IEEE Transactions on Nuclear Science, Vol. 35, No. 2, April 1988 991

AN EXPERT DISPLAY SYSTEM AND NUCLEAR POWER PLANT CONTROL ROOMS

Leo Be l t r a c c h i U.S. Nuc lear R e g u l a t o r y Commission

Washington DC, 20555

ABSTRACT

.An e x p e r t d i s p l a y system c o n t r o l s a u t o m a t i c a l l y t h e d i s p l a y o f segments on a cathode r a y t u b e ' s sc reen t o fo rm an image o f p l a n t o p e r a t i o n s . The image c o n s i s t s o f an i c o n o f : 1) t h e process ( h e a t eng ine c y c l e ) , 2) p l a n t c o n t r o l systems, and 3) s a f e t y systems. A s e t o f d a t a - d r i v e n , f o r w a r d - c h a i n i n g computer s t o r e d r u l e s c o n t r o l t h e d i s p l a y o f segments. As p l a n t o p e r a t i o n changes, measured p l a n t d a t a a r e p rocessed t h r o u g h t h e r u l e s , and t h e r e s u l t s c o n t r o l t h e d e l e t i o n and a d d i - t i o n o f segments t o t h e d i s p l a y fo rmat . The i c o n con- t a i n s i n f o r m a t i o n needed by c o n t r o l rooms o p e r a t o r s t o m o n i t o r p l a n t o p e r a t i o n s .

One example o f an e x p e r t d i s p l a y i s i l l u s t r a t e d f o r t h e o p e r a t o r ' s t a s k o f m o n i t o r i n g leakage f rom a s a f e t y v a l v e i n a steam l i n e o f a b o i l i n g w a t e r r e a c t o r (BWR). p l a y t o m o n i t o r p l a n t o p e r a t i o n s d u r i n g p r e - t r i p , t r i p , and p o s t - t r i p o p e r a t i o n s i s d iscussed as a u n i v e r s a l d i s p l a y .

The v i e w p o i n t s and o p i n i o n s expressed h e r e i n a r e t h e a u t h o r ' s persona l ones, and t h e y a r e n o t t o be i n t e r - p r e t e d as Nuc lear R e g u l a t o r y Commission c r i t e r i a , r e - qu i rements , o r g u i d e l i n e s .

INTRODUCTION

Graph ics speak f a s t e r t h a n words and numbers. I n t e r - a c t i v e computer g r a p h i c techn iques f a c i l i t a t e t h e pro- cess ing , d i s p l a y , and communicat ion o f da ta . P r o p e r l y des igned g r a p h i c s , such as i c o n s , may be used t o convey l a r g e q u a n t i t i e s o f i n f o r m a t i o n t h a t i s easy t o read, easy t o unders tand, and f r e e o f c l u t t e r .

For example, a t r e n d p l o t o f a p rocess v a r i a b l e on t h e screen o f a ca thode- ray t u b e (CRT) i s much e a s i e r t o unders tand t h a n two columns o f numbers, one r e p r e s e n t - i n g t ime, and t h e o t h e r t h e magnitude o f t h e process v a r i a b l e .

F o l e y (Ref. 1) s t a t e s t h a t t h e system d e s i g n e r must f i r s t develop i n t e r a c t i o n techn iques t h a t min imize t h e work r e q u i r e d by t h r e e b a s i c human processes: percep- t i o n , c o g n i t i o n , and motor a c t i v i t y . To ach ieve t h i s g o a l , t h e d e s i g n e r must have a thorough unders tand ing o f t h e performance and c h a r a c t e r i s t i c s o f i n t e r a c t i v e dev ices . The d e s i g n e r must a l s o p e r f o r m f u n c t i o n and t a s k ana lyses t o i d e n t i f y t h e d a t a needed by humans t o p e r f o r m t h e i r ass igned work. One c r i t i c a l p rob lem f o r t h e d e s i g n e r i s how t o f o r m a t and p r e s e n t t h e d a t a and i n f o r m a t i o n needed w i t h a minimum number o f d i s p l a y pages. maximize communicat ion f rom a l a r g e d a t a base.

The E l e c t r i c Power Research I n s t i t u t e (EPRI) p u b l i s h e d d i s p l a y des ign g u i d e l i n e s (Ref. 2) f o r t h e development o f computer-generated d i s p l a y systems. The g u i d e l i n e s s u p p o r t a t h r e e - s t e p d e s i g n process: 1) a n a l y s i s , 2 ) s y n t h e s i s , and 3 ) e v a l u a t i o n . i n c l u d e s f u n c t i o n and t a s k a n a l y s i s w i t h a goa l o f i d e n t i f y i n g i n f o r m a t i o n requ i rements . s t e p d i s p l a y formats a r e developed u s i n g t h e p r o d u c t s from t h e a n a l y s i s s tep . The e v a l u a t i o n s t e p i n c l u d e s t h e assessment o f computer-based o p e r a t o r a i d s , such as t h e c o m p a t i b i l i t y o f t h e d i s p l a y w i t h a u s e r ' s sensory and p e r c e p t u a l c a p a b i l i t i e s .

I n another example, t h e use o f an e x p e r t d i s -

The goal i s t o min imize human search t i m e and

The a n a l y s i s s t e p

I n t h e s y n t h e s i s

W i t h CRTs as d i s p l a y dev ices , a d e s i g n e r may use c o l o r t o code i n f o r m a t i o n . Murch (Ref. 3) s t a t e s t h a t most o f t e n c o l o r is used i n a q u a l i t a t i v e r a t h e r t h a n a q u a n t i t a t i v e f a s h i o n t o show t h a t one i t e m i s d i f f e r e n t f rom another . However, t h e use o f c o l o r becomes more complex as t h e number o f b i t p l a n e s i n d i s p l a y systems i n c r e a s e a l l o w i n g f o r thousands o f c o l o r s . As Murch c o r r e c t l y no tes , t o maximize t h e p o t e n t i a l o f g r a p h i c s systems, a d e s i g n e r must draw upon s c i e n c e ' s under- s t a n d i n g o f how t h e human eye c r e a t e s c o l o r sensat ions . Because o f sensor l i m i t a t i o n s i n t h e human eye, o n l y a few c o l o r s may be used t o e f f e c t i v e l y code da ta . Murch 's g u i d e l i n e s on t h e use o f c o l o r a r e e x c e l l e n t .

Hayes-Roth's t u t o r i a l (Ref. 4) on knowledge-based ex- p e r t systems s t a t e s t h a t computer -s to red s k i l l s o f s p e c i a l i s t s may be used t o a i d o p e r a t o r s i n s o l v i n g problems. A m a j o r b e n e f i t f rom such systems i s t h e c o n s i s t e n t a p p l i c a t i o n o f l o g i c and t i m e l y s o l u t i o n s t o problems. n u c l e a r i n d u s t r y i s i n a t e c h n i c a l paper by G i m m y (Ref. 5). I n t h i s example, t h e au tomat ic d i a g n o s i s o f m u l t i - p l e alarms by an e x p e r t system i s d iscussed. From t h e d e s c r i p t i o n p r o v i d e d by G i m m y , t h e knowledge base appears thorough, t h e i n f e r e n c e eng ine i s based upon t a b l e - d r i v e n l o g i c , and t h e u s e r ' s i n t e r f a c e appears t o be v e r y e f f e c t i v e . Gimmy's paper p r o v i d e s e x c e l l e n t g u i d e l i n e s on how t o implement e x p e r t systems i n n u c l e a r f a c i l i t i e s .

Computer-dr iven cathode r a y tubes a r e used as d i s p l a y dev ices i n t h e c o n t r o l rooms o f n u c l e a r power p l a n t s . The fo rmat o f t h e d a t a on t h e screens takes many shapes. For example, v e r t i c a l b a r s , w i t h l a b e l s and process parameter va lues , mimic ana log meters on t h e c o n t r o l board. A l s o , t r e n d p l o t s o f p rocess parameters a r e c o l o r and shape coded t o f a c i l i t a t e t h e o p e r a t o r ' s use o f t h i s da ta .

An example o f an e x p e r t system i n t h e

The d i g i t a l computer may mimic t h e human o p e r a t o r by au tomat ing o p e r a t o r t a s k s and t h e n d i s p l a y i n g processed da ta . The e x p e r t d i s p l a y d iscussed i n t h i s paper i n t e - g r a t e s i n d i v i d u a l p rocess parameters f rom t h e p l a n t t o fo rm and d i s p l a y a model o f t h e process . I n d o i n g these t a s k s , t h e computer mimics an e x p e r t o p e r a t o r by i n t e g r a t i n g and s t r u c t u r i n g t h e d a t a t o s u p p o r t d e c i - s i o n making by t h e human. The s p e c i f i c d i s p l a y s i n t h i s paper a r e p r o t o t y p e s developed by t h e a u t h o r on a g r a p h i c s w o r k s t a t i o n . They serve t o i l l u s t r a t e a d i f - f e r e n t t y p e o f d i s p l a y d e s i g n and au tomat ion , b u t t h e y a r e by no means a complete des ign .

To p r o v i d e a b a s i s f o r a d i s c u s s i o n , t h e f o l l o w i n g terms a r e d e f i n e d :

Graph ic p r i m i t i v e s : 1. The g r a p h i c elements d i s p l a y e d on a t e r m i n a l ;

d i s p l a y . 2. The fundamental u n i t s o f a

Segment: 1. A combined s e r i e s o f g r a p h i c p r i m i t i v e s ; A r e u s a b l e c o l l e c t i o n o f g r a p h i c p r i m i - t i v e s and p r i m i t i v e a t t r i b u t e s s t o r e d i n memory.

2 .

A t t r i b u t e : A c h a r a c t e r i s t i c o f a p r i m i t i v e , such as c o l o r , w i d t h , e t c .

U.S. Government work not protected by US. Copyright

992

Dynamic

Panel :

a t t r i b u t e : Those a t t r i b u t e s t h a t can be changed a f t e r t h e segment i s d e f i n e d .

The s e t o f p i x e l s t h a t l i e i n s i d e a c l o s e d boundary on a d i s p l a y s u r f a c e . A "panel d e f i n i t i o n " i s a s e r i e s o f MOVES and DRAWS t h a t fo rm a pane l boundary. A "pane l " may be i d e n t i f i e d as a segment.

I con : An image composed f rom segments. A "process i c o n " models t h e process w i t h i n t h e p l a n t . "system i c o n " mimics p l a n t systems.

A

Ob jec t : A computer-generated g r a p h i c element t h a t can be a c t e d upon by t h e human user .

Background elements: The t i m e i n v a r i a n t segments i n an i c o n .

A c t i v e elements: The t i m e v a r i a n t segments i n an icon .

Graph ic p r i m i t i v e s a r e t h e b a s i c g r a p h i c elements t h a t a t e r m i n a l d i s p l a y s i n response t o a command. One g r a p h i c p r i m i t i v e i s a v e c t o r , a s t r a i g h t l i n e drawn between two p o i n t s on a d i s p l a y s u r f a c e . A s e r i e s o f v e c t o r s i s used t o fo rm a c i r c l e , a r e c t a n g l e , o r a pane l . A t t r i b u t e s o f a g r a p h i c p r i m i t i v e may i n c l u d e c o l o r , l i n e s t y l e ( s o l i d , dashed, e t c . ) , and w i d t h . For example, a tempera ture-en t ropy diagram o f two-phase w a t e r ( l i q u i d and vapor) may be shown on a CRT as a s e r i e s o f v e c t o r s t h a t fo rm a pane l . The c o l o r o f t h e s u r f a c e , such as w h i t e , i s a d e s i g n e r - s p e c i f i e d a t t r i - b u t e o f t h e pane l .

A segment i s a c o l l e c t i o n o f g r a p h i c p r i m i t i v e s and t h e i r a t t r i b u t e s t h a t t h e d i s p l a y t e r m i n a l t r e a t s as a s i n g l e o b j e c t . s i n g l e g r a p h i c p r i m i t i v e , o r as much as an e n t i r e d i s p l a y . An example o f a segment i s a symbol f o r a v a l v e , wh ich i s composed o f s e v e r a l s t r a i g h t l i n e s ( p r i m i t i v e s ) .

A segment may c o n t a i n as l i t t l e as a

I n t h e f o l l o w i n g d i s c u s s i o n , segments a r e used t o code d a t a and i n f o r m a t i o n f o r p rocess f u n c t i o n s and f o r p l a n t systems. Severa l segments a r e t h e n used t o com- pose an i c o n t h a t models p l a n t o p e r a t i o n s . Some seg- ments a r e used t o compose t h e background elements i n t h e d i s p l a y fo rmat . The use o f a c t i v e segments i n t h e d i s p l a y fo rmat i s c o n t r o l l e d by pre-de termined r u l e s s t o r e d i n t h e memory o f a computer. d r i v e n , w i t h t h e d a t a o b t a i n e d f rom sampl ing p l a n t sensors. For example, when a measured process v a r i - a b l e , such as pressure , exceeds a s e t p o i n t f o r a v a l v e t o open, a new segment f o r t h e v a l v e ( i n d i c a t i n g an open v a l v e ) i s added t o t h e d i s p l a y . T h i s overv iew p r o v i d e s an i n t r o d u c t i o n t o an e x p e r t d i s p l a y .

EXPERT SAFETY VALVE MONITOR

An i m p o r t a n t t a s k ass igned o p e r a t o r s i s m o n i t o r i n g s a f e t y v a l v e s f o r leakage a f t e r a s a f e t y v a l v e has l i f t e d and t h e n c losed. Many t i m e s these v a l v e s do n o t f u l l y c l o s e and leakage occurs . G e n e r a l l y , a s a f e t y v a l v e serves as a s i n g l e component and i s n o t backed up by a b l o c k va lve . Thus, leakage o f c o o l a n t f rom a s a f e t y v a l v e i s a f a u l t i n t h e p r e s s u r e boundary and a concern i n m a i n t a i n i n g s a f e p l a n t o p e r a t i o n .

D u r i n g normal o p e r a t i o n o f a BWR, t h e s a f e t y v a l v e i n t h e steam l i n e i s c losed. Should a l a r g e i n c r e a s e i n p r e s s u r e occur d u r i n g a t r a n s i e n t and t h e p r e s s u r e i n t h e steam l i n e exceed t h e s e t p o i n t f o r t h e s a f e t y v a l v e , t h e v a l v e opens. The s e t p o i n t f o r t h e s a f e t y v a l v e i s t y p i c a l l y 1230 p s i g . When t h e v a l v e i s open, steam escapes t o t h e d i s c h a r g e p i p e , t h e n t o t h e d r y - w e l l , and u l t i m a t e l y t o t h e suppress ion p o o l .

The r u l e s a r e d a t a

O b e r t (Ref. 6) d e f i n e s a t h r o t t l i n g process as one t h a t occurs when a f l u i d expands f rom a r e g i o n o f h i g h p r e s s u r e t o a r e g i o n o f lower p ressure . t h e f l u i d d i s s i p a t e s energy t h a t c o u l d have been t r a n s - formed i n t o work. s a f e t y v a l v e ach ieves a h i g h v e l o c i t y , wh ich i s d i s - s i p a t e d i n a imless t u r b u l e n c e i n t h e d i s c h a r g e p i p e . Thermodynamical ly, t h e e n t h a l p y o f t h e d i s s i p a t e d steam i n t h e d i s c h a r g e p i p e i s t h e same as t h e e n t h a l p y o f t h e steam i n t h e steam l i n e . However, t h e e n t r o p y o f t h e d i s s i p a t e d steam i s much g r e a t e r t h a n t h e e n t r o p y o f t h e steam i n t h e steam l i n e . The amount o f e n t r o p y i n c r e a s e d u r i n g t h e t h r o t t l i n g process i s a measure o f t h e d i s s i p a t e d energy.

For t h e purpose o f t h i s d i s c u s s i o n , t h e d i s c h a r g e p i p e f o r t h e s a f e t y v a l v e i s i n s t r u m e n t e d w i t h a thermo- c o u p l e and w i t h an a c o u s t i c m o n i t o r i n g dev ice . The thermocouple measures t h e tempera ture o f t h e f l u i d i n t h e d i s c h a r g e p i p e . A c o u s t i c m o n i t o r s , such as p i e - z o e l e c t r i c sensors (acce le rometers and a c o u s t i c emis- s i o n sensors), a r e e x c e l l e n t dev ices t o m o n i t o r t h e s t a t u s o f v a l v e s (Ref. 8). These sensors measure t h e a c o u s t i c response t h a t r e s u l t s f r o m t h e f l o w o f f l u i d t h r o u g h t h e s a f e t y va lve .

F i g u r e 1 d e p i c t s t h e steam l i n e , t h e s a f e t y v a l v e , t h e d i s c h a r g e p i p e , t h e d r y w e l l , t h e suppress ion p o o l , and t h e sensors i n t h e d i s c h a r g e p i p e . The symbol P 1 r e - p r e s e n t s t h e o p e r a t i n g p r e s s u r e i n t h e steam l i n e , and h l r e p r e s e n t s t h e e n t h a l p y o f t h e steam i n t h e steam l i n e . For a BWR o p e r a t i n g a t 1000 p s i a steam l i n e pressure , t h e steam i s g e n e r a l l y s a t u r a t e d steam ( o r a t most, a few degrees superheated). The e n t h a l p y o f s a t u r a t e d steam a t 1000 p s i a i s 1192.9 BTU/#m. case o f a l e a k i n g s a f e t y va lve , t h e e n t h a l p y o f t h e t h r o t t l e d , d i s s i p a t e d steam i s a l s o 1192.9 BTU/#m. For t h e purpose o f t h i s d i s c u s s i o n , i t i s assumed t h a t t h e p r e s s u r e o f t h e d i s s i p a t e d steam, P2, i s a tmospher ic p ressure , 14.7 p s i a . Thus, based on t h e p r o p e r t i e s o f steam and t h e t h r o t t l i n g process , T2, t h e tempera ture o f t h e d i s s i p a t e d steam i s 300 degrees F a h r e n h e i t (300 F). t h e steam shou ld r e a d about 300 F , wh ich i s reached a f t e r t h e i n i t i a l response l a g o f t h e sensor. A t 300 F and a tmospher ic p r e s s u r e , t h e steam i s superheated because t h e s a t u r a t i o n tempera ture i s 212 F a t a tmospher ic p ressure . I n a d d i t i o n t o tempera ture , t h e s i g n a l f rom t h e a c o u s t i c m o n i t o r wou ld be used t o con- f i r m v a l v e leakage.

Thus, steam l i n e pressure , steam l i n e e n t h a l p y , p res- s u r e o f t h e d i s s i p a t e d steam i n t h e d i s c h a r g e p i p e , t h e d i s c h a r g e p i p e ' s thermocouple read ing , and t h e a n a l y t i - c a l l y de termined tempera ture ( f r o m t h e steam t a b l e s ) o f t h e d i s s i p a t e d steam a r e used t o d e t e c t leakage f rom t h e s a f e t y va lve . Readings f rom t h e a c o u s t i c m o n i t o r a l s o c o n f i r m t h e presence o f leakage.

The thermodynamic p r o p e r t i e s o f steam f o r a t h r o t t l i n g process may be harnessed t o d e t e c t an open s a f e t y va lve . O f course, t h e p r e s s u r e i n t h e steam l i n e must be g r e a t e r t h a n o r equal t o t h e s e t p o i n t p r e s s u r e f o r t h e v a l v e t o open. Tab le 1 c o n t a i n s examples t h a t i l l u s t r a t e n u m e r i c a l l y t h e t h r o t t l i n g process f o r an open v a l v e w i t h s e t p o i n t steam l i n e p r e s s u r e , and f o r a c l o s e d , l e a k i n g v a l v e w i t h normal steam l i n e pressure .

The process o f d e t e c t i n g an open s a f e t y v a l v e , o r leakage f rom a c l o s e d s a f e t y v a l v e , may be automated. A d i g i t a l computer implements r u l e s t h a t a r e d r i v e n by measured p l a n t d a t a t o c o n t r o l t h e d i s p l a y o f messages and segments on t h e screen o f a CRT.

I n d o i n g so,

The steam expanding t h r o u g h t h e

I n t h e

The thermocoup le 's measured tempera ture o f

T h i s d i s c u s s i o n assumes t h a t t h e r u l e s used a r e those s t a t e d i n Tab le 2 , wh ich a r e s e l f - e x p l a n a t o r y . The s t a t u s o f each r u l e i s de termined by comparing measured

993

t o d e s i g n and a c c u r a t e l y implement t h e s o f t w a r e , be- cause g r e a t c a r e must be t a k e n t o a v o i d m i s l e a d i n g t h e o p e r a t o r .

A UNIVERSAL DISPLAY

Much more p o w e r f u l uses o f an e x p e r t d i s p l a y a r e p o s s i b l e o t h e r t h a n t h e case d iscussed above. example, on a r e a c t o r t r i p , c o n t r o l room o p e r a t o r s must m o n i t o r l a r g e q u a n t i t i e s o f d a t a t o de termine t h e s t a t u s o f t h e p l a n t ' s p rocess , o f t h e p l a n t ' s o p e r a t i n g systems, and t h e n t o respond t o component f a i l u r e s , shou ld t h e y occur . Furthermore, t h e r e a c t o r t r i p may demand t h e o p e r a t i o n o f s a f e t y systems t o s u s t a i n s a f e p l a n t o p e r a t i o n s . When t h e s a f e t y systems a r e opera t - i n g , t h e p r i n c i p a l h e a t removal p a t h f rom t h e r e a c t o r c o r e ( h e a t source) t o t h e environment ( h e a t s i n k ) may be o t h e r t h a n t h e p l a n t ' s condenser. p o s s i b l e h e a t removal pa ths may e x i s t a f t e r a t r i p , o p e r a t o r s must q u i c k l y i d e n t i f y t h e p a t h i n use and m o n i t o r performance o f t h e a s s o c i a t e d p l a n t systems t o ensure t h a t adequate l i q u i d - p h a s e water i s a v a i l a b l e t o remove t h e heat . An e x p e r t d i s p l a y system c o u l d be a p o w e r f u l t o o l f o r o p e r a t o r s i n p e r f o r m i n g these f u n c t i o n s and t a s k s .

For

Because many

p l a n t d a t a w i t h t h e a p p r o p r i a t e , p r e - d e f i n e d s e t - p o i n t ( s ) and t o l e r a n c e ( s ) . The r e s u l t s f rom a p p l y i n g each r u l e a r e t h e n used t o de termine t h e messages and segments d i s p l a y e d t o c o n t r o l room personne l .

F i g u r e 2 c o n t a i n s an i c o n o f t h e b o i l i n g process i n a BWR, w i t h a steam l i n e p r e s s u r e o f 1000 p s i a and s a t u r a t i o n tempera ture o f 544.6 F . For t h e purpose o f t h i s and subsequent d i s c u s s i o n , t h i s i c o n i s a p rocess i c o n . T h i s f i g u r e and subsequent f i g u r e s a r e drawings o f c o l o r e d p r i n t s made f rom a CRT screen ( t h e y l a c k d e t a i l , b u t a r e much more economical t o use t h a n t h e c o l o r e d v e r s i o n ) . Severa l segments a r e used t o compose t h e i c o n . The c e n t r a l , b e l l - s h a p e d pane l i s t h e seg- ment t h a t r e p r e s e n t s t h e tempera ture ( v e r t i c a l ) - e n t r o p y ( h o r i z o n t a l ) p r o p e r t i e s o f two-phase w a t e r ( l i q u i d and vapor) . segment. The t h i n band t h a t serves as a b o r d e r i s another segment, wh ich r e p r e s e n t s conta inment . t i t l e , da te , and t i m e comprise another segment. p rocess o f b o i l i n g s a t u r a t e d water t o s a t u r a t e d steam i n t h e r e a c t o r c o r e and t h e w a t e r l e v e l i n t h e c o r e fo rm a segment t h a t i s l o c a t e d i n t h e two-phase r e g i o n o f water .

The s a f e t y v a l v e i n t h e steam l i n e ( F i g u r e 2) i s f u l l y seated; t h i s c o n d i t i o n i s de termined f rom t h e e x e c u t i o n of t h e s t o r e d r u l e s (Tab le 2) d r i v e n by t h e measured v a r i a b l e s o f steam l i n e pressure , t h e d i s c h a r g e p i p e thermocouple r e a d i n g , and t h e a c o u s t i c m o n i t o r read ing . The a n a l y t i c a l l y c a l c u l a t e d tempera ture o f t h e d i s s i - p a t e d steam f rom t h e t h r o t t l e p rocess i s a l s o needed. T h i s i s de termined f rom t h e d r y w e l l p ressure , and t h e s a t u r a t i o n p r o p e r t i e s o f t h e steam i n t h e steam l i n e . Thus, t h e message: SRV 50201 SEATED i s d i s p l a y e d as a segment.

F i g u r e 3 c o n t a i n s a p rocess i c o n t h a t i l l u s t r a t e s a l e a k i n g s a f e t y v a l v e . cess, f rom 1000 p s i a steam l i n e p r e s s u r e t o a tmospher ic p r e s s u r e i n t h e d r y w e l l , i s a d i s p l a y segment. The use o f t h i s segment and o f t h e message segment i s c o n t r o l - l e d by t h e a p p r o p r i a t e r u l e s i n Tab le 2. The tempera- t u r e o f t h e t h r o t t l e d steam i s 300 F , wh ich i s superheated steam.

F i g u r e 4 c o n t a i n s a p rocess i c o n t h a t i l l u s t r a t e s oper- a t i o n w i t h an open s a f e t y va lve . t i o n s i l l u s t r a t e d a r e those s t a t e d i n Tab le 1. The d i s p l a y s o f t h e t h r o t t l e p a t h and t h e message a r e c o n t r o l l e d by t h e a p p r o p r i a t e r u l e s and measured p l a n t d a t a .

F i g u r e s 2, 3, and 4 a r e c o p i e s o f d i s p l a y screens genera ted on a T e k t r o n i x 41158 D i s p l a y System. r u l e s (Tab le 2) were coded i n FORTRAN 86 by t h e use o f l o g i c a l IF and B L O C K I F program s ta tements . The f i g u r e s i l l u s t r a t e how an e x p e r t d i s p l a y may be used i n m o n i t o r i n g a s a f e t y va lve . t h i s t y p e , t h e need f o r a human t o search t h e compu- t e r ' s d a t a base i s e l i m i n a t e d because t h e d i s p l a y i s updated a u t o m a t i c a l l y .

The r u l e s i n Tab le 2 a r e f o r i l l u s t r a t i o n purposes o n l y . comprehensive s e t . For example, r u l e s t o d e t e c t a s t u c k open v a l v e wou ld be u s e f u l . f a c t o r t o assess t h e c e r t a i n t y o f a s o l u t i o n wou ld be h e l p f u l . I f i n s u f f i c i e n t o r c o n f l i c t i n g d a t a a r e p r e s e n t , a low p r o b a b i l i t y f a c t o r i s ass igned, wh ich e s s e n t i a l l y g i v e s t h e prob lem t o t h e human t o r e s o l v e . W i t h v a l i d a t e d p l a n t d a t a , t h e r u l e s c o u l d be expanded t o r e s o l v e c o n f l i c t s . Furthermore, t h e r u l e s shou ld be expanded t o t e s t f o r and d e t e c t s a t u r a t e d steam a t t h e measured p r e s s u r e w i t h i n t h e d i s c h a r g e p i p e . However, t h i s steam may be p r e s e n t f o r o t h e r reasons. As t h e r u l e s become more complex, a g r e a t e r e f f o r t i s needed

The tempera ture g r i d i s another

The The

The p a t h o f t h e t h r o t t l i n g p r o -

The o p e r a t i n g cond i -

The

W i t h an e x p e r t d i s p l a y o f

New r u l e s must be added t o genera te a r o b u s t and

A lso , a p r o b a b i l i t y

F i g u r e 5 c o n t a i n s an i c o n i c d i s p l a y o f a p r e s s u r i z e d water r e a c t o r (PWR) a t d e s i g n power. The i c o n i c d i s - p l a y i s composed o f p rocess segments and system segments. f u n c t i o n s and v a r i a b l e s f o r t h e p r i m a r y c o o l a n t system and secondary c o o l a n t system ( i n terms o f tempera ture and e n t r o p y p r o p e r t i e s o f water , see Reference 7 f o r f u r t h e r d e t a i l s ) . A l s o , t h e process segments c o n t a i n d a t a on: 1) subcooled water i n t h e p r i m a r y c o o l a n t sys- tem and t h e secondary c o o l a n t system, and 2) w a t e r l e v e l d a t a f o r t h e p r e s s u r i z e r , steam genera tors , and condenser h o t w e l l (see Reference 7 on how these d a t a a r e encoded as process knowledge).

Several system segments a r e c o n t a i n e d i n t h e PWR HEAT ENGINE i c o n ( F i g u r e 5). The segment f o r t h e condenser c o o l i n g w a t e r system i s near t h e condensat ion process f u n c t i o n p o r t i o n o f t h e process i c o n . The segments f o r t h e condensate s t o r a g e t a n k (CST) and a s s o c i a t e d p i p i n g , v a l v e s , and pump a r e near t h e segment f o r t h e condensat ion process . The system segments f o r t h e makeup and le tdown system c o n t a i n t h e volume c o n t r o l t a n k (VCT), r e g e n e r a t i v e h e a t exchanger ( R H X ) , l e tdown h e a t exchanger (LHX), and a s s o c i a t e d p i p i n g , v a l v e s , and pumps. F i n a l l y , t h e h i g h p r e s s u r e c h a r g i n g system, w i t h t h e r e f u e l i n g w a t e r s t o r a g e tank , boron i n j e c t i o n t a n k (B IT) , v a l v e s , and pump i s a l s o shown i n t h e i c o n .

Mnemonics a r e a l s o encoded i n F i g u r e 5. t u r e g r i d and s c a l e serve a u s e r ' s t a s k t o e v a l u a t e c o o l a n t tempera tures w i t h i n t h e process . A l s o , t h e r e a c t o r power l e v e l (99.6%) i s s t a t e d n u m e r i c a l l y and p o s i t i o n e d near t h e d i s p l a y segment f o r p r i m a r y c o o l a n t . Fur thermore , a d d i t i o n a l d a t a c o u l d be coded i n t o F i g u r e 5 and s t i l l n o t r e s u l t i n c l u t t e r . For example, t h e tempera ture o f t h e w a t e r e n t e r i n g and l e a v i n g t h e LHX and RHX c o u l d be added a l o n g w i t h t h e water f l o w r a t e s . n o t a completed des ign .

A normal r e a c t o r t r i p i s one where: 1) t h e c o n t r o l rods i n s e r t i n t o t h e r e a c t o r and a s a f e t y i n j e c t i o n s i g n a l i s n o t p r e s e n t , 2) t h e t u r b i n e bypass v a l v e opens on demand, 3) t h e a u x i l i a r y feedwater system responds on demand, 4) t h e t u r b i n e v a l v e s c l o s e on demand, 5) t h e feedwater system t r i p s on demand, and 6) t h e condenser serves as a component i n t h e h e a t removal c y c l e . These c o n d i t i o n s may be formed i n t o r u l e s t h a t w i t h t h e appro- p r i a t e measured p l a n t d a t a , would be used t o c o n t r o l t h e d i s p l a y o f segments. F i g u r e 6 i l l u s t r a t e s how t h e i c o n p r e s e n t s o p e r a t i o n o f t h e p l a n t f o l l o w i n g a normal

The process segments p r e s e n t t h e process

The tempera-

F i g u r e 5 i s an i l l u s t r a t i o n o n l y ,

994

t r i p . The source o f t h e a u x i l i a r y feedwater f o r t h e steam g e n e r a t o r s i s t h e condensate s t o r a g e t a n k .

F i g u r e 7 i l l u s t r a t e s how t h e i c o n would l o o k when t h e a u x i 1 i a r y feedwater system f a i 1 s t o respond upon a r e a c t o r t r i p . The word i s used because t h e a u t h o r d i d n o t have d a t a f rom a computer s i m u l a t i o n o f t h e e v e n t t o genera te t h e d i s p l a y . Severa l i m p o r t a n t events a r e coded i n t o t h i s i con : 1) t h e blowdown o f t h e steam g e n e r a t o r s t o t h e condenser by a t h r o t t l e p rocess th rough t h e t u r b i n e bypass v a l v e , 2) a p r e s s u r i z e r t h a t i s n e a r l y f u l l o f w a t e r , and 3) a blowdown o f t h e p r e s s u r i z e r t o t h e p r e s s u r i z e r r e l i e f t a n k (PRT) by a t h r o t t l e p rocess t h r o u g h t h e p r e s s u r e r e l i e f va lves . The s a f e t y systems c o n s i s t o f 1) t h e accumula tors (ACUM), 2) t h e upper head i n j e c t i o n system (UHI), 3) t h e s a f e t y i n j e c t i o n system ( S I ) , and 4) t h e c h a r g i n g system (CHG). The p r i m i t i v e s o f t h e d i s p l a y segments wou ld be updated on a r e a l - t i m e b a s i s t o r e f l e c t t h e c u r r e n t s t a t u s o f t h e p l a n t . p a t h f rom t h e r e a c t o r t o t h e environment c o n s i s t s o f t h e t h r o t t l e p rocess t h r o u g h t h e r e l i e f v a l v e s i n t h e p r e s s u r i z e r , con ta inment sump, and t h e h e a t exchangers i n t h e r e s i d u a l h e a t removal system.

F i g u r e 8 i l l u s t r a t e s how t h e i c o n wou ld d i s p l a y p l a n t o p e r a t i o n s a f t e r a r e a c t o r t r i p i n wh ich a l l t u r b i n e bypass v a l v e s f a i l t o open on demand. The a u x i l i a r y feedwater system responds and p r o v i d e s w a t e r t o t h e steam genera tors . The a f t e r h e a t f rom t h e r e a c t o r i s removed i n t h e process o f b o i l i n g t h e a u x i l i a r y feed- w a t e r i n t h e steam genera tors . r e l e a s e d t o t h e atmosphere by a t h r o t t l i n g process t h r o u g h t h e g e n e r a t o r ' s r e l i e f va lves .

F i n a l l y , F i g u r e 9 i l l u s t r a t e s a p r i m a r y c o o l a n t system t h a t i s thermodynamica l l y uncoupled f rom t h e secondary c o o l a n t system. The v e r t i c a l b a r between t h e p r e s s u r e b a r o f t h e p r i m a r y system and t h e steam g e n e r a t o r ' s s a t u r a t i o n tempera ture would be c o l o r e d r e d ; i t serves as a p e r c e p t u a l cue t o a t t r a c t t h e u s e r ' s a t t e n t i o n . The t r i a n g u l a r symbol l o c a t e d on t h e p r e s s u r e b a r i n d i c a t e s t h e w a t e r l e v e l i n t h e r e a c t o r core . The p o s i t i o n o f t h e square symbol on t h e p r e s s u r e b a r , l o c a t e d near t h e s a t u r a t e d steam l i n e , i n d i c a t e s a p r e s s u r i z e r empty o f water .

An e x p e r t d i s p l a y t o a s s i s t o p e r a t o r s i n m o n i t o r i n g p l a n t o p e r a t i o n s d u r i n g normal o p e r a t i o n s , a n t i c i p a t e d t r a n s i e n t s , and emergency c o n d i t i o n s i s a u n i v e r s a l d i s p l a y and t e c h n i c a l l y f e a s i b l e . from t h e c o r e f o l l o w i n g a r e a c t o r t r i p must be ach ieved s u c c e s s f u l l y t o m a i n t a i n safe o p e r a t i o n o f t h e p l a n t . An e x p e r t d i s p l a y t h a t a u t o m a t i c a l l y i d e n t i f i e s and p r e s e n t s t h e c u r r e n t h e a t t r a n s f e r p a t h f rom t h e h e a t source ( r e a c t o r ) t o h e a t s i n k (env i ronment ) wou ld s i m p l i f y t h e f u n c t i o n s and t a s k s ass igned o p e r a t o r s .

The main h e a t removal

The steam i s t h e n

A f t e r h e a t removal

ACKNOWLEDGEMENTS

The a u t h o r thanks John G a b r i e l and R ichard L indsay o f Argonne N a t i o n a l Labora tory f o r t h e i r r e v i e w and com- ments on d r a f t s o f t h i s paper. The a u t h o r a l s o thanks Thomas R o t e l l a , a s t a f f c o l l e a g u e , f o r h i s c o n s t r u c t i v e r e v i e w comments.

CONCLUSIONS

Knowledge o f t h e p l a n t ' s h e a t eng ine c y c l e / h e a t removal c y c l e i s encoded as c o m p u t e r - c o n t r o l l e d d i s p l a y seg- ments on a ca thode- ray t u b e ' s screen. T h i s knowledge i s based on t h e thermodynamic p r i n c i p l e s and models used by mechanical eng ineers t o des ign a n u c l e a r power p l a n t . The g r a p h i c a l segments on t h e screen fo rm an i c o n o f t h e p l a n t ' s o p e r a t i o n , wh ich f a c i l i t a t e s t h e communicat ion o f t h e encoded knowledge t o t h e user .

The d a t a w i t h i n t h e i c o n a l l o w a u s e r t o e v a l u a t e t h e i n t e r a c t i o n between p l a n t systems and t h e process .

The r u l e s ( c o l l e c t i o n o f e x p e r t i s e ) needed t o c o n t r o l t h e d i s p l a y o f segments, as d e s c r i b e d h e r e i n , a r e few i n number. However, t h e r u l e s a r e e x t r e m e l y i m p o r t a n t because t h e i r imp lementa t ion automates t h e t a s k s o f a c q u i s i t i o n and communicat ion o f knowledge, i n r e a l t i m e , as a f u n c t i o n o f p l a n t s t a t u s . T h i s techn ique a l l o w s t h e d e s i g n e r t o d i s p l a y t h e most r e l e v a n t da ta ; t h a t i s , t h e d a t a an e x p e r t would use t o m o n i t o r and e v a l u a t e t h e c u r r e n t s t a t e o f t h e p l a n t .

These f e a t u r e s reduce a u s e r ' s work load by e l i m i n a t i n g t h e search f o r d a t a and t h e y enhance a s k i l l - b a s e d response from t h e o p e r a t o r t h r o u g h t h e l o g i c a l s t r u c - t u r e o f t h e d i s p l a y e d da ta .

The i l l u s t r a t i o n s i n t h i s paper - an e x p e r t s a f e t y v a l v e m o n i t o r and a u n i v e r s a l d i s p l a y - a r e i l l u s t r a - t i o n s o n l y . A c o n s i d e r a b l e amount o f work remains t o be done t o d e s i g n and v a l i d a t e t h e system descr ibed. However, f rom t h e i l l u s t r a t i o n s , i t may be seen t h a t a d d i t i o n a l f u n c t i o n s , such as process c o n t r o l and a n n u n c i a t i o n s , c o u l d be added t o expand t h e u t i l i t y o f t h e u n i v e r s a l d i s p l a y . f u r t h e r m o r e , t h e use o f a v i d e o r e c o r d e r , w i t h a f a s t r e p l a y f e a t u r e , p r o v i d e s a u s e f u l means o f m o n i t o r i n g and d i a g n o s i n g p l a n t t r a n s i e n t s and t r i p s . W i t h a f a s t r e p l a y , f u n c t i o n t r e n d s c o u l d be mon i to red as a near r e a l t i m e a i d i n t h e d i a g n o s i s o f an event . A new l e v e l o f human f a c t o r s f o r t h e o p e r a t o r - p l a n t i n t e r f a c e i s ach ieveab le w i t h techno logy t h a t c u r r e n t l y e x i s t s !

T h e u s e o f t h e e x p e r t d i s p l a y s presented i n t h i s paper w i l l :

e l i m i n a t e t h e need t o g a t h e r and process r e l a t e d d a t a f rom d i v e r s e p o i n t s w i t h i n t h e c o n t r o l room;

e l i m i n a t e t h e peephole e f f e c t o f a CRT screen as a v i e w p o r t t o a l a r g e d a t a base o f i n f o r m a t i o n ;

e l i m i n a t e t h e search e f f o r t needed i n i n t e r a c t - i n g w i t h a keyboard t o f i n d t h e d i s p l a y f o r m a t s p e r t i n e n t t o c u r r e n t p l a n t o p e r a t i o n s .

e l i m i n a t e d i s p l a y c l u t t e r because o n l y segments p e r t i n e n t t o c u r r e n t p l a n t o p e r a t i o n s a r e p r e - sented r a t h e r t h a n a l l d i s p l a y segments a t t h e same t i m e ; and

g i v e c o n t r o l room o p e r a t o r s i n f o r m a t i o n an e x p e r t wou ld use i n e v a l u a t i n g t h e c u r r e n t s t a t u s o f t h e p l a n t .

However, t h e s e b e n e f i t s can o n l y be ach ieved i f :

- t h e knowledge base i s a c c u r a t e l y and t h o r o u g h l y d e f i n e d ; and

- t h e r u l e s implemented i n t o computer code a r e f r e e o f e r r o r and c o n f l i c t .

A s t r u c t u r e d d e s i g n process , a l o n g w i t h e f f e c t i v e q u a l i t y assurance programs and d e s i g n v e r i f i c a t i o n and v a l i d a t i o n programs, w i l l m in imize t h e d e s i g n e r r o r s i n t h e code.

REFERENCES

1. Foe ly , J. D. , Wal lace, V. L. , and Chan, P . , "The Human F a c t o r s o f Computer Graph ic I n t e r a c t i o n Techniques," IEEE Computer Graph ics and Appl i c a %, Volume 4, Number 11, November 1984, pp 1 3 - 48.

995

2. "Computer-Generated D i s p l a y System G u i d e l i n e s , 6. Ober t , E. F . , Elements of Thermodynamics and Heat Volume 1: D i s p l a y Design, Volume 2: Deve lop ing an T r a n s f e r , F i r s t E d i t i o n , 1949, McGraw H i l l Book E v a l u a t i o n P lan , " NP - 3701, E l e c t r i c Power Company, I n c . New York, New York. Research I n s t i t u t e , September 1984.

7. B e l t r a c c h i , L., " A P r o c e s d E n g i n e e r e d Safeguards I c o n i c D i s p l a y , " Proceedings o f t h e Symposium on New Techno log ies i n Nuc lear Power P l a n t Ins t rumen t a t i o n and C o n t r o l , Washington, DC, November 28 -

" A c o u s t i c M o n i t o r i n g o f Nuc lear S a f e t y and R e l i e f Valves," NP-3332, Research P r o j e c t 1246-2, E lec- t r i c Power Research I n s t i t u t e , Pa lo A l t o , C a l i - f o r n i a , F i n a l Report , December, 1983.

3. Murch, G. M. , " P h y s i o l o g i c a l P r i n c i p l e s f o r t h e E f f e c t i v e Use o f C o l o r , " IEEE Computer Graph ics and A p p l i c a t i o n s , Volume 4, Number 11, November 1984, pp 49 - 54. 30, 1984.

4. Hayes - Roth, F . , "The Knowledge-Based E x p e r t System: A T u t o r i a l , " IEEE Computer, September 1984, pp 11 - 28.

8.

5. G immy, K. L . , and Nomm, E . , "Au tomat ic D iagnos is o f M u l t i p l e Alarms f o r Reactor C o n t r o l Rooms," Proceedings o f ANS Annual Meet ing , Los Angeles, CA, June 6 - 11, 1982.

TABLE 1

THE THROTTLE PROCESS

1. S a f e t y v a l v e open

Steam l i n e :

Pressure: 1250 p s i a

Temperature: 572.4 F

( s a t u r a t e d steam)

Entha lpy : 1182.6 BTU/#m

S a f e t y v a l v e s e t p o i n t : 1245 p s i a

D ischarge p i p e :

Pressure: 14.7 p s i a

Temperature: 279 F (superheated steam)

2. S a f e t y v a l v e l e a k i n g

Steam l i n e :

Pressure : 1000 p s i a

Temperature: 544.6 F ( s a t u r a t e d steam)

Entha lpy : 1192.9 BTU/#m

Discharge p i p e :

Pressure : 14 .7 p s i a

Temperature: 300 F (superheated steam)

TABLE 2

EXPERT RULES

Rules

~ ~~

S t a t u s

Steam l i n e p r e s s u r e 2 True F a l s e F s a f e t y v a l v e ' s s e t p o i n t

A c o u s t i c m o n i t o r r e a d i n g 2 T F T

s e t p o i n t v a l u e

Thermocouple r e a d i n g 1 T F T

( c a l c u l a t e d temp- to le rance)

T T

F T

T F

Message on v a l v e s t a t u s Va lve Va lve Va lve I n s u f f i c i e n t

Open Closed Leak ing Data

996

P i = PRESSURE

H i = ENTHALPY STEAM LINE

DRYWELL

ACOUSTIC MONITOR

DISCHARGE PIPE

I I

Figure 1 BWR steam l i n e safe ty valve

991

BWR - SAFETY VALVE CHECK

11 /OW85 09: 15:OO

T T E E M M P P

700

600

500

400

300

m 100

I-ZZ2F-l Figure 2 Icon: Safety valve f u l l y seated

BWR - SAFETY VALVE CHECK

1 1 109185' 09:15:OO

SRV 50201 LEAKING I

~~

Figure 3 Icon: Safety valve leaking

998

BWR - SAFETY VALVE CHECK

11 109185' 09: 15:OO

T T E E M M P P

Figure 4 Icon: S a f e t y v a l v e open

PWR HEAT ENGINE

09121 185 07:OO:OO

T E M P

F igure 5 Icon: PWR heat engine

999

PWR HEAT REMOVAL CYCLE

09/21 185' 07: 1O:OO

ALL RODS IN

Figure 6 Icon: PWR heat removal cycle , normal t r i p

PWR HEAT REMOVAL CYCLE

09/21 185' 07: 15:OO

ALL RODS IN

.-.-.-.-.-.-.-.-.-.

1M

50

0

Figure 7 Icon: PWR heat removal cyc le , no aux feedwater

PWR HEAT REMOVAL CYCLE /

09/21 I85 07:15:00

ALL RODS IN

Figure 8 Icon: P W R heat removal cycle, bypass valves fail to open

Figure 9 Icon: P W R heat removal cycle, uncoupled primary system