monitoring capability during the limited time period allowed by the proposed

change. The 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> (once per shift) performance of primary containment or drywell

grab samples and monitoring by administrative means is reasonable given the availability

of the atmospheric gaseous radiation monitor. The 7 day Completion Time to restore

another monitor to Operable status is reasonable given the diverse methods employed in

the Required Actions to detect an RCS leak and the low probability of a large RCS leak

during this period.

5.0 Regulatory Analysis

5.1 No Significant Hazards Consideration

The Technical Specification Task Force (TSTF) has evaluated whether or not a

significant hazards consideration is involved with the proposed generic change by

focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as

discussed below:

1. Does the proposed change involve a significant increase in the probability or

consequences of an accident previously evaluated?

Response: No.

The proposed change clarifies the Operability requirements for the Reactor

Coolant System (RCS) leakage detection instrumentation and reduces the time

allowed for the plant to operate when the only Operable RCS leakage detection

instrumentation monitor is the atmospheric gaseous radiation monitor. The

monitoring of RCS leakage is not a precursor to any accident previously evaluated.

The monitoring of RCS leakage is not used to mitigate the consequences of any

accident previously evaluated.

Therefore, it is concluded that this change does not involve a significant increase

in the probability or consequences of an accident previously evaluated.

2. Does the proposed change create the possibility of a new or different kind of

accident from any accident previously evaluated?

Response: No.

The proposed change clarifies the Operability requirements for the Reactor

Coolant System (RCS) leakage detection instrumentation and reduces the time

allowed for the plant to operate when the only Operable RCS leakage detection

instrumentation monitor is the atmospheric gaseous radiation monitor. The

proposed change does not involve a physical alteration of the plant (no new or

different type of equipment will be installed) or a change in the methods

governing normal plant operation.

Therefore, it is concluded that this change does not create the possibility of a new

or different kind of accident from any accident previously evaluated.

3. Does the proposed change involve a significant reduction in a margin of safety?

Response: No.

The proposed change clarifies the Operability requirements for the Reactor

Coolant System (RCS) leakage detection instrumentation and reduces the time

allowed for the plant to operate when the only Operable RCS leakage detection

instrumentation monitor is the atmospheric gaseous radiation monitor. Reducing

the amount of time the plant is allowed to operate with only the atmospheric

gaseous radiation monitor Operable increases the margin of safety by increasing

the likelihood that an increase in RCS leakage will be detected before it

potentially results in gross failure.

Therefore, it is concluded that this change does not involve a significant reduction

in a margin of safety.

Based on the above, the TSTF concludes that the proposed change presents no significant

hazards considerations under the standards set forth in 10 CFR 50.92(c), and, accordingly,

a finding of "no significant hazards consideration" is justified.

5.2 Applicable Regulatory Requirements/Criteria

10 CFR 50, Appendix A, "General Design Criteria for Nuclear Power Plants," Criterion

30, "Quality of reactor coolant pressure boundary," requires that means be provided for

detecting and, to the extent practical, identifying the location of the source of reactor

coolant leakage. The specific attributes of the reactor coolant leakage detection systems

are outlined in Regulatory Positions 1 through 9 of Regulatory Guide 1.45, Rev. 0.

10 CFR 50.36, "Technical Specifications," paragraph (c)(2)(ii)(A), specifies that a

Limiting Condition for Operation be established for installed instrumentation that is used

to detect and indicate in the control room a significant abnormal degradation of the

reactor coolant pressure boundary. This instrumentation is required by the "RCS

Leakage Detection Instrumentation" Specification. The modification of the Actions in

the Specification is not in conflict with the 10 CFR 50.36 requirements. The proposed

changes do not adversely impact the ability of the Reactor Coolant System leakage

detection system to function as designed and do not impact conformance to the applicable

GDCs. Therefore, the proposed changes are consistent with all applicable regulatory

requirements or criteria.

Based on the considerations discussed above, (1) there is reasonable assurance that the

health and safety of the public will not be endangered by operation in the proposed

manner, (2) such activities will be conducted in compliance with the Commission’s

regulations, and (3) the approval of the proposed change will not be inimical to the

common defense and security or to the health and safety of the public.

6.0 Environmental Consideration

A review has determined that the proposed change would change a requirement with

respect to installation or use of a facility component located within the restricted area, as

defined in 10 CFR 20, or would change an inspection or surveillance requirement.

However, the proposed change does not involve (i) a significant hazards consideration, (ii)

a significant change in the types or significant increase in the amounts of any effluent that

may be released offsite, or (iii) a significant increase in individual or cumulative

occupational radiation exposure. Accordingly, the proposed change meets the eligibility

criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to

10 CFR 51.22(b), no environmental impact statement or environmental assessment need

be prepared in connection with the proposed change.

7.0 References

None.