UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                               January 3, 1992


NRC INFORMATION NOTICE 92-02:  RELAP5/MOD3 COMPUTER CODE ERROR ASSOCIATED
                               WITH THE CONSERVATION OF ENERGY EQUATION


Addressees

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information 
notice to alert addressees of an error in the RELAP5/MOD3 computer code 
associated with the conservation of energy equation.  The computer codes in 
the RELAP5 Series are general purpose, thermal hydraulic system codes used 
to simulate the response of systems such as the reactor coolant system (RCS) 
to transients and accidents.  It is expected that recipients will review the 
information for applicability to their facilities and consider actions, as 
appropriate, to avoid similar problems.  However, suggestions contained in 
this information notice are not NRC requirements; therefore, no specific 
action or written response is required.  

Description of Circumstances

On November 25, 1991, Northeast Utilities forwarded the enclosed 10 CFR Part 
21 initial notification to the NRC Operations Center, regarding an error in 
the RELAP5/MOD3 simulation of the response of the Haddam Neck Plant terry 
turbine room to a postulated steam line break.  The equipment environmental 
qualification (EEQ) profile for the room would have been nonconservative by 
approximately 100�F had the simulation been accepted.  Although the error in 
determining the environmental conditions could be significant, the effect of 
the error on the evaluation of the nuclear steam supply system (NSSS) 
response to a loss-of-coolant accident (LOCA) and steam line break has been 
determined to be negligible.  Appropriate corrections in the code are the 
responsibility of the Idaho National Engineering Laboratory (INEL).  

Codes in the RELAP5 Series are not intended to be used as containment 
analysis codes.  Containment analysis specific codes exist for that purpose.  
The primary purpose of the RELAP5 codes is analysis of the response of the 
NSSS to accident and transient conditions.

9112270227 
.

                                                            IN 92-02
                                                            January 3, 1991
                                                            Page 2 of 2


This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
the technical contact listed below or the appropriate Office of Nuclear 
Reactor Regulation (NRR) project manager. 




                                   Charles E. Rossi, Director
                                   Division of Operational Events Assessment
                                   Office of Nuclear Reactor Regulation


Technical contact:  Nancy Campbell, NRR
                    (301) 504-2836


Attachments:  
1.  Northeast Utilities 10 CFR Part 21 Notification
2.  List of Recently Issued NRC Information Notices
.