United States Nuclear Regulatory Commission - Protecting People and the Environment

Technical Specifications for Generic Letter 83-28, Items 4.3 and 4.4 (Generic Letter No. 85-10)



                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                           WASHINGTON, D. C. 20555

                                May 23, 1985

TO ALL BABCOCK AND WILCOX PRESSURIZED WATER REACTOR LICENSEES AND APPLICANTS

Gentlemen: 

SUBJECT:  TECHNICAL SPECIFICATIONS FOR GENERIC LETTER 83-28, ITEMS 4.3 AND 
          4.4 (Generic Letter 85-10) 

Item 4.3 of Generic Letter 83-28, "Required Actions Based on Generic 
Implications of Salem ATWS Events," established the requirement for the 
automatic actuation of the shunt trip attachment for B&W plants. Also, 
licensees are to submit any needed technical specification change requests 
as soon as practical following staff review and approval of the modified 
design. Item 4.4 of Generic Letter 83-28 requires that the appropriate . 
surveillance and test sections of the technical specifications be revised to
include testing of the silicon controlled rectifiers used to interrupt power
to control rods.  

In the staff's evaluation of the B&W generic design modifications for 
automatic actuation of the shunt trip attachment, as described in individual
letters to all B&W operating reactors, dated September 12, 1983, the staff 
concluded that technical specification changes should be proposed by 
licensees and that they would be reviewed on a plant specific basis. In the 
staff's review of plant specific responses to the generic letter, some 
licensees have indicated that changes to the technical specifications are 
not required. In such cases, the staff has found this to be unacceptable and 
has indicated that proposed technical specification changes should be 
submitted to reflect independent testing of the shunt and undervoltage trip 
attachments consistent with the design of the test features provided. 

Therefore, licensees are requested to submit proposed technical 
specification changes which are responsive to the guidance noted in the 
enclosure. The enclosed guidance will be used to revise the Standard 
Technical Specifications for B&W plants, and it will be used by the staff as 
a basis to review changes to technical specifications submitted by licensees 
and for the review of proposed technical specifications for operating 
license applications. 

For plants which have implemented the shunt trip modifications, a schedule 
for submittal of proposed technical specification changes should be 
established through discussions with the individual Project Manager for each
facility. 


8505210131 


                                    - 2 - 

In addition, discussions with the individual Project Managers should 
establish a schedule for plants which have not implemented the shunt trip 
modifications. Proposed technical specifications should be submitted as soon
as practical following staff review and approval of modified design. For 
operating license applicants, proposed technical specifications should 
include requirements which are responsive to the enclosed guidance. 

This request for information was approved by the Office of Management and 
Budget under clearance number 3150-0011 which expires April 30, 1985. Should
you have an questions, the staff contact is R. Karsch. Mr. Karsch can be 
reached on (301) 492-8563. 


                              Hugh L. Thompson, Jr., Director 
                              Division of Licensing 

Enclosure:
Sample of Technical Specifications
List of Generic Letters


                                  ENCLOSURE

                       TECHNICAL SPECIFICATION CHANGES
                          FOR REACTOR TRIP BREAKERS
                                 (B&W PLANT)

Background 

As a consequence of the Salem ATWS event, Item 4.3 of Generic Letter 83-28 
established the requirements for the automatic actuation of the shunt trip 
attachment for reactor trip breakers. Further, licensees are to submit any 
needed technical specification change requests prior to declaring the 
modified system operable. A number of the responses from operating reactors 
have indicated that no technical specification changes are required for this
modification. 

The staff has reviewed the guidance provided in the Standard Technical 
Specifications (STS) for B&W Plants, NUREG-0103, and finds that additional 
clarification of both the limiting conditions of operation and surveillance 
requirements are appropriate as a result of the design modifications to 
include automatic actuation of the shunt trip attachments. In addition, Item
4.4 of the generic letter requires that technical specification surveillance
requirements be revised to include testing of the silicon controlled 
rectifiers (SCR). The STS for B&W Plants will be revised to include the 
changes noted herein. Pending formal revision of the STS, this document 
provides guidance to licensees and operating license applicants on 
appropriate technical specifications in response to Items 4.3 and 4.4 of the
Generic Letter. 

                                    - 2 - 

Discussion 

The operability requirements for the reactor trip breakers are specified in 
Table 3.3-1 of the STS (see Attachment 2). The specification states that 
both reactor trip breakers shall be operable in Modes 1 and 2, and when the 
breakers are in the closed position, the control rod drive system is capable
of rod withdrawal, and fuel is in the reactor vessel. The action statement 
for an inoperable breaker requires that the breaker be placed in a tripped 
condition within one hour. 

With the addition of the automatic actuation of the shunt trip attachment 
(STA), diverse features exist to effect a reactor trip for each breaker. If 
one of these diverse trip features is inoperable, a decision would have to 
be made with regard to the operability status of the reactor trip breaker. 
The definition of OPERABLE-OPERABILITY in Section 1.0 of the STS states that
a component shall be operable or have operability when it is capable of 
performing its safety function. Since either trip feature being operable 
would initiate a breaker trip on demand, it would be overly conservative to 
treat a breaker as inoperable if one of these diverse trip features were 
inoperable. However, on the other hand the reliability of the reactor trip 
system would be reduced if each diverse trip feature is not maintained in an
operable status. 

                                    - 3 - 

The reactor trip breaker surveillance test should independently verify the 
operability of the shunt and undervoltage trip features of the reactor trip 
breaker as part of a single sequential test procedure. Therefore, the 
surveillance test which identifies a failure of one diverse trip feature 
also confirms the operability of the other trip feature. As a consequence, 
there is a higher degree of confidence that this trip feature would be 
capable of initiating a reactor trip in the next 48 hours. Accordingly, an 
additional action statement will be included in the STS for the reactor trip 
breakers as follows: 

     ACTION - With one of the diverse trip features (undervoltage or shunt 
     trip attachment) inoperable, restore it to OPERABLE status in 48 hours 
     or place the breaker in trip in the next hour. 

In accordance with the requirements of Item 4.4 of the Generic Letter, the 
SCR relays have also been included in the changes to Table 3.3-1 to define 
their operability requirements. The reactor trip system design for B&W 
plants includes two basic configurations; the Oconee design shown in Figure 
3.4 and the Davis Besse design shown in Figure 3.5 (see Attachment 1). In 
the Oconee design the SCR relays for the regulating rods duplicate the trip 
function of the DC breakers for the safety rods. Therefore, for this design 
an inoperable channel should be placed in trip as required by action 
statement 7. However, in the Davis Besse design, the SCR relays provide a 
third means to insure that power is removed from all rods to initiate a 

                                    - 4 - 

reactor trip. Therefore, placing inoperable channels of SCR relays in trip 
would only increase the potential for inadvertent reactor trips without 
significantly reducing the potential of an ATWS event, when considering the 
increased reliability of the reactor trip breaker afforded by the 
incorporation of diverse trip features. For plants with the Davis Besse 
design, a new action statement will be included in Table 3.3-1 of the STS as
follows: 

     ACTION - With one or both channels of SCR relays inoperable, restore 
     the channels to OPERABLE status during the next COLD SHUTDOWN exceeding 
     24 hours. 

The B&W generic design modification includes test features which permit 
independent testing to verify the operability of the shunt and undervoltage 
trip attachments. As noted above, operability as applied to the diverse trip
features of breakers may have different degrees of safety significance. In 
order to be consistent with the intent to the test features provided, the 
following notation will be included in the surveillance requirements 
specified in STS Table 4.3-1 for reactor trip breakers (see Attachment 2): 

     "The CHANNEL FUNCTIONAL TEST shall independently verify the OPERABILITY
     of the undervoltage and shunt trip attachments of the Reactor Trip 
     Breakers." 

                                    - 5 - 

Consistent with the requirements of Item 4.4 of the Generic Letter, the 
surveillance requirements for SCR relays will also be included in Table 
4.3-1. For plants with the Oconee design, the channel functional test of the
SCR-relays will be specified as monthly since the SCR relays used for the 
regulating rods duplicate the trip function of the DC breakers for the 
safety rods. For plants with the Davis Besse design, the frequency of the 
channel functional test of the SCR relays will be specified as at least once 
per 18 months. The less frequent testing for the SCR relays in the Davis 
Besse design is due to their less critical, i.e., duplicative, safety 
function. 

Attached are marked-up pages of the applicable STS tables with these 
changes. Proposed changes to plant specific technical specifications will be 
evaluated by the staff based on this guidance. 
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